Americium-239m

Properties and data of the isotope ²³⁹Am.

Content

General data

Name of the isotope:Americium-239m; Am-239mSymbol:²³⁹Am or 23995AmMass number A:239 (= number of nucleons)Atomic number Z:95 (= number of protons)Neutrons N:144Isotopic mass:239.0530228(21) u (atomic weight of Americium-239m)
Excitation energy: 2500 keVNuclide mass:239.0009149 u (calculated nuclear mass without electrons)Mass excess:49.39042 MeVMass defect:1.938103144 u (per nucleus)Nuclear binding energy:1805.33145002 MeV (per nucleus)
7.55368808 MeV (average binding energy per nucleon)Half-life:163(12) nsDecay constant λ:4252436.6905518 s^-1Specific activity α:1.071496767718 × 10⁺²⁸ Bq g^-1
2.895937210049 × 10⁺¹⁷ Ci g^-1Spin and parity:
(nuclear angular momentum)(7/2+)Magnetic dipole moment:μ(μ_N) = +2.59(18)Nuclear g-factor:g_l = 0.74

Radioactive Decay

Half-life T_½ = 163(12) ns respectively 1.63 × 10^-7 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
SZ	^div	≤ 100 %

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
²³⁹Am		11.9(1) h	(5/2)-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 144) and isobaric (same nucleon number A = 239) with Americium-239m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 144	Isobar A = 239
85	²²⁹At
86	²³⁰Rn
87	²³¹Fr
88	²³²Ra
89	²³³Ac
90	²³⁴Th
91	²³⁵Pa	²³⁹Pa
92	²³⁶U	²³⁹U
93	²³⁷Np	²³⁹Np
94	²³⁸Pu	²³⁹Pu
95	²³⁹Am	²³⁹Am
96	²⁴⁰Cm	²³⁹Cm
97	²⁴¹Bk	²³⁹Bk
98	²⁴²Cf	²³⁹Cf
99	²⁴³Es
100	²⁴⁴Fm
101	²⁴⁵Md