Insights on the site-selective fragmentation of CF₂Cl₂ and CH₂Cl₂ at the chlorine K-edge from ab initio calculations

A theoretical study of CF₂Cl₂ and CH₂Cl₂ photoabsorption spectra and photofragmentation profiles at the chlorine K-edge is presented. We simulated the NEXAFS spectra at the Core-Valence Separated Coupled Cluster Singles and Doubles (CVS-CCSD) level and interpreted the photofragmentation profile in terms of the potential energy surfaces (PES) computed at the complete active space self-consistent field (CASSCF) level along the C–Cl bond cleavage for the 1_sCl → σ*_C-Cl' 1_sCl → 7b₂, and 1_sCl → ∞ states. the PES of CF2Cl2 shows that the chlorine's 1s → σ* transition tends to fragment into the CF₂Cl* radical and the Cl (1s¹2s²2p⁶3s²3p⁶) excited atom, whereas the 1_sCl → 7b₂, and 1_sCl → ∞ states are less prone to undergo this fragmentation channel. The same tendency was observed for the CH₂Cl₂ molecule, suggesting that the F atom has little influence on the PES