A new laser concept for isotopically selective analysis of noble gases

Abstract

A new laser approach for the isotopically selective analysis of noble gases is presented. This approach uses noble gas atoms prepared in the 1s 5 metastable state. Hyperfine levels in the 1s 5 and 2p 9 states form two-level systems in Ne, Ar, Kr, and Xe which can be excited by a commercially available single-frequency laser system. Absorption of photons from such a laser, and the resulting momentum transfer, can be used to selectively deflect the desired isotope from a supersonic atomic beam into a detection area. Light from the same laser can then be used to selectively count atoms of the desired isotope using the photon-burst technique. Thus, enrichment and selective detection are accomplished with a single laser in a single pass through the apparatus. The problem of analyzing for85Kr in a sample of noble gases extracted from the air is examined in detail. This is a stringent test of the selectivity of this approach because85Kr has the same nuclear spin, and thus similar hyperfine splittings, as naturally occurring83Kr. Calculations indicate that isotopic selectivity of the new approach is easily adequate to resolve85Kr in a 1010 excess of83Kr.