Photochemistry of CH2BrCl:  An ab Initio and Dynamical Study

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 106; no. 46; pp. 11150 - 11161
• Main Authors: Rozgonyi, Tamás, González, Leticia
• Format: Journal Article
• Language: English
• Published: American Chemical Society 21.11.2002
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp026877x

The photochemistry of CH2BrCl has been studied using laser-induced wave packet propagations on coupled multistate CASPT2 potentials calculated for the electronic ground and low-lying excited states, as a function of two reaction coordinates corresponding to the two halogen eliminations. The results indicate that the lowest excited state, with character 1(nσ*), is strongly repulsive in both the C−Br and C−Cl directions. As a consequence, one-photon resonant excitation induces halogen fragmentation that occurs around 100 fs. The weaker C−Br bond dissociates directly, whereas the fragmentation of the stronger C−Cl bond involves a nσ*(C−Br)/nσ*(C−Cl) curve crossing pathway. The vertical spectrum for the resulting CH2Br and CH2Cl radicals has also been calculated, giving energies and oscillator strengths in close agreement with experimental UV spectral range and measured absorption cross-sections.