Comparison of experimental and calculated attachment rate constants forCFCl3andCCl4in the temperature range 294–500 K

Abstract

Electron-attachment cross sections and rate constants have been measured and calculated for the dissociative attachment processes e+${\mathrm{CFCl}}_3$→${\mathrm{Cl}}^{\mathrm{-}}$+${\mathrm{CFCl}}_2$ and e+${\mathrm{CCl}}_4$→${\mathrm{Cl}}^{\mathrm{-}}$+${\mathrm{CCl}}_3$. Good agreement over the electron-energy range 1–200 meV is found in energy dependence between present calculated cross sections and experimental (krypton photoionization) cross sections at 300 K. The same calculation, with suitable adjustment of thermal populations, was used to calculate electron-attachment rate constants k(ɛ¯) in the range 50–600 K. Experimental rate constants for ${\mathrm{CFCl}}_3$ and ${\mathrm{CCl}}_4$ were measured at temperatures of 294, 404, and 496 K (${\mathrm{CFCl}}_3$) and 294, 400, and 500 K (${\mathrm{CCl}}_4$) using the Cavalleri electron-density sampling method. Good agreement is found between present measurements and calculations, poor agreement with flowing-afterglow Langmuir-probe (FALP) data in ${\mathrm{CFCl}}_3$ at the higher temperatures, and reasonable agreement with FALP data for ${\mathrm{CCl}}_4$.