The author- or copyrights of the listed research articles below
are held by the respective authors or site operators, who are also
responsible for the content of the presentations.
More current articles from Chemistry Journals same topic: see
the navigation menu on the left.
To list your article here please contact us by eMail.
To search this web page for specific words type "Ctrl" +
"F" on your keyboard (Command + "F" on a Mac). Then: type the word
you are searching for in the window that pops up!
On this page considered journals:
Chemical Physics - published by Elsevier
Chemical Physics welcomes experimental and theoretical papers in the molecular, biological and materials sciences
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Yasushi Shibuta, James A. Elliott The interaction energy between a rigid defect-free graphene sheet and a fixed Ni(111) surface with respect to rotational and translational displacements is examined using an empirical bond order potential. The Rosei (hollow site) structure, and others in which metal atoms are adjacent to hollow sites in graphene, give rise to global and local energy minima, respectively, whereas the interaction energy is almost constant for incommensurate structures. Only a few degrees rotation from the Rosei structure substantially diminishes the energy barrier for translational displacement.
Graphical abstract
Graphical abstractHighlights
? Interaction between graphene and nickel surface with various orientations is examined. ? The Rosei and other hollow structures give rise to global and local energy minima. ? Interaction energy is almost constant for incommensurate structures. ? A few degrees rotation from Rosei structure diminishes energy barrier for translation.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Miko?aj M. Miko?ajczyk, ?aneta Czy?nikowska, Przemys?aw Czele?, Urszula Bielecka, Robert Zale?ny, Petr Toman, Wojciech Bartkowiak In this study, we report on the results of MD/QM computations of charge–transfer integrals for nucleic acid base complexes in stacked configurations containing 7-deazaadenine. A strong dependence of charge–transfer integrals on torsional parameters was observed in case of all studied complexes. However, a very important finding of this study is that in proximity of equilibrium configuration, the values of charge–transfer integral are not sensitive to the replacement of adenine with 7-deazaadenine. Likewise, the analysis of distribution of charge–transfer integrals, determined for structures taken from molecular dynamics simulations, revealed that their changes upon adenine modification are not a key factor influencing charge transport.
Graphical abstract
Graphical abstractHighlights
? The substitution of adenine with 7-deazaadenine in selected complexes was considered. ? The interaction energy and charge transfer integrals profiles were calculated. ? The key parameters determining charge transport were discussed. ? The site energy seems to be a key factor determining charge transport.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Masahiro Ehara, Thomas Sommerfeld The complex absorbing potential (CAP)/symmetry-adapted cluster-configuration interaction (SAC-CI) method has been developed to investigate resonance states of metastable anions. The method has been implemented in the projected scheme and applied to the ?? resonance state of formaldehyde. The dependence on both valence and diffuse basis sets up to g-function, the number of SAC-CI states in the projection, and the effect of perturbation selection are examined. The potential energy curve and decay width are calculated in the C–O stretching coordinate, and the Franck–Condon factors for transitions from neutral to resonance state are evaluated to interpret the electron transmission (ET) spectrum.
Graphical abstract
Graphical abstractHighlights
? The complex absorbing potential (CAP)/symmetry-adapted cluster-configuration interaction (SAC-CI) method was developed. ? The method was implemented in the projected scheme and applied to the resonance of formaldehyde. ? The electron transmission spectrum of formaldehyde can be understood in terms of the C–O stretching vibration only.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Luca Valentini, Silvia Bittolo Bon, Marta Cardinali, Orietta Monticelli, Josè M. Kenny In this Letter, a novel method for the preparation of surface modified graphene oxide (GO) sheets is proposed, by the vaporization of amino-functionalized polyhedral oligomeric silsesquioxanes (POSS) on the GO sheets. The chemical composition, surface morphology as well as the surface properties of the prepared films were investigated by means of Fourier transform infrared spectroscopy, water contact angle measurements and field emission electron microscopy. When exposed to visible light the film obtained by grafting the amino-functionalized POSS on GO sheets showed a photoconductivity response.
Graphical abstract
Graphical abstractHighlights
? Functionalization of GO sheets by the vaporization of amino-functionalized POSS. ? Change of surface wettability of POSS modified GO sheets. ? Photoresponsive integrated thin film when exposed to visible light.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Shao-long Wu, Ting Zhang, Rui-ting Zheng, Guo-an Cheng This Letter presents a novel low-cost light detector based on radial silicon nanowire heterostructures. Photoelectrochemical responses of silicon nanowire arrays with different morphologies, prepared by a metal assisted chemical etching method, have been systematically investigated. The photoresponsivity of the black silicon nanowire arrays is 73 times larger than that of the planar silicon at 0.2V bias under white light illumination. The relationship between the photoresponsivity and nanowire morphology and doping level is discussed. Our results demonstrate that the heterostructures of the nanowire arrays with an optimized morphology are promising for light detection and other optoelectronic devices.
Graphical abstract
Graphical abstractHighlights
? A light detector based on radial heterostructures of 1D semiconductor nanostructures is proposed. ? The detector performs high collection efficiency of photogenerated carriers. ? Photoelectrochemical responses of Si nanowires with different morphologies are investigated. ? The photoresponsivity of the black sample is 73 times larger than that of the planar silicon at 0.2 V.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Antal A. Koós, Frank Dillon, Rebecca J. Nicholls, Lyubov Bulusheva, Nicole Grobert The insertion of dopant atoms into the carbon nanotube framework allows one to tailor their electronic properties, reactivity and structure. We investigated the effect of the reaction parameters on the yield and quality of N-doped single-walled carbon nanotubes (N-SWCNTs) produced via aerosol chemical vapour deposition. In this context, aerosols of ethanol/benzylamine mixtures in conjunction with ferrocene were pyrolysed at temperatures between 950 and 1100°C. As a result, we were able to produce N-SWCNTs with a nitrogen content of ca. 1at.%, diameters ranging between 0.9 and 1.8nm, and production rates of more than 10mg/h.
Graphical abstract
Graphical abstractHighlights
? We were able to produce N-SWCNTs with a nitrogen content of ca. 1at.%. ? Yields were higher than 10mg/h. ? We used a cheap and scalable method which does not require catalyst preparation step.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Wenjie Mai, Zhiwen Liang, Long Zhang, Xiang Yu, Pengyi Liu, Hanming Zhu, Xiang Cai, Shaozao Tan The nature of contacts between ZnO semiconductor nanowires and metal pads has attracted great research interests since its impact on enhancing sensitivity of the sensors. Herein, ZnO nanowire arrays were synthesized by a scalable wet chemical method and ZnO nanowire-polymer composite strain sensors were fabricated by utilizing Schottky contact. The electrical transport response to strain was attributed to piezoelectric-effect-induced Schottky barrier height changes at the metal–semiconductor junction under various strained states. When the strain increased from 0% to 0.12%, the average barrier height change increased to 26meV, inducing sensitive current changes in these strain sensors.
Graphical abstract
Graphical abstractHighlights
? A facile method was developed to fabricate ZnO nanowire-polymer composite strain sensors. ? The response to strain was attributed to Schottky barrier height changes. ? Thermionic emission–diffusion was the dominant process in this kind of devices.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Tetsu Yonezawa, Shigeo Arai, Hironori Takeuchi, Takeo Kamino, Kotaro Kuroda Naked silver nanoparticles supported on SiO2 were prepared in a TEM chamber in order to be directly observed in situ their structural changes at high temperature. Without exposing the samples in air, this method give a possibility to understand the behavior of metal itself without any contamination or oxidation. Melting temperature depression according to the particle size could be observed.
Graphical abstract
Graphical abstractHighlights
? We prepared naked silver nanoparticles supported on SiO2 directly in a TEM column. ? Structural changes of Ag nanoparticles at high temperature were observed in situ. ? Size depending melting temperature depression was directly observed.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Silvina Fioressi, Daniel E. Bacelo, R.C. Binning Density functional theory calculations have been conducted on 20- and 32-atom dodecahedral and face-capped dodecahedral cage clusters of beryllium and silicon. Stable Be24Si8, Be12Si8 and Be12Si20 cages are described, as is a stuffed cluster consisting of dodecahedral Si20 with an endohedral icosahedral Be12. Especial stability is associated with clusters in which faces are capped by silicon atoms, acting as electron donors to beryllium atoms.
Graphical abstract
Graphical abstractHighlights
? DFT calculations have been conducted on cage clusters of beryllium and silicon. ? Stable Be24Si8, Be12Si8 and Be12Si20 cages are described. ? Especial stability is associated with clusters in which faces are capped by silicon atoms.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Mariusz Wojcik, M. Tachiya We present an analytical theory of geminate charge recombination in donor–acceptor heterojunction systems based on the Smoluchowski equation. We show that the differential equation describing this problem is mathematically equivalent to that describing geminate recombination in a four-dimensional anisotropic system. By combining this result with already available analytical results for n-dimensional homogeneous systems, we predict that the survival probability of electron–hole pairs in heterojunction systems decays as t?1 at long times. We prove this by analyzing the results of kinetic Monte Carlo simulations. We also explain clearly why the ultimate escape probability is increased by introducing the heterojunction.
Graphical abstract
Graphical abstractHighlights
? Analytical theory of geminate recombination in heterojunction systems is presented. ? Survival probability of geminate electron–hole pairs decays as t?1 at long times. ? Analytical results are confirmed by kinetic Monte Carlo simulations. ? Explanation is given for the increased escape probability in heterojunction systems.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Roberto A. Garza-López, Jack Brzezinski, John J. Kozak Supramolecular architectures provide a reproducible template on which surficial processes can be studied. We consider the irreversible reaction A+B?C where B is a stationary reaction center and A is a coreactant diffusing on a finite, discretized d=2 dimensional surface of a supramolecular assembly. A lattice-statistical model is developed to quantify how the reaction efficiency changes when the template is planar, Euler characteristic ?=0, or wrapped on the surface of a d=3 host, ?=2. We find that for aperiodic or regular surfaces of finite spatial extent, dispersed ?=2 assemblies better optimize surficial reactions than ?=0 planar hosts.
Graphical abstract
Graphical abstractHighlights
? We study the reaction efficiency of diffusion-controlled processes on surfaces. ? We consider finite, aperiodic planar lattices and supramolecular architectures. ? We consider the irreversible reaction A+B?C on a finite, discretized d=2 surface. ? A lattice-statistical model is developed to quantify the reaction efficiency. ? Aperiodic or regular surfaces better optimize surficial reactions than ?=0 hosts.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Marek Wi?niewski, Sylwester Furmaniak, Piotr Kowalczyk, Karolina M. Werengowska, Gerhard Rychlicki We studied the thermodynamics of benzene adsorption on a series of oxidized closed-ended multiwalled carbon nanotubes at 298K. Combined experimental and simulation results showed the significant effect of the surface heterogeneity on the benzene adsorption enthalpy and entropy at low surface coverages. For oxidized carbon nanotubes and low benzene uptakes, the differential entropy of the adsorbed phase is close to the differential entropy of solid benzene. Therefore, benzene molecules interacting with surface heterogeneities are ordered in quasi-solid structures at 298K. At higher surface coverages, the ordering and packing of benzene molecules is liquid-like.
Graphical abstract
Graphical abstractHighlights
? The thermodynamics of benzene adsorption on carbon nanotubes is studied. ? The series of systematic modified nanotubes is analyzed. ? The simple model of surface heterogeneity is proposed. ? The results of computer simulations reproduce observed experimentally regularities.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Xiaoan Wang, Y.J. Nie, G.S. Huang, J.R. Wu, K.W. Xiang The dynamic crossover of the sub-Rouse modes (a transition from one Vogel–Fulcher–Tamman law to another in relaxation map) above glass transition in poly(n-alkyl methacrylates) (PnAMA) was observed and compared for the first time. The ? and ?? relaxations become better resolved from each other with increasing side chain length, while the crossover relaxation time is 10?0.5±0.5s, essentially independent of side chain length of the PnAMA, indicating the universal presence of the sub-Rouse modes in PnAMA. Analysis of the mechanical spectra shows that the crossover originates from change of intermolecular coupling of the sub-Rouse modes when temperature crosses TB.
Graphical abstract
Graphical abstractHighlights
Temperature dependence of average relaxation times of PnAMA for mechanical ?? and ? relaxations. The ? relaxations are fitted by a single corresponding VFT equation, while the ?? relaxations are fitted by two VFT equations, indicating the presence of the dynamic crossover of ?? relaxation.?Relaxation behavior of poly(n-alkyl methacrylates) was investigated by the high precision shear mechanical spectroscopy. ? The dynamic crossover of the sub-Rouse modes above glass transition in poly(n-alkyl methacrylates) was observed and compared. ? The crossover relaxation time is essentially independent of side chain length and constant. ? The crossover is supposed to be the distinct variation of intermolecular coupling and cooperativity at TB.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Ke-Yu Lai, Rongshun Zhu, M.C. Lin The reactions of N2H4 with N2O4 isomers have been investigated at the G2M(CC3)//B3LYP/6-311++G(3df,2p) level. The results show that the reactions of N2H4 with sym-N2O4 (D2h), cis-ONONO2 (Cs), and NO2 have to overcome 14.2, 10.6, and 7.6kcal/mol barriers, respectively. However, N2H4 can react spontaneously with trans-ONONO2 (Cs) and cis-ONONO2 (C1) to produce HONO2+H2NN(H)NO with the near gas-kinetic rate constant, 4×10?10cm3molecule?1s?1 above 250K. The H2NN(H)NO thus formed can rapidly fragment to give reactive N2H3 radical with rate constant >1×107s?1 at 1000K, which is fast enough to initiate the hypergolic chain reactions with NO2 and N2O4.
Graphical abstract
Graphical abstractHighlights
? This Letter elucidates how the hypergolic reaction of N2H4 and N2O4 occurs. ? The reactions of N2H4 with N2O4 isomers have been investigated computationally. ? N2H4 can react spontaneously with trans-ONONO2 (Cs) and cis-ONONO2 (C1). ? The H2NN(H)NO formed in the reactions can rapidly produce N2H3 radical. ? N2H3 radical can initiate chain reactions with NO2 and N2O4.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Samir F. Matar, Bernard Chevalier, Rainer Pöttgen The electronic structure and chemical bonding properties of CeRh2Sb2 are provided based on ab initio DFT calculations of the two model forms. The energy results show a stabilization of simple tetragonal ST versus body centered tetragonal BCT. Chemical bonding indicating the strongest interactions within the Rh–Sb substructure in both forms also shows two types of anti-bonding interactions involving antimony (Sb–Sb and Sb–Rh) in BCT. This could be at the origin of the instability of the Sb substructure which becomes defective as observed experimentally. It is also significant for the destabilization of BCT versus ST which presents more bonding like interactions.
Graphical abstract
Graphical abstractHighlights
? CeRh2Sb2 known in simple tetragonal ST-CaGe2Ge2 and body centered BCT ThCr2Si2 types. ? Energy results from ab initio DFT calculations show a stabilization of ST versus BCT. ? Chemical bonding indicates strongest interactions in Rh–Sb layers. ? Antibonding Sb–Sb and Rh–Sb in BCT lead to instability and defects observed experimentally.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Ganglong Cui, You Lu, Walter Thiel We report a theoretical study on the electronically excited states and the mechanisms of photodissociation of C6H5CHO and C6H5COCH3. For both molecules, we find an S1/T2/T1 three-state intersection region, which allows for an efficient S1?T1 intersystem crossing via the T2 state that acts as a relay. Consequently, T1 reactions become the major radical photodissociation channels. According to the computed energy profiles, T1 photodissociation mainly yields phenyl and formyl radicals in the case of benzaldehyde, and benzoyl and methyl radicals in the case of acetophenone, with different C–C bonds being cleaved preferentially. The computational results agree well with the available experimental data.
Graphical abstract
Graphical abstractHighlights
? S1/T2/T1 three-state intersection region in both C6H5CHO and C6H5COCH3. ? Efficient S1/T1 intersystem to T1 via the T2 state as a relay. ? On the T1 state, different bond-fission scenarios.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Yani Chen, Hongbin Zhao, Leimei Sheng, Liming Yu, Kang An, Jiaqiang Xu, Yoshinori Ando, Xinluo Zhao Large-scale production of graphene sheets has been achieved by direct current arc discharge evaporation of pure graphite electrodes in various H2–inert gas mixtures. The as-prepared few-layer graphene sheets have high purity, high crystallinity and high oxidation resistance temperature. Their electrochemical characteristics have been evaluated in coin-type cells versus metallic lithium. The first cell discharge capacity reached 1332mAhg?1 at a current density of 50mAg?1. After 350 cycles, the discharge capacity still remained at 323mAhg?1. Graphene sheets produced by this method should be a promising candidate for the electrode material of lithium-ion batteries.
Graphical abstract
Graphical abstractHighlights
? Gram-scale graphene sheets were produced by using hydrogen arc discharge method. ? Few-layered graphene sheets have high crystalline structure. ? Arc-discharged graphene sheets were used as anodes of lithium-ion batteries. ? The graphene sheets anodes show excellent cyclic performance.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Sung-Ryong Kim, Mohammad Al-Mamun, Young-Hui Ko The photovoltaic performances and charge recombination of the dye sensitized solar cells (DSSCs) using N-modified TiO2 photoelectrodes were investigated under different ion-beam conditions. N-modified TiO2 films exhibited significantly enhanced BET surface area of 92.19m2/g with the pore volume of 0.283cm3/g compared to the surface area of 56.65m2/g with a pore volume of 0.141cm3/g of pristine TiO2 film. The interstitial and substitutional affixations of nitrogen atom inside the TiO2 lattice were confirmed by XPS and Raman spectroscopy. A 26% improvement in conversion efficiency was achieved by using N+ ion-beam treated TiO2 photoelectrode.
Graphical abstract
Graphical abstractHighlights
? Porous channel for effective dye adsorption by N+ ion-beam treatment. ? Effectively tailored surface properties of TiO2 film. ? Retardation of charge recombination in dye sensitized solar cells. ? Enhanced conversion efficiency of DSSCs by N+ ion-beam treatment.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Cristina A. Barboza, Ramiro Arratia-Pérez, Desmond MacLeod Carey The effect of the 3,3? substitution in 9,9,9?,9?-tetramethyl-fluorene-dimers with electron donor and withdrawing groups was analyzed. Ground state potential energy surfaces were obtained at DFT level using B3LYP/6-31+G(d,p). All studied dimers are nonplanar at their electronic ground states. The electronic transitions were investigated through the time-dependent-DFT method at their optimized ground states. The chemical potential (?) as well as the HOMO and LUMO eigenvalues were plotted against the Hammet parameters, showing a good linear correlation, giving us insights about the modulation of the electronic properties, e.g. HOMO–LUMO gap, by means of the functionalization of fluorene dimers at strategical positions.
Graphical abstract
Graphical abstractHighlights
? We study the substitution with electron donor and attracting groups in fluorene dimers. ? Optical properties can be tuned by the substitution of the fluorene backbone. ? Electronic excitations are assigned mainly to ???? transitions. ? Linear correlations were found among EHOMO, EHOMO–LUMO and ? versus ?p.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Suresh Yarlagadda, Sheo Mukund, S.G. Nakhate Jet-cooled laser-induced fluorescence spectra of LaH molecules in the range 15500–18700cm?1 showed four new vibronic bands. Rotational analysis confirmed a 1?+ symmetry for the ground state, identified a 0+(3??) electronic state at 15622.9(1)cm?1 via intercombination transition observed for the first time in LaH and two more excited electronic states with ?=1 at 17397.9(1) and 17549.0(1)cm?1. Also observed the transition of type ??=0–??=1 with band origin at 18508.8(1)cm?1. Comparison of the present data with earlier ab initio results indicated the overestimation of calculated energies and internuclear distances for the ground and excited electronic states.
Graphical abstract
Graphical abstractHighlights
? 1?+ symmetry for the ground state of LaH molecule confirmed. ? Three new excited electronic states, one with ?=0 and two with ?=1 observed. ? First observation of intercombination transition 0+(3??)–X1?+ in LaH. ? Internuclear distances for new excited electronic states measured. ? Spectroscopic data on observed excited electronic states compared with ab initio results.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Asuka Fujii, Hiromasa Hayashi, Seiji Tsuzuki Infrared spectroscopy has been applied to benzene–ethane clusters to investigate the preferential contact structures due to the CH/? interaction between an alkyl group and a single phenyl ring. Stable structure search of the clusters by high-level ab initio calculations has been also carried out. The observed infrared spectra are well accounted for by the presence of the isomer which has the monodentate structure. The speculated isomer with a tridentate structure has been ruled out by analyses of the observed infrared spectra and theoretical calculations.
Graphical abstract
Graphical abstractHighlights
? The benzene–ethane cluster is a simple but important model for the CH/? interaction. ? Infrared spectra of the cluster were observed. ? Ab initio calculations searched stable structure of the cluster. ? Only the isomer of the monodentate structure was supported.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 G.M.A. Junqueira, L.C. Rocha, V.T. Cotta, E.T. César In this Letter, a discussion on global reactivity indexes – electronic chemical potential (?), chemical hardness (?) and electrophilicity (?) – for dicarba-closo-dodecarboranes isomers, in gas phase and aqueous solution is reported. A sequential Monte Carlo/quantum mechanics methodology (S-MC/QM) was used in simulations. The results obtained showed the solvent must be considered on reactivity properties of the studied compounds. Generally, the solvated isomers become softer (? decreases) and the ? increases comparing to gas phase values, indicating the charge transfer from solvent to the solute.
Graphical abstract
Graphical abstractHighlights
? We study reactivity properties of dicarba-closo-dodecarboranes isomers. ? We calculated reactivity indexes in gas phase and in solution. ? We used explicit molecules (S-MC/QM) and continuum model (PCM) to include the solvent in calculations.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Yongping Zeng, Junmei Hu, Yu Yuan, Xiaobin Zhang, Shengui Ju Car–Parrinello molecular dynamics simulations have been performed on Na+ in water, methanol and ethanol. The structure of the first solvation shell around the Na+ is in a good agreement with the experimental data. It has been found the Na+ has a coordination number (5.13) in water greater than that in methanol and ethanol. However, the decay of orientational correlations for solvation shell methanol and ethanol molecules shows slower relaxation compared to that of bulk. Translational dynamics of Na+ in these systems is affected in a small degree by molecular size. It produces a significant difference on their relative relevance bands.
Graphical abstract
Graphical abstractHighlights
Structure and dynamics properties of Na+ in water, methanol and ethanol.? CPMD is used to investigate the properties of Na+ in solutions. ? The structure properties are in reasonable agreement with experiment. ? Reorientational correlations and translational dynamics in these systems is affected in a small degree by molecular size.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Jacek Gli?ski, Andrzej Burakowski A model assuming that equilibrium reaction of formation of non-compressible dimers dominates in and governs the acoustic properties of liquid mixtures of alcohols in inert hydrocarbon solvents was developed. It was found to describe satisfactorily the observed compressibility dependences on composition of the title systems, in particular those containing long-chained components. This attempt allows to estimate the dimerization equilibrium constants from the compressibility data.
Graphical abstract
Graphical abstractHighlights
? We model properties of hydrocarbon+alcohol mixtures. ? The experimental data are reproduced well even with rough assumptions. ? Assuming only dimerization reproduces the system compressibility.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Maojie Xu, Xiaoming Dou, Yuxiang Bu, Yafei Zhang The microhydration of the complexes formed by trivalent metal ions (Al3+, Ga3+, In3+) and zwitterionic glycine biomolecule has been investigated systematically by first-principles calculations. A first solvation shell with a hexacoordinate configuration is found to occur at the metal center due to the delicate equilibrium between the steric hindrance and the charge transfer from the ligands to the metal. The hydrogen bond forms between the water ligand and glycine bioligand in the first solvation shell, providing an energetically favorable pathway for the proton transfer from the inner shell to the outer shell.
Graphical abstract
Graphical abstractHighlights
? A first solvation shell with a hexacoordinate configuration at the metal center for GlyZwitt.M3+(H2O)5 complex. ? The intramolecular hydrogen bond in Gly ligand. ? The intermolecular bond between one water ligand and Gly ligand in GlyZwitt.M3+(H2O)n complexes (n=3–6). ? The computed infrared and Raman spectra predicting the vibrational properties of GlyZwitt.M3+(H2O)5 complex.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 E.B. Starikov, B. Nordén Enthalpy–entropy compensation (EEC) has a definite physical sense. Here, we review EEC from a new standpoint, using the notion of correlation. The latter has two basic meanings: (a) ‘A’ is correlated to ‘B’ means ‘A’ results from ‘B’ or vice versa; (b) this same means there is some real, but hidden ‘C’ in connection to both ‘A’ and ‘B’). In accordance with the interpretation (b), we try rationalizing EEC in terms of hidden, but physically real factors.
Graphical abstract
Graphical abstractHighlights
? Enthalpy–entropy compensation (EEC) has a definite physical sense. ? Here, we review EEC from a new standpoint using the notion of correlation. ? We rationalize EEC in terms of hidden, but physically real factors.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Wolff-Ragnar Kiebach, Christodoulos Chatzichristodoulou, Rebecka M. Larsen Werchmeister, Anke Hagen Praseodymium doped ceria, a material of interest for electrochemical flue gas purification, was investigated with in situ X-ray Absorption Near Edge Structure spectroscopy between room temperature and 500°C in air and diluted nitrogen(II) oxide (NO/Ar) (1% NO in Ar). For temperatures above 400°C in NO/Ar a reversible energy shift towards lower energy was observed for the Pr edge, indicating a reduction of Pr4+ to Pr3+, while the edge position of Ce remained unchanged. The concentration of Pr3+ ions was quantified and obtained results are in good agreement with predictions from defect thermodynamic modeling.
Graphical abstract
Graphical abstractHighlights
? The reduction of Pr4+ to Pr3+ in Ce0.8Pr0.2O2 was investigated in situ up to 500°C. ? The reversibility of the reaction can be monitored in situ. ? Measured Pr3+concentration is in agreement with thermodynamic calculations. ? Role of oxygen partial pressure and catalytic reactions evaluated.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 N.Kh. Ibrayev, D.A. Afanasyev The triplet–triplet annihilation (TTA) was studied in mixed Langmuir–Blodgett films of 7-decyloxy-3 (4?-ethoxyphenyl)-coumarin molecules and palmitic acid. The thermal activation of the TTA process is observed due to the inhomogeneous broadening of triplet energy levels. Modulation of the TTA rate constant in the external magnetic field for the multilayer films shows the dependence that is characteristic of crystals. Only negative magnetic effect is observed for the monolayers. Time dependence of the magnetic effect in conditions of high rate constant of triplet excitons migration is connected with the dominating contribution of ordered clusters or randomly oriented molecule clusters into the TTA process.
Graphical abstract
Graphical abstractHighlights
? The triplet–triplet annihilation in mixed Langmuir–Blodgett films with coumarin dye. ? Thermal activation process of TTA. ? Time and temperature dependence of magnetic field effects on delayed fluorescence. ? Dominance into process of TTA of contribution of ordered clusters or randomly oriented molecules clusters.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Yevgeniy Lushtak, Samantha B. Dannenberg, C.M. Evans, G.L. Findley We present for the first time the quasi-free electron energy V0(?) in helium from low density to the density of the triple point liquid (gaseous helium/liquid helium I/liquid helium II triple point), on a noncritical isotherm and on an isotherm near the critical temperature. These data were obtained using field enhanced photoemission, a new experimental technique for the characterization of dense fluids. A novel critical point effect in helium is presented and is accurately fitted to the local Wigner–Seitz model. This model, which was developed for attractive fluids, is thereby shown to be applicable to repulsive fluids as well.
Graphical abstract
Graphical abstractHighlights
? Field enhanced photoemission (FEP) is used to experimentally determine V0(?) in He. ? V0(?) in He from low density to the gas/liquid He (I)/liquid He (II) triple point is obtained. ? Critical point effect in V0(?) in He is presented for the first time. ? Local Wigner–Seitz approach, developed for attractive fluids, is shown to model V0(?) in He.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Rodolfo Guillermo Pereyra, Aleida J. Bermúdez di Lorenzo, David C. Malaspina, Marcelo A. Carignano We studied by molecular dynamics simulations the relation existing between the lifetime of hydrogen bonds, the tetrahedral order and the diffusion coefficient of model water. We tested four different models: SPC/E, TIP4P-Ew, TIP5P-Ew and Six-Site, these last two having sites explicitly resembling the water lone pairs. While all the models perform reasonably well at ambient conditions, their behavior is significantly different for temperatures below 270K. The models with explicit lone-pairs have a longer hydrogen bond lifetime, a better tetrahedral order and a smaller diffusion coefficient than the models without them.
Graphical abstract
Graphical abstractHighlights
? H-bond dynamics and tetrahedral order for SPC/E, TIP4P-Ew, TIP5P-Ew and Six-Site water. ? Explicit lone pairs sites favor tetrahedral order and slowdown dynamics at low T. ? Difference between models with and without lone pairs is very important at low T.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 M. Owczarek, R. Jakubas, V. Kinzhybalo, W. Medycki, D. Kruk, A. Pietraszko, M. Ga?a¸zka, P. Zieli?ski 1-Aminopyridinium iodide (API) undergoes a reversible first-order phase transition (PT) II?I at 384K. The single-crystal X-ray diffraction studies have been carried out at 110, 280 and 401K. The compound crystallizes in the monoclinic space group P21/c (phase II) and exhibits ferroelastic properties. High temperature paraelastic phase (I) is described by the trigonal symmetry (space group ) with the 6-site cations disorder. The mechanism of PT is governed by both cationic dynamics and shifts of the I? anions. The conductivity that emerges when approaching the PT temperature is believed to be associated with the charge transfer from I? anion to the 1-aminopyridinium cation.
Graphical abstract
Graphical abstractHighlights
? Ferroelastic properties of 1-aminopyridinium iodide at room temperature. ? Electric conductivity in the high temperature phase I caused by charge transfer. ? Molecular motions discussed on the basis of 1H NMR spin–lattice relaxation time.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Wentao Wu, Kechen Wu, Zuju Ma, Rongjian Sa The thermoelectric properties of p-type doped AgGaTe2 with chalcopyrite structure have been investigated within DFT theoretical framework. The electrical transportations of AgGaTe2 strongly depend on the doping level as well as the temperature. The Seebeck coefficients at various temperatures corresponding to the optimal doping level are all about 270?V/K. Thus the optimal doped AgGaTe2 could be obtained by adjusting the Seebeck coefficient to 270?V/K in the future experiment. The figure of merit of AgGaTe2 at 900K reaches 1.19 under optimal doping level indicating AgGaTe2 is a very promising thermoelectric material.
Graphical abstract
Graphical abstractHighlights
? Electrical transportations of AgGaTe2 strongly depend on the doping level and temperature. ? Optimal doped level of AgGaTe2 can be obtained by adjusting the Seebeck coefficient to 270?V/K. ? Figure of merit of AgGaTe2 at 900K reaches 1.19 under optimal doping level. ? By doping and temperature tuning AgGaTe2 is a very promising thermoelectric material.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Chunrui Wang, Shu Liu, Dong H. Zhang A six-dimensional state-to-state quantum dynamics study is carried out for the prototypical complex-formation OH+CO?H+CO2 reaction from the ground and two vibrationally excited initial states on the Lakin–Troya–Schatz–Harding potential energy surface for the total angular momentum J=0, using the multiple-step reactant–product decoupling method. With three heavy atoms and deep wells on the reaction path, the reaction represents a huge challenge for accurate quantum dynamics study. The effects of reagent vibrational excitation on product CO2 vibrational state distributions and product energy partition were investigated for reagents in the ground rotational state. It is found that the initial CO vibrational excitation essentially has the same effect on the product energy partition as the reagent translational excitation, while the initial OH excitation leads to slightly more internal energy in CO2.
Graphical abstract
Graphical abstractHighlights
? We carried out a 6D state-to-state quantum dynamics study for the OH+CO reaction. ? Reagent translational and CO vibrational excitation has essentially the same effect. ? Initial OH excitation leads to slightly more internal energy in CO2.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Min Kyoung Yim, Joong Chul Choe Potential energy surfaces for the formation of covalently bound HCN dimers from two molecules of HCN or HNC were determined from CBS-QB3/APNO calculations. Several novel pathways, with and without the aid of protons, were found for the formation of iminoacetonitrile (HNCHCN), an intermediate in adenine synthesis from HCN by oligomerization. Covalent C–C or C–N bonds between the two monomers were formed after rearrangement of bimolecular complex intermediates. Energetic and kinetic analyses suggest that the proton-catalyzed dimerizations substantially lower reaction barriers but cannot occur efficiently under interstellar conditions.
Graphical abstract
Graphical abstractHighlights
? Theoretical (CBS-QB3/APNO) reaction pathways for the dimerization of HCN. ? Thermal formation of iminoacetonitrile from 2HCN is not efficient. ? Proton catalysis significantly lowers the dimerization barriers.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Dawid G?szowski, Marek Ilczyszyn H-bonding-like interactions between Xe and twelve A–H acids is examined by analysis of calculated A–H?Xe geometry and the 129Xe shielding. It was shown that ?(129Xe) is proportional to the 129Xe shielding anisotropy in most cases, generally increases with the A–H proton deshielding and depends on the A–H acidity (PA) on two ways: for stronger and weaker acids ?(129Xe) increases and decreases with PA, respectively. The highest contribution to the ?(129Xe) tensor variations comes from its principal components perpendicular to the H?Xe bond. These components are also sensitive on side interactions in non-linear dimers.
Graphical abstract
Graphical abstractHighlights
? Shielding of 129Xe in H-bonded-like A–H?Xe dimers depends on A–H acidity. ? Isotropic 129Xe shielding follows its tensor anisotropy. ? The highest shielding tensor component is parallel to H?Xe. ? Additional, strong 129Xe deshielding is predicted for protonated Xe.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Tomonori Ito, Kazuhiro Egashira, Koichi Tsukiyama, Akira Terasaki Oxidation processes of chromium cluster cations, and , are investigated by kinetics measurements under multiple-collision conditions by using a temperature-controlled ion trap. Both of the reactants commonly generate Cr+ and CrO+ as final products. However, the major reaction pathway to CrO+ presents a sharp contrast; produces it directly by a single O2 collision, whereas does via an intermediate Cr2O+. Comparison of the kinetics of the intermediate with that of cold Cr2O+ generated in the cluster source reveals that the intermediate Cr2O+ is thermalized promptly with the buffer gas filling the trap.
Graphical abstract
Graphical abstractHighlights
? Reaction of and with O2 molecules in an ion trap. ? Measurements of reaction kinetics. ? Identification of reaction rates, products, and pathways.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Sandeep Nigam, Chiranjib Majumder We report the structure and electronic properties of AgmPdn bimetallic clusters (m, n=1–2) in gas phase and deposited on the ?-Al2O3(0001) surface using plane wave pseudopotential approach. The ground state geometry of the mixed clusters is significantly modified after deposition. For Ag2Pd2 tetramer, the gas phase compact tetrahedron structure reorients to open bent rhombus. The charge distribution analysis shows that small amount of charge is accumulated at the Pd site and depleted at the Ag site. The electronic density of states analysis reveals that after deposition, the bands near the Fermi energy become wider.
Graphical abstract
Graphical abstractHighlights
? Bimetallic AgmPdn clusters deposited on alumina support. ? Tetrahedron structure of Ag2Pd2 cluster transform into bent rhombus on deposition. ? Overall charge transfer from surface to the deposited cluster. ? Broadening of electronic energy states for deposited AgmPdn clusters.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Moein Goodarzi, Morteza Vahedpour, Mohammad Solimannejad The mechanism of SO2+O2 and O+SO3(D3h) reactions have been investigated at the MP2/6-31+G(d) and CCSD(T)/cc-pV(Q+d)Z//MP2 levels on the triplet and singlet PESs. Although, no stable collision complexes have been found for the SO2+O2(3 ), O(3P)+SO3(D3h) and O(1D)+SO3(D3h) reactions, 1IN(O2S–O2) has been considered on the singlet PES for the SO2+O2(1?g) reaction. The results show that there are no favorable paths for the OSO ring formation of SO4(C2v) in the atmospheric reactions of the SO2+O2(3 ), SO2+O2(1?g) and O(3P)+SO3(D3h) while, the O(1D)+SO3(D3h) reaction can be suitable for the SO4(C2v) formation on the singlet PES.
Graphical abstract
Graphical abstractHighlights
? The mechanism of the OSO ring formation in SO4(C2v) molecule has been investigated, theoretically. ? There are no favorable paths in the SO2+O2(3 ), SO2+O2(1?g) and O(3P)+SO3 reactions. ? The O(1D)+SO3 reaction is suitable for the OSO ring formation on the singlet PES.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Janet E. Del Bene, Goar Sanchez-Sanz, Ibon Alkorta, José Elguero Ab initio MP2/aug’-cc-pVTZ calculations have been performed to determine if intermolecular P–P distances, Z–P–P angles, binding energies, 31P chemical shieldings, or EOM–CCSD spin–spin coupling constants can differentiate between corresponding C2 (homochiral) and Ci (heterochiral) dimers (PHFX)2, X=Cl, CN, CH3, NC. With one exception, Ci isomers have shorter P–P distances than corresponding C2 isomers. Neither binding energies, Z–P–P angles, chemical shieldings, nor spin–spin coupling constants 1pJ(P–P) exhibit patterns which distinguish between corresponding C2 and Ci isomers. 1pJ(P–P) values correlate linearly with P–P distances, so that experimental values of 1pJ(P–P) could be used to extract intermolecular P–P distances.
Graphical abstract
Graphical abstractHighlights
The C2 and Ci dimers of (PHFCl)2 with Cl–P?P–Cl linear? Optically active molecules PHFX give rise to homo- and heterochiral dimers (PHFX)2. ? Properties of (PHFX)2 depend primarily on X and Z in the linear Z–P?P–Z alignment. ? Binding energies of corresponding C2 and Ci dimers differ by only 1–3kJ/mol. ? P–P distances in Ci isomers tend to be shorter than in corresponding C2 isomers. ? 1pJ(P–P) coupling constants fail to distinguish between corresponding isomers.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Janet E. Del Bene, Ibon Alkorta, Goar Sanchez-Sanz, José Elguero Ab initio MP2/aug’-cc-pVTZ calculations have been carried out to determine the structures and binding energies of binary complexes formed by HBO with a series of small molecules A. Three different types of structures have been identified, which depend on the nature of A. In one structure A:HBO, HBO acts as a weak proton donor. In the second HBO:A, HBO is a relatively strong base. The third type of complex A||HBO has HBO and A in an approximately parallel arrangement. The dipole moment of A influences both the type of complex formed and its binding energy.
Graphical abstract
Graphical abstractHighlights
Binary complexes of HBO illustrating various bonding motifs.? Complexes of HBO with A may exhibit three types of structures. ? Dipole moment of A and interaction type influence structures and binding energies. ? HBO may act as a weak proton-donor acid or a relatively strong base. ? HBO forms parallel complexes with some A.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Jeng-Da Chai, Shan-Ping Mao Without the use of any empirical fitting to experimental or high-level ab initio data, we present a double-hybrid density functional approximation for the exchange–correlation energy, combining the exact Hartree–Fock exchange and second-order Møller–Plesset (MP2) correlation with the Perdew–Burke–Ernzerhof (PBE) functional. This functional, denoted as PBE0-2, is shown to be accurate for a wide range of applications, when compared with other functionals and the ab initio MP2 method. The qualitative failures of conventional density functional approximations, such as self-interaction error and noncovalent interaction error, are significantly reduced by PBE0-2.
Graphical abstract
Graphical abstractHighlights
? We propose a double-hybrid density functional without fitting to accurate data. ? This new functional is shown to perform well for self-interaction problems. ? This new functional is shown to perform well for noncovalent interactions.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Iwona ?wierszcz, Piotr Skurski The concept of rendering the electronically unstable anions stable is presented for the arbitrary chosen organic molecules whose inability to form bound electronically stable anionic states is well established. It is shown that introducing a superhalogen-like substituent to either ethane, ethylene or benzene results in obtaining a molecule that binds an excess electron relatively strongly. The electronic stabilities of such resulting daughter anions are always positive and large (4.09–6.66eV). Instead of considering the species studied as the organic molecules substituted with the superhalogen-like substituents and the excess electron attached, one may alternatively view them as the structurally modified superhalogen anions having one ligand replaced with the hydrocarbon group.
Graphical abstract
Graphical abstractHighlights
? The concept of rendering the electronically unstable anions stable is presented. ? Introducing a superhalogen substituent results in obtaining a molecule forming stable anions. ? The concept proposed is verified for variously substituted ethane, ethylene and benzene molecules.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Huiqin Qian, Lizhen Jiang, Ateeq-Ur-Rehman, Hanjie Zhang, Haiyang Li, Pimo He, Shining Bao The adsorption of FePc on the Ag(110) substrate has been investigated by ultraviolet photoelectron spectroscopy (UPS). The emission features corresponding to the adsorbed organic molecules are located at 1.03, 4.04, 6.53 and 9.22eV below the Fermi level. The features shift in binding energy with increasing the thickness of the organic films indicates an interaction between FePc and the Ag(110) substrate. ARUPS measurements suggest that the molecular plane is nearly parallel to the substrate in the case of a monolayer. The theoretical calculation confirms the experimental results and indicates that the top site is the most stable adsorption configuration.
Graphical abstract
Graphical abstractHighlights
? Four emission features corresponding to the FePc that adsorbed on Ag(110) are found. ? There is an interaction between the molecule FePc and the Ag(110) substrate. ? The molecular plane is nearly parallel to the substrate in the case of a monolayer. ? The top site is the most stable adsorption configuration.
Publication year: 2012 Source:Chemical Physics Letters, Volume 538 Xiaomin Han, Xinhe Wang, Tao Wang, Wei Xiong, Xingcan Dai The state of has been observed using the infrared infrared double resonance method. The low part of the potential curve of the state is characterized for the first time. The absolute vibrational numbers are determined with isotope effect. The molecular constants of this state are obtained from a Dunham fit and the potential curve of the state is constructed using the Rydberg–Klein–Rees method.
Graphical abstract
Graphical abstractHighlights
? We observed the state of Rb2 using infrared double resonance method. ? The absolute vibrational number is assigned. ? The molecular constants and the RKR potential curve are obtained.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Brent R. Wilson, Katheryn Shi, Angela K. Wilson Since the discovery that rare gases may form metastable compounds with electronegative atoms, much research has been devoted to the determination of novel bound species. In this work, our laboratory has used B3LYP as a survey method to identify possible new potential rare gas molecules. The ab initio methods, MP2 and CCSD(T), in combination with aug-cc-pVnZ (n=D, T and Q) basis sets have been used to confirm the results of the B3LYP calculations. Our calculations predict that FKrOH should exist and we report optimized geometries, vibrational frequencies and relative energies as evidence of our prediction.
Graphical abstract
Graphical abstractHighlights
? Forty seven rare gas systems have been identified as potentially bound species. ? B3LYP, MP2, and CCSD(T) have been used with aug-cc-pVnZ basis sets (n=D, T and Q). ? The impact of methodology upon false positives has been noted. ? FKrOH is predicted to possibly exist.
Publication year: 2012 Source:Chemical Physics Letters, Volume 537 Norawit Krainara, Francesc Illas, Jumras Limtrakul Hybrid (B3LYP) density functional calculations have been carried out to study the stability and electronic structure of adenine and its rare isomer Cu(II) complexes as well as their interaction with BN-doped fullerene. While the resulting two Cu(II)-tautomer complexes are almost isoenergetic complexes and exhibit very similar electronic structures which make their chemical identification difficult, we present evidence that BN modified fullerene could serve as a potentially viable nanoscale sensor to differentiate among these two Cu(II) complexes. The present results would suggest that the current conclusions are likely to hold for the adenine–thymine and adenine-rare-tautomer-thymine Cu(II) complexes as well.
Graphical abstract
Graphical abstractHighlights
? BN-C60 serving as a sensor for differentiating tautomer’s of adenine Cu(II) complexes. ? BN-doped fullerene interacted with adenine Cu(II) complexes were studied by DF calcs. ? Tautomers of adenine and their Cu(II) complexes differentiated by using energy gaps.
Publication year: 2012 Source:Chemical Physics, Volume 400 A. Penzkofer The absorption and emission behavior of riboflavin and lumiflavin in water, tetrahydrofuran (THF), water–starch, THF–polystyrene, starch films, and polystyrene films was studied at room temperature. Absorption cross-section spectra, fluorescence quantum distributions, and fluorescence quantum yields were determined. For the starch films additionally phosphorescence and delayed fluorescence spectra as well as phosphorescence lifetimes and delayed fluorescence lifetimes were measured and their quantum yields of intersystem-crossing, intrinsic triplet-based phosphorescence quantum yields, T1–S0 radiative lifetimes, and S0–T1 absorption strengths were calculated. A method of absolute intrinsic luminescence quantum distribution and quantum yield determination for dye doped films on transparent plates with a fluorimeter is described.
Graphical abstract
Graphical abstractHighlights
? Delayed fluorescence and phosphorescence spectra of flavins in starch films measured. ? Quantum yield of singlet–triplet intersystem determined with a new approach. ? Theory developed for determination of luminescence quantum yields of films. ? Delayed fluorescence and phosphorescence lifetimes of flavins in starch films measured. ? Singlet and triplet relevant parameters of riboflavin and lumiflavin determined.
Publication year: 2012 Source:Chemical Physics Valentina Villari, Placido Mineo, Emilio Scamporrino, Norberto Micali Small angle X-ray measurements on concentrated solutions of Cobalt-bis-porphyrins showed, at all the investigated concentration values, the presence of small aggregates which possess a sphere-like shape with a homogeneous electron density distribution. Such an aggregation, however, is proven not to affect the binding properties of the molecules with amino acids. Indeed, the Cobalt ion of the bis-porphyrins are available for coordinating the nitrogen atom of the amino acid to form a stable complex, as indicated by UV–vis and circular dichroism spectroscopy. The ability of these uncharged water-soluble bis-porphyrins to act as molecular sensors of amino acids in a wide concentration range takes great relevance in biosensing applications for which high concentration might be required.
Graphical abstract
Graphical abstractHighlights
? Molecular recognition properties of metal bis-porphyrins at high concentration. ? The formation of the complex causes the disruption of the aggregates. ? High sensitivity for the optical detection of low amount of amino acids. ? Potential applications as a selective molecular sensor of amino acids.
Publication year: 2012 Source:Chemical Physics Susmita Kar, S. Ghosh, S.P. Bhattacharyya We have studied the effects of spatial symmetry-preserving bichromatic fluctuations in symmetric double well systems. The rate of tunneling is enhanced or suppressed depending on the temporal nature of fluctuations,number of fluctuation frequencies, the commensurability of the frequencies or the lack of it, fluctuation intensities, etc. Localization with complete quenching of tunneling, however occurs only when a symmetry-breaking perturbation is applied. The tunneling dynamics of the system is studied using the time-dependent Fourier grid Hamiltonian method and the analysis is done using the Floquet technique and the time-dependent Hellman-Feynman theorem.We predict that by controlling the frequency and intensity ratios and the spatio-temporal nature of the fluctuating fields, a wide variety of situations can be created for effective control of tunneling.
Graphical abstract
Graphical abstractHighlights
? Spatial symmetry preserving bichromatic fluctuations lead to control of tunneling in SDWP. ? The temporal nature of the fluctuations is an important ingredient for control. ? Commensurability of component frequencies and their intensities are important control parameters. ? Complete localization is observed only in the presence of spatial symmetry broken perturbation. ? Analysis based on TDHFT and Floquet theory match.
Publication year: 2012 Source:Chemical Physics, Volume 400 Wiktor Zierkiewicz For many years isoflurane has been used clinically as the volatile anaesthetic, however, its mechanism of action is still not fully understood. In this work, a fragment of the crystallographic structure of the isoflurane–apoferritin complex reported by Liu et al. [12] has been taken as a model for studying the interactions between isoflurane and four residues of apoferritin. A density functional method augmented with an empirical dispersion term (RI-TPSS-D) was used. To evaluate the qualitative and quantitative interactions between isoflurane and apoferritin, three complexes: isoflurane–leucine 24, isoflurane–leucine 31 and isoflurane–serine 27-tyrosine 28, were considered. The RI-TPSS-D/TZVP calculated binding energies for these complexes are: ?1.3, ?1.4 and ?3.8kcalmol?1, respectively. The DFT–SAPT results show that the dispersion contribution is the dominant component of the total attraction forces.
Publication year: 2012 Source:Chemical Physics, Volume 400 Santiago Aparicio, Mert Atilhan The effect of water content on CO2 absorption in 2-hydroxyethyl-trimethylammonium L-(+)-lactate and tris(2-hydroxyethyl)methylammonium methylsulfate ionic liquids was studied using classical molecular dynamics simulations. The analysis of structural and dynamic properties, together with the energy contributions, showed that molecular-level structuring of CO2–ionic liquids is not affected by the presence of water molecules. Ion–water interactions are developed while maintaining the previous fluids’ structuring. The predicted dynamic properties show decreasing molecular mobility, that should lead to increasing viscosity upon water addition for the studied concentration range. Nevertheless, water has a moderate effect on CO2 transport within the studied hydroxylammonium fluids.
Graphical abstract
Graphical abstractHighlights
? The effect of absorbed water is a moderate weakening of ion–ion interactions. ? Water molecules decrease CO2–ion interactions and lead to a rearrangement of CO2 spatial distribution around ions. ? Weak effect of water molecules that should lead to a viscosity decrease maintaining the CO2 absorption ability. ? Water content may be considered adequate, favouring CO2 transport within the studied hydroxylammonium fluids.
Publication year: 2012 Source:Chemical Physics, Volume 400 Ling Yang, Chaoyuan Zhu, Jianguo Yu, Sheng Hsien Lin Intensities and profiles of vibronic spectra of the low-lying singlet excited states were investigated with anharmonic and harmonic Franck–Condon simulations for pyrimidine. The first-order anharmonic correction shows dynamic shift of spectra that is exactly same as difference of reorganization energy between ground and excited states. The first-order correction show intensity enhancement of absorption and intensity weakening of fluorescence for S1 state, and dynamic shift is also significant. On the other hand, the first-order correction is negligible for S2 state. The main spectral progressions are well described by totally symmetry modes ?6a, ?1 and ?12. One mode from non-total symmetry ?16a contributes to the weak band at 16a2 transition for S1 state. Four ab initio methods were employed in simulation; CASSCF, CASPT2, DFT and TD-DFT, and coupled-cluster singles-doubles (CCSD) and the equation-of-motion (EOM-CCSD) methods. They all work well, but CASSCF method show the best agreement with experiment for the weak-band intensities.
Graphical abstract
Graphical abstractHighlights
? Dynamic shift of spectra is equal to difference of reorganization energy. ? Intensity enhancement of absorption is against intensity weakening of fluorescence. ? The CASSCF method provides good accuracy for simulation of geometry difference. ? The first-order anharmonic correction is leading contribution to vibronic spectra.
Publication year: 2012 Source:Chemical Physics Danielis Rutkauskas, Jevgenij Chmeliov, Matthew Johnson, Alexander Ruban, Leonas Valkunas Non-photochemical quenching, NPQ, is the process by which plants protect themselves against photodamage by converting excess excitation energy into harmless heat. Aggregation of the major light-harvesting complexes LHCII in vitro is associated with similar quenching and its molecular mechanism is considered to be the same as that of NPQ. Although aggregates present a useful model system, the analysis of their time-resolved data is complicated by the uncertainty and heterogeneity of their size. Recently NPQ has been induced in vitro also in isolated, non-aggregated LHCII complexes. We used this new quenching model to study the dynamics of excitation energy migration in quenched state unaffected by aggregation. The obtained dependency of the decay times of chlorophyll electronic excitations depending on sample conditions allowed us to conclude that LHCII is an extremely adaptable biological macromolecule capable of adjusting its structural and spectral properties to the varying environmental conditions.
Graphical abstract
Graphical abstractHighlights
? We study non-photochemical quenching in non-aggregated LHCIIs. ? Excitation annihilation is a sensitive conformational probe. ? LHCII conformation is found to change with environmental conditions.
Publication year: 2012 Source:Chemical Physics Niranjan Shivaram, Henry Timmers, Xiao-Min Tong, Arvinder Sandhu We present experimental results and a theoretical framework for understanding the ionization dynamics in atoms exposed to XUV attosecond pulse trains and strong multi-cycle infrared (IR) fields. We invoke the Floquet formalism to model dressed atomic states as a manifold of Fourier components spaced by the laser frequency. In XUV-IR pump-probe measurements, we observe that the ionization yield oscillates due to quantum interference between photo-excitation paths to a Floquet state. We show that the intensity-dependent shifts of atomic structure modify the ionization channels and the associated interference phase. We extract this phase variation and compare it with simulations. These results provide a comprehensive description of the two-color ionization process and enable new schemes for control of attosecond ionization and fragmentation dynamics.
Graphical abstract
Graphical abstractHighlights
Ionization in the presence of attosecond pulse trains and strong IR fields exhibits oscillations which are due to interferences between Fourier components of Floquet states. The quantum phase difference between interfering paths determines the phase of oscillations.? We study two-color ionization atoms with attosecond pulse trains and strong fields. ? Floquet formalism is used to explain interferences in ionization. ? We discuss the control of photoionization with use of strong fields.
Publication year: 2012 Source:Chemical Physics Sheng-Wen Zhou, Yun-Hui Wang, Rui-Feng Lu The quasi-classical trajectory calculations are carried out for the reaction H+OCl?OH+Cl on the singlet ground state potential energy surface. The reaction probability for total angular momentum J=0 and the integral cross section as a function of collision energy are presented. Furthermore, the product rotational alignment <P2(j?·k)> has been obtained, and the value tends to decrease with the increasing of collision energy with fluctuations. To investigate the collision-energy-dependent effects on chemical stereodynamics, the four generalized polarization-dependent differential cross sections (2?/?)(d?00/d?t), (2?/?)(d?20/d?t), (2?/?)(d?22+/d?t) and (2?/?)(d?21?/d?t), the distribution P(?r) of the angle between j?–k and the angle distribution P(?r) in terms of k–k?–j? correlation have also been calculated.
Graphical abstract
Graphical abstractHighlights
? The first QCT investigation for the reaction H+OCl?OH+Cl. ? The influence of collision energy on scalar properties including reaction probability and the integral cross-section. ? Full information about stereodynamics of product alignment and orientation.
Publication year: 2012 Source:Chemical Physics, Volume 400 Sabyasachi Bagchi, Debasish Mandal, Deepanwita Ghosh, Abhijit K. Das The structure, bonding, and energetics of the complexes obtained from the interaction between the most stable tautomeric forms of free DNA and RNA bases and Zn2+, Cd2+ and Hg2+ cations have been studied using density functional B3LYP method. The 6-311+G (2df, 2p) basis set along with LANL2DZ pseudopotentials for the cations are used in the calculations. The tautomerization paths of the nucleobases are investigated and transition states between the tautomeric forms of the free bases are located. The relative stability of the complexes and the tautomers of the free nucleobases are discussed referring to MIA and relative energy values. For uracil, thymine and adenine, interaction of the metal cations with the most stable tautomers form the least stable molecular complexes. For cytosine and guanine, the stability of the metalated complexes differs significantly. The enthalpy (?H), entropy (T?S) and free energy (?G) of the complexes at 298K have also been calculated.
Graphical abstract
Graphical abstractHighlights
? We studied the complexes formed by free nucleobases and transition metal cations. ? We located the stable tautomers of the free nucleobases. ? The tautomerization paths of the nucleobases have been determined. ? We estimated the metal ion affinities for all the tautomers of the nucleobases. ? We calculated the enthalpy, entropy and free energy of the complexes at 298K.
Publication year: 2012 Source:Chemical Physics, Volume 400 Nathalie Piétri, Bintou Sessouma, Fabien Borget, Thierry Chiavassa, Isabelle Couturier-Tamburelli The identification of new bands appearing on the IR spectrum of cyanoacetylene when ammonia is added in argon matrix is discussed. Compared with DFT calculations and isotopic experiments, a 1:1 complex has been characterized. This complex has a linear structure with formation of hydrogen bond between the hydrogen atom of HC3N and nitrogen atom of NH3. This shows that HC3N acts as an electrophile with ammonia.
Graphical abstract
Graphical abstractHighlights
? Identification of the complex between HC3N and NH3 molecules. ? FTIR spectroscopy and quantum chemistry computations are used in the study. ? Study reveals the presence of only one complex in argon matrix. ? This pre-reaction states can leads to route to the aminoacrylonitrile synthesis.
Publication year: 2012 Source:Chemical Physics, Volume 400 Félix Moncada, Edwin Posada, Roberto Flores-Moreno, Andrés Reyes An efficient nuclear molecular orbital methodology is presented. This approach combines an auxiliary density functional theory for electrons (ADFT) and a localized Hartree product (LHP) representation for the nuclear wave function. A series of test calculations conducted on small molecules exposed that energy and geometry errors introduced by the use of ADFT and LHP approximations are small and comparable to those obtained by the use of electronic ADFT. In addition, sample calculations performed on (HF)n chains disclosed that the combined ADFT/LHP approach scales cubically with system size (n) as opposed to the quartic scaling of Hartree–Fock/LHP or DFT/LHP methods. Even for medium size molecules the improved scaling of the ADFT/LHP approach resulted in speedups of at least 5x with respect to Hartree–Fock/LHP calculations. The ADFT/LHP method opens up the possibility of studying nuclear quantum effects on large size systems that otherwise would be impractical.
Graphical abstract
Graphical abstractHighlights
? It is possible to perform cubic-scaling Non-Born–Oppenheimer calculations. ? The errors introduced by the approximations used in this methodology are small. ? This method makes possible calculations of molecules with more than a hundred atoms.
Publication year: 2012 Source:Chemical Physics S.V. Novikov, A.P. Tyutnev, L.B. Schein Using Monte Carlo simulation we investigated time of flight current transients predicted by the dipolar glass model for a random spatial distribution of hopping centers. Behavior of the carrier drift mobility was studied at room temperature over a broad range of electric field and sample thickness. A flat plateau followed by current decay is the most common feature of the simulated transients. Poole-Frenkel mobility field dependence was confirmed over 5 to 200 V/m as well as its independence of the sample thickness. Universality of transients with respect to both field and sample thickness has been observed. A simple phenomenological model to describe simulated current transients has been proposed. Simulation results agree well with the reported Poole-Frenkel slope and shape of the transients for a prototype molecularly doped polymer.
Graphical abstract
Graphical abstractHighlights
? Monte Carlo simulation of charge transport in molecularly doped polymer was performed. ? Results agrees wel with the experiment without using any fitting parameter. ? Transients demonstrates well-defined plateau and power law tail. ? Transients are universal with respect to electric field and sample thickness. ? Quasi-ballistic model has been suggested to describe general features of transients.
Publication year: 2012 Source:Chemical Physics Udo Kaatze At temperatures between 10 and 50 °C complex dielectric spectra of mixtures of glycerol and ethanol have been measured in the frequency range from 400 kHz to 3 GHz. Within the frequency range of measurement the dielectric spectra reveal one dispersion/dielectric loss region, indicating a rather uniform relaxation of both constituents. Exhibiting a continuous but asymmetric relaxation time distribution, the spectra are analyzed in terms of a Davidson – Cole relaxation function to yield the static permittivity, an effective dipole orientation correlation factor, the principal relaxation time, the enthalpy of activation and the Davidson – Cole parameter that measures the width of the relaxation time distribution. These parameters are discussed and compared to those for mixtures of glycerol with water. Effects from the chain-like hydrogen bond structure of the monohydric alcohol, on the one hand, and from the tetrahedral hydrogen network of water, on the other hand, are explored thereby.
Graphical abstract
Graphical abstractHighlights
? Dielectric spectra display asymmetric relaxation time distribution. ? Dipole orientation correlation factor shows a minimum at equimolar composition. ? Relaxation times reveal hydrogen bond linking different from glycerol-water. ? Activation enthalpy increases substantially with glycerol content.
Publication year: 2012 Source:Chemical Physics, Volume 400 Jie Yu, Wei Zhang, Jing Yang, Shu-Lin Cong We investigate theoretically the field-free molecular orientation driven by a modulated two-color laser pulse together with a delayed half-cycle THz pulse, with the LiH molecule as an example. The field-free molecular orientation and the population of the target state are controlled by adjusting the phase of envelope ? and the period Tp of the modulated two-color laser field. At ps, more molecules are populated to the target state and more efficient molecular orientation is achieved. The effect of temperature on molecular orientation is also discussed.
Graphical abstract
Graphical abstractHighlights
? A modulated two-color laser (MTCL) is used to enhance the field-free orientation. ? LiH molecules are oriented by MTCL together with delayed half-cycle THz pulse. ? Maximum of orientation degree changes periodically with the phase of envelope of MTCL. ? The phase and period of MTCL has some influence on molecular orientation.
Publication year: 2012 Source:Chemical Physics, Volume 400 Marcin Rybicki, Ewa Hawlicka Molecular dynamics simulations of MgCl2 solutions in methanol–water mixtures, over the whole range of the methanol mole fraction at room temperature have been performed. The methanol and water molecules have been modeled as flexible three-site bodies. Solvation of the magnesium ions has been discussed on the basis of the radial and angular distribution functions, the orientation of the solvent molecules and their geometrical arrangement in the coordination shells. Analysis of the H-bonds of the solvent molecules coordinated by Mg2+ has been based on a geometric criterion of the H-bond. Persistence of the primary and secondary shell has been estimated. In all studied solutions Mg2+ is six-coordinated and the solvent molecules form an octahedron. The antidipole orientation of the molecules favours the water molecules as H-donors in the first shell and the methanol molecules as H-acceptor in the second shell. Thus an excess of water and an excess of methanol has been observed in the first and the second shells of Mg2+. An exchange of the solvent molecules between the primary and secondary shells occur. The persistence of the second shell is longer than the shells of monovalent ions.
Graphical abstract
Graphical abstractHighlights
? Magnesium ion favours water molecules in its first coordination shells despite stronger interactions with methanol. ? An excess of methanol is observed in the second coordination shells of the cation. ? The primary shells of magnesium ions are very stable and they persist over the whole time of the simulation. ? The second shells of Mg2+ persist is longer than the first shells of monovalent ions.
Publication year: 2012 Source:Chemical Physics, Volume 400 Arup Kumar Pathak We investigate structural, energetic and spectroscopic aspects of the finite size hydrated ·nH2O (n=1–8) clusters based on the first principles electronic structure calculations. It is observed that the geometrical parameters at MP2/6-311++G(d,p) level are almost equal to that of calculated at B3LYP/6-311++G(d,p) level for the higher size of clusters (n>3). Our results reveal that total interaction energy and its components do vary linearly with the size of the clusters. Two types of scaling factors are implemented in two different regions to account the effect of anharmonic vibrations. The degeneracy of in-plane bending and asymmetric NO stretching mode in nitrate system is lifted due to hydration. An excellent agreement is observed between the present calculated H2O bending and asymmetric NO stretching frequencies with the experimental results (within 4% w.r.t. experimentally measured values). Understanding the nature of normal modes of vibration at the molecular level provides information of the local hydration environment during stepwise solvation.
Graphical abstract
Graphical abstractHighlights
? Geometrical parameters at MP2 level are almost equal to that of B3LYP level. ? Interaction energy and its components are varied linearly with size of the cluster. ? Two scaling factors are applied to account the anharmonic nature of vibrations. ? Excellent agreement between calculated and experimental frequencies is observed. ? Molecular level vibrations provide information of the local hydration environment.
Publication year: 2012 Source:Chemical Physics, Volume 400 Shyamal Kumar Biring, Pinaki Chaudhury This paper proposes Simulated Annealing based search to locate critical points in mixed noble gas clusters where Ne and Xe are individually doped in Ar-clusters. Using Lennard–Jones (LJ) atomic interaction we try to explore the search process of transformation through Minimum Energy Path (MEP) from one minimum energy geometry to another via first order saddle point on the potential energy surface of the clusters. Here we compare the results based on diagonalization of the full Hessian all through the search and quasi-gradient only technique to search saddle points and construction of reaction path (RP) for three sizes of doped Ar-clusters, and .
Graphical abstract
Graphical abstractHighlights
? Estimation of critical points in Noble-gas clusters. ? Evaluation of first order saddle point or transition states. ? Construction of reaction path for structural change in clusters. ? Use of Monte-Carlo Simulated Annealing to study structural changes.
Publication year: 2012 Source:Chemical Physics, Volume 400 Marta ?abuda, Jesús González-Vázquez, Fernando Martín, Leticia González The collisional system S3++H?S2++H+ has been studied using a time-dependent wavepacket methodology in two-dimensions. Using available potential energy surfaces and coupling matrix elements obtained from multireference ab initio calculations, five non-adiabatically coupled electronic states of 1? symmetry have been included in the dynamical simulations. The collision has been studied in the low energy regime of 1–10eV. The wavepacket treatment accounts for the description of the collision including all possible impact parameters simultaneously in all spatial directions of the considered plane. The molecular movie of the scattered products arising from charge transfer yields the angular distribution and the total charge transfer probability vs. initial kinetic energy of the projectile. A detailed analysis of the forward, sideways, and backward scattering mechanisms showing different patterns is presented.
Graphical abstract
Graphical abstractHighlights
? S3++H charge transfer process. ? Low energy collision in the [1–10] eV range. ? Non-adiabatic wavepacket quantum dynamical study. ? 2D time-dependent wavepacket approach in the femtosecond time scale.
Publication year: 2012 Source:Chemical Physics, Volume 400 Yasuyuki Kowaka, Naofumi Nakayama, Takayoshi Ishimoto, Umpei Nagashima, Takaya Yamanaka, Norifumi Ozawa, Masaaki Baba Fluorescence excitation spectra and fluorescence lifetimes at single vibronic levels in the state have been observed for jet-cooled pyrene. The fluorescence lifetimes at the zero-vibrational levels of the states of pyrene- and pyrene- are 1480 and 1470ns, respectively, and the relaxation is considered to be dominated by the radiative process. For some vibrational levels, however, the lifetimes are remarkably shorter such as 765ns at the 221 vibronic level of pyrene- ( (); C–H bending and skeletal deforming mode), indicating that nonradiative transition occurs at a specific vibrational level. In this study, we demonstrate that the main process is internal conversion to the state caused by nonadiabatic vibronic interaction via promoting modes.
Graphical abstract
Graphical abstractHighlights
? Fluorescence lifetimes were accurately observed for each single vibronic level of pyrene. ? Nonradiative internal conversion in the S1 state is enhanced via specific vibrations. ? The structure of the isolated pyrene molecule was determined by ab initio calculation.
Publication year: 2012 Source:Chemical Physics, Volume 400 E.M. Vess, C.N. Anderson, V.E. Awadalla, E.J. Estes, C. Jeon, C.J. Wallace, X.F. Hu, D.K. Havey A photoacoustic spectrometer is used to evaluate the accuracy of an energy-gap model for collisional energy transfer. For photoacoustic measurements involving the transition of molecular oxygen the conversion of photon energy to thermal energy is inefficient and proceeds through the a1?g state. This results in attenuation of the photoacoustic signal. The magnitude of the attenuation can be predicted with an energy-gap model whose accuracy has been previously confirmed to within 3±5%. However, this prior result does not rule out incomplete rotational relaxation of O2 in the a1?g state. In this study, high-resolution spectra of H2O in air are used to calibrate the photoacoustic spectrometer. This work binds the relative uncertainty in the energy-gap relaxation factor for O2A-band photoacoustic signals to be approximately 1%. During one acoustic cycle, this result implies negligible collisional relaxation to the state of O2 and nearly complete collisional relaxation to the a1?g state.
Graphical abstract
Graphical abstractHighlights
? We investigate an energy transfer model for photoacoustic measurements of the O2A-band. ? We measure the response of a photoacoustic spectrometer for known quantities of H2O and O2. ? We fit multiple theoretical spectral line profiles to the data. ? We bind the relative uncertainty of the energy transfer model to less than 1%. ? We demonstrate that speed-dependence is an important line shape effect for these experiments.
Publication year: 2012 Source:Chemical Physics, Volume 400 Pham Tien Lam, Ayumu Sugiyama, Takashi Masuda, Tatsuya Shimoda, Nobuo Otsuka, Dam Hieu Chi We report on an ab initio calculation study of intermolecular interactions between cyclopentasilane (CPS) molecules in liquid CPS. Our calculations show that the SiH bonds that are oriented toward the center of the ring of a CPS molecule play a significant role in the interaction between CPS molecules. This interaction results in the formation of special bonds between CPS molecules, which resemble hydrogen bonds. These hydrogen bonds cause a red shift of IR absorption peaks corresponding to the SiH stretch vibration. The formation of hydrogen bonds in the liquid phase of CPS was further confirmed by ab-initio molecular dynamics simulations. The analysis of pair correlation functions has shown a significant contribution of hydrogen bonds to the structure of the CPS liquid system.
Graphical abstract
Graphical abstractHighlights
? We studied the intermolecular interactions and structure of liquid cyclopentasilane. ? We found that hydrogen bonds can be formed between CPS molecules. ? Ab-initio MD simulations confirm the formation of the hydrogen bonds in solution. ? The hydrogen bonds significantly contribute to the structure of the CPS liquid.
Publication year: 2012 Source:Chemical Physics, Volume 400 Ioan Bâldea The influence of the stochastic fluctuations at contacts on the electron transport through molecular junctions based on alkanedithiols is investigated theoretically. Results are presented, which demonstrate that the transition voltage Vt is insensitive to fluctuations in the electrode–molecule hopping integrals. By contrast, reasonably large fluctuations in the Coulomb contact interaction J, included via an extended Newns–Anderson model, lead to fluctuations in the molecular orbital energetic alignment , which are consistent with the fluctuations in Vt observed experimentally. The impact of these J- (or -) fluctuations on the conductance G is considerably stronger than on Vt. The G-fluctuations driven by represent a substantial fraction of the fluctuations displayed by experimental conductance histograms. The electron system for is correlated, i.e., it cannot be described within a single-particle (Landauer-based) picture. However, in the J-range of interest, the ratio turns out to be only weakly dependent on J. The weak impact of J on the ratio is important because it suggests that, even in the presence of realistically strong electron correlations, transition voltage spectroscopy can be a useful tool of investigation.
Graphical abstract
Highlights
? Work devoted to transition voltage spectroscopy, a hot topic in molecular electronics. ? First theoretical study on the physical origin of stochastic fluctuations in TVS. ? First theoretical study that considers effects of electron correlations on TVS. ? Supporting the idea that the transition voltage is a molecular signature. ? Validation of the Newns–Anderson model for molecular junctions of interest.
Publication year: 2012 Source:Chemical Physics, Volume 399 Pablo Villarreal, Salvador Miret-Artés, Octavio Roncero, José Campos-Martínez
Highlights
? Preface for “New Trends in Atomic and Molecular Clusters”. ? There are ?35 papers plus 1 review with the most relevant topics in cluster science. ? Advanced experimental/theoretical tools applied to small and mesoscopic species.
Publication year: 2012 Source:Chemical Physics Saman Alavi, Mahdi Taghikhani We extend previous work on nitric acid–ammonia and nitric acid–alkylamine complexes to illustrate that proton exchange reaction coordinates involve the rocking motion of the base moiety in many double hydrogen-bonded gas phase strong acid–strong base complexes. The complexes studied involve the biologically and atmospherically relevant glycine, formic, acetic, propionic, and sulfuric acids with ammonia/alkylamine bases. In these complexes, the magnitude of the imaginary frequencies associated with the proton exchange transition states are <400cm?1. This contrasts with widely studied proton exchange reactions between symmetric carboxylic acid dimers or asymmetric DNA base pair and their analogs where the reaction coordinate is localized in proton motions and the magnitude of the imaginary frequencies for the transition states are >1100cm?1. Calculations on complexes of these acids with water are performed for comparison. Variations of normal vibration modes along the reaction coordinate in the complexes are described.
Graphical abstract
Graphical abstractHighlights
? Proton exchange in acid–base complexes is studied. ? The structures, binding energies, and normal mode vibrations are calculated. ? Transition state structures of proton exchange mechanism are determined. ? In the complexes studied, the reaction coordinate involves heavy atom rocking. ? The reaction coordinate is not simply localized in the proton movements.
Publication year: 2012 Source:Chemical Physics Sayali P. Joshi, Achintya Kumar Dutta, Sourav Pal, Nayana Vaval In this paper we study the harmonic vibrational frequencies, infrared(IR) intensities, Raman intensities and depolarization ratio using extended coupled cluster method. Raman and IR intensities are mixed derivatives of energy with respect to the electric field and geometric perturbation whereas vibrational frequencies are derivatives of energy with respect to electric field. We use semi-numerical approach to obtain these derivatives. We have studied the effect of electron correlation and basis set for the above properties. We compare our results with non-variational coupled cluster and experimental values, wherever available. We have studied HF, BH, CH+, CO and H2CO molecules in different basis sets. For HF molecule, benchmarking is done with full CI values and basis set convergence is studied for this molecule. Effect of triples is studied for all the molecules.
Graphical abstract
Graphical abstractHighlights
? We have used Extended Coupled Cluster Method to study IR and Raman spectroscopic properties for small molecules. ? Our approach is semi-numerical. ? Basis set dependence and electron correlation is studied. ? Effect of partial triples makes the result closer to experimental and full CI values.
Publication year: 2012 Source:Chemical Physics, Volume 400 R. Khordad The Gay–Berne (GB) potential model is an interesting and useful model to study the real systems. Using the potential model, we intend to examine the thermodynamical properties of some anisotropic binary mixtures in two different phases, liquid and gas. For this purpose, we apply the integral equation method and solve numerically the Percus–Yevick (PY) integral equation. Then, we obtain the expansion coefficients of correlation functions to calculate the thermodynamical properties. Finally, we compare our results with the available experimental data [e.g., HFC-125+propane, R-125/143a, methanol+toluene, benzene+methanol, cyclohexane+ethanol, benzene+ethanol, carbon tetrachloride+ethyl acetate, and methanol+ethanol]. The results show that the GB potential model is capable for predicting the thermodynamical properties of binary mixtures with acceptable accuracy.
Graphical abstract
Graphical abstractHighlights
? Most useful potential model to study the real systems is the Gay–Berne (GB) potential. ? We use GB model to examine thermodynamical properties of some anisotropic binary mixtures in two different phases. ? The integral equation methods are applied to solve numerically the Percus–Yevick (PY) equation. ? We obtain expansion coefficients of correlation functions needed to calculate the properties of studied mixtures. ? The results are compared with the available experimental data [e.g., HFC-125+propane, R-125/143a, methanol+toluene, etc.]
Publication year: 2012 Source:Chemical Physics, Volume 400 Ae Ran Lim The NMR spectra and the spin–lattice relaxation times, T1, of the 1H and 133Cs nuclei in (NH4)2?xCsxZnCl4 (x=0, 1, and 2) single crystals were determined by using NMR spectroscopy. We investigated the crystallographic structures of these crystals by determining the NH4 and Cs occupation probabilities of the two cationic sites. Our NMR experimental results confirm that in (NH4)2ZnCl4 there are two crystallographically inequivalent NH4 groups, NH4(1) and NH4(2), occupying the A1 and A2 sites, and that in Cs2ZnCl4 there are two crystallographically inequivalent Cs ions, Cs(1) and Cs(2), occupying the A1 and A2 sites. Both types of NH4 ions and both types of Cs ions are found in mixed NH4CsZnCl4 crystals; the occupation rates of the two different sites are 1 and 1 for Cs(1) and Cs(2), respectively, and 1 and 1 for NH4(1) and NH4(2), respectively.
Graphical abstract
Graphical abstractHighlights
? The 1H and 133Cs NMR spectra in (NH4)2?xCsxZnCl4 (x=0, 1, and 2). ? The spin–lattice relaxation times of 1H and 133Cs in (NH4)2?xCsxZnCl4 (x=0, 1, and 2). ? The NH4 and Cs occupation probabilities of the two cationic sites.
Publication year: 2012 Source:Chemical Physics, Volume 400 Nirmal Kr Datta, Suvajit Pal, Manas Ghosh We investigate the excitation behavior of a repulsive impurity doped quantum dot under the combined influence of oscillatory confinement potential and oscillatory magnetic field. In view of this the ratio of two oscillation frequencies has been exploited meticulously. We have considered Gaussian impurity centers. The investigation reveals that a variation in the aforesaid frequency ratio causes maximization in the time-average excitation rate for different dopant locations. To make the analysis more realistic and rational, concomitant oscillation in the spatial stretch of the dopant is also considered in a stepwise manner. Although the consideration makes the calculation much more tedious and involved, yet this adequately describes the role played by the undulating impurity domain exclusively in modulating the excitation rate.
Graphical abstract
Graphical abstractHighlights
? The excitation profile of impurity doped quantum dot has been investigated. ? The dot is subject to combined influence of oscillatory confinement potential and magnetic field. ? Maximization in excitation rate is observed as a function of two oscillation ratios. ? Concomitant time-dependence in spatial stretch of impurity has been introduced. ? This introduction interestingly modifies the excitation rate.
Publication year: 2012 Source:Chemical Physics Marta Waligórska, Andrzej Molski When two fluorophores (donor and acceptor) are attached to an immobilized biomolecule, anti-correlated fluctuations of the donor and acceptor fluorescence caused by Förster resonance energy transfer (FRET) report on the conformational kinetics of the molecule. Here we assess the maximum likelihood-based analysis of donor and acceptor photon arrival trajectories as a method for extracting the conformational kinetics. Using computer generated data we quantify the accuracy and precision of parameter estimates and the efficiency of the Akaike information criterion (AIC) and the Bayesian information criterion (BIC) in selecting the true kinetic model. We find that the number of observed photons is the key parameter determining parameter estimation and model selection. For long trajectories, one can extract mean dwell times that are comparable to inter-photon times.
Graphical abstract
Graphical abstractHighlights
? We study model selection and parameter recovery from single-molecule FRET experiments. ? We examine the maximum likelihood-based analysis of two-color photon trajectories. ? The number of observed photons determines the performance of the method. ? For long trajectories, one can extract mean dwell times that are comparable to inter-photon times.
Publication year: 2012 Source:Chemical Physics, Volume 400 Pham Vu Nhat, Ngo Tuan Cuong, Pham Khac Duy, Minh Tho Nguyen Properties of a series of MnXn with X=H, F, Cl, Br and n=1–4 are investigated using DFT, CCSD(T) and CASPT2 computations. The B3P86/6-311++G(3df,2d) method appears to be suitable for predicting their structures whose geometries and IR spectra are dependent on the charge state. While MnX2 are linear, MnX3 and MnX4 are characterized by high symmetry shape. The ?-bonding type is observed for and . In halides, a different type of bonds is formed as p-orbitals of halogens can overlap with empty metal d-orbitals allowing a more effective electron transfer and high spin ground electronic states. Vibrational frequencies and basic energetic quantities are computed and compared with available experiments. Several previous thermochemical quantities are re-evaluated, and the heats of formation of Mn-compounds can be determined with reasonable accuracy using the B3LYP functional. However, while calculated ionization energies are in agreement with experiment, electron affinities are obtained with large deviations.
Graphical abstract
Graphical abstractHighlights
? The B3P86 functional is found to be reliable in predictions of molecular structures and vibrational spectra. ? The hybrid B3LYP is more reliable for energetic parameters such as heats of formation. ? We also propose several new assignments for heats of formation and ionization energies of a number of species considered.
Publication year: 2012 Source:Chemical Physics M.S.A. El-Kader, G. Maroulis, E. Bich Quantum mechanical lineshapes of collision-induced absorption (CIA) at different temperatures and of collision-induced light scattering (CILS) at room temperature are computed for gaseous molecular hydrogen using theoretical values for induced dipole moments and pair-polarizability trace and anisotropy as input. Comparison with measured spectra of absorption, isotropic and anisotropic light scattering shows satisfactory agreement, for which the uncertainty in measurement of its spectral moments is seen to be large. Empirical models of the dipole moment and pair-polarizability trace and anisotropy which reproduce the experimental spectra and the first three spectral moments more closely than the fundamental theory are also given. Good agreement between computed and experinental lineshapes of both absorption and scattering is obtained when potential models which are constructed from the thermophysical, transport, total scattering cross-section and spectroscopic properties are used. Also, the use of the new potential in lattice dynamic calculations yields good results for several properties of solid hydrogen.
Highlights
? We have determined an isotropic intermolecular potential for the interaction of hydrogen. ? The thermophysical and transport properties are calculated for this system. ? The rovibrational energy levels and scattering cross-sections are determined. ? We have adopted a model for the induced dipole moment ?(r) with adjustable parameters. ? The quantum lineshapes of absorption and scattering are calculated.
Publication year: 2012 Source:Chemical Physics, Volume 400 M. Karbowiak, P. Gnutek, C. Rudowicz Crystal field (CF) analysis of energy levels for Nd3+ and Er3+ ions in LaAlO3, YAlO3, and LaGaO3 single crystals is presented. It is shown that a combined approach comprising the ascent/descent in symmetry (ADS) method combined with superposition model (SPM) analysis can be successfully used for analysis of low-symmetry systems. The present ADS/SPM approach is less labor and time consuming as compared, e.g., with Monte-Carlo method and it also allows maintaining the relationship between the crystallographic axis system and the nominal axis systems of fitted CFP sets. For orthogallates and orthoaluminates the actual Cs symmetry, resulting from distortion of perovskite structure, may be successfully approximated for both systems by the ADS chain C4v?C3 (D3)?Cs or C3 (D3)?Cs symmetry. The possibility of using of approximated symmetries for orthogallates or orthoaluminates can be useful for interpretation of energy levels for this family of compounds of technological importance, particularly in the case when the number of available experimental energy levels is insufficient for full Cs parameterization. The novel aspect of the combined ADS/SPM approach is that possible higher symmetry approximations employing also the axis systems oriented differently than for the actual symmetry are searched for, taking advantages of the transformation properties of CF parameters sets.
Graphical abstract
Graphical abstractHighlights
? CF analysis of energy levels for Nd3+ and Er3+ ions in ABO3 crystals is presented. ? Combined ADS/SPM strategy is employed. ? Its usefulness for successful analysis of low-symmetry systems is proved. ? Structural relationships between different ion–host systems are emphasized.
Publication year: 2012 Source:Chemical Physics, Volume 400 Hiroya Abe, Yukiyoshi Ohtsuki We extend our previous optimal control simulation to explicitly include the polarization effects of a laser pulse. The simulation is applied to a rigid rotor model of a nitrogen molecule with two illustrative objectives to evaluate its numerical performance and examine the role of optimal time-dependent polarization vectors. The first example aims at aligning a molecule along the space-fixed z-axis that is perpendicular to the polarization vectors on the xy-plane, which leads to a circularly polarized pulse as an optimal solution. The second objective is to create a rotational wave packet that aligns two directions specified by y=±x simultaneously. The optimal polarization direction changes with time from y=+x to y=?x, alternately. These examples illustrate the importance of examining an optimal pulse as a vector wave, and the present simulation provides a useful means to explore the best (time-dependent) polarization conditions of a laser pulse.
Graphical abstract
Graphical abstractHighlights
? Nonresonant optimal control including polarization effects of a laser pulse. ? The monotonically convergent algorithm shows high numerical accuracy. ? Specified molecular alignment controlled by time-dependent polarization.
Publication year: 2012 Source:Chemical Physics, Volume 400 Jaroslav K?íž, Ji?í Dybal, Emanuel Makrlík, Zde?ka Sedláková Binding interaction of Tl+, Cs+, Li+Br?, and Cs+Br? with meso-octamethylcalix[4]pyrrole (1) in nitrobenzene-d5 was studied using 1H, 13C, 7Li, and 133Cs NMR spectroscopy and DFT quantum-chemical calculations. Although originally declared as typical anion and ion pair receptor, 1 is shown to bind fairly strongly Tl+ cations (equilibrium constant K=1600±80mol?1L?1). The binding of Cs+ is much weaker (K=370±18mol?1L?1). Neither of these cations invert the conformation of 1. Li+Br? binds to 1 (K=1790±160mol?1L?1) forming at least four energetically close complexes without much change in its conformation. Cs+ Br? prepared in situ from Li+Br? and the cesium salt of dicarbollyl cobaltate in the presence of 1 binds strongly to 1 (K=103514±4000mol?1L?1, log K=5.015) in spite of the slight competition of Li+ ions. The cooperative binding of Cs+ and Br? ions is shown, in accord with a recent suggestion in literature, to invert the natural conformation of 1, the four NH groups binding to Br? by hydrogen bonds and the aromatic rings forming a cup binding the embedded Cs+ by its interaction with the ? electron orbitals.
Graphical abstract
Graphical abstractHighlights
? Thallium is strongly bound by calixpyrrole as a bare cation. ? The bond of cesium as a bare cation is weak. ? In cooperation with bromide ion, cesium is strongly bound as an ion pair.
Publication year: 2012 Source:Chemical Physics Cristian E. Botez, Joshua Morris, Michael P. Eastman We have used frequency-resolved (100 Hz < f < 10,000 Hz) ac magnetic susceptibility measurements to directly determine the Néel and Brown relaxation times in 30-nm-size Fe3O4 / hexane magnetic fluids at temperatures between 200 and 300 K. Our data collected on both powder and magnetic fluid samples allow the separation of the contributions from the Néel and Brown relaxation mechanisms that act concomitantly within the above-mentioned temperature range. At all temperatures we find that the Brown relaxation times (?B) are shorter than their Néel counterparts (?N), evidence that the Brown mechanism yields the major contribution towards the system’s overall superspin dynamics. ?B exhibits a steep two-order-of-magnitude decrease upon heating, from ?B=1×10-3s at T=237K to ?B=1.5×10-5s at T=270K, a behavior mostly driven by the heating-induced reduction of the liquid carrier’s viscosity.
Graphical abstract
Graphical abstractHighlights
? Néel and Brown magnetic relaxation are investigated in Fe3O4-based magnetic fluids. ? Brown mechanism yields the major contribution to the overall superspin dynamics. ? Brown relaxation time exhibits a100-fold decrease upon heating from 237 to 270K. ? Observed behavior is driven by the reduction of the magnetic fluid’s viscosity.
Publication year: 2012 Source:Chemical Physics Kelly A. Fransted, Gregory S. Engel Quantum beating signals in two-dimensional (2D) spectroscopy arise from coherent evolution of superpositions of Hamiltonian eigenstates and have been used extensively to study electronic dynamics of photosynthetic complexes. Definitively distinguishing between vibrational and electronic coherences proves challenging in a 2D spectrum because ultrashort pulses can excite either type of coherence. Here, we present 2D spectra of the laser dye, PM650, to characterize vibrational quantum beats. Our experiments show quantum beating throughout the spectrum in both the rephasing and nonrephasing signals. While this ubiquitous beating can be rationalized for a vibrational coherence, it is not what would be expected for an electronic coherence where the quantum beats would be located on the peaks of the states associated with the coherence. Our results suggest that location of the beat frequency within the 2D spectra can be used to distinguish between vibrational and electronic coherences.
Graphical abstract
Graphical abstractHighlights
? Two Dimensional Electronic Spectroscopy of Pyrromethene 650. ? PM650 demonstrates vibrational coherence beating signals in 2D spectroscopy. ? PM650 exemplifies limiting case of solely vibrational coherences. ? Signal shows beating throughout spectrum in rephasing and nonrephasing signals. ? Beating pattern in contrast to quantum beats attributed to electronic coherences.
Publication year: 2012 Source:Chemical Physics Cássio E.A. Santos, Márcio A.R.C. Alencar, Pedro Migowski, Jairton Dupont, Jandir M. Hickmann The influence of the anionic and cationic parts on the nonlocal nonlinearity of ionic liquids was investigated using the Z-scan technique. The tetrafluoroborate (BF4-), hexafluorophosphate (PF6-) or bis (trifluoromethylsulfonyl)imide (Tf2N-) were employed as anionic parts, while the cationic part was composed by five different derivatives of imidazolium (CnMI, with n = 4, 6, 8, 10 and 12). The thermal diffusivity, nonlinear refractive indexes of thermal origin, heat capacity, thermo-optical coefficients and degree of nonlocality were obtained. Our results indicate that ionic liquids can be exploited as nonlinear media with large nonlocal character.
Graphical abstract
Graphical abstractHighlight
? We investigated the nonlocal nonlinearity of ionic liquids. ? Large values of thermal nonlinear response and degree of nonlocality were obtained. ? Structures with Tf2N- as the anion present lower nonlinear response. ? Changing the cationic part does not modify the significantly the thermal nonlinearity. ? Ionic liquids can be exploited as nonlinear media with large nonlocal character.
Publication year: 2012 Source:Chemical Physics, Volume 400 Santhanamoorthi Nachimuthu, Jiali Gao, Donald G. Truhlar We present benchmark calculations of nine selected points on potential energy surfaces describing proton transfer processes in three model systems, , CH3OH…H+…OH2, and CH3COOH…OH2. The calculated relative energies of these geometries are compared to those calculated by various wave function and density functional methods, including the polarized molecular orbital (PMO) model recently developed in our research group and other semiempirical molecular orbital methods. We found that the SCC-DFTB and PMO methods (the latter available so far only for molecules consisting of only O and H and therefore only for the first of the three model systems) give results that are, on average, within 2kcal/mol of the benchmark results. Other semiempirical molecular orbital methods have mean unsigned errors (MUEs) of 3–8kcal/mol, local density functionals have MUEs in the range 0.7–3.7kcal/mol, and hybrid density functionals have MUEs of only 0.3–1.0kcal/mol, with the best density functional performance obtained by hybrid meta-GGAs, especially M06 and PW6B95.
Graphical abstract
Graphical abstractHighlights
? We present benchmark calculations of energies of complexation and barriers for proton transfer to water. ? Benchmark calculations are used to test methods suitable for application to large and complex systems. ? Methods tested include hybrid meta-GGAs, M06-L, PW6B95, SOGGA11, MP2, SCC-DFTB, PMO, and NDDO.
Publication year: 2012 Source:Chemical Physics, Volume 400 Zhijun Zhang, Bin Li, Zhitao Shen, Yinghui Ren, Wensheng Bian We present full-dimensional quantum mechanical calculations of the vibrational states of acetylene. The calculation scheme is a combination of several methods. The molecular Hamiltonian is represented in CH–CH diatom–diatom Jacobi coordinates. Phase space optimized discrete variable representation is used to construct effective one-dimensional basis functions for radial coordinates, and a basis contraction strategy is applied to angular coordinates. Parity and diatom–diatom permutation symmetry are exploited. The final Hamiltonian matrix is sparse, and an iterative technique combined with an efficient preconditioner is employed to calculate the eigenvalues within desired spectral windows. It is shown that our computation is efficient and accurate, and nearly ideal scaling with respect to increasing energy is achieved.
Graphical abstract
Graphical abstractHighlights
? Full-dimensional calculations of vibrational states of acetylene are performed. ? The calculation scheme is accurate and efficient. ? Nearly ideal scaling with respect to increasing energy is achieved. ? The normal-to-local mode transition observed experimentally is confirmed.
Publication year: 2012 Source:Chemical Physics, Volume 400 Sang Kyu Ryu, Young Chan Bae In our previous work, a new close-packed lattice model was developed for multi-component system of chain fluids with taking the chain length dependence from Monte-Carlo (MC) simulation results into account. In this work, we further extend this model to describe pressure, volume and temperature (PVT) properties, such as vapor–liquid equilibrium (VLE). To consider the effect of pressure on the phase behavior, the volume change effect is taken into account by introducing holes into the incompressible lattice model with two mixing steps. The corresponding new lattice fluid equation of state (LF-EoS) is applied to predict the thermodynamic properties of pure and binary mixtures of hydrocarbons as well as pure polymer solutions. The results of the proposed model are compared to other predictive approaches based on VLE calculations using predetermined pure model parameters without further adjustment. Thermodynamic properties predicted using the method developed in this work are consistent with the experimental data.
Graphical abstract
Graphical abstractHighlights
? We have developed a close-packed lattice model for chain-like molecules. ? The chain length dependencedetermined from Monte-Carlo simulation results were used. ? To consider the volume effect, hole theory and two mixing steps were used. ? A lattice fluid equation of state (LF-EoS) is presented for VLE of hydrocarbon mixtures. ? Correlation of pure polymer solutions data with use of the LF-EoS.
Publication year: 2012 Source:Chemical Physics Marc Brecht, Martin Hussels, Jana B. Nieder, Fang Hui, Celine Elsässer Single-molecule spectroscopy has been used to investigate the plasmonic interaction effects of nanometer-sized hexagonal arrays of Au- and Ag-triangles on the fluorescence properties of photosystem I (PSI) – a key component of the photosynthetic apparatus. The fluorescence emission of PSI is intensified upon coupling with these nanostructures. For single PSI trimers, enhancement factors of up to 10.5 (Au) and 15 (Ag) were observed. The average enhancement is 2.2/5.7 for Au/Ag, respectively. Comparison of the emission spectra shows that the enhancement depends on the wavelength. This wavelength dependence can be explained by the multichromophore composition of PSI. Furthermore, plasmonic interaction increases the fluorescence emission of spectral components, which are barely visible under natural conditions. The metal nanostructures produced via nanosphere lithography turned out to be beneficial tools for signal enhancement due to the very low intensity of their autoluminescence signal.
Graphical abstract
Graphical abstractHighlights
? Fischer patterns are used to enhance the function of photosystem I. ? Fischer patterns of Ag and Au show vanishing auto-luminescence. ? Coupling of photosystem I to these nanostructures modifies the protein function. ? Dark states of photosystem I become accessible using plasmonic interactions
Publication year: 2012 Source:Chemical Physics, Volume 400 Arindam Bankura, Amalendu Chandra We have investigated the hydration structure and dynamics of OH?(H2O)n clusters (n=4, 8, 16 and 20) by means of quantum chemical and ab initio molecular dynamics calculations. Quantum chemical calculations reveal that the solvation structure of the hydroxide ion transforms from three and four-coordinated surface states to five-coordinated interior state with increase in cluster size. Several other isomeric structures with energies not very different from the most stable isomer are also found. Ab initio simulations show that the most probable configurations at higher temperatures need not be the lowest energy isomeric structure. The rates of proton transfer in these clusters are found to be slower than that in bulk water. The vibrational spectral calculations reveal distinct features for free OH (deuterated) stretch modes of water in different hydrogen bonding states. Effects of temperature on the structural and dynamical properties are also investigated for the largest cluster considered here.
Graphical abstract
Graphical abstractHighlights
? A theoretical study of hydroxide ion-water clusters is carried for varying cluster size and temperature. ? The structures of OH?(H2O)n are found out through quantum chemical calculations for n=4, 8, 16 and 20. ? The finite temperature behavior of the clusters is studied through ab initio dynamical simulations. ? The spectral features of OH modes (deuterated) and their dependence on hydrogen bonding states of water are discussed. ? The mechanism and kinetics of proton transfer processes in these anionic clusters are also investigated.
Publication year: 2012 Source:Chemical Physics, Volume 400 Tiberius O. Cheche, Valentin Barna, Ioan Stamatin Existence of representative longitudinal optical (LO) phonon modes is theoretically discussed for the case of polar semiconductor cylindrical quantum dots embedded in a semiconductor matrix. The approach is developed within the dielectric continuum model considering the Fröhlich interaction between electrons and the confined LO phonons. The theory is applied to cylindrical GaAs/AlAs quantum dots within an adiabatic treatment.
Graphical abstract
Graphical abstractHighlights
? We model the exciton-longitudinal optical phonon coupling for cylinder quantum dot. ? We predict a representative optical phonon mode for GaAs/AlAs quantum dot. ? Huang–Rhys factors increases with radius decreasing of GaAs/AlAs quantum dot.
Publication year: 2012 Source:Chemical Physics, Volume 399 J.A. Beswick, N. Halberstadt, K.C. Janda As part of this special issue in honor of Gerardo Delgado Barrio, we have reviewed the interplay between experimental and theoretical work on halogen and interhalogen diatomic molecule bonded to one or more noble gas atoms and also ionic clusters consisting of noble gas atoms. Although the Madrid group has worked on many theoretical issues, they have made particularly important contributions to these two topics. Delgado Barrio has often chosen topics for study for which close interactions between theorists and experimentalists are especially useful. During the historical span of the group, we have progressed from approximate models whose goal was to capture the essence of a process even if the details were impossible to reproduce, to an era in which theory is an equal partner with experiment, and, in fact, often provides a detailed understanding beyond that obtained from a careful analysis of state-of-the-art data.
Graphical abstract
Graphical abstractHighlights
Energy flow in excited molecules can result in intramolecular vibrational redistribution (IVR) followed by vibrational (or electronic) predissociation. Van der Waals (vdW) clusters with one molecule (the chromophore) weakly bound to one or several rare-gas atoms are ideal prototypes for the study of these energy transfer processes. Since the molecule retains most of its individual properties, one can, under suitable conditions, excite the system with the excess energy localized in electronic, vibrational and/or rotational degrees of freedom of the chromophore and follow the energy disposal and redistribution in the cluster.? We present a review on halogen molecules bonded to noble gas atoms. ? We also review ionic clusters of noble gas atoms. ? We emphasize on the experimental and theoretical interplay.
Posted on 28 May 2012 | 12:51 pm
Other notes:
Information about this site:
The author- or copyrights of
the listed Internet pages are held by
the respective authors or site
operators, who are also responsible for
the content of the presentations.
To see your page listed here: Send us an
eMail! Condition: Subject-related
content on chemistry, biochemistry and
comparable academic disciplines!
