PHOTORESONANT IONIZATION OF GASEOUS MEDIA BY EXCIMER-LASER RADIATION

An identification is made of twenty five elements whose resonance line s overlap the emission lines of high-power pulsed ultraviolet gas lase rs or lie in the immediate vicinity of them, so that the mechanism las er ionization based on resonance saturation (LIBORS) can be used to io nize the vapor of these elements. Resonance transitions of atoms and i ons excited by the same laser (by krypton fluoride and xenon fluoride lasers, respectively) are observed for tantalum and uranium. It is has been suggested that these elements may be used as ''catalysts'' for ' 'catalytic'' resonance ionization (CATRION) of dense multicomponent ga s mixtures. Experiments have been carried out to study the krypton flu oride laser irradiation of expanding vapor clouds of different element al composition, created by the evaporation of targets with a ruby lase r. Photographs obtained with an image converter, measurements of the r efractive index gradient from the deflection of the laser beam, as wel l as probe and spectroscopic measurements indicate that the clouds und ergo photoresonant ionization if they contain tantalum vapor but that the laser radiation has no influence otherwise. (C) 1997 American Inst itute of Physics.