Cosmogenic Radionuclides

 

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A radionuclide disintegrates to another nuclide, mostly under emission of radiation. Very often the word radioisotope is used in the same meaning. The concentration of a radionuclide, or its activity, can be measured by counting its decays. It is limited by either the  difficulty to detect the emitted radiation, or by the very low count rate in case of a long half-life. AMS overcomes these difficulties by counting individual atoms.

Of special interest are long-lived cosmogenic radionuclides, which production occurs by, or under influence of, cosmic rays in the Earth's atmosphere, oceans, surface (and in extraterrestrial matter).  The table shows the radionuclides measured by AMS.

Radionuclide

Half life [year]

Production targets

10Be

1.52 0.05 million

atmosphere: O, N
surface rock: O

14C

5370 40

atmosphere: O, N,
surface rock, ice: O

26Al

0. 71 0.02 million

surface rock: Si

36Cl

0. 301 0.002 million

atmosphere: Ar
surface rock: Ca

41Ca

0. 104 0.005 million

surface rock: Ca

129I

17 1 million

stratosphere: Xe