VIBRATIONAL ENHANCEMENT ON BEAM SURFACE-IONIZATION PROCESSES

The SF6 + Ba (surface) reactions have been studied as a function of th e vibrational excitation of the polyatomic molecule. A tunable CO2 las er was used to excite vibrationally an SF, beam which collides with a Ba surface target under high vacuum conditions. Only negative ion sign als were observed over the 930-970 cm-1 wavenumber range. The total ne gative ion yield was measured as a function of the laser wavelength. T he results show a strong vibrational enhancement of the beam-surface r eactions indicating important laser-assisted negative ionization effec ts. The results are discussed in the light of several possible reactio n mechanisms based on linear resonant infrared absorption of the SF6 m olecule.