Rubidium-85

Properties and data of the isotope ⁸⁵Rb.

Contents

General Data

Parent Nuclides

NMR Data

Isotones und Isobares

Literature

Rubidium-85 is a stable isotope of the chemical element rubidium, which has 48 neutrons in its atomic nucleus in addition to the element-specific 37 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 85. Rb-85 accounts for 72,17 % of natural terrestrial rubidium deposits.

The discovery of Rubidium-85 using a Cavendish mass spectrograph was reported in 1921 [1].

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

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:48Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.2972972972973 (= neutron-proton ratio)Neutron excess (N-Z):11Isotopic mass:84.911789736(5) u (atomic weight of Rubidium-85)Nuclide mass:84.8914931 u (calculated nuclear mass without electrons)Mass excess:-82.16733 MeVMass defect:0.793652416 u (per nucleus)Nuclear binding energy:739.28246359 MeV (per nucleus)
8.69744075 MeV (average binding energy per nucleon)Separation energy:S_N = 10.4797(22) MeV (first neutron)
S_P = 7.016966(6) 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	84.911789736(5) u	72.17(2) %	stable	5/2-
Isotope ⁸⁷Rb	86.909180529(6) u	27.83(2) %	4.97(3) × 10¹⁰ a	3/2-

NMR data

Nuclear magnetic properties and parameters 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^-1
4.12577 MHz T^-1Nuclear g-factor:g_l = 0.541224Quadrupole moment Q:+0.276(1) barn (100 fm²)Line width parameter (factor):l = 243.76 fm⁴Resonance frequency:v₀ = 4.1253 MHz at 1 TRelative Sensitivity:[related to ¹H = 1.000]:
0.01061 (H₀ = const.)
1.1304 (v₀ = const.)
0.00767 (at natural abundance)
relative receptivity as compared to ¹³C:
45.0 (at natural abundance)
62.4 (enriched)Reference compound:
(conditions)In ⁸⁵Rb-NMR, a solution of 0.01M rubidium chloride (RbCl) in deuterium oxide> (D₂O) is used for calibration.Frequency ratio:Ξ(⁸⁵Rb) = 9.654943 % [based on the reference substance]Chemical shift range:ca. 110 ppm [-80 to +30]

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.

Z	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
50	⁹⁸Sn