Cerium-121

Properties and data of the isotope ¹²¹Ce.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Cerium-121 is a radioisotope of the chemical element cerium, which has 63 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 121. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ¹²¹Ce is exclusively for academic purposes.

According to a 1997 report, cerium-121 was produced in a fusion-evaporation reaction in which a molybdenum-92 target was bombarded with a 171 MeV sulfur-32 beam. The proton-rich nuclide was produced as a reaction residue of the reaction ⁹²Mo(³²S,3n)¹²¹Ce and, after production, was transported to the measuring station via a helium-jet recoil fast-moving tape-transport system. The identification was based on coincidence measurements of β-delayed protons with γ-radiation; The 186 keV γ transition in the daughter nuclide Barium-120 served as a signature for the assignment of the βp precursor ¹²¹Ce [1].

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

General data

Name of the isotope:Cerium-121; Ce-121Symbol:¹²¹Ce or 12158CeMass number A:121 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:63Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.0862068965517 (= neutron-proton ratio)Neutron excess (N-Z):5Isotopic mass:120.94344(43) u (atomic weight of Cerium-121)Nuclide mass:120.9116246 u (calculated nuclear mass without electrons)Mass excess:-52.6853 MeVMass defect:1.056301564 u (per nucleus)Nuclear binding energy:983.93856906 MeV (per nucleus)
8.13172371 MeV (average binding energy per nucleon)Separation energy:S_N = 11.032(641) MeV (first neutron)
S_P = 2.409(500) MeV (first proton)Half-life:1.1(1) sDecay constant λ:0.63013380050904 s^-1Specific activity α:3.162295422727 × 10⁺²¹ Bq g^-1
85467443857.495 Ci g^-1Spin and parity:
(nuclear angular momentum)(5/2+)Year of discovery:1997

Radioactive Decay

Half-life T_½ = 1.1(1) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC, β⁺	¹²¹La	> 99 %	9.500 (501) MeV
β⁺	¹²⁰Ba	< 1 %

Parent Nuclides

Direct parent isotope is: ¹²¹Pr.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 63) and isobaric (same nucleon number A = 121) with Cerium-121. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 63	Isobar A = 121
35	⁹⁸Br
36	⁹⁹Kr
37	¹⁰⁰Rb
38	¹⁰¹Sr
39	¹⁰²Y
40	¹⁰³Zr
41	¹⁰⁴Nb
42	¹⁰⁵Mo
43	¹⁰⁶Tc	¹²¹Tc
44	¹⁰⁷Ru	¹²¹Ru
45	¹⁰⁸Rh	¹²¹Rh
46	¹⁰⁹Pd	¹²¹Pd
47	¹¹⁰Ag	¹²¹Ag
48	¹¹¹Cd	¹²¹Cd
49	¹¹²In	¹²¹In
50	¹¹³Sn	¹²¹Sn
51	¹¹⁴Sb	¹²¹Sb
52	¹¹⁵Te	¹²¹Te
53	¹¹⁶I	¹²¹I
54	¹¹⁷Xe	¹²¹Xe
55	¹¹⁸Cs	¹²¹Cs
56	¹¹⁹Ba	¹²¹Ba
57	¹²⁰La	¹²¹La
58	¹²¹Ce	¹²¹Ce
59	¹²²Pr	¹²¹Pr

External data and identifiers

Adopted Levels, Gammas:NuDat 121Ce

Literature and References

[1] - Li Zhankui, Xu Shuwei, Xie Yuanxiang et al.:
New β-delayed proton precursor ¹²¹Ce.
In: Physical Review C, 56, 1157, (1997), DOI 10.1103/PhysRevC.56.1157.