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

The characteristics of laser-induced plasmas vary greatly with the composition of the analyte in the focal volume region. The plasma size, stability and emission properties change with any alteration of the pressure, 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. The emissions in the ultraviolet and visible region resulting from the formation of laser-induced plasmas in helium at various pressures, without a solid target, as well as on the surfaces of aluminum and copper are examined. The time-resolved emission spectra and electronic excitation temperature profiles are presented. These results are then compared with those produced in argon.