Cerium-157

Properties and data of the isotope ¹⁵⁷Ce.

Contents

Cerium-157 is a radioisotope of the chemical element cerium, which has 99 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 157. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ¹⁵⁷Ce is exclusively for academic purposes.

According to a 2018 report, the neutron-rich isotope cerium-157 was produced by fragmenting uranium-238 ions with an energy of 345 MeV per nucleon on a beryllium target foil. The resulting reaction products were then precisely separated, analyzed, and unambiguously identified using the BigRIPS separator at the RIKEN Institute in Japan [1].

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

General data

Name of the isotope:Cerium-157; Ce-157Symbol:¹⁵⁷Ce or 15758CeMass number A:157 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:99Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.7068965517241 (= neutron-proton ratio)Neutron excess (N-Z):41Isotopic mass:156.95713(43) u (atomic weight of Cerium-157)Nuclide mass:156.9253146 u (calculated nuclear mass without electrons)Mass excess:-39.93315 MeVMass defect:1.35454854 u (per nucleus)Nuclear binding energy:1261.75383772 MeV (per nucleus)
8.03664865 MeV (average binding energy per nucleon)Separation energy:S_N = 3.182(500) MeV (first neutron)
S_P = 14.169(565) MeV (first proton)Half-life:175(41) msDecay constant λ:3.9608410317711 s^-1Specific activity α:1.529021962637 × 10⁺²² Bq g^-1
413249179091.19 Ci g^-1Spin and parity:
(nuclear angular momentum)(7/2+)Year of discovery:2017

Radioactive Decay

Half-life T_½ = 175(41) ms respectively 1.75 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹⁵⁷Pr	100 %	8.50(40) MeV
β^-, n	¹⁵⁶Pr	?	3.57(45) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 99) and isobaric (same nucleon number A = 157) with Cerium-157. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 99	Isobar A = 157
57	¹⁵⁶La
58	¹⁵⁷Ce	¹⁵⁷Ce
59	¹⁵⁸Pr	¹⁵⁷Pr
60	¹⁵⁹Nd	¹⁵⁷Nd
61	¹⁶⁰Pm	¹⁵⁷Pm
62	¹⁶¹Sm	¹⁵⁷Sm
63	¹⁶²Eu	¹⁵⁷Eu
64	¹⁶³Gd	¹⁵⁷Gd
65	¹⁶⁴Tb	¹⁵⁷Tb
66	¹⁶⁵Dy	¹⁵⁷Dy
67	¹⁶⁶Ho	¹⁵⁷Ho
68	¹⁶⁷Er	¹⁵⁷Er
69	¹⁶⁸Tm	¹⁵⁷Tm
70	¹⁶⁹Yb	¹⁵⁷Yb
71	¹⁷⁰Lu	¹⁵⁷Lu
72	¹⁷¹Hf	¹⁵⁷Hf
73	¹⁷²Ta	¹⁵⁷Ta
74	¹⁷³W	¹⁵⁷W
75	¹⁷⁴Re
76	¹⁷⁵Os
77	¹⁷⁶Ir
78	¹⁷⁷Pt
79	¹⁷⁸Au
80	¹⁷⁹Hg
81	¹⁸⁰Tl
82	¹⁸¹Pb