Multimode operation of a cw CO₂laser with an unstable cavity in the presence of phase inhomogeneities

Abstract

An Isotopic Abundance Rule F. C. Frank has recently (1948) drawn attention to the exceptions to the rule requiring even-odd nuclei to have at least one even-even neighbour of greater abundance. To the exceptions which he quotes (lz9Xe, lr7Sm, l4@Sm, lgsPt, sssU) may be added ggRu, which is slightly more abundant than looRu (Ewald 1943). We should like to comment on these exceptions.The abundances of these lsotopes have almo3t certainly been enhanced by the decay, during geological time, of ,B;Tc (half-llfe 4 x lo6 years) and of lz9I, respectively.It seems likely (see Katcoff 1947) that lZgI has a sufficiently long half-life to have survived beyond the solidification of the earth's crust. Assuming that the excess la9Xe content o f the atmosphere is derived from aZgI originally in rocks which have by now suffered erosion, one can make a rough calculation of the half-life of lz8I. The value we obtain is about 4 X lo8 years, in approximate agreement with the value suggested by Katcoff. Experiments."Ru, leBXe.