Molecular dissociation dynamics of H2S at 193.3 nm studied via emission spectroscopy

Publisher Website
Google Scholar
Abstract
We present a study of the fragmentation dynamics of H2S excited at 193.3 nm using the technique of emission spectroscopy of dissociating molecules. The emission spectrum measured extends from near 50 000 cm−1 to 35 000 cm−1, corresponding to emission to vibrational levels in the ground electronic state with seven quanta of S–H stretching vibration. We assigned the emission to previously unobserved vibrational levels of H2S using the calculated energies of Halonen and Carrington [J. Chem. Phys. 8 8, 4171 (1988)]. The early part of the spectrum contains progressions in both symmetric stretching and in symmetric/antisymmetric combination bands, as well as stretching progressions in combination with one quantum in the bend. In the latter part of the spectrum, which reflects the latter part of the dissociation dynamics, emission occurs selectively to vibrational levels characterized best in a local mode basis as having the vibrational energy localized in one of the two S–H bonds. We interpret emission to these local mode vibrations as evidencing the evolution of the dynamics into dissociative motion of one of the S–H bonds with little HSH bending or vibrational excitation of the other S–H bond, which correlates to the SH fragment. The emission spectrum thus reveals the progression of the dynamics, providing a crucial link between the absorption spectrum and the final observed SH product quantum state distributions.