Cerium-136m

Properties and data of the isotope ^136mCe.

Contents

Cer-136m is a nuclear isomeric (metastable) state of the isotope cerium-136 with an excitation energy of 3095.0 keV. The isomer was identified in the early 1990s in connection with high-spin spectroscopy studies of neutron-deficient rare-earth nuclei [1].

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

General data

Name of the isotope:Cerium-136m; Ce-136mSymbol:^136mCe or 136m58CeMass number A:136 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:78Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.3448275862069 (= neutron-proton ratio)Neutron excess (N-Z):20Excitation energy:3095.0(6) keVIsotopic mass:135.907129(3) u (atomic weight of Cerium-136m)Nuclide mass:135.8753136 u (calculated nuclear mass without electrons)Mass excess:-86.50878 MeVMass defect:1.222586304 u (per nucleus)Nuclear binding energy:1138.83180666 MeV (per nucleus)
8.37376328 MeV (average binding energy per nucleon)Half-life:1.96(9) μsDecay constant λ:364814.30555787 s^-1Specific activity α:1.627380100584 × 10⁺²⁷ Bq g^-1
4.398324596175 × 10⁺¹⁶ Ci g^-1Spin and parity:
(nuclear angular momentum)10+Magnetic dipole moment:μ(μ_N) = -1.80(2)Nuclear g-factor:g_l = -0.18Year of discovery:1991

Radioactive Decay

Half-life T_½ = 1.96(9) μs respectively 1.9 × 10^-6 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹³⁶Ce	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
¹³⁶Ce		stable	0+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 78) and isobaric (same nucleon number A = 136) with Cerium-136m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 78	Isobar A = 136
43	¹²¹Tc
44	¹²²Ru
45	¹²³Rh
46	¹²⁴Pd
47	¹²⁵Ag
48	¹²⁶Cd
49	¹²⁷In	¹³⁶In
50	¹²⁸Sn	¹³⁶Sn
51	¹²⁹Sb	¹³⁶Sb
52	¹³⁰Te	¹³⁶Te
53	¹³¹I	¹³⁶I
54	¹³²Xe	¹³⁶Xe
55	¹³³Cs	¹³⁶Cs
56	¹³⁴Ba	¹³⁶Ba
57	¹³⁵La	¹³⁶La
58	¹³⁶Ce	¹³⁶Ce
59	¹³⁷Pr	¹³⁶Pr
60	¹³⁸Nd	¹³⁶Nd
61	¹³⁹Pm	¹³⁶Pm
62	¹⁴⁰Sm	¹³⁶Sm
63	¹⁴¹Eu	¹³⁶Eu
64	¹⁴²Gd	¹³⁶Gd
65	¹⁴³Tb	¹³⁶Tb
66	¹⁴⁴Dy
67	¹⁴⁵Ho
68	¹⁴⁶Er
69	¹⁴⁷Tm
70	¹⁴⁸Yb
71	¹⁴⁹Lu

External data and identifiers

Adopted Levels, Gammas:NuDat 136Ce

Literature and References

[1] - Takeshi Murakami et al.:
Isomer Decay of ¹³⁶Ce Studied by Gas Filled Recoil Ion Separator.
In: Journal of the Physical Society of Japan, 60, 4, (1991), DOI 10.1143/JPSJ.60.1424.