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Neptunium-237

Properties and data of the isotope 237Np.

 

Neptunium-237 is a radioactive isotope of the element neptunium. The atomic nucleus of this radioisotope has 144 neutrons in addition to the element-specific 93 protons.

See also: list of Neptunium isotopes.

 

General data

Name of the isotope:Neptunium-237; Np-237Symbol:237NpMass number A:237Atomic number Z:93 (= number of protons)Neutrons N:144Isotopic mass:237.0481717(12) u (atomic weight of Neptunium-237)Nuclide mass:236.9971606 u (calculated nuclear mass without electrons)Mass excess:44.87165 MeVMass defect:1.92730418 u (per nucleus)Nuclear binding energy:1795.27227984 MeV (per nucleus)
7.57498852 MeV (average binding energy per nucleon)
Separation energy:SN = 6.58(5) MeV (first neutron)
SP = 4.86195(25) MeV (first proton)
Half-life:2.144(7) × 106 aDecay constant λ:1.025165714071 × 10-14 s-1Spin and parity:5/2+Year of discovery:1948

 

Radioactive Decay

Half-life T½ = 2.144(7) × 106 a respectively 6.7613184 × 1013 seconds s.

Decay modeDaughterProbabilityDecay energyγ energy
(intensity)
α233Paca. 100 %4,9573(7) MeV
SZdivtraces

 

Neptunium Series

The neptunium series is the natural decay series of the neptunium isotope 237Np. Their final nuclide is the thallium isotope 205Tl. The series can also be continued beyond the Neptunium to even heavier transuranic elements.

 

Neptunium series

 

Parent Nuclides

Direct parent isotopes are: 241Am, 237Pu, 237U.

 

Formation

Small amounts of neptunium-237 are formed by (n,2n) reactions in Uranium-238. The fast neutrons required for this come from spontaneous fission or cosmic rays. However, this reaction is so rare that man-made Np-237 is now present on Earth in far greater abundance than that resulting from this process.

 

Occurrence

Comparison of the natural Neptunium isotopes including isotopic abundance (proportion of the isotope mixture):

 

Atomic Mass maQuantityHalf-lifeSpin
Neptunium
Isotopic mixture
237,048174914 u100 %
Isotope 237Np237,0481717(12) u100 %2.144(7) × 106 a5/2+

 

NMR data

237Np belongs to the NMR active Nuclides.

Isotope:237Np-NMRQuantity:100 %Spin:5/2+Nuclearmagnetic moment
μ/μN:
+ 3,14(4)Gyromagnetic ratio
107 rad T-1 s-1:
3,1Quadrupole moment
Q fm-2:
+ 388,6(6)Resonance frequency
v0 at 1 T:
9,57Relative Sensitivity:0,13264 (H0 = const.)
2,6234 (v0 = const.)
[related to 1H = 1,000]

 

Radiation Protection

The German Radiation Protection Ordinance, for example, specifies the following limit values for the isotope Neptunium-237 (exemption limits, clearance values and other values as a radioactive or highly radioactive source of radiation (HASS)):

Isotope:Np-237+Exemption level:103 BqExemption level per gram:1 Bq/g
Unrestricted handling of solids and liquids.
Activity HASS:0,07 TBqSurface contamination:0,1 Bq cm-2Half-life:2100000 a

 

Nuclear Isomers

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

Nuclear IsomerExcitation EnergyHalf-lifeSpin
237mNp945,2(1) keV0,71(4) μs(11/2,13/2)

 

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 144) and isobaric (same nucleon number A = 237) with Neptunium-237. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

 

OZIsotone N = 144Isobar A = 237
85229At
86230Rn
87231Fr
88232Ra
89233Ac
90234Th237Th
91235Pa237Pa
92236U237U
93237Np237Np
94238Pu237Pu
95239Am237Am
96240Cm237Cm
97241Bk237Bk
98242Cf237Cf
99243Es
100244Fm
101245Md

 

External data and identifiers

Adopted Levels, Gammas:NuDat 237Np

 


Category: Isotopes

Last update: 26.11.2022



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