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Properties and data of the isotope 241Am.


Americium-241 is the artificial radioisotope of the element Americium, whose atomic nucleus has 146 neutrons in addition to the element-specific 95 protons, resulting in a mass number of 241: 241Am.

See also: list of Americium isotopes.


General data

Name of the isotope:Americium-241; Am-241Symbol:241AmMass number A:241Atomic number Z:95 (= number of protons)Neutrons N:146Isotopic mass:241.0568273(12) u (atomic weight of Americium-241)Nuclide mass:241.0047194 u (calculated nuclear mass without electrons)Mass excess:52.93429 MeVMass defect:1.951628476 u (per nucleus)Nuclear binding energy:1817.93021562 MeV (per nucleus)
7.5432789 MeV (average binding energy per nucleon)
Separation energy:SN = 6.647(14) MeV (first neutron)
SP = 4.47996(17) MeV (first proton)
Cross section:σ(n.γ) = 628(22) barn (thermal neutron capture cross-section)
σ(n.f) = 3.15(10) b (gap cross-section)
Half-life:432.6(6) aDecay constant λ:5.08079296727 × 10-11 s-1Spin and parity:5/2-Charge radius:5.8928(42) femtometer fmYear of discovery:1949


Radioactive Decay

Half-life T½ = 432.6(6) a respectively 1.36425 × 1010 seconds s.

Decay modeDaughterProbabilityDecay energyγ energy
α237Npca. 100 %5,63782(12) MeV59,5409(1) keV
35,9(4) %
0,02138(22) MeV/Bq-s


Americium-241 radioactive decay chain


Parent Nuclides

Direct parent isotopes are: 245Bk, 241Cm, 241Pu.


NMR data

241Am belongs to the NMR active Nuclides.

Isotope:241Am-NMRQuantity:Does not occur in nature!Spin:5/2-Nuclearmagnetic moment
+ 1,58(1)Gyromagnetic ratio
107 rad T-1 s-1:
1,04Quadrupole moment
Q fm-2:


Radiation Protection

The German Radiation Protection Ordinance, for example, specifies the following limit values for the isotope Americium-241 (exemption limits, clearance values and other values as a radioactive or highly radioactive source of radiation (HASS)):

Isotope:Am-241Exemption level:104 BqExemption level per gram:0,1 Bq/g
Unrestricted handling of solids and liquids.
Activity HASS:0,06 TBqSurface contamination:0,1 Bq cm-2Half-life:432.8 a


Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear IsomerExcitation EnergyHalf-lifeSpin
241mAm2200(100) keV1,2(3) μs


Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 146) and isobaric (same nucleon number A = 241) with Americium-241. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.


OZIsotone N = 146Isobar A = 241


External data and identifiers

CAS:14596-10-2InChI Key:LXQXZNRPTYVCNG-YPZZEJLDSA-NSMILES:[241Am]PubChem:ID 104726Adopted Levels, Gammas:NuDat 241Am


Literature and References

[1] - Shoji Nakamura et al.:
Thermal-Neutron Capture Cross Section and Resonance Integral of Americium-241.
In: Journal of Nuclear Science and Technology, (2007), DOI 10.1080/18811248.2007.9711399.


Category: Isotopes

Last update: 26.11.2022

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