Cesium-152

Properties and data of the isotope ¹⁵²Cs.

Contents

Cesium-152 is a radioisotope of the chemical element cesium, which has 97 neutrons in its atomic nucleus in addition to the element-specific 55 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 152. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ¹⁵²Cs is exclusively for academic purposes.

The discovery of the extremely neutron-rich isotope cesium-152 was first reported in January 2026 [2].

The nuclide was produced via in-flight projectile fragmentation of a high-energy uranium-238 beam with an energy of 345 MeV per nucleon on a Be target. Using the BigRIPS separator, the reaction products were separated with high efficiency, and Cs-152 was unambiguously identified based on its mass-to-charge ratio (p-value: p < 0.05) .

Prior to this definitive experimental confirmation in 2026, some nuclide charts erroneously listed 1987 as the year of Cs-152 discovery [1]. However, this earlier assignment was not based on quantitative data or evidence from direct observation.

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

General data

Name of the isotope:Cesium-152; Cs-152Symbol:¹⁵²Cs or 15255CsMass number A:152 (= number of nucleons)Atomic number Z:55 (= number of protons)Neutrons N:97Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.7636363636364 (= neutron-proton ratio)Neutron excess (N-Z):42Isotopic mass:151.96873(54) u (atomic weight of Cesium-152)Nuclide mass:151.9385601 u (calculated nuclear mass without electrons)Mass excess:-29.12782 MeVMass defect:1.302143612 u (per nucleus)Nuclear binding energy:1212.93896172 MeV (per nucleus)
7.97986159 MeV (average binding energy per nucleon)Separation energy:S_N = 2.921(707) MeV (first neutron)Half-life:17 msDecay constant λ:40.77336356235 s^-1Specific activity α:1.615746440936 × 10⁺²³ Bq g^-1
4366882272801.1 Ci g^-1Spin and parity:
(nuclear angular momentum)Year of discovery:2026

Radioactive Decay

Half-life T_½ = 17 ms respectively 1.7 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹⁵²Ba	?
β^-, xn ?

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 97) and isobaric (same nucleon number A = 152) with Cesium-152. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 97	Isobar A = 152
55	¹⁵²Cs	¹⁵²Cs
56	¹⁵³Ba	¹⁵²Ba
57	¹⁵⁴La	¹⁵²La
58	¹⁵⁵Ce	¹⁵²Ce
59	¹⁵⁶Pr	¹⁵²Pr
60	¹⁵⁷Nd	¹⁵²Nd
61	¹⁵⁸Pm	¹⁵²Pm
62	¹⁵⁹Sm	¹⁵²Sm
63	¹⁶⁰Eu	¹⁵²Eu
64	¹⁶¹Gd	¹⁵²Gd
65	¹⁶²Tb	¹⁵²Tb
66	¹⁶³Dy	¹⁵²Dy
67	¹⁶⁴Ho	¹⁵²Ho
68	¹⁶⁵Er	¹⁵²Er
69	¹⁶⁶Tm	¹⁵²Tm
70	¹⁶⁷Yb	¹⁵²Yb
71	¹⁶⁸Lu	¹⁵²Lu
72	¹⁶⁹Hf
73	¹⁷⁰Ta
74	¹⁷¹W
75	¹⁷²Re
76	¹⁷³Os
77	¹⁷⁴Ir
78	¹⁷⁵Pt
79	¹⁷⁶Au
80	¹⁷⁷Hg
81	¹⁷⁸Tl
82	¹⁷⁹Pb

Literature and References

[1] - H. L. Ravn:
Radioactive ion beams available at on-line mass separators.
In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 26, 1-3, (1987), DOI 10.1016/0168-583X(87)90735-X.

[2] - Toshiyuki Sumikama, Naoki Fukuda, Toshiyuki Kubo et al.:
Expanding the Isotopic Frontier: Seven New Neutron-Rich Rare-Earth Isotopes Observed at RIKEN RI Beam Factory.
In: Journal of the Physical Society of Japan, 95, 2, (2026), DOI 10.7566/JPSJ.95.024202.