Cerium-140m

Properties and data of the isotope ^140mCe.

Contents

Cer-140m is a nuclear isomeric (metastable) state of the isotope cerium-140 with an excitation energy of 2107.854 keV. This state was first experimentally characterized in 1966 and is one of the short-lived, highly excited ¹⁴⁰Ce levels.

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

General data

Name of the isotope:Cerium-140m; Ce-140mSymbol:^140mCe or 140m58CeMass number A:140 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:82Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.4137931034483 (= neutron-proton ratio)Neutron excess (N-Z):24Excitation energy:2107.854(24) keVIsotopic mass:139.90544(2) u (atomic weight of Cerium-140m)Nuclide mass:139.8736246 u (calculated nuclear mass without electrons)Mass excess:-88.08207 MeVMass defect:1.258934968 u (per nucleus)Nuclear binding energy:1172.69036908 MeV (per nucleus)
8.37635978 MeV (average binding energy per nucleon)Half-life:7.3(15) μsDecay constant λ:94951.668569856 s^-1Specific activity α:4.11375771952 × 10⁺²⁶ Bq g^-1
1.111826410681 × 10⁺¹⁶ Ci g^-1Spin and parity:
(nuclear angular momentum)6+Year of discovery:1966

Radioactive Decay

Half-life T_½ = 7.3(15) μs respectively 7.3 × 10^-6 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹⁴⁰Ce	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
¹⁴⁰Ce		stable	0+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 82) and isobaric (same nucleon number A = 140) with Cerium-140m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 82	Isobar A = 140
45	¹²⁷Rh
46	¹²⁸Pd
47	¹²⁹Ag
48	¹³⁰Cd
49	¹³¹In
50	¹³²Sn	¹⁴⁰Sn
51	¹³³Sb	¹⁴⁰Sb
52	¹³⁴Te	¹⁴⁰Te
53	¹³⁵I	¹⁴⁰I
54	¹³⁶Xe	¹⁴⁰Xe
55	¹³⁷Cs	¹⁴⁰Cs
56	¹³⁸Ba	¹⁴⁰Ba
57	¹³⁹La	¹⁴⁰La
58	¹⁴⁰Ce	¹⁴⁰Ce
59	¹⁴¹Pr	¹⁴⁰Pr
60	¹⁴²Nd	¹⁴⁰Nd
61	¹⁴³Pm	¹⁴⁰Pm
62	¹⁴⁴Sm	¹⁴⁰Sm
63	¹⁴⁵Eu	¹⁴⁰Eu
64	¹⁴⁶Gd	¹⁴⁰Gd
65	¹⁴⁷Tb	¹⁴⁰Tb
66	¹⁴⁸Dy	¹⁴⁰Dy
67	¹⁴⁹Ho	¹⁴⁰Ho
68	¹⁵⁰Er
69	¹⁵¹Tm
70	¹⁵²Yb
71	¹⁵³Lu
72	¹⁵⁴Hf
73	¹⁵⁵Ta
74	¹⁵⁶W

External data and identifiers

Adopted Levels, Gammas:NuDat 140Ce

Literature and References

[1] - H. W. Baer, J. J. Reidy, M. L. Wiedenbeck:
The level structure of the nucleus ¹⁴⁰Ce.
In: Nuclear Physics, 86, 2, (1966), DOI 10.1016/0029-5582(66)90541-4.