Rubidium-81

Properties and data of the isotope ⁸¹Rb.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

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

General data

Name of the isotope:Rubidium-81; Rb-81Symbol:⁸¹Rb or 8137RbMass number A:81 (= number of nucleons)Atomic number Z:37 (= number of protons)Neutrons N:44Isotopic mass:80.918994(5) u (atomic weight of Rubidium-81)Nuclide mass:80.8986973 u (calculated nuclear mass without electrons)Mass excess:-75.4566 MeVMass defect:0.751788488 u (per nucleus)Nuclear binding energy:700.28646584 MeV (per nucleus)
8.64551192 MeV (average binding energy per nucleon)Separation energy:S_N = 11.353(5) MeV (first neutron)
S_P = 4.852(5) MeV (first proton)Half-life:4.572(4) hDecay constant λ:4.211305413142 × 10^-5 s^-1Specific activity α:3.170134300269 × 10⁺¹⁷ Bq g^-1
8567930.5412697 Ci g^-1Spin and parity:
(nuclear angular momentum)3/2-Magnetic dipole moment:μ(μ_N) = + 2.0591(14)Quadrupole moment Q:+ 0.398(23) barn (100 fm²)Nuclear g-factor:g_l = 1.3727333333333Charge radius:4.2213(51) femtometer fmYear of discovery:1949

Radioactive Decay

Half-life T_½ = 4.572(4) h (hours) respectively 1.64592 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	⁸¹Kr	100 %	2.23826 MeV

Parent Nuclides

Direct parent isotope is: ⁸¹Sr.

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
^81mRb	86.31(7) keV	30.5(3) min	9/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 44) and isobaric (same nucleon number A = 81) with Rubidium-81. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 44	Isobar A = 81
22	⁶⁶Ti
23	⁶⁷V
24	⁶⁸Cr
25	⁶⁹Mn
26	⁷⁰Fe
27	⁷¹Co
28	⁷²Ni
29	⁷³Cu	⁸¹Cu
30	⁷⁴Zn	⁸¹Zn
31	⁷⁵Ga	⁸¹Ga
32	⁷⁶Ge	⁸¹Ge
33	⁷⁷As	⁸¹As
34	⁷⁸Se	⁸¹Se
35	⁷⁹Br	⁸¹Br
36	⁸⁰Kr	⁸¹Kr
37	⁸¹Rb	⁸¹Rb
38	⁸²Sr	⁸¹Sr
39	⁸³Y	⁸¹Y
40	⁸⁴Zr	⁸¹Zr
41	⁸⁵Nb	⁸¹Nb
42	⁸⁶Mo	⁸¹Mo
43	⁸⁷Tc
44	⁸⁸Ru
45	⁸⁹Rh
46	⁹⁰Pd