Half-Lives of Argon-37, Argon-39, and Argon-42.

The half-lives of three argon isotopes have been carefully determined, with the following results: Ar(37), 35.1 +/- 0.1 days; Ar(39) 269 +/- 3 years; Ar(42), 32.9 +/- 1.1 years. By combining the Ar(42) value with earlier data, a cross section of 0.5 +/- 0.1 barn is calculated for the reaction, with thermal neutrons, Ar(41)(n,gamma)Ar(42).