Cerium-125

Properties and data of the isotope ¹²⁵Ce.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Cerium-125 is a radioisotope of the chemical element cerium, which has 67 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 125. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ¹²⁵Ce is exclusively for academic purposes.

The first observation of the neutron-poor nuclide Cer-125 was described in 1968. The isotope was created by fusion-evaporation reactions in which a sulfur-36 beam with an energy of 190 MeV was fired at Ru targets (ruthenium-96 and ruthenium-98). The reaction residues were mass-separated and detected using X-rays and β-radiation: ^96,98Ru(³⁶S,xn)¹²⁵Ce (x = 7, 9) [1].

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

General data

Name of the isotope:Cerium-125; Ce-125Symbol:¹²⁵Ce or 12558CeMass number A:125 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:67Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.1551724137931 (= neutron-proton ratio)Neutron excess (N-Z):9Isotopic mass:124.92844(21) u (atomic weight of Cerium-125)Nuclide mass:124.8966246 u (calculated nuclear mass without electrons)Mass excess:-66.65771 MeVMass defect:1.105961228 u (per nucleus)Nuclear binding energy:1030.19624811 MeV (per nucleus)
8.24156998 MeV (average binding energy per nucleon)Separation energy:S_N = 9.813(357) MeV (first neutron)
S_P = 3.688(204) MeV (first proton)Half-life:9.7(3) sDecay constant λ:0.071458472222675 s^-1Specific activity α:3.47042730129 × 10⁺²⁰ Bq g^-1
9379533246.7486 Ci g^-1Spin and parity:
(nuclear angular momentum)(7/2-)Year of discovery:1978

Radioactive Decay

Half-life T_½ = 9.7(3) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	¹²⁵La	< 100 %	7.101(198) MeV
β⁺, p	¹²⁴Ba	?

Parent Nuclides

Direct parent isotope is: ¹²⁵Pr.

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
^125mCe	93.6(4) keV	13(10) s	(1/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 67) and isobaric (same nucleon number A = 125) with Cerium-125. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 67	Isobar A = 125
38	¹⁰⁵Sr
39	¹⁰⁶Y
40	¹⁰⁷Zr
41	¹⁰⁸Nb
42	¹⁰⁹Mo
43	¹¹⁰Tc
44	¹¹¹Ru
45	¹¹²Rh	¹²⁵Rh
46	¹¹³Pd	¹²⁵Pd
47	¹¹⁴Ag	¹²⁵Ag
48	¹¹⁵Cd	¹²⁵Cd
49	¹¹⁶In	¹²⁵In
50	¹¹⁷Sn	¹²⁵Sn
51	¹¹⁸Sb	¹²⁵Sb
52	¹¹⁹Te	¹²⁵Te
53	¹²⁰I	¹²⁵I
54	¹²¹Xe	¹²⁵Xe
55	¹²²Cs	¹²⁵Cs
56	¹²³Ba	¹²⁵Ba
57	¹²⁴La	¹²⁵La
58	¹²⁵Ce	¹²⁵Ce
59	¹²⁶Pr	¹²⁵Pr
60	¹²⁷Nd	¹²⁵Nd
61	¹²⁸Pm
62	¹²⁹Sm
63	¹³⁰Eu

External data and identifiers

Adopted Levels, Gammas:NuDat 125Ce

Literature and References

[1] - D. D. Bogdanov, A. V. Demyanov, V. A. Karnaukhov et al.:
New neutron-deficient isotopes of lanthanum and cerium.
In: Nuclear Physics A, 307, 3, (1978), DOI 10.1016/0375-9474(78)90457-8.