Photodissociation Dynamics of Benzaldehyde-d5 at 205 nm:The H Atom Production Channel.

Abstract

Photodissociation dynamics of benzaldehyde-d5 (C6D5CHO) at 205 nm was investigated by measuring laser-induced fluorescence spectra of fragment H atoms. From the Doppler-broadened spectra, center-of-mass translational energy release into the C6D5CO + H channel was obtained as 68.8 ± 5.8 kJ/mol with the absolute quantum yield, 0.17 ± 0.03. The observed translational energy was successfully estimated from two-dimensional potential energy surfaces along the C-H dissociation coordinate and the CCO bent angle and the out-of-plane H angle, respectively calculated at the B3LYP/cc-pVDZ level. The dissociation of H should take place along the triplet surface via intersystem crossing from S1 after internal conversion from the initially excited S3 state and on the triplet surface, the dissociation proceeds along the CCO bent-linear-bent configuration with H being planar to nonplanar pathway.