Cerium-129

Properties and data of the isotope ¹²⁹Ce.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Cerium-129 is a radioisotope of the chemical element cerium, which has 71 neutrons in its atomic nucleus in addition to the element-specific 58 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 129. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ¹²⁹Ce is exclusively for academic purposes.

Cerium-129 was first clearly identified in 1977. The isotope was created in a fusion-evaporation reaction in which tin-116 was bombarded with an oxygen-16 beam from a cyclotron: ¹¹⁶Sn(¹⁶O,3n)¹²⁹Ce [1].

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

General data

Name of the isotope:Cerium-129; Ce-129Symbol:¹²⁹Ce or 12958CeMass number A:129 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:71Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.2241379310345 (= neutron-proton ratio)Neutron excess (N-Z):13Isotopic mass:128.918100(30) u (atomic weight of Cerium-129)Nuclide mass:128.8862846 u (calculated nuclear mass without electrons)Mass excess:-76.28936 MeVMass defect:1.150960892 u (per nucleus)Nuclear binding energy:1072.11316513 MeV (per nucleus)
8.31095477 MeV (average binding energy per nucleon)Separation energy:S_N = 8.825(40) MeV (first neutron)
S_P = 4.951(61) MeV (first proton)Half-life:3.5(3) minDecay constant λ:0.0033007008598093 s^-1Specific activity α:1.552912930803 × 10⁺¹⁹ Bq g^-1
419706197.51449 Ci g^-1Spin and parity:
(nuclear angular momentum)(5/2+)Year of discovery:1977

Radioactive Decay

Half-life T_½ = 3.5(3) min (minutes) respectively 2.10 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	¹²⁹La	100 %	5.036(35) MeV

Parent Nuclides

Direct parent isotope is: ¹²⁹Pr.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 71) and isobaric (same nucleon number A = 129) with Cerium-129. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 71	Isobar A = 129
40	¹¹¹Zr
41	¹¹²Nb
42	¹¹³Mo
43	¹¹⁴Tc
44	¹¹⁵Ru
45	¹¹⁶Rh
46	¹¹⁷Pd	¹²⁹Pd
47	¹¹⁸Ag	¹²⁹Ag
48	¹¹⁹Cd	¹²⁹Cd
49	¹²⁰In	¹²⁹In
50	¹²¹Sn	¹²⁹Sn
51	¹²²Sb	¹²⁹Sb
52	¹²³Te	¹²⁹Te
53	¹²⁴I	¹²⁹I
54	¹²⁵Xe	¹²⁹Xe
55	¹²⁶Cs	¹²⁹Cs
56	¹²⁷Ba	¹²⁹Ba
57	¹²⁸La	¹²⁹La
58	¹²⁹Ce	¹²⁹Ce
59	¹³⁰Pr	¹²⁹Pr
60	¹³¹Nd	¹²⁹Nd
61	¹³²Pm	¹²⁹Pm
62	¹³³Sm	¹²⁹Sm
63	¹³⁴Eu
64	¹³⁵Gd
65	¹³⁶Tb

External data and identifiers

Adopted Levels, Gammas:NuDat 129Ce

Literature and References

[1] - J. Gizon, A. Gizon, R.M. Diamond, F.S. Stephens:
The h₁₁₂ and g₇₂ band structures in ¹³¹Ce and ¹²⁹Ce.
In: Nuclear Physics A, 290, 1, (1977), DOI 10.1016/0375-9474(77)90679-0.