Rubidium-85

Properties and data of the isotope ⁸⁵Rb.

Content

General data

Name of the isotope:Rubidium-85; Rb-85Symbol:⁸⁵Rb or 8537RbMass number A:85 (= number of nucleons)Atomic number Z:37 (= number of protons)Neutrons N:48Isotopic mass:84.91178974(3) u (atomic weight of Rubidium-85)Nuclide mass:84.8914931 u (calculated nuclear mass without electrons)Mass excess:-82.16733 MeVMass defect:0.793652412 u (per nucleus)Nuclear binding energy:739.28245986 MeV (per nucleus)
8.6974407 MeV (average binding energy per nucleon)Separation energy:S_N = 10.4797(22) MeV (first neutron)
S_P = 7.01697 MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)5/2-Magnetic dipole moment:μ(μ_N) = +1.35306(4)Charge radius:4.2036(23) femtometer fmYear of discovery:1921

Parent Nuclides

Direct parent isotopes are: ⁸⁵Kr, ⁸⁵Sr.

Occurrence

Comparison of the natural Rubidium isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):

	Atomic Mass m_a	Quantity	Half-life	Spin
Rubidium Isotopic mixture	85.4678 u	100 %
Isotope ⁸⁵Rb	84.91178974(3) u	72.17(2) %	stable	5/2-
Isotope ⁸⁷Rb	86.909180531(6) u	27.83(2) %	4.97(3) × 10¹⁰ a	3/2-

NMR data

Nuclear magnetic properties of the NMR active Nuclide ⁸⁵Rb

Isotope:⁸⁵Rb-NMRQuantity:72.17(2) %Spin:5/2-Nuclearmagnetic moment
μ/μ_N:+1.35306(4)Gyromagnetic ratio γ:2.5923 · 10⁷ rad T^-1 s^-1Nuclear g-factor:g_l = 0.541224Quadrupole moment Q:+ 0.276(1) barn (100 fm²)Resonance frequency:v₀ = 4.1253 at 1 TRelative Sensitivity:0.01061 (H₀ = const.)
1.1304 (v₀ = const.)
[related to ¹H = 1.000]

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
^85mRb	514.0065(22) keV	1.015 μs	9/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 48) and isobaric (same nucleon number A = 85) with Rubidium-85. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 48	Isobar A = 85
26	⁷⁴Fe
27	⁷⁵Co
28	⁷⁶Ni
29	⁷⁷Cu
30	⁷⁸Zn	⁸⁵Zn
31	⁷⁹Ga	⁸⁵Ga
32	⁸⁰Ge	⁸⁵Ge
33	⁸¹As	⁸⁵As
34	⁸²Se	⁸⁵Se
35	⁸³Br	⁸⁵Br
36	⁸⁴Kr	⁸⁵Kr
37	⁸⁵Rb	⁸⁵Rb
38	⁸⁶Sr	⁸⁵Sr
39	⁸⁷Y	⁸⁵Y
40	⁸⁸Zr	⁸⁵Zr
41	⁸⁹Nb	⁸⁵Nb
42	⁹⁰Mo	⁸⁵Mo
43	⁹¹Tc	⁸⁵Tc
44	⁹²Ru	⁸⁵Ru
45	⁹³Rh
46	⁹⁴Pd
47	⁹⁵Ag
48	⁹⁶Cd
49	⁹⁷In