Isotope separation by selective laser-assisted repression of condensation in supersonic free jets

Separation of gaseous molecules in supersonic free jets by laser-assisted selective condensation repression is reviewed. It is shown to have evolved from Becker's pre-laser "Nozzle Separator" concept of 1956 by simple addition of a laser. Although useful to separate mixtures of dissimilar gases, the technique has mostly been applied to isotope separation. To enrich iSF₆ for example, SF₆ mixed with an inert carrier gas G is expanded through a nozzle into a low-pressure chamber, where it forms a supersonic jet and creates van der Waals hetero- or homodimers SF₆:G and SF₆:SF₆ if T < 150 K. By coaxial or cross irradiation of the free jet with a tunable laser, dimerization of selectively excited jSF₆ is prevented. As radial out-of-the-jet-core diffusion depends on molecular mass, nondimerizable laser-excited jSF₆ monomers enrich the background "rim" gases, which are separated by a skimmer from much heavier nonexcited iSF₆:G and iSF₆:SF₆ dimers in the jet's core. © 2010 American Institute of Chemical Engineers AIChE J, 2010