Rutherfordium-257m

Properties and data of the isotope ²⁵⁷Rf.

Content

See also: list of Rutherfordium isotopes.

General data

Name of the isotope:Rutherfordium-257m; Rf-257mSymbol:²⁵⁷Rf or 257104RfMass number A:257 (= number of nucleons)Atomic number Z:104 (= number of protons)Neutrons N:153Isotopic mass:257.102918(12) u (atomic weight of Rutherfordium-257m)
Excitation energy: 75 keVNuclide mass:257.0458746 u (calculated nuclear mass without electrons)Mass excess:95.8675 MeVMass defect:2.036617476 u (per nucleus)Nuclear binding energy:1897.09695919 MeV (per nucleus)
7.38170023 MeV (average binding energy per nucleon)Half-life:4.1(4) sDecay constant λ:0.16906028794145 s^-1Specific activity α:3.961497540096 × 10⁺²⁰ Bq g^-1
10706750108.37 Ci g^-1Spin and parity:
(nuclear angular momentum)(11/2-)

Radioactive Decay

Half-life T_½ = 4.1(4) s.

Decay mode	Daughter	Probability
EE	²⁵⁷Lr	11(2) %
SZ	div.	≤ 1.4 %
α	²⁵³No	88(2) %

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
²⁵⁷Rf		4.4(3) s	(1/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 153) and isobaric (same nucleon number A = 257) with Rutherfordium-257m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 153	Isobar A = 257
94	²⁴⁷Pu
95	²⁴⁸Am
96	²⁴⁹Cm
97	²⁵⁰Bk
98	²⁵¹Cf
99	²⁵²Es	²⁵⁷Es
100	²⁵³Fm	²⁵⁷Fm
101	²⁵⁴Md	²⁵⁷Md
102	²⁵⁵No	²⁵⁷No
103	²⁵⁶Lr	²⁵⁷Lr
104	²⁵⁷Rf	²⁵⁷Rf
105	²⁵⁸Db	²⁵⁷Db
106	²⁵⁹Sg
107	²⁶⁰Bh