Cerium-159

Properties and data of the isotope ¹⁵⁹Ce.

Contents

Cerium-159 is a radioisotope of the chemical element cerium, which has 101 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 159.

The neutron-rich nuclide was first mentioned in the literature in 2015 [N. Fukuda et al., RIKEN Accel. Prog. Rep 48 (2015) 72.].

The discovery of the extremely neutron-rich isotope cerium-159 was finally reported for the first time in January 2026. It was produced via in-flight projectile fragmentation of a high-energy uranium-238 beam - with an energy of 345 MeV per nucleon - impinging on a beryllium target at the RIKEN RI Beam Factory, with subsequent detection achieved using the BigRIPS separator. Neither mass nor other physical parameters were measured in the experiment [1].

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

General data

Name of the isotope:Cerium-159; Ce-159Symbol:¹⁵⁹Ce or 15958CeMass number A:159 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:101Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.7413793103448 (= neutron-proton ratio)Neutron excess (N-Z):43Isotopic mass:158.96636(54) u (atomic weight of Cerium-159)Nuclide mass:158.9345446 u (calculated nuclear mass without electrons)Mass excess:-31.33546 MeVMass defect:1.362648372 u (per nucleus)Nuclear binding energy:1269.29878263 MeV (per nucleus)
7.98301121 MeV (average binding energy per nucleon)Separation energy:S_N = 2.872(640) MeV (first neutron)Half-life:Spin and parity:
(nuclear angular momentum)1/2-Year of discovery:2026

Radioactive Decay

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹⁵⁹Pr	?

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 101) and isobaric (same nucleon number A = 159) with Cerium-159. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 101	Isobar A = 159
57	¹⁵⁸La
58	¹⁵⁹Ce	¹⁵⁹Ce
59	¹⁶⁰Pr	¹⁵⁹Pr
60	¹⁶¹Nd	¹⁵⁹Nd
61	¹⁶²Pm	¹⁵⁹Pm
62	¹⁶³Sm	¹⁵⁹Sm
63	¹⁶⁴Eu	¹⁵⁹Eu
64	¹⁶⁵Gd	¹⁵⁹Gd
65	¹⁶⁶Tb	¹⁵⁹Tb
66	¹⁶⁷Dy	¹⁵⁹Dy
67	¹⁶⁸Ho	¹⁵⁹Ho
68	¹⁶⁹Er	¹⁵⁹Er
69	¹⁷⁰Tm	¹⁵⁹Tm
70	¹⁷¹Yb	¹⁵⁹Yb
71	¹⁷²Lu	¹⁵⁹Lu
72	¹⁷³Hf	¹⁵⁹Hf
73	¹⁷⁴Ta	¹⁵⁹Ta
74	¹⁷⁵W	¹⁵⁹W
75	¹⁷⁶Re	¹⁵⁹Re
76	¹⁷⁷Os
77	¹⁷⁸Ir
78	¹⁷⁹Pt
79	¹⁸⁰Au
80	¹⁸¹Hg
81	¹⁸²Tl
82	¹⁸³Pb
83	¹⁸⁴Bi

Literature and References

[1] - Toshiyuki Sumikama, Naoki Fukuda, Toshiyuki Kubo et al.:
Toshiyuki Sumikama, Naoki Fukuda, Toshiyuki Kubo et al..
In: Journal of the Physical Society of Japan, 95, 2, (2026), DOI 10.7566/JPSJ.95.024202.