Tracers argon isotopes

Argon-40 [7440-37-1] is created by the decay of potassium-40. The various isotopes of radon, all having short half-Hves, are formed by the radioactive decay of radium, actinium, and thorium. Krypton and xenon are products of uranium and plutonium fission, and appreciable quantities of both are evolved during the reprocessing of spent fuel elements from nuclear reactors (qv) (see Radioactive tracers). 

The name comes from the Greek xenon, meaning stranger. Xenon was discovered by William Ramsay (1852-1916) and Morris W. Travers (1872-1961) in 1898 as part of their search for a noble gas between helium and argon. It is present as a trace element in atmospheric air. It is the heaviest of the noble gases. It is used commercially in specialty lamps and lasers, as well as in sophisticated laboratory equipment such as bubble chambers and as a radioactive isotope used as a tracer. 

In Isotopes of noble gases as tracers in enviromnental studies. IAEA, Vieima, p 73-85 Loosli HH, Lehmaim BE, Balderer W (1989) Aigon-39, argon-37 and kiypton-85 isotopes in Stripa ground waters. Geochim Cosmochim Acta 53 1825-1829... 

Fig. 6 Normalised experimental (symbols) and simulated (solid lines) responses of a) argon tracer, b) gas phase methane (CD bands) and c) hydroxyl groups (OD bands) after the isotopic switch CHi/He -> CDjnt at 1013 K over 3Mo/HZSM-5.

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