Rutherfordium-253

Properties and data of the isotope ²⁵³Rf.

Contents

Rutherfordium-253 is a radioisotope of the chemical element rutherfordium, which has 149 neutrons in its atomic nucleus in addition to the element-specific 104 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 253. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²⁵³Rf is exclusively for academic purposes.

F. P. Heßberger et al. reported the discovery in 1997. The superheavy nuclide was observed and identified during the irradiation of a lead-204 template with titanium-50 ions [1]: 204Pb(⁵⁰Ti,n)²⁵³Rf.

It has not yet been clarified which nuclear isomeric Rf-253 nuclide represents the ground state of rutherfordium-253 [3, 4].

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

General data

Name of the isotope:Rutherfordium-253; Rf-253Symbol:²⁵³Rf or 253104RfMass number A:253 (= number of nucleons)Atomic number Z:104 (= number of protons)Neutrons N:149Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.4326923076923 (= neutron-proton ratio)Neutron excess (N-Z):45Isotopic mass:253.10053(44) u (atomic weight of Rutherfordium-253)Nuclide mass:253.0434866 u (calculated nuclear mass without electrons)Mass excess:93.64309 MeVMass defect:2.004345812 u (per nucleus)Nuclear binding energy:1867.0360978 MeV (per nucleus)
7.37958932 MeV (average binding energy per nucleon)Separation energy:
S_P = 2.184(450) MeV (first proton)Half-life:9.9(12) msDecay constant λ:70.014866723227 s^-1Specific activity α:1.666558852557 × 10⁺²³ Bq g^-1
4504213115019.5 Ci g^-1Spin and parity:
(nuclear angular momentum)(1/2+)Year of discovery:1997

Radioactive Decay

Half-life T_½ = 9.9(12) ms respectively 9.9 × 10^-3 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁴⁹No	17(6) %	9.43(30) MeV
SZ	div	83(6) %

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
^253mRf	+y keV	52.8(44) μs	(7/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 149) and isobaric (same nucleon number A = 253) with Rutherfordium-253. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 149	Isobar A = 253
91	²⁴⁰Pa
92	²⁴¹U
93	²⁴²Np
94	²⁴³Pu
95	²⁴⁴Am
96	²⁴⁵Cm
97	²⁴⁶Bk	²⁵³Bk
98	²⁴⁷Cf	²⁵³Cf
99	²⁴⁸Es	²⁵³Es
100	²⁴⁹Fm	²⁵³Fm
101	²⁵⁰Md	²⁵³Md
102	²⁵¹No	²⁵³No
103	²⁵²Lr	²⁵³Lr
104	²⁵³Rf	²⁵³Rf

External data and identifiers

Adopted Levels, Gammas:NuDat 253Rf

Literature and References

[1] - F. P. Heßberger et al.:
Spontaneous fission and alpha-decay properties of neutron deficient isotopes ^257-253104 and ²⁵⁸106.
In: Zeitschrift für Physik A, (1997), DOI 10.1007/s002180050422.

[2] - A. Lopez-Martens, K. Hauschild, A. I. Svirikhin et al.:
Fission properties of ²⁵³Rf and the stability of neutron-deficient Rf isotopes.
In: Physical Review C, 105, L021306, (2022), DOI 10.1103/PhysRevC.105.L021306.

[3] - A. Lopez-Martens, K. Hauschild, A. I. Svirikhin et al.:
Fission hindrances in transfermium nuclei.
In: EPJ Web of Conferences 290, 02027, (2023), DOI 10.1051/epjconf/202329002027.

[4] - Fritz Peter Hessberger:
Low lying isomers in the region of superheavy nuclei.
In: arXiv:2510.05953, (2025), DOI 10.48550/arXiv.2510.05953.