Photodissociation of vibrationally excited SH and SD radicals at 288 and 291 nm: the S(1D2) channel.

Ultraviolet photodissociation of SH (X 2Pi, upsilon"=2-7) and SD (X 2Pi, upsilon"=3-7) has been studied at 288 and 291 nm, using the velocity map imaging technique to probe the angular and speed distributions of the S(1D2) products. Photodissociation cross sections for the A 2Sigma+<--X 2Pi(upsilon") and 2Delta<--X 2Pi(upsilon") transitions have been obtained by ab initio calculations at the CASSCF-MRSDCI/aug-cc-pV5Z level of theory. Both the experimental and theoretical results show that SH/SD photodissociation from X 2Pi (upsilon"<or=7) proceeds via the repulsive wall of the A 2Sigma+ state. The angular distributions of S(1D2) indicate that the dissociation approaches the sudden recoil limit of the A 2Sigma+ state, yielding strongly polarized fragments. The S(1D2) atoms are predominantly produced with total electronic angular momentum perpendicular to the recoil axis.