Dissociation of fluorine by electron impact

Abstract

Using a previously developed F-atom diagnostic technique, the efficiency of F2 dissociation by an electron beam or an electron-beam-sustained discharge was systematically studied. By monitoring the transient concentration of ions generated during the electron-beam-sustained discharge, we have determined the F−+F+2 ion-ion recombination and F2 dissociative attachment rate constants at various E/P conditions. The dissociative attachment rate constant of F2 at an average electron energy of 1 eV was found to be about (2.3±0.3) ×10−9 cm3/molecule sec−1 and increased with decreasing electron energy. The F−+F+2→3F recombination rate constant at an E/P of 18 kV/cm/atm was found to be about (1.5±0.2) ×10−8 cm3/molecule sec−1 and also increases with decreasing E/P values. The sustained-discharge enhancement of F-atom production from these experiments is F2 is small, ∼1.7.