Cerium-139m

Properties and data of the isotope ^139mCe.

Contents

Cer-139m is a nuclear isomeric (metastable) state of the isotope cerium-139 with an excitation energy of 0.75424 MeV. The state was first experimentally characterized in 1967 [1].

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

General data

Name of the isotope:Cerium-139m; Ce-139mSymbol:^139mCe or 139m58CeMass number A:139 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:81Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.3965517241379 (= neutron-proton ratio)Neutron excess (N-Z):23Excitation energy:754.24(8) keVIsotopic mass:138.9066470(22) u (atomic weight of Cerium-139m)Nuclide mass:138.8748316 u (calculated nuclear mass without electrons)Mass excess:-86.95776 MeVMass defect:1.249063052 u (per nucleus)Nuclear binding energy:1163.49473856 MeV (per nucleus)
8.37046575 MeV (average binding energy per nucleon)Half-life:57.58(32) sDecay constant λ:0.012037985073983 s^-1Specific activity α:5.253220419227 × 10⁺¹⁹ Bq g^-1
1419789302.494 Ci g^-1Spin and parity:
(nuclear angular momentum)11/2-Year of discovery:1967

Radioactive Decay

Half-life T_½ = 57.58(32) s respectively 5.758 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹³⁹Ce	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
¹³⁹Ce		137.642(22) d	3/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 81) and isobaric (same nucleon number A = 139) with Cerium-139m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 81	Isobar A = 139
45	¹²⁶Rh
46	¹²⁷Pd
47	¹²⁸Ag
48	¹²⁹Cd
49	¹³⁰In
50	¹³¹Sn	¹³⁹Sn
51	¹³²Sb	¹³⁹Sb
52	¹³³Te	¹³⁹Te
53	¹³⁴I	¹³⁹I
54	¹³⁵Xe	¹³⁹Xe
55	¹³⁶Cs	¹³⁹Cs
56	¹³⁷Ba	¹³⁹Ba
57	¹³⁸La	¹³⁹La
58	¹³⁹Ce	¹³⁹Ce
59	¹⁴⁰Pr	¹³⁹Pr
60	¹⁴¹Nd	¹³⁹Nd
61	¹⁴²Pm	¹³⁹Pm
62	¹⁴³Sm	¹³⁹Sm
63	¹⁴⁴Eu	¹³⁹Eu
64	¹⁴⁵Gd	¹³⁹Gd
65	¹⁴⁶Tb	¹³⁹Tb
66	¹⁴⁷Dy	¹³⁹Dy
67	¹⁴⁸Ho
68	¹⁴⁹Er
69	¹⁵⁰Tm
70	¹⁵¹Yb
71	¹⁵²Lu
72	¹⁵³Hf