Laser-induced migration and isotope separation of epi-thermal monomers and dimers in supercooled free jets

摘要

Explicit relations are developed to estimate the outflux of migrating isotoporners (i)QF(6) to the outskirts of a supersonic supercooled free jet whose core is irradiated by a co-axial laser beam and intercepted by a skimmer that separates core gas from peripheral gases. The QF(6) target gas is diluted in carrier gas G (G = He, N-2, Ar, Xe, SF6, etc.) which determines the jet's supersonic characteristics and forms QF6:G dimers at low temperatures. Under isotope-selective laser excitation, excited (i)QF*(6) convert their vibrational energy V into kinetic energy T after forming transient (i)QF*(6):G dimers that dissociate in sub-microseconds. Three migrating groups with different transport parameters are created in the jet: thermal monomers, faster-moving epithermal monomers, and slower-moving dimers. Jet-core-fleeing QF6 is enriched in (i)QF(6) due to enhanced outwards migration of (i)QF(6)(1) epithermals and reduced escape of (j)QF(6):G dimers in the jet. Isotope enrichments in the rim gases are highest for heavier carrier gases such as G = Xe or G = SF6.