Isotopes of rubidium

Isotopes of rubidium (₃₇Rb)
γ	–
β+	84Kr
γ	–
β−	84Sr
γ	–
Standard atomic weight Ar°(Rb)
	85.4678±0.0003; 85.468±0.001 (abridged);
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Rubidium (₃₇Rb) has 36 isotopes, with naturally occurring rubidium being composed of just two isotopes; ⁸⁵Rb (72.2%) and the radioactive ⁸⁷Rb (27.8%).

⁸⁷Rb has a half-life of 4.92×10¹⁰ years. It readily substitutes for potassium in minerals, and is therefore fairly widespread. ⁸⁷Rb has been used extensively in dating rocks; ⁸⁷Rb decays to stable strontium-87 by emission of a beta particle (an electron ejected from the nucleus). During fractional crystallization, Sr tends to become concentrated in plagioclase, leaving Rb in the liquid phase. Hence, the Rb/Sr ratio in residual magma may increase over time, resulting in rocks with increasing Rb/Sr ratios with increasing differentiation. The highest ratios (10 or higher) occur in pegmatites. If the initial amount of Sr is known or can be extrapolated, the age can be determined by measurement of the Rb and Sr concentrations and the ⁸⁷Sr/⁸⁶Sr ratio. The dates indicate the true age of the minerals only if the rocks have not been subsequently altered. See rubidium–strontium dating for a more detailed discussion.

Other than ⁸⁷Rb, the longest-lived radioisotopes are ⁸³Rb with a half-life of 86.2 days, ⁸⁴Rb with a half-life of 33.1 days, and ⁸⁶Rb with a half-life of 18.642 days. All other radioisotopes have half-lives less than a day.

⁸²Rb is used in some cardiac positron emission tomography scans to assess myocardial perfusion. It has a half-life of 1.273 minutes. It does not exist naturally, but can be made from the decay of ⁸²Sr.

List of isotopes

Nuclide ^{[n 1]}	Z	N	Isotopic mass (Da) ^{[n 2]}^{[n 3]}	Half-life ^{[n 4]}^{[n 5]}	Decay mode ^{[n 6]}	Daughter isotope ^{[n 7]}^{[n 8]}	Spin and parity ^{[n 9]}^{[n 5]}	Natural abundance (mole fraction)
Nuclide ^{[n 1]}	Excitation energy^{[n 5]}			Half-life ^{[n 4]}^{[n 5]}	Decay mode ^{[n 6]}	Daughter isotope ^{[n 7]}^{[n 8]}	Spin and parity ^{[n 9]}^{[n 5]}	Normal proportion	Range of variation
⁷¹Rb	37	34	70.96532(54)#		p	⁷⁰Kr	5/2−#
⁷²Rb	37	35	71.95908(54)#	<1.5 μs	p	⁷¹Kr	3+#
^72mRb	100(100)# keV			1# μs	p	⁷¹Kr	1−#
⁷³Rb	37	36	72.95056(16)#	<30 ns	p	⁷²Kr	3/2−#
⁷⁴Rb	37	37	73.944265(4)	64.76(3) ms	β⁺	⁷⁴Kr	(0+)
⁷⁵Rb	37	38	74.938570(8)	19.0(12) s	β⁺	⁷⁵Kr	(3/2−)
⁷⁶Rb	37	39	75.9350722(20)	36.5(6) s	β⁺	⁷⁶Kr	1(−)
⁷⁶Rb	37	39	75.9350722(20)	36.5(6) s	β⁺, α (3.8×10⁻⁷%)	⁷²Se	1(−)
^76mRb	316.93(8) keV			3.050(7) μs			(4+)
⁷⁷Rb	37	40	76.930408(8)	3.77(4) min	β⁺	⁷⁷Kr	3/2−
⁷⁸Rb	37	41	77.928141(8)	17.66(8) min	β⁺	⁷⁸Kr	0(+)
^78mRb	111.20(10) keV			5.74(5) min	β⁺ (90%)	⁷⁸Kr	4(−)
^78mRb	111.20(10) keV			5.74(5) min	IT (10%)	⁷⁸Rb	4(−)
⁷⁹Rb	37	42	78.923989(6)	22.9(5) min	β⁺	⁷⁹Kr	5/2+
⁸⁰Rb	37	43	79.922519(7)	33.4(7) s	β⁺	⁸⁰Kr	1+
^80mRb	494.4(5) keV			1.6(2) μs			6+
⁸¹Rb	37	44	80.918996(6)	4.570(4) h	β⁺	⁸¹Kr	3/2−
^81mRb	86.31(7) keV			30.5(3) min	IT (97.6%)	⁸¹Rb	9/2+
^81mRb	86.31(7) keV			30.5(3) min	β⁺ (2.4%)	⁸¹Kr	9/2+
⁸²Rb	37	45	81.9182086(30)	1.273(2) min	β⁺	⁸²Kr	1+
^82mRb	69.0(15) keV			6.472(5) h	β⁺ (99.67%)	⁸²Kr	5−
^82mRb	69.0(15) keV			6.472(5) h	IT (.33%)	⁸²Rb	5−
⁸³Rb	37	46	82.915110(6)	86.2(1) d	EC	⁸³Kr	5/2−
^83mRb	42.11(4) keV			7.8(7) ms	IT	⁸³Rb	9/2+
⁸⁴Rb	37	47	83.914385(3)	33.1(1) d	β⁺ (96.2%)	⁸⁴Kr	2−
⁸⁴Rb	37	47	83.914385(3)	33.1(1) d	β⁻ (3.8%)	⁸⁴Sr	2−
^84mRb	463.62(9) keV			20.26(4) min	IT (>99.9%)	⁸⁴Rb	6−
^84mRb	463.62(9) keV			20.26(4) min	β⁺ (<.1%)	⁸⁴Kr	6−
⁸⁵Rb^{[n 10]}	37	48	84.911789738(12)	Stable			5/2−	0.7217(2)
⁸⁶Rb	37	49	85.91116742(21)	18.642(18) d	β⁻ (99.9948%)	⁸⁶Sr	2−
⁸⁶Rb	37	49	85.91116742(21)	18.642(18) d	EC (.0052%)	⁸⁶Kr	2−
^86mRb	556.05(18) keV			1.017(3) min	IT	⁸⁶Rb	6−
⁸⁷Rb^{[n 11]}^{[n 12]}^{[n 10]}	37	50	86.909180527(13)	4.923(22)×10¹⁰ y	β⁻	⁸⁷Sr	3/2−	0.2783(2)
⁸⁸Rb	37	51	87.91131559(17)	17.773(11) min	β⁻	⁸⁸Sr	2−
⁸⁹Rb	37	52	88.912278(6)	15.15(12) min	β⁻	⁸⁹Sr	3/2−
⁹⁰Rb	37	53	89.914802(7)	158(5) s	β⁻	⁹⁰Sr	0−
^90mRb	106.90(3) keV			258(4) s	β⁻ (97.4%)	⁹⁰Sr	3−
^90mRb	106.90(3) keV			258(4) s	IT (2.6%)	⁹⁰ Rb	3−
⁹¹Rb	37	54	90.916537(9)	58.4(4) s	β⁻	⁹¹Sr	3/2(−)
⁹²Rb	37	55	91.919729(7)	4.492(20) s	β⁻ (99.98%)	⁹²Sr	0−
⁹²Rb	37	55	91.919729(7)	4.492(20) s	β⁻, n (.0107%)	⁹¹Sr	0−
⁹³Rb	37	56	92.922042(8)	5.84(2) s	β⁻ (98.65%)	⁹³Sr	5/2−
⁹³Rb	37	56	92.922042(8)	5.84(2) s	β⁻, n (1.35%)	⁹²Sr	5/2−
^93mRb	253.38(3) keV			57(15) μs			(3/2−,5/2−)
⁹⁴Rb	37	57	93.926405(9)	2.702(5) s	β⁻ (89.99%)	⁹⁴Sr	3(−)
⁹⁴Rb	37	57	93.926405(9)	2.702(5) s	β⁻, n (10.01%)	⁹³Sr	3(−)
⁹⁵Rb	37	58	94.929303(23)	377.5(8) ms	β⁻ (91.27%)	⁹⁵Sr	5/2−
⁹⁵Rb	37	58	94.929303(23)	377.5(8) ms	β⁻, n (8.73%)	⁹⁴Sr	5/2−
⁹⁶Rb	37	59	95.93427(3)	202.8(33) ms	β⁻ (86.6%)	⁹⁶Sr	2+
⁹⁶Rb	37	59	95.93427(3)	202.8(33) ms	β⁻, n (13.4%)	⁹⁵Sr	2+
^96mRb	0(200)# keV			200# ms [>1 ms]	β⁻	⁹⁶Sr	1(−#)
					IT	⁹⁶Rb
					β⁻, n	⁹⁵Sr
⁹⁷Rb	37	60	96.93735(3)	169.9(7) ms	β⁻ (74.3%)	⁹⁷Sr	3/2+
⁹⁷Rb	37	60	96.93735(3)	169.9(7) ms	β⁻, n (25.7%)	⁹⁶Sr	3/2+
⁹⁸Rb	37	61	97.94179(5)	114(5) ms	β⁻(86.14%)	⁹⁸Sr	(0,1)(−#)
					β⁻, n (13.8%)	⁹⁷Sr
					β⁻, 2n (.051%)	⁹⁶Sr
^98mRb	290(130) keV			96(3) ms	β⁻	⁹⁷Sr	(3,4)(+#)
⁹⁹Rb	37	62	98.94538(13)	50.3(7) ms	β⁻ (84.1%)	⁹⁹Sr	(5/2+)
⁹⁹Rb	37	62	98.94538(13)	50.3(7) ms	β⁻, n (15.9%)	⁹⁸Sr	(5/2+)
¹⁰⁰Rb	37	63	99.94987(32)#	51(8) ms	β⁻ (94.25%)	¹⁰⁰Sr	(3+)
					β⁻, n (5.6%)	⁹⁹Sr
					β⁻, 2n (.15%)	⁹⁸Sr
¹⁰¹Rb	37	64	100.95320(18)	32(5) ms	β⁻ (69%)	¹⁰¹Sr	(3/2+)#
¹⁰¹Rb	37	64	100.95320(18)	32(5) ms	β⁻, n (31%)	¹⁰⁰Sr	(3/2+)#
¹⁰²Rb	37	65	101.95887(54)#	37(5) ms	β⁻ (82%)	¹⁰²Sr
¹⁰²Rb	37	65	101.95887(54)#	37(5) ms	β⁻, n (18%)	¹⁰¹Sr
¹⁰³Rb^[4]	37	66		26 ms	β⁻	¹⁰³Sr
¹⁰⁴Rb^[5]	37	67		35# ms (>550 ns)	β⁻?	¹⁰⁴Sr
¹⁰⁵Rb^[6]	37	68
¹⁰⁶Rb^[6]	37	69
This table header & footer: view

^ ^mRb – Excited nuclear isomer.
^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
^ Bold half-life – nearly stable, half-life longer than age of universe.
^ ^a ^b ^c # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
^ Modes of decay:

EC: Electron capture

IT: Isomeric transition

n: Neutron emission

p: Proton emission
^ Bold italics symbol as daughter – Daughter product is nearly stable.
^ Bold symbol as daughter – Daughter product is stable.
^ ( ) spin value – Indicates spin with weak assignment arguments.
^ ^a ^b Fission product
^ Primordial radionuclide
^ Used in rubidium–strontium dating

Rubidium-87

Rubidium-87 was the first and the most popular atom for making Bose–Einstein condensates in dilute atomic gases. Even though rubidium-85 is more abundant, rubidium-87 has a positive scattering length, which means it is mutually repulsive, at low temperatures. This prevents a collapse of all but the smallest condensates. It is also easy to evaporatively cool, with a consistent strong mutual scattering. There is also a strong supply of cheap uncoated diode lasers typically used in CD writers, which can operate at the correct wavelength.

Rubidium-87 has an atomic mass of 86.9091835 u, and a binding energy of 757,853 keV. Its atomic percent abundance is 27.835%, and has a half-life of 4.92×10¹⁰ years.

References

^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
^ "Standard Atomic Weights: Rubidium". CIAAW. 1969.
^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
^ Ohnishi, Tetsuya; Kubo, Toshiyuki; Kusaka, Kensuke; et al. (2010). "Identification of 45 New Neutron-Rich Isotopes Produced by In-Flight Fission of a ²³⁸U Beam at 345 MeV/nucleon". J. Phys. Soc. Jpn. 79 (7). Physical Society of Japan: 073201. arXiv:1006.0305. Bibcode:2010JPSJ...79g3201T. doi:10.1143/JPSJ.79.073201.
^ Shimizu, Yohei; et al. (2018). "Observation of New Neutron-rich Isotopes among Fission Fragments from In-flight Fission of 345 MeV/Nucleon 238U: Search for New Isotopes Conducted Concurrently with Decay Measurement Campaigns". Journal of the Physical Society of Japan. 87 (1): 014203. Bibcode:2018JPSJ...87a4203S. doi:10.7566/JPSJ.87.014203.
^ ^a ^b Sumikama, T.; et al. (2021). "Observation of new neutron-rich isotopes in the vicinity of 110Zr". Physical Review C. 103 (1): 014614. Bibcode:2021PhRvC.103a4614S. doi:10.1103/PhysRevC.103.014614. hdl:10261/260248. S2CID 234019083.

Isotope masses from:
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
Isotopic compositions and standard atomic masses from:
- de Laeter, John Robert; Böhlke, John Karl; De Bièvre, Paul; Hidaka, Hiroshi; Peiser, H. Steffen; Rosman, Kevin J. R.; Taylor, Philip D. P. (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- Wieser, Michael E. (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
"News & Notices: Standard Atomic Weights Revised". International Union of Pure and Applied Chemistry. 19 October 2005.
Half-life, spin, and isomer data selected from the following sources.
- Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", Nuclear Physics A, 729: 3–128, Bibcode:2003NuPhA.729....3A, doi:10.1016/j.nuclphysa.2003.11.001
- National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
- Holden, Norman E. (2004). "11. Table of the Isotopes". In Lide, David R. (ed.). CRC Handbook of Chemistry and Physics (85th ed.). Boca Raton, Florida: CRC Press. ISBN 978-0-8493-0485-9.

[4] Rb – Excited nuclear isomer.

[5] ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.

[TMS-6] # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).

[7] Bold half-life – nearly stable, half-life longer than age of universe.

[TNN-8] # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).

[9] Modes of decay:

EC: Electron capture

IT: Isomeric transition

n: Neutron emission

p: Proton emission

[10] Bold italics symbol as daughter – Daughter product is nearly stable.

[11] Bold symbol as daughter – Daughter product is stable.

[12] ( ) spin value – Indicates spin with weak assignment arguments.

[FP-13] Fission product

[14] Primordial radionuclide

[15] Used in rubidium–strontium dating

[NUBASE2020-1] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.

[2] "Standard Atomic Weights: Rubidium". CIAAW. 1969.

[CIAAW2021-3] Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.

[Ohnishi-16] Ohnishi, Tetsuya; Kubo, Toshiyuki; Kusaka, Kensuke; et al. (2010). "Identification of 45 New Neutron-Rich Isotopes Produced by In-Flight Fission of a ²³⁸U Beam at 345 MeV/nucleon". J. Phys. Soc. Jpn. 79 (7). Physical Society of Japan: 073201. arXiv:1006.0305. Bibcode:2010JPSJ...79g3201T. doi:10.1143/JPSJ.79.073201.

[Shimizu-17] Shimizu, Yohei; et al. (2018). "Observation of New Neutron-rich Isotopes among Fission Fragments from In-flight Fission of 345 MeV/Nucleon 238U: Search for New Isotopes Conducted Concurrently with Decay Measurement Campaigns". Journal of the Physical Society of Japan. 87 (1): 014203. Bibcode:2018JPSJ...87a4203S. doi:10.7566/JPSJ.87.014203.

[Sumikama(Rb)-18] Sumikama, T.; et al. (2021). "Observation of new neutron-rich isotopes in the vicinity of 110Zr". Physical Review C. 103 (1): 014614. Bibcode:2021PhRvC.103a4614S. doi:10.1103/PhysRevC.103.014614. hdl:10261/260248. S2CID 234019083.

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