Rutherfordium-261m

Properties and data of the isotope ^261mRf.

Contents

General Data

Radioactive Decay

Isotones und Isobares

See notes under Rutherfordium-261 (ground state).

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

General data

Name of the isotope:Rutherfordium-261m; Rf-261mSymbol:^261mRf or 261m104RfMass number A:261 (= number of nucleons)Atomic number Z:104 (= number of protons)Neutrons N:157Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.5096153846154 (= neutron-proton ratio)Neutron excess (N-Z):53Excitation energy:70(100) keVIsotopic mass:261.108770(70) u (atomic weight of Rutherfordium-261m)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)Half-life:74(5) sDecay constant λ:0.0093668537913506 s^-1Specific activity α:2.160345361431 × 10⁺¹⁹ Bq g^-1
583877124.71116 Ci g^-1Spin and parity:
(nuclear angular momentum)(11/2-)

Radioactive Decay

Half-life T_½ = 74(5) s respectively 7.4 × 10¹ seconds s.

Decay mode	Daughter	Probability
α	²⁵⁷No	ca. 100 %
SZ	div	?
EC β⁺	²⁶¹Lr	?

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		2.1(2) s	(3/2+)

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.

Z	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