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 excit ation of the UV photoprepared OCS with intense 1.06 mu m laser pulses bleac hes the UV processes listed above and induces a new excitation channel of O CS: 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 centr al role in the excitation and dissociation dynamics. Additionally, the alig nment effect of OCS by nonresonant infrared laser pulse, which appears on t he angular distribution of the photofragment, is discussed. (C) 2000 Americ an Institute of Physics. [S0021- 9606(00)00316-0].