Isotopes of rubidium

Rubidium (₃₇Rb) has 35 known isotopes, from ⁷²Rb to ¹⁰⁶Rb, with naturally occurring rubidium composed of two: stable ⁸⁵Rb (72.2%) and radioactive ⁸⁷Rb (27.8%). The primordial radionuclide ⁸⁷Rb has a half-life of , beta decaying to stable ⁸⁷Sr. It is, as the element is, widespread on Earth as rubidium readily substitutes for potassium in all minerals. The decay of ⁸⁷Rb has been used extensively in dating rocks; 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 32.82 days, and ⁸⁶Rb with a half-life of 18.645 days. All other radioisotopes have half-lives less than a day, most less than 20 minutes. Of the isomeric states the most stable is ^82mRb at 6.472 hours.

The ground state of ⁸²Rb has a much shorter half-life of 1.2575 minutes. It is used medically in some cardiac positron emission tomography scans to assess myocardial perfusion. It is synthesized through the longer-lived ⁸²Sr, made in a cyclotron, though a generator. It may be administered as the chloride.

List of isotopes

|-id=Rubidium-72 | ⁷²Rb | style="text-align:right" | 37 | style="text-align:right" | 35 | 71.95885(54)# | 103(22)&nbsp;ns | p | ⁷¹Kr | 1+# | | |-id=Rubidium-73 | ⁷³Rb | style="text-align:right" | 37 | style="text-align:right" | 36 | 72.950605(44) | <81&nbsp;ns | p | ⁷²Kr | 3/2−# | | |-id=Rubidium-74 | ⁷⁴Rb | style="text-align:right" | 37 | style="text-align:right" | 37 | 73.9442659(32) | 64.78(3)&nbsp;ms | β⁺ | ⁷⁴Kr | 0+ | | |-id=Rubidium-75 | ⁷⁵Rb | style="text-align:right" | 37 | style="text-align:right" | 38 | 74.9385732(13) | 19.0(12)&nbsp;s | β⁺ | ⁷⁵Kr | 3/2− | | |-id=Rubidium-76 | rowspan=2|⁷⁶Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 39 | rowspan=2|75.9350730(10) | rowspan=2|36.5(6)&nbsp;s | β⁺ | ⁷⁶Kr | rowspan=2|1− | rowspan=2| | rowspan=2| |- | β⁺, α (3.8×10^{−7}%) | ⁷²Se |-id=Rubidium-76m | style="text-indent:1em" | ^76mRb | colspan="3" style="text-indent:2em" | 316.93(8)&nbsp;keV | 3.050(7)&nbsp;μs | IT | ⁷⁶Rb | (4+) | | |-id=Rubidium-77 | ⁷⁷Rb | style="text-align:right" | 37 | style="text-align:right" | 40 | 76.9304016(14) | 3.78(4)&nbsp;min | β⁺ | ⁷⁷Kr | 3/2− | | |-id=Rubidium-78 | ⁷⁸Rb | style="text-align:right" | 37 | style="text-align:right" | 41 | 77.9281419(35) | 17.66(3)&nbsp;min | β⁺ | ⁷⁸Kr | 0+ | | |-id=Rubidium-78m1 | style="text-indent:1em" | ^78m1Rb | colspan="3" style="text-indent:2em" | 46.84(14)&nbsp;keV | 910(40)&nbsp;ns | IT | ⁷⁸Rb | (1−) | | |-id=Rubidium-78m2 | rowspan=2 style="text-indent:1em" | ^78m2Rb | rowspan=2 colspan="3" style="text-indent:2em" | 111.19(22)&nbsp;keV | rowspan=2|5.74(3)&nbsp;min | β⁺ (91%) | ⁷⁸Kr | rowspan=2|4− | rowspan=2| | rowspan=2| |- | IT (9%) | ⁷⁸Rb |-id=Rubidium-79 | ⁷⁹Rb | style="text-align:right" | 37 | style="text-align:right" | 42 | 78.9239901(21) | 22.9(5)&nbsp;min | β⁺ | ⁷⁹Kr | 5/2+ | | |-id=Rubidium-80 | ⁸⁰Rb | style="text-align:right" | 37 | style="text-align:right" | 43 | 79.9225164(20) | 33.4(7)&nbsp;s | β⁺ | ⁸⁰Kr | 1+ | | |-id=Rubidium-80m | style="text-indent:1em" | ^80mRb | colspan="3" style="text-indent:2em" | 493.9(5)&nbsp;keV | 1.63(4)&nbsp;μs | IT | ⁸⁰Rb | (6+) | | |-id=Rubidium-81 | ⁸¹Rb | style="text-align:right" | 37 | style="text-align:right" | 44 | 80.9189939(53) | 4.572(4)&nbsp;h | β⁺ | ⁸¹Kr | 3/2− | | |-id=Rubidium-81m | rowspan=2 style="text-indent:1em" | ^81mRb | rowspan=2 colspan="3" style="text-indent:2em" | 86.31(7)&nbsp;keV | rowspan=2|30.5(3)&nbsp;min | IT (97.6%) | ⁸¹Rb | rowspan=2|9/2+ | rowspan=2| | rowspan=2| |- | β⁺ (2.4%) | ⁸¹Kr |- | ⁸²Rb | style="text-align:right" | 37 | style="text-align:right" | 45 | 81.9182090(32) | 1.2575(2)&nbsp;min | β⁺ | ⁸²Kr | 1+ | | |-id=Rubidium-82m | style="text-indent:1em" | ^82mRb | colspan="3" style="text-indent:2em" | 69.0(15)&nbsp;keV | 6.472(6)&nbsp;h | β⁺ | ⁸²Kr | 5− | | |-id=Rubidium-83 | ⁸³Rb | style="text-align:right" | 37 | style="text-align:right" | 46 | 82.9151142(25) | 86.2(1)&nbsp;d | EC | ⁸³Kr | 5/2− | | |-id=Rubidium-83m | style="text-indent:1em" | ^83mRb | colspan="3" style="text-indent:2em" | 42.0780(20)&nbsp;keV | 7.8(7)&nbsp;ms | IT | ⁸³Rb | 9/2+ | | |-id=Rubidium-84 | rowspan=2|⁸⁴Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 47 | rowspan=2|83.9143752(24) | rowspan=2|32.82(7)&nbsp;d | β⁺ (96.1%) | ⁸⁴Kr | rowspan=2|2− | rowspan=2| | rowspan=2| |- | β^− (3.9%) | ⁸⁴Sr |-id=Rubidium-84m | style="text-indent:1em" | ^84mRb | colspan="3" style="text-indent:2em" | 463.59(8)&nbsp;keV | 20.26(4)&nbsp;min | IT | ⁸⁴Rb | 6− | | |-id=Rubidium-85 | ⁸⁵Rb | style="text-align:right" | 37 | style="text-align:right" | 48 | 84.9117897360(54) | colspan=3 align=center|Stable | 5/2− | 0.7217(2) | |-id=Rubidium-85m | style="text-indent:1em" | ^85mRb | colspan="3" style="text-indent:2em" | 514.0065(22)&nbsp;keV | 1.015(1)&nbsp;μs | IT | ⁸⁵Rb | 9/2+ | | |-id=Rubidium-86 | rowspan=2|⁸⁶Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 49 | rowspan=2|85.91116744(21) | rowspan=2|18.645(8)&nbsp;d | β^− (99.9948%) | ⁸⁶Sr | rowspan=2|2− | rowspan=2| | rowspan=2| |- | EC (0.0052%) | ⁸⁶Kr |-id=Rubidium-86m | style="text-indent:1em" | ^86mRb | colspan="3" style="text-indent:2em" | 556.05(18)&nbsp;keV | 1.017(3)&nbsp;min | IT | ⁸⁶Rb | 6− | | |- | ⁸⁷Rb | style="text-align:right" | 37 | style="text-align:right" | 50 | 86.909180529(6) | 4.97(3)×10¹⁰&nbsp;y | β^− | ⁸⁷Sr | 3/2− | 0.2783(2) | |-id=Rubidium-88 | ⁸⁸Rb | style="text-align:right" | 37 | style="text-align:right" | 51 | 87.91131559(17) | 17.78(3)&nbsp;min | β^− | ⁸⁸Sr | 2− | | |-id=Rubidium-88m | style="text-indent:1em" | ^88mRb | colspan="3" style="text-indent:2em" | 1373.8(3)&nbsp;keV | 123(13)&nbsp;ns | IT | ⁸⁸Rb | (7+) | | |-id=Rubidium-89 | ⁸⁹Rb | style="text-align:right" | 37 | style="text-align:right" | 52 | 88.9122781(58) | 15.32(10)&nbsp;min | β^− | ⁸⁹Sr | 3/2− | | |-id=Rubidium-90 | ⁹⁰Rb | style="text-align:right" | 37 | style="text-align:right" | 53 | 89.9147976(69) | 158(5)&nbsp;s | β^− | ⁹⁰Sr | 0− | | |-id=Rubidium-90m | rowspan=2 style="text-indent:1em" | ^90mRb | rowspan=2 colspan="3" style="text-indent:2em" | 106.90(3)&nbsp;keV | rowspan=2|258(4)&nbsp;s | β^− (97.4%) | ⁹⁰Sr | rowspan=2|3− | rowspan=2| | rowspan=2| |- | IT (2.6%) | ⁹⁰ Rb |-id=Rubidium-91 | ⁹¹Rb | style="text-align:right" | 37 | style="text-align:right" | 54 | 90.9165373(84) | 58.2(3)&nbsp;s | β^− | ⁹¹Sr | 3/2− | | |-id=Rubidium-92 | rowspan=2|⁹²Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 55 | rowspan=2|91.9197285(66) | rowspan=2|4.48(3)&nbsp;s | β^− (99.99%) | ⁹²Sr | rowspan=2|0− | rowspan=2| | rowspan=2| |- | β^−, n (0.0107%) | ⁹¹Sr |-id=Rubidium-93 | rowspan=2|⁹³Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 56 | rowspan=2|92.9220393(84) | rowspan=2|5.84(2)&nbsp;s | β^− (98.61%) | ⁹³Sr | rowspan=2|5/2− | rowspan=2| | rowspan=2| |- | β^−, n (1.39%) | ⁹²Sr |-id=Rubidium-93m | style="text-indent:1em" | ^93mRb | colspan="3" style="text-indent:2em" | 4423.1(15)&nbsp;keV | 111(11)&nbsp;ns | IT | ⁹³Rb | (27/2−) | | |-id=Rubidium-94 | rowspan=2|⁹⁴Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 57 | rowspan=2|93.9263948(22) | rowspan=2|2.702(5)&nbsp;s | β^− (89.7%) | ⁹⁴Sr | rowspan=2|3− | rowspan=2| | rowspan=2| |- | β^−, n (10.3%) | ⁹³Sr |-id=Rubidium-94m1 | style="text-indent:1em" | ^94m1Rb | colspan="3" style="text-indent:2em" | 104.2(2)&nbsp;keV | 130(15)&nbsp;ns | IT | ⁹⁴Rb | (0−) | | |-id=Rubidium-94m2 | style="text-indent:1em" | ^94m2Rb | colspan="3" style="text-indent:2em" | 2074.9(14)&nbsp;keV | 107(16)&nbsp;ns | IT | ⁹⁴Rb | (10−) | | |-id=Rubidium-95 | rowspan=2|⁹⁵Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 58 | rowspan=2|94.929264(22) | rowspan=2|377.7(8)&nbsp;ms | β^− (91.3%) | ⁹⁵Sr | rowspan=2|5/2− | rowspan=2| | rowspan=2| |- | β^−, n (8.7%) | ⁹⁴Sr |-id=Rubidium-95m | style="text-indent:1em" | ^95mRb | colspan="3" style="text-indent:2em" | 835.0(6)&nbsp;keV | <500&nbsp;ns | IT | ⁹⁵Rb | 9/2+# | | |-id=Rubidium-96 | rowspan=2|⁹⁶Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 59 | rowspan=2|95.9341334(36) | rowspan=2|201.5(9)&nbsp;ms | β^− (86.3%) | ⁹⁶Sr | rowspan=2|2− | rowspan=2| | rowspan=2| |- | β^−, n (13.7%) | ⁹⁵Sr |-id=Rubidium-96m1 | style="text-indent:1em" | ^96m1Rb | colspan="3" style="text-indent:2em" | 0(200)#&nbsp;keV | 200#&nbsp;ms<br />[>1&nbsp;ms] | | | 1(+#) | | |-id=Rubidium-96m2 | style="text-indent:1em" | ^96m2Rb | colspan="3" style="text-indent:2em" | 1134.6(11)&nbsp;keV | 1.80(4)&nbsp;μs | IT | ⁹⁶Rb | (10−) | | |-id=Rubidium-97 | rowspan=2|⁹⁷Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 60 | rowspan=2|96.9371771(21) | rowspan=2|169.1(6)&nbsp;ms | β^− (74.5%) | ⁹⁷Sr | rowspan=2|3/2+ | rowspan=2| | rowspan=2| |- | β^−, n (25.5%) | ⁹⁶Sr |-id=Rubidium-97m | style="text-indent:1em" | ^97mRb | colspan="3" style="text-indent:2em" | 76.6(2)&nbsp;keV | 5.7(6)&nbsp;μs | IT | ⁹⁷Rb | (1/2,3/2)− | | |-id=Rubidium-98 | rowspan=3|⁹⁸Rb | rowspan=3 style="text-align:right" | 37 | rowspan=3 style="text-align:right" | 61 | rowspan=3|97.941632(17) | rowspan=3|115(6)&nbsp;ms | β^−(85.65%) | ⁹⁸Sr | rowspan=3|(0−) | rowspan=3| | rowspan=3| |- | β^−, n (14.3%) | ⁹⁷Sr |- | β^−, 2n (0.054%) | ⁹⁶Sr |-id=Rubidium-98m1 | style="text-indent:1em" | ^98m1Rb | colspan="3" style="text-indent:2em" | 73(26)&nbsp;keV | 96(3)&nbsp;ms | β^− | ⁹⁸Sr | (3+) | | |-id=Rubidium-98m2 | style="text-indent:1em" | ^98m2Rb | colspan="3" style="text-indent:2em" | 178.5(4)&nbsp;keV | 358(7)&nbsp;ns | IT | ⁹⁸Rb | (2−) | | |-id=Rubidium-99 | rowspan=2|⁹⁹Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 62 | rowspan=2|98.9451192(43) | rowspan=2|54(4)&nbsp;ms | β^− (82.7%) | ⁹⁹Sr | rowspan=2|(3/2+) | rowspan=2| | rowspan=2| |- | β^−, n (17.3%) | ⁹⁸Sr |-id=Rubidium-100 | rowspan=3|¹⁰⁰Rb | rowspan=3 style="text-align:right" | 37 | rowspan=3 style="text-align:right" | 63 | rowspan=3|99.950332(14) | rowspan=3|51.3(16)&nbsp;ms | β^− (94.3%) | ¹⁰⁰Sr | rowspan=3|4−# | rowspan=3| | rowspan=3| |- | β^−, n (5.6%) | ⁹⁹Sr |- | β^−, 2n (0.15%) | ⁹⁸Sr |-id=Rubidium-101 | rowspan=2|¹⁰¹Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 64 | rowspan=2|100.954302(22) | rowspan=2|31.8(33)&nbsp;ms | β^− (72%) | ¹⁰¹Sr | rowspan=2|3/2+# | rowspan=2| | rowspan=2| |- | β^−, n (28%) | ¹⁰⁰Sr |-id=Rubidium-102 | rowspan=2|¹⁰²Rb | rowspan=2 style="text-align:right" | 37 | rowspan=2 style="text-align:right" | 65 | rowspan=2|101.960008(89) | rowspan=2|37(4)&nbsp;ms | β^−, n (65%) | ¹⁰¹Sr | rowspan=2| (4+) | rowspan=2| | rowspan=2| |- | β^− (35%) | ¹⁰²Sr |-id=Rubidium-103 | ¹⁰³Rb | style="text-align:right" | 37 | style="text-align:right" | 66 | 102.96440(43)# | 26(11)&nbsp;ms | β^− | ¹⁰³Sr | 3/2+# | | |-id=Rubidium-104 | ¹⁰⁴Rb | style="text-align:right" | 37 | style="text-align:right" | 67 | 103.97053(54)# | 35#&nbsp;ms<br />[>550&nbsp;ns] | | | | | |-id=Rubidium-105 | ¹⁰⁵Rb | style="text-align:right" | 37 | style="text-align:right" | 68 | | | | | | | |-id=Rubidium-106 | ¹⁰⁶Rb | style="text-align:right" | 37 | style="text-align:right" | 69 | | | | | | |

Rubidium-87

Rubidium-87 is one of two natural isotopes of rubidium, with an abundance of 27.835%, and a half-life of , with beta decay to strontium-87, a stable isotope.

During fractional crystallization of igneous rock, 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. The age of a mineral, if it has not been subsequently altered, is determined by the parent and daughter abundances, the half-life, and the original content of the daughter, here strontium; the ⁸⁷Sr/⁸⁶Sr ratio helps in its calculation. See rubidium-strontium dating for further detail.

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.

See also

Daughter products other than rubidium

• Isotopes of strontium
• Isotopes of krypton
• Isotopes of selenium

References