Cerium-127m2

Properties and data of the isotope ^127m2Ce.

Contents

Cerium-127m2 is the second metastable state of the cerium-127 isotope. It was first identified in 1995 during decay studies following the production of Praseodymium-127 in heavy-ion reactions. Analysis of the β-decay spectrum and γ-γ coincidences led to the determination of an excited state at 36.9(11) keV. This state has a spin/parity of (7/2⁻) and decays isomerically via an internal transition with a half-life of more than 10 µs.

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

General data

Name of the isotope:Cerium-127m2; Ce-127m2Symbol:^127m2Ce or 127m258CeMass number A:127 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:69Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.1896551724138 (= neutron-proton ratio)Neutron excess (N-Z):11Excitation energy:36.9(11) keVIsotopic mass:126.92273(3) u (atomic weight of Cerium-127m2)Nuclide mass:126.8909146 u (calculated nuclear mass without electrons)Mass excess:-71.97654 MeVMass defect:1.12900106 u (per nucleus)Nuclear binding energy:1051.65771338 MeV (per nucleus)
8.2807694 MeV (average binding energy per nucleon)Half-life:> 10 μsDecay constant λ:69314.718055995 s^-1Specific activity α:3.312880919047 × 10⁺²⁶ Bq g^-1
8.953732213642 × 10⁺¹⁵ Ci g^-1Spin and parity:
(nuclear angular momentum)(7/2-)Year of discovery:1995

Radioactive Decay

Half-life T_½ = > 10 μs respectively 1 × 10^-5 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹²⁷Ce	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
¹²⁷Ce		34(2) s	(1/2+)
^127mCe	7.3(11) keV	28.6(7) s	(5/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 69) and isobaric (same nucleon number A = 127) with Cerium-127m2. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 69	Isobar A = 127
38	¹⁰⁷Sr
39	¹⁰⁸Y
40	¹⁰⁹Zr
41	¹¹⁰Nb
42	¹¹¹Mo
43	¹¹²Tc
44	¹¹³Ru
45	¹¹⁴Rh	¹²⁷Rh
46	¹¹⁵Pd	¹²⁷Pd
47	¹¹⁶Ag	¹²⁷Ag
48	¹¹⁷Cd	¹²⁷Cd
49	¹¹⁸In	¹²⁷In
50	¹¹⁹Sn	¹²⁷Sn
51	¹²⁰Sb	¹²⁷Sb
52	¹²¹Te	¹²⁷Te
53	¹²²I	¹²⁷I
54	¹²³Xe	¹²⁷Xe
55	¹²⁴Cs	¹²⁷Cs
56	¹²⁵Ba	¹²⁷Ba
57	¹²⁶La	¹²⁷La
58	¹²⁷Ce	¹²⁷Ce
59	¹²⁸Pr	¹²⁷Pr
60	¹²⁹Nd	¹²⁷Nd
61	¹³⁰Pm	¹²⁷Pm
62	¹³¹Sm
63	¹³²Eu

Literature and References

[1] - A. Gizon, J. Genevey, D. Barnéoud et al.:
¹²⁷Ce levels populated in the 4.2 s ¹²⁷Pr beta-decay.
In: Zeitschrift für Physik A, 351, (1995), DOI 10.1007/BF01291139.