Isotopes of rubidium
Encyclopedia
Rubidium
(Rb) has 32 isotope
s, with naturally occurring rubidium being composed of just two isotopes; 85Rb (72.2%) and the radioactive 87Rb (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.
87Rb has a half-life
of 4.92×1010 years. It readily substitutes for potassium
in mineral
s, and is therefore fairly widespread. 87Rb has been used extensively in dating rocks; 87Rb 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 pegmatite
s. 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 PET
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.
of rubidium
. Rubidium-87 was the first and the most popular atom for making Bose–Einstein condensate
s in dilute atomic gasses. Even though rubidium-85 is more abundant, rubidium-87 has a positive scattering length, which means it is mutually repulsive, at low temperatures. This prevent 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 757853 keV. Its atomic percent abundance is 27.835%, and has a half-life of .
Rubidium
Rubidium is a chemical element with the symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group. Its atomic mass is 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other elements in group 1, such as very rapid...
(Rb) has 32 isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s, with naturally occurring rubidium being composed of just two isotopes; 85Rb (72.2%) and the radioactive 87Rb (27.8%). Normal mixes of rubidium are radioactive enough to fog photographic film
Photographic film
Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...
in approximately 30 to 60 days. Standard atomic mass is 85.4678(3) u.
87Rb has a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 4.92×1010 years. It readily substitutes for potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
in mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s, and is therefore fairly widespread. 87Rb has been used extensively in dating rocks; 87Rb decays to stable strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
-87 by emission of a negative beta particle
Beta particle
Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay...
. During fractional crystallization
Fractional crystallization (geology)
Fractional crystallization is one of the most important geochemical and physical processes operating within the Earth's crust and mantle. Fractional crystallization is the removal and segregation from a melt of mineral precipitates; except in special cases, removal of the crystals changes the...
, Sr tends to become concentrated in plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
, leaving Rb in the liquid phase. Hence, the Rb/Sr ratio in residual magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
may increase over time, resulting in rocks with increasing Rb/Sr ratios with increasing differentiation. Highest ratios (10 or higher) occur in pegmatite
Pegmatite
A pegmatite is a very crystalline, intrusive igneous rock composed of interlocking crystals usually larger than 2.5 cm in size; such rocks are referred to as pegmatitic....
s. 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
Rubidium-strontium dating
The rubidium-strontium dating method is a radiometric dating technique that geologists use to determine the age of rocks.Development of this process was aided by Fritz Strassmann, who later went on to discover nuclear fission with Otto Hahn and Lise Meitner....
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 PET
Positron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...
scans to assess myocardial perfusion
Myocardial perfusion scan
Myocardial perfusion scan is a nuclear medicine procedure that illustrates the function of the heart muscle .It evaluates many heart conditions from coronary artery disease to hypertrophic cardiomyopathy and myocardial wall motion abnormalities. The function of the myocardium is also evaluated by...
. It has a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 1.273 minutes. It does not exist naturally, but can be made from the decay of 82Sr.
Rubidium-87
Rubidium-87 is an isotopeIsotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
of rubidium
Rubidium
Rubidium is a chemical element with the symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group. Its atomic mass is 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other elements in group 1, such as very rapid...
. Rubidium-87 was the first and the most popular atom for making Bose–Einstein condensate
Bose–Einstein condensate
A Bose–Einstein condensate is a state of matter of a dilute gas of weakly interacting bosons confined in an external potential and cooled to temperatures very near absolute zero . Under such conditions, a large fraction of the bosons occupy the lowest quantum state of the external potential, at...
s in dilute atomic gasses. Even though rubidium-85 is more abundant, rubidium-87 has a positive scattering length, which means it is mutually repulsive, at low temperatures. This prevent 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 757853 keV. Its atomic percent abundance is 27.835%, and has a half-life of .
Table
| nuclide symbol |
Z(p Proton The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number.... ) |
N(n Neutron The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of... ) |
isotopic mass (u) |
half-lifeBold for isotopes with half-lives longer than the age of the universe (nearly stable) | decay mode(s)Abbreviations: EC: Electron capture Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino... IT: Isomeric transition Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... |
daughter isotope(s)Bold for stable isotopes |
nuclear spin |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
|---|---|---|---|---|---|---|---|---|---|
| excitation energy | |||||||||
| 71Rb | 37 | 34 | 70.96532(54)# | p Proton decay In particle physics, proton decay is a hypothetical form of radioactive decay in which the proton decays into lighter subatomic particles, such as a neutral pion and a positron... |
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+ Beta decay In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a... |
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(-) | ||
| β+, α Alpha decay Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less... (3.8×10−7%) |
72Se | ||||||||
| 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(-) | ||||
| IT Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... (10%) |
78Rb | ||||||||
| 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+ | ||||
| β+ (2.4%) | 81Kr | ||||||||
| 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- | ||||
| IT (.33%) | 82Rb | ||||||||
| 83Rb | 37 | 46 | 82.915110(6) | 86.2(1) d | EC Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino... |
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- | ||
| β- (3.8%) | 84Sr | ||||||||
| 84mRb | 463.62(9) keV | 20.26(4) min | IT (>99.9%) | 84Rb | 6- | ||||
| β+ (<.1%) | 84Kr | ||||||||
| 85RbFission product Fission product Nuclear fission products are the atomic fragments left after a large atomic nucleus fissions. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons and a large release of energy in the form of heat , gamma rays and neutrinos. The... |
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- | ||
| EC (.0052%) | 86Kr | ||||||||
| 86mRb | 556.05(18) keV | 1.017(3) min | IT | 86Rb | 6- | ||||
| 87RbPrimordial Primordial nuclide In geochemistry and geonuclear physics, primordial nuclides or primordial isotopes are nuclides found on the earth that have existed in their current form since before Earth was formed. Only 288 such nuclides are known... radionuclide Radionuclide A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma... Used in rubidium-strontium dating Rubidium-strontium dating The rubidium-strontium dating method is a radiometric dating technique that geologists use to determine the age of rocks.Development of this process was aided by Fritz Strassmann, who later went on to discover nuclear fission with Otto Hahn and Lise Meitner.... |
37 | 50 | 86.909180527(13) | 4.923(22)×1010 a | 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- | ||||
| IT (2.6%) | 90 Rb | ||||||||
| 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- | ||
| β-, n Neutron emission Neutron emission is a type of radioactive decay of atoms containing excess neutrons, in which a neutron is simply ejected from the nucleus. Two examples of isotopes which emit neutrons are helium-5 and beryllium-13... (.0107%) |
91Sr | ||||||||
| 93Rb | 37 | 56 | 92.922042(8) | 5.84(2) s | β- (98.65%) | 93Sr | 5/2- | ||
| β-, n (1.35%) | 92Sr | ||||||||
| 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(-) | ||
| β-, n (10.01%) | 93Sr | ||||||||
| 95Rb | 37 | 58 | 94.929303(23) | 377.5(8) ms | β- (91.27%) | 95Sr | 5/2- | ||
| β-, n (8.73%) | 94Sr | ||||||||
| 96Rb | 37 | 59 | 95.93427(3) | 202.8(33) ms | β- (86.6%) | 96Sr | 2+ | ||
| β-, n (13.4%) | 95Sr | ||||||||
| 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+ | ||
| β-, n (25.7%) | 96Sr | ||||||||
| 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+) | ||
| β-, n (15.9%) | 98Sr | ||||||||
| 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+)# | ||
| β-, n (31%) | 100Sr | ||||||||
| 102Rb | 37 | 65 | 101.95887(54)# | 37(5) ms | β- (82%) | 102Sr | |||
| β-, n (18%) | 101Sr | ||||||||