Rutherfordium-261m

Properties and data of the isotope ²⁶¹Rf.

Content

See also: list of Rutherfordium isotopes.

General data

Name of the isotope:Rutherfordium-261m; Rf-261mSymbol:²⁶¹Rf or 261104RfMass number A:261 (= number of nucleons)Atomic number Z:104 (= number of protons)Neutrons N:157Isotopic mass:261.10877(5) u (atomic weight of Rutherfordium-261m)
Excitation energy: 234+x keVNuclide mass:261.0517266 u (calculated nuclear mass without electrons)Mass excess:101.3186 MeVMass defect:2.06542514 u (per nucleus)Nuclear binding energy:1923.93112536 MeV (per nucleus)
7.37138362 MeV (average binding energy per nucleon)Half-life:1.9(4) sDecay constant λ:3.648143055578 × 10^-5 s^-1Specific activity α:8.417483278886 × 10⁺¹⁶ Bq g^-1
2274995.4807802 Ci g^-1Spin and parity:
(nuclear angular momentum)

Radioactive Decay

Half-life T_½ = 1.9(4) s respectively 1.9 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
SF	div.	73(6) %
α	²⁵⁷No	27(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
²⁶¹Rf		68(3) s

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 157) and isobaric (same nucleon number A = 261) with Rutherfordium-261m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 157	Isobar A = 261
97	²⁵⁴Bk
98	²⁵⁵Cf
99	²⁵⁶Es
100	²⁵⁷Fm
101	²⁵⁸Md
102	²⁵⁹No	²⁶¹No
103	²⁶⁰Lr	²⁶¹Lr
104	²⁶¹Rf	²⁶¹Rf
105	²⁶²Db	²⁶¹Db
106	²⁶³Sg	²⁶¹Sg
107	²⁶⁴Bh	²⁶¹Bh
108	²⁶⁵Hs
109	²⁶⁶Mt
110	²⁶⁷Ds