Vibrational enhancement on beam–surface ionization processes

Abstract

The SF₆+ Ba (surface) reactions have been studied as a function of the vibrational excitation of the polyatomic molecule. A tunable CO₂ laser was used to excite vibrationally an SF₆ beam which collides with a Ba surface target under high vacuum conditions. Only negative ion signals were observed over the 930–970 cm^–1 wavenumber range. The total negative ion yield was measured as a function of the laser wavelength. The results show a strong vibrational enhancement of the beam–surface reactions indicating important laser-assisted negative ionization effects. The results are discussed in the light of several possible reaction mechanisms based on linear resonant infrared absorption of the SF₆ molecule.