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Isotopes of Neptunium

List, data and properties of all known isotopes of Neptunium as well as radioactive decay products and intermediate products.

 

Neptunium isotopes

All atomic nuclei of the chemical element neptunium are summarized under neptunium isotopes; these all consist of an atomic nucleus with 93 protons and, in the uncharged state, 93 electrons. The difference between the individual neptunium isotopes is based on the number of neutrons in the nucleus.

The chemical element neptunium in the form of the nuclide Np-239 was first produced in 1940 by bombarding uranium with neutrons. To date, a total of 20 isotopes and several nuclear isomers of the actinide metal have been characterized.

All isotopes of neptunium are unstable and decay, releasing radioactive radiation. The longest-lived neptunium nuclides are Np-237 with a half-life of 2.14 million years, Np-236 with 154000 years and Np-235 with 396 days. The element that occurs in nature at most in the smallest traces is produced and used within the framework of nuclear technology.

 

Isotope Table: Neptunium

 

Atomic Properties

Isotope
Nuclide
ZANNameAtomic Mass
[Nuclear Mass]
{Mass Excess}
Spin I
(h/2π)
μParent
123456789
219Np93219126Neptunium-219219.03162(9) u
[218.9806089 u]
{29.45384 MeV}
(9/2-)223Am
225Np93225132Neptunium-225225.03391(8) u
[224.9828989 u]
{31.58696 MeV}
(9/2-)
226Np93226133Neptunium-226226.03519(9) u
[225.9841789 u]
{32.77927 MeV}
227Np93227134Neptunium-227227.03496(8) u
[226.9839489 u]
{32.56503 MeV}
228Np93228135Neptunium-228228.03607(5) u
[227.9850589 u]
{33.59899 MeV}
229Np93229136Neptunium-229229.03626(9) u
[228.9852489 u]
{33.77597 MeV}
230Np93230137Neptunium-230230.03783(6) u
[229.9868189 u]
{35.23842 MeV}
234Am
231Np93231138Neptunium-231231.03824(5) u
[230.9872289 u]
{35.62033 MeV}
(5/2-)235Am
231Pu
232Np93232139Neptunium-232232.04011(11) u
[231.9890989 u]
{37.36222 MeV}
(4+)236Am
232Pu
233Np93233140Neptunium-233233.04074(5) u
[232.9897289 u]
{37.94907 MeV}
(5/2+)237Am
233Pu
234Np93234141Neptunium-234234.042893(9) u
[233.9918819 u]
{39.95457 MeV}
(0+)238Am
234Pu
235Np93235142Neptunium-235235.0440616(15) u
[234.9930505 u]
{41.04312 MeV}
5/2+239Am
235Pu
236Np93236143Neptunium-236236.04657(5) u
[235.9955589 u]
{43.37968 MeV}
(6-)240Am
236mNp93236143Neptunium-236m236.04657(5) u
[235.9955589 u]
{43.37968 MeV}
1
237Np93237144Neptunium-237237.0481717(12) u
[236.9971606 u]
{44.87165 MeV}
5/2++ 3.14(4)241Am
237Pu
237U
237mNp93237144Neptunium-237m237.0481717(12) u
[236.9971606 u]
{44.87165 MeV}
(11/2,13/2)
238Np93238145Neptunium-238238.0509447(12) u
[237.9999336 u]
{47.45468 MeV}
2+242Am
238mNp93238145Neptunium-238m238.0509447(12) u
[237.9999336 u]
{47.45468 MeV}
239Np93239146Neptunium-239239.0529376(14) u
[239.0019265 u]
{49.31106 MeV}
5/2+243Am
239U
240Np93240147Neptunium-240240.056164(18) u
[240.0051529 u]
{52.31643 MeV}
(5+)240U
240mNp93240147Neptunium-240m240.056164(18) u
[240.0051529 u]
{52.31643 MeV}
(1+)
241Np93241148Neptunium-241241.05825(8) u
[241.0072389 u]
{54.25953 MeV}
5/2+
242Np93242149Neptunium-242242.06164(21) u
[242.0106289 u]
{57.41729 MeV}
(1+)242U
242mNp93242149Neptunium-242m242.06164(21) u
[242.0106289 u]
{57.41729 MeV}
(6+)
243Np93243150Neptunium-243243.06428(3) u
[243.0132689 u]
{59.87643 MeV}
(5/2)
244Np93244151Neptunium-244244.06785(32) u
[244.0168389 u]
{63.20187 MeV}
(7-)

 

Radioactive Decay Properties

IsotopeRadioactive DecayAEExtern
Half-lifeDecay ModeProbabilityEnergy
1101112131415
Np-2195 μsα → 215Pa9.17(5) MeV
Np-2253.6(-76-27) msα → 221Pa
EC/β+225U
100 %
?
8.79(5) MeV
4.21(7) MeV
AL
Np-22635(10) msα → 222Pa100 %8.20(5) MeVAL
Np-2270.51(6) sα → 223Pa100 %7.816(14) MeVAL
Np-22861.4(14) sα → 224Pa
EC → 228U
40(7) %
60(7) %
7.31(5) MeV
4.37(5) MeV
AL
Np-2294.0(2) minα → 225Pa
EC → 229U
68(11) %
32(11) %
7.01(5) MeV
2.57(9) MeV
AL
Np-2304.6(3) minα → 226Pa
EC/β+230U
≥ 3 %
≤ 97 %
6.78(5) MeV
3.62(5) MeV
AL
Np-23148.8(2) minα → 227Pa
EC → 231U
2(1) %
98(1) %
6.37(5) MeV
1.82(5) MeV
AL
Np-23214.7(3) minα → 228Pa
EC/β+232U
0.0002 %
99.9998 %
6.01(10) MeV
2.75(10) MeV
AL
Np-23336.2(1) minα → 229Pa
EC → 233U
≤ 0.001 %
≥ 99.999 %
5.63(5) MeV
1.03(5) MeV
AL
Np-2344.4(1) dEC/β+234U100 %1.81(8) MeVAL
Np-235396.1(12) dα → 231Pa
EC → 235U
0.00260(13) %
99.99740(13) %
5.1938(15) MeV
0.1243(18) MeV
AL
Np-236153000 aα → 232Pa
EC → 236U
β-236Pu
0.16(4) %
86.3(8) %
13.5(8) %
5.01(5) MeV
0.93(5) MeV
0.48(5) MeV
AL
Np-236m22.5(4) hEC → 236U
β-236Pu
50(3) %
50(3) %

+x keVAL
Np-2372.144(7) × 106 aα → 233Pa
SF div
ca. 100 %
Spuren
4.9573(7) MeV
AL
Np-237m0.71(4) μsIso → 237Np100 %945.2(1) keV
Np-2382.099(2) dβ-238Pu100 %1.2914(5) MeVAL
Np-238m112(39) nsSF div≤ 100 %2300 keVAL
Np-2392.356(3) dβ-239Pu100 %0.7228(9) MeVAL
Np-24061.9(2) minβ-240Pu100 %2.191(17) MeVAL
Np-240m7.22(2) minβ-240Pu
Iso → 240Np
99.88(1) %
0.12(1) %

+x keVAL
Np-24113.9(2) minβ-241Pu100 %1.30(7) MeVAL
Np-2422.2(2) minβ-242Pu100 %2.7(2) MeVAL
Np-242m5.5(1) minβ-242Pu100 %+y keVAL
Np-2431.85(15) minβ-243Pu100 %2.12(3) MeVAL
Np-2442.29(16) minβ-244Pu100 %3.4(3) MeVAL

 

Notes (related to the columns):

1 - nuclide, isotope symbol.
2 - Z = number of protons (atomic number).
3 - Mass number A.
4 - N = number of neutrons.
5 - Identification of the Neptunium isotope.
6 - Relative atomic mass of the Neptunium isotope (isotopic mass including electrons) and the mass of the atomic nucleus in square brackets (nuclear mass, nuclide mass without electrons), each related to 12C = 12.00000 [2]. In addition, the mass excess is given in MeV.
7 - Nuclear spin I, unit: h/2π.
8 - Nuclear magnetic moment μmag.
9 - Source nuclides: Possible, assumed or actual source nuclides (mother nuclides, parent nuclides). If applicable, the corresponding decay modes can be found in the data for the respective starting nuclide.
10 - Decay: Half-live of the Neptunium isotope (a = years; ; d = days; h = hours; min = minutes; s = seconds).
11 - Decay: type of decay into the respective daughter nuclides with n = neutron emission; p = proton emission; α = alpha decay; β- = beta minus decay with electron emission; EC = electron capture; β+ = positron emission; ε = β+ and/or EC; Iso = isomeric transition; CD = cluster decay; SF = spontaneous decay.
12 - Decay percentage in percent (%).
13 - Decay energy; Particle energy related to decay type.
14 - AE = Excitation energy for metastable nuclei.
15 - Other information and notes: AL = Adopted Levels (link to external data [1]).

Miscellaneous:

()- Numbers in brackets: uncertainty to represent the spread of the reported value.
~ - Theoretical values or systematic trends.
  - unlisted-: Nuclides that have already been mentioned in the literature but for some reason can no longer be found in the current nuclide tables because their discovery e.g. has not confirmed.

 

NMR active Neptunium nuclides

Nuclide
quantity 1)
spin
Nuclear magnetic
moment
μ/μN
Gyromagnetic
ratio
107 rad T-1 s-1
Quadrupole
moment
Q fm-2
Resonant
frequency
v0 bei 1 T
Relative
sensitivity
H0 = const.
v0 = const. 2)
237Np
100 %
5/2+
+ 3,14(4)3,1+ 388,6(6)9,570,13264
2,6234

1) Quantity Percentage of natural occurrence.

2) Related to 1H = 1,000.

 

Radiation Protection

According to the Radiation Protection Ordinance (StrlSchV 2018, Germany), the following values (columns 1 to 7) apply to the handling of Neptunium radionuclides:

NuclideLimit ValueHASS limitSCDaughter NuclidesHalf-life
Np-232106 Bq10 Bq/g14.7 min
Np-233107 Bq100 Bq/g36.2 min
Np-234106 Bq10 Bq/g4.4 d
Np-235107 Bq100 Bq/g20 TBq395.9 d
Np-236107 Bq1 Bq/g150000 a
Np-236m107 Bq1 Bq/g22.5 h
Np-237+103 Bq1 Bq/g0,07 TBq0,1 Bq cm-2Pa-2332100000 a
Np-238106 Bq100 Bq/g2.1 d
Np-239107 Bq100 Bq/g0,5 TBq10 Bq cm-22.4 d
Np-240106 Bq10 Bq/g1 Bq cm-265.0 min

(HASS = High-Activity Sealed Radioactive Sources; SC = surface contamination)

 

Literature Sources and References

Properties of the Neptunium nucleides

[1] - NuDat: National Nuclear Data Center, Brookhaven National Laboratory, based on ENSDF and the Nuclear Wallet Cards.

[2] - G. Audi et. al.: The NUBASE evaluation of nuclear and decay properties. Nuclear Physics, (2003), DOI 10.1016/j.nuclphysa.2003.11.001.

[3] - Live Chart of Nuclides. Nuclear structure and decay data.

Neptunium: NMR properties - 237Np-NMR

[4] - N. J. Stone: Table of nuclear magnetic dipole and electric quadrupole moments. Atomic Data and Nuclear Data Tables, (2005), DOI 10.1016/j.adt.2005.04.001.

[5] - Pekka Pyykkö: Year-2008 nuclear quadrupole moments. Molecular Physics, (2008), DOI 10.1080/00268970802018367.

[6] - Pekka Pyykkö: Year-2017 nuclear quadrupole moments. Molecular Physics, (2018), DOI 10.1080/00268976.2018.1426131.

[7] - N. J. Stone: Table of recommended nuclear magnetic dipole moments. IAEA, (2019).

More sources:

[8] - Isotopic abundances, atomic weights and isotopic masses: see respective keyword.

[9] - L. B. Magnusson, S. G. Thompson, G. T. Seaborg:
New Isotopes of Neptunium.
In: Physical Review, (1950), DOI 10.1103/PhysRev.78.363.

[10] - J. E. Gindler, J. R. Huizenga, D. W. Engelkemeir:
Neptunium Isotopes: 234, 235, 236.
In: Physical Review, (1958), DOI 10.1103/PhysRev.109.1263.

[11] - Richard M. Lessler, Maynard C. Michel:
Isotopes Np240 and Np241.
In: Physical Review, (1960), DOI 10.1103/PhysRev.118.263.

 


Category: Isotopes

Last update: 05.07.2020



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