Analysis of optical emissions produced by dissociative electron impact on CCl2F2

Abstract

We analyzed the optical emissions in the wavelength region 2000–8000 Å produced by dissociative electron impact on CCl2F2. Absolute photoemission cross sections have been determined for a variety of neutral and ionic fluorine and chlorine lines as well as for the strong diatomic CCl and CCl+ bands at 2778 and 2368 Å, respectively. In many cases comparisons between experimentally determined appearance potentials and spectroscopic and thermochemical data enabled a unique identification of the underlying break-up mechanism of the parent molecule upon electron impact. Atomic fluorine emissions which are the result of the total fragmentation of the parent molecule dominate the spectrum from 6000 to 8000 Å with absolute emission cross sections in the range of 0.1 to 3.5×10−19 cm2 at 100 eV for individual 3p→3s fine structure lines. The prominent continuous emission between 2200 and 4000 Å was found to consist of two contributions, the D 2B2→X 2B2 emission of the CCl2F+2 parent ion with an appearance potential of 14.2±1.0 eV and a second emission feature with an appearance potential around 42 eV which has not been uniquely identified.