Gadolinium-173

Properties and data of the isotope ¹⁷³Gd.

Contents

Gadolinium-173 is a radioisotope of the chemical element gadolinium, which has 109 neutrons in its atomic nucleus in addition to the element-specific 64 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 173. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ¹⁷³Gd is exclusively for academic purposes.

The discovery of the extremely neutron-rich isotope gadolinium-173 was 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 Gadolinium isotopes (and general data sources).

General data

Name of the isotope:Gadolinium-173; Gd-173Symbol:¹⁷³Gd or 17364GdMass number A:173 (= number of nucleons)Atomic number Z:64 (= number of protons)Neutrons N:109Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.703125 (= neutron-proton ratio)Neutron excess (N-Z):45Isotopic mass:173 u (atomic weight of Gadolinium-173)Nuclide mass:172.9648937 u (calculated nuclear mass without electrons)Mass excess:0 MeVMass defect:1.445277892 u (per nucleus)Nuclear binding energy:1346.26768473 MeV (per nucleus)
7.78189413 MeV (average binding energy per nucleon)Half-life:Spin and parity:
(nuclear angular momentum)Year of discovery:2026

Radioactive Decay

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

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 109) and isobaric (same nucleon number A = 173) with Gadolinium-173. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 109	Isobar A = 173
64	¹⁷³Gd	¹⁷³Gd
65	¹⁷⁴Tb	¹⁷³Tb
68	¹⁷⁷Er	¹⁷³Er
69	¹⁷⁸Tm	¹⁷³Tm
70	¹⁷⁹Yb	¹⁷³Yb
71	¹⁸⁰Lu	¹⁷³Lu
72	¹⁸¹Hf	¹⁷³Hf
73	¹⁸²Ta	¹⁷³Ta
74	¹⁸³W	¹⁷³W
75	¹⁸⁴Re	¹⁷³Re
76	¹⁸⁵Os	¹⁷³Os
77	¹⁸⁶Ir	¹⁷³Ir
78	¹⁸⁷Pt	¹⁷³Pt
79	¹⁸⁸Au	¹⁷³Au
80	¹⁸⁹Hg	¹⁷³Hg
81	¹⁹⁰Tl
82	¹⁹¹Pb
83	¹⁹²Bi
84	¹⁹³Po
85	¹⁹⁴At
86	¹⁹⁵Rn

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.