Neptunium-242

Properties and data of the isotope ²⁴²Np.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Neptunium-242 is a radioisotope of the chemical element neptunium, which has 149 neutrons in its atomic nucleus in addition to the element-specific 93 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 242. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²⁴²Np is exclusively for academic purposes.

In 1979 a report appeared in which the isotope neptunium-242 was described for the first time. In the experiments presented there, samples of plutonium-244 were irradiated with 30–160 MeV neutrons, and after subsequent chemical separation the nuclides uranium-242 and Neptunium-242 were identified by γ- and β-spectroscopy. The isotope neptunium-242 was formed according to the reaction

²⁴⁴Pu(n,2pn)²⁴²U → β^- → ²⁴²Np.

See also: List of individual Neptunium isotopes (and general data sources).

General data

Name of the isotope:Neptunium-242; Np-242Symbol:²⁴²Np or 24293NpMass number A:242 (= number of nucleons)Atomic number Z:93 (= number of protons)Neutrons N:149Isotopic mass:242.06164(21) u (atomic weight of Neptunium-242)Nuclide mass:242.0106289 u (calculated nuclear mass without electrons)Mass excess:57.41729 MeVMass defect:1.95716046 u (per nucleus)Nuclear binding energy:1823.08322553 MeV (per nucleus)
7.53340176 MeV (average binding energy per nucleon)Separation energy:S_N = 4.970(224) MeV (first neutron)
S_P = 6.069(280) MeV (first proton)Half-life:2.2(2) minDecay constant λ:0.005251115004242 s^-1Specific activity α:1.306733645755 × 10⁺¹⁹ Bq g^-1
353171255.60949 Ci g^-1Spin and parity:
(nuclear angular momentum)(1+)Year of discovery:1979

Radioactive Decay

Half-life T_½ = 2.2(2) min (minutes) respectively 1.32 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	²⁴²Pu	100 %	2.7(2) MeV

Parent Nuclides

Direct parent isotope is: ²⁴²U.

Nuclear Isomers

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

Nuclear Isomer	Excitation Energy	Half-life	Spin
^242mNp	50(50) keV	5.5(1) min	(6+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 149) and isobaric (same nucleon number A = 242) with Neptunium-242. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 149	Isobar A = 242
91	²⁴⁰Pa
92	²⁴¹U	²⁴²U
93	²⁴²Np	²⁴²Np
94	²⁴³Pu	²⁴²Pu
95	²⁴⁴Am	²⁴²Am
96	²⁴⁵Cm	²⁴²Cm
97	²⁴⁶Bk	²⁴²Bk
98	²⁴⁷Cf	²⁴²Cf
99	²⁴⁸Es	²⁴²Es
100	²⁴⁹Fm	²⁴²Fm
101	²⁵⁰Md
102	²⁵¹No
103	²⁵²Lr
104	²⁵³Rf

External data and identifiers

Adopted Levels, Gammas:NuDat 242Np

Literature and References

[1] - P. E. Haustein, H -C. Hseuh, R. L. Klobuchar et al.:
Identification and decay of ²⁴²U and ²⁴²Np.
In: Physical Review C, 19, 2332, (1979), DOI 10.1103/PhysRevC.19.2332.