Rutherfordium-261

Properties and data of the isotope ²⁶¹Rf.

Content

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

See also: list of Rutherfordium isotopes.

General data

Name of the isotope:Rutherfordium-261; Rf-261Symbol: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-261)Nuclide 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)Separation energy:S_N = 5.90(21) MeV (first neutron)
S_P = 4.25(13) MeV (first proton)Half-life:68(3) sDecay constant λ:0.010193340890587 s^-1Specific activity α:2.35194385733 × 10⁺¹⁹ Bq g^-1
635660501.9827 Ci g^-1Spin and parity:
(nuclear angular momentum)Year of discovery:1970

Radioactive Decay

Half-life T_½ = 68(3) s respectively 6.8 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁵⁷No	100 %	8.65(5) MeV

Parent Nuclides

Direct parent isotope is: ²⁶⁵Sg.

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
^261mRf	234+x keV	1.9(4) 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-261. 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