Cerium-138m

Properties and data of the isotope ¹³⁸Ce.

Content

General data

Name of the isotope:Cerium-138m; Ce-138mSymbol:¹³⁸Ce or 13858CeMass number A:138 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:80Isotopic mass:137.90599(7) u (atomic weight of Cerium-138m)
Excitation energy: 2129.17(12) keVNuclide mass:137.8741746 u (calculated nuclear mass without electrons)Mass excess:-87.56975 MeVMass defect:1.241055136 u (per nucleus)Nuclear binding energy:1156.03541285 MeV (per nucleus)
8.37706821 MeV (average binding energy per nucleon)Half-life:8.73(20) msDecay constant λ:79.398302469639 s^-1Specific activity α:3.490129646073 × 10⁺²³ Bq g^-1
9432782827224.9 Ci g^-1Spin and parity:
(nuclear angular momentum)7-

Radioactive Decay

Half-life T_½ = 8.73(20) ms respectively 8.73 × 10^-3 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹³⁸Ce	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
¹³⁸Ce		stable	0+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 80) and isobaric (same nucleon number A = 138) with Cerium-138m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 80	Isobar A = 138
44	¹²⁴Ru
45	¹²⁵Rh
46	¹²⁶Pd
47	¹²⁷Ag
48	¹²⁸Cd
49	¹²⁹In
50	¹³⁰Sn	¹³⁸Sn
51	¹³¹Sb	¹³⁸Sb
52	¹³²Te	¹³⁸Te
53	¹³³I	¹³⁸I
54	¹³⁴Xe	¹³⁸Xe
55	¹³⁵Cs	¹³⁸Cs
56	¹³⁶Ba	¹³⁸Ba
57	¹³⁷La	¹³⁸La
58	¹³⁸Ce	¹³⁸Ce
59	¹³⁹Pr	¹³⁸Pr
60	¹⁴⁰Nd	¹³⁸Nd
61	¹⁴¹Pm	¹³⁸Pm
62	¹⁴²Sm	¹³⁸Sm
63	¹⁴³Eu	¹³⁸Eu
64	¹⁴⁴Gd	¹³⁸Gd
65	¹⁴⁵Tb	¹³⁸Tb
66	¹⁴⁶Dy	¹³⁸Dy
67	¹⁴⁷Ho
68	¹⁴⁸Er
69	¹⁴⁹Tm
70	¹⁵⁰Yb
71	¹⁵¹Lu