Effect of molecular bending on the photodissociation of OCS

At 230 nm, the photodissociation of OCS via a hot band and a triplet state was investigated by selective probing of high rotational levels of product CO (J=45-67) with photofragment imaging spectroscopy: OCS(v=0)+h nu(UV)--> CO(X (1)Sigma(+),J greater than or equal to 65)+S(P-3), OCS(v=1)+h nu(UV) --> CO(X (1)Sigma(+),J similar to 65)+S(D-1). Additional two-photon IR excitation of the UV photoprepared OCS with intense 1.06 mu m laser pulses bleaches the UV processes listed above and induces a new excitation channel of OCS: OCS(v=0)+h nu(UV)--> OCS*, OCS*+2h nu(IR)--> CO(X (1)Sigma(+),J similar to 74)+S(S-1). The bending mode of OCS in the excited states plays a central role in the excitation and dissociation dynamics. Additionally, the alignment effect of OCS by nonresonant infrared laser pulse, which appears on the angular distribution of the photofragment, is discussed. (C) 2000 American Institute of Physics. [S0021- 9606(00)00316-0].