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Isotopes of Neptunium

List, data and properties of all known isotopes of Neptunium.

Content
Atomic properties
Decay properties
NMR active nuclides
Radiation protection
References
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

The two following tables list the most important data and properties of the Neptunium isotopes. Further information on the individual Neptunium isotopes is listed on separate pages and can be accessed via the link in column 1.

 

Atomic Properties

Isotope
Nuclide		ENAtomic Mass
[Nuclear Mass]
{Mass Excess}		Spin I
(h/2π)		Parent
123456
Neptunium-21921993Np126219.03162(9) u
[218.9806089 u]
{29.45384 MeV}		(9/2-)223Am
Neptunium-22522593Np132225.03391(8) u
[224.9828989 u]
{31.58696 MeV}		(9/2-)
Neptunium-22622693Np133226.03519(9) u
[225.9841789 u]
{32.77927 MeV}
Neptunium-22722793Np134227.03496(8) u
[226.9839489 u]
{32.56503 MeV}
Neptunium-22822893Np135228.03607(5) u
[227.9850589 u]
{33.59899 MeV}
Neptunium-22922993Np136229.03626(9) u
[228.9852489 u]
{33.77597 MeV}		233Am
Neptunium-23023093Np137230.03783(6) u
[229.9868189 u]
{35.23842 MeV}		234Am
Neptunium-23123193Np138231.03824(5) u
[230.9872289 u]
{35.62033 MeV}		(5/2-)235Am
231Pu
Neptunium-23223293Np139232.04011(11) u
[231.9890989 u]
{37.36222 MeV}		(4+)236Am
232Pu
Neptunium-23323393Np140233.04074(5) u
[232.9897289 u]
{37.94907 MeV}		(5/2+)237Am
233Pu
Neptunium-23423493Np141234.042893(9) u
[233.9918819 u]
{39.95457 MeV}		(0+)238Am
234Pu
Neptunium-23523593Np142235.0440616(15) u
[234.9930505 u]
{41.04312 MeV}		5/2+239Am
235Pu
Neptunium-23623693Np143236.04657(5) u
[235.9955589 u]
{43.37968 MeV}		(6-)240Am
Neptunium-236m236m93Np143236.04657(5) u
[235.9955589 u]
{43.37968 MeV}		1
Neptunium-23723793Np144237.0481717(12) u
[236.9971606 u]
{44.87165 MeV}		5/2+241Am
237Pu
237U
Neptunium-237m237m93Np144237.0481717(12) u
[236.9971606 u]
{44.87165 MeV}		(11/2,13/2)
Neptunium-23823893Np145238.0509447(12) u
[237.9999336 u]
{47.45468 MeV}		2+242Am
Neptunium-238m238m93Np145238.0509447(12) u
[237.9999336 u]
{47.45468 MeV}
Neptunium-23923993Np146239.0529376(14) u
[239.0019265 u]
{49.31106 MeV}		5/2+243Am
239U
Neptunium-24024093Np147240.056164(18) u
[240.0051529 u]
{52.31643 MeV}		(5+)240U
Neptunium-240m240m93Np147240.056164(18) u
[240.0051529 u]
{52.31643 MeV}		(1+)
Neptunium-24124193Np148241.05825(8) u
[241.0072389 u]
{54.25953 MeV}		5/2+
Neptunium-24224293Np149242.06164(21) u
[242.0106289 u]
{57.41729 MeV}		(1+)242U
Neptunium-242m242m93Np149242.06164(21) u
[242.0106289 u]
{57.41729 MeV}		(6+)
Neptunium-24324393Np150243.06428(3) u
[243.0132689 u]
{59.87643 MeV}		(5/2)
Neptunium-24424493Np151244.06785(32) u
[244.0168389 u]
{63.20187 MeV}		(7-)

 

Radioactive Decay Properties

IsotopeRadioactive DecayExtern
Half-lifeDecay ModeProbabilityEnergy
789101112
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) %		7.020(59) MeV
2.591(101) 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		≤ 0.0007 %
100 %		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) %
AL
Np-2372.144(7) × 106 aα → 233Pa
SF div		ca. 100 %
Spuren		4.9573(7) MeV
AL
Np-237m0.71(4) μsIso → 237Np100 %
Np-2382.099(2) dβ- → 238Pu100 %1.2914(5) MeVAL
Np-238m112(39) nsSF div≤ 100 %AL
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) %
AL
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 %AL
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 - name of the nuclide, isotope.
2 - E: isotope symbol with mass number (superscript; number of nucleons) and Atomic number (subscript; number of protons).
3 - N: number of neutrons.
4 - 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.
5 - nuclear spin I, unit: h/2π.
6 - 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.

7 - isotope notation in short form.
8 - decay: half-live of the Neptunium isotope (a = years; ; d = days; h = hours; min = minutes; s = seconds).
9 - decay mode: 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.
10 - decay probability in percent (%).
11 - decay energy; Particle energy related to decay type.
12 - 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
{Quadrupole moment}		Resonant
frequency
v0 bei 1 T		Relative
sensitivity
H0 = const.
v0 = const. 3)
237Np
100 %
5/2+		+ 3,14(4)3,1
{+ 3,886(6)}		9,570,13264
2,6234

1) Quantity Percentage of natural occurrence.

2) Gyromagnetic ratio: 107 rad T-1 s-1
    Quadrupole moment: Q [barn] = [100 fm2]

3) 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.

 

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