Americium-238m

Properties and data of the isotope ²³⁸Am.

Content

General data

Name of the isotope:Americium-238m; Am-238mSymbol:²³⁸Am or 23895AmMass number A:238 (= number of nucleons)Atomic number Z:95 (= number of protons)Neutrons N:143Isotopic mass:238.05198(5) u (atomic weight of Americium-238m)
Excitation energy: 2500 keVNuclide mass:237.9998721 u (calculated nuclear mass without electrons)Mass excess:48.41906 MeVMass defect:1.930481028 u (per nucleus)Nuclear binding energy:1798.2314947 MeV (per nucleus)
7.55559452 MeV (average binding energy per nucleon)Half-life:35 μsDecay constant λ:19804.205158856 s^-1Specific activity α:5.011080381752 × 10⁺²⁵ Bq g^-1
1.354346049122 × 10⁺¹⁵ Ci g^-1Spin and parity:
(nuclear angular momentum)

Radioactive Decay

Half-life T_½ = 35 μs respectively 3.5 × 10^-5 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
²³⁸Am		98(2) min	1+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 143) and isobaric (same nucleon number A = 238) with Americium-238m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 143	Isobar A = 238
84	²²⁷Po
85	²²⁸At
86	²²⁹Rn
87	²³⁰Fr
88	²³¹Ra
89	²³²Ac
90	²³³Th	²³⁸Th
91	²³⁴Pa	²³⁸Pa
92	²³⁵U	²³⁸U
93	²³⁶Np	²³⁸Np
94	²³⁷Pu	²³⁸Pu
95	²³⁸Am	²³⁸Am
96	²³⁹Cm	²³⁸Cm
97	²⁴⁰Bk	²³⁸Bk
98	²⁴¹Cf	²³⁸Cf
99	²⁴²Es
100	²⁴³Fm
101	²⁴⁴Md