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Isotopes of rubidium



Rubidium (Rb) has 24 isotopes, with naturally occurring rubidium being composed of just two isotopes; Rb-85 (72.2%) and the radioactive Rb-87 (27.8%). Normal mixes of rubidium are radioactive enough to fog photographic film in approximately 30 to 60 days. Standard atomic mass is 85.4678(3) u

Additional recommended knowledge

Rb-87 has a half-life of 4.88×1010 years. It readily substitutes for potassium in minerals, and is therefore fairly widespread. Rb has been used extensively in dating rocks; Rb-87 decays to stable strontium-87 by emission of a negative beta particle. 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. 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 Sr-87/Sr-86 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.

Table

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
excitation energy
71Rb 37 34 70.96532(54)# 5/2-#
72Rb 37 35 71.95908(54)# <1.5 µs 3+#
72mRb 100(100)# keV 1# µs 1-#
73Rb 37 36 72.95056(16)# <30 ns 3/2-#
74Rb 37 37 73.944265(4) 64.76(3) ms (0+)
75Rb 37 38 74.938570(8) 19.0(12) s (3/2-)
76Rb 37 39 75.9350722(20) 36.5(6) s 1(-)
76mRb 316.93(8) keV 3.050(7) µs (4+)
77Rb 37 40 76.930408(8) 3.77(4) min 3/2-
78Rb 37 41 77.928141(8) 17.66(8) min 0(+)
78mRb 111.20(10) keV 5.74(5) min 4(-)
79Rb 37 42 78.923989(6) 22.9(5) min 5/2+
80Rb 37 43 79.922519(7) 33.4(7) s 1+
80mRb 494.4(5) keV 1.6(2) µs 6+
81Rb 37 44 80.918996(6) 4.570(4) h 3/2-
81mRb 86.31(7) keV 30.5(3) min 9/2+
82Rb 37 45 81.9182086(30) 1.273(2) min 1+
82mRb 69.0(15) keV 6.472(5) h 5-
83Rb 37 46 82.915110(6) 86.2(1) d 5/2-
83mRb 42.11(4) keV 7.8(7) ms 9/2+
84Rb 37 47 83.914385(3) 33.1(1) d 2-
84mRb 463.62(9) keV 20.26(4) min 6-
85Rb 37 48 84.911789738(12) STABLE 5/2- 0.7217(2)
86Rb 37 49 85.91116742(21) 18.642(18) d 2-
86mRb 556.05(18) keV 1.017(3) min 6-
87Rb 37 50 86.909180527(13) 4.923(22)E+10 a 3/2- 0.2783(2)
88Rb 37 51 87.91131559(17) 17.773(11) min 2-
89Rb 37 52 88.912278(6) 15.15(12) min 3/2-
90Rb 37 53 89.914802(7) 158(5) s 0-
90mRb 106.90(3) keV 258(4) s 3-
91Rb 37 54 90.916537(9) 58.4(4) s 3/2(-)
92Rb 37 55 91.919729(7) 4.492(20) s 0-
93Rb 37 56 92.922042(8) 5.84(2) s 5/2-
93mRb 253.38(3) keV 57(15) µs (3/2-,5/2-)
94Rb 37 57 93.926405(9) 2.702(5) s 3(-)
95Rb 37 58 94.929303(23) 377.5(8) ms 5/2-
96Rb 37 59 95.93427(3) 202.8(33) ms 2+
96mRb 0(200)# keV 200# ms [>1 ms] 1(-#)
97Rb 37 60 96.93735(3) 169.9(7) ms 3/2+
98Rb 37 61 97.94179(5) 114(5) ms (0,1)(-#)
98mRb 290(130) keV 96(3) ms (3,4)(+#)
99Rb 37 62 98.94538(13) 50.3(7) ms (5/2+)
100Rb 37 63 99.94987(32)# 51(8) ms (3+)
101Rb 37 64 100.95320(18) 32(5) ms (3/2+)#
102Rb 37 65 101.95887(54)# 37(5) ms

Notes

  • Geologically exceptional samples are known in which the isotopic composition lies outside the reported range. The uncertainty in the atomic mass may exceed the stated value for such specimens.
  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References

  • Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
  • Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure Appl. Chem. Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).
  • Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
    • Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128 (2003).
    • National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (retrieved Sept. 2005).
    • David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.


Isotopes of krypton Isotopes of rubidium Isotopes of strontium
Index to isotope pages
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Isotopes_of_rubidium". A list of authors is available in Wikipedia.
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