Time-resolving the UV-initiated photodissociation dynamics of OCS
Abstract
We present a time-resolved study of the photodissociation dynamics of OCS after UV-photoexcitation at λ=237 nm. OCS molecules (X\,1+) were primarily excited to the 1\,1\!A'' and the 2\,1\!A' Renner-Teller components of the 1- and 1\! states. Dissociation into CO and S fragments was observed through time-delayed strong-field ionisation and imaging of the kinetic energy of the resulting CO+ and S+ fragments by intense 790 nm laser pulses. Surprisingly, fast oscillations with a period of 100 fs were observed in the S+ channel of the UV dissociation. Based on wavepacket-dynamics simulations coupled with a simple electrostatic-interaction model, these oscillations do not correspond to the known highly-excited rotational motion of the leaving CO(X\,1+,J0) fragments, which has a timescale of 140 fs. Instead, we suggest to assign the observed oscillations to the excitation of vibrational wavepackets in the 2\,3\!A'' or 2\,1\!A'' states of the molecule that predissociate to form S(3\!PJ) photoproducts.