Cerium-137m

Properties and data of the isotope ^137mCe.

Contents

Cerium-137m is a nuclear isomeric state of the isotope cerium-137 with an excitation energy of 254.29 keV. This isomeric state was first detected in 1949 during experiments to produce ¹³⁷Ce via the reaction ¹³⁹La(d,4n)^137m. Its decay occurs predominantly via β⁺ emission to the daughter nuclide lanthanum-137, accompanied by a small probability of an isomeric transition (IT) to the ground state [1].

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

General data

Name of the isotope:Cerium-137m; Ce-137mSymbol:^137mCe or 137m58CeMass number A:137 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:79Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.3620689655172 (= neutron-proton ratio)Neutron excess (N-Z):21Excitation energy:254.29(5) keVIsotopic mass:136.9077624(4) u (atomic weight of Cerium-137m)Nuclide mass:136.875947 u (calculated nuclear mass without electrons)Mass excess:-85.91877 MeVMass defect:1.23061782 u (per nucleus)Nuclear binding energy:1146.31311562 MeV (per nucleus)
8.36724902 MeV (average binding energy per nucleon)Half-life:34.4(3) hDecay constant λ:5.597118706071 × 10^-6 s^-1Specific activity α:2.478429210128 × 10⁺¹⁶ Bq g^-1
669845.73246724 Ci g^-1Spin and parity:
(nuclear angular momentum)11/2-Magnetic dipole moment:μ(μ_N) = 1.01(4)Nuclear g-factor:g_l = 0.18363636363636Year of discovery:1948

Radioactive Decay

Half-life T_½ = 34.4(3) h (hours) respectively 1.23840 × 10⁵ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹³⁷Ce	99.21(4) %	0.254 MeV
EC/β⁺	¹³⁷La	0.79(4) %

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
¹³⁷Ce		9.0(3) h	3/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 79) and isobaric (same nucleon number A = 137) with Cerium-137m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 79	Isobar A = 137
44	¹²³Ru
45	¹²⁴Rh
46	¹²⁵Pd
47	¹²⁶Ag
48	¹²⁷Cd
49	¹²⁸In	¹³⁷In
50	¹²⁹Sn	¹³⁷Sn
51	¹³⁰Sb	¹³⁷Sb
52	¹³¹Te	¹³⁷Te
53	¹³²I	¹³⁷I
54	¹³³Xe	¹³⁷Xe
55	¹³⁴Cs	¹³⁷Cs
56	¹³⁵Ba	¹³⁷Ba
57	¹³⁶La	¹³⁷La
58	¹³⁷Ce	¹³⁷Ce
59	¹³⁸Pr	¹³⁷Pr
60	¹³⁹Nd	¹³⁷Nd
61	¹⁴⁰Pm	¹³⁷Pm
62	¹⁴¹Sm	¹³⁷Sm
63	¹⁴²Eu	¹³⁷Eu
64	¹⁴³Gd	¹³⁷Gd
65	¹⁴⁴Tb	¹³⁷Tb
66	¹⁴⁵Dy
67	¹⁴⁶Ho
68	¹⁴⁷Er
69	¹⁴⁸Tm
70	¹⁴⁹Yb
71	¹⁵⁰Lu

External data and identifiers

Adopted Levels, Gammas:NuDat 137Ce

Literature and References

[1] - J. B. Chubbuck and I. Perlman:
Neutron Deficient Isotopes of Cerium and Lanthanum.
In: Physical Review, 74, 982, (1948), DOI 10.1103/PhysRev.74.982.2.