TIME-RESOLVED EMISSION CHARACTERISTICS AND TEMPERATURE PROFILES OF LASER-INDUCED PLASMAS IN HELIUM

The characteristics of laser-induced plasmas vary greatly with the com position of the analyte in the focal volume region. The plasma size, s tability and emission properties change with any alteration of the pre ssure, concentration or phase of the plasma medium. Choice of a buffer gas suitable for laser-induced plasma studies involves examining the spectral interferences, plasma energy, collisional quenching, as well as efficiency of energy transfer as observed by signal enhancement. Th e emissions in the ultraviolet and visible region resulting from the f ormation of laser-induced plasmas in helium at various pressures, with out a solid target, as well as on the surfaces of aluminum and copper are examined. The time-resolved emission spectra and electronic excita tion temperature profiles are presented. These results are then compar ed with those produced in argon.