TEA CO2-LASER INDUCED SF6-SURFACE IONIZATION(BA BEAM)

A TEA CO2-laser induced SF6 + Ba beam-surface ionization process has b een studied when vibrational excitation of SF, molecules was carried o ut at (and near) the polished surface of the electrically heated up to 675 K polycristalline Ba. Electron emission and negative molecular io n signal were detected. The dependence of the molecular ion signal on laser fluence and frequency (on SF, molecular absorption) as well as o n the SF6 gas pressure in the nozzle were studied. The results reveal a nonlinear, probably multiphoton character of the molecular ion forma tion and a clear vibrational selectivity i.e. vibrational enhancement, of the SF, + Ra beam-surface ionization process. Possible mechanisms of the negative molecular ion formation in the IR laser induced SF6 Ba beam-surface ionization process are discussed.