Photodissociation Dynamics of OCS at 217 nm

Abstract

The S(1D2)+CO(X1Σ+) product channel from photodissociation of OCS at 217 nm has been measured using the DC slice velocity map imaging (VMI) technique in combination with resonance enhanced multiphoton ionization (REMPI). Two different REMPI intermediate states (1F3 and 1P1) and several pump-probe laser polarization geometries are used to detect the angular momentum polarization of the photofragmented S(1D2). The molecular-frame polarization parameters, as well as the laboratory-frame anisotropy parameters, for individual rotational states of co-fragment CO, are determined using two different full quantum theories. The measured total kinetic energy release spectrum from photodissociation of OCS indicates two dissociation channels, corresponding to the fast and slow recoiling velocities of S(1D2), respectively. The slow channel is concluded to originate from an initial photoexcitation to the A(1A′) state, followed by a non-adiabatic transition to the ground state. The fast channel is found to follow a coherent excitation to A(1A′) and B(1A″) states, where contributions of the two states are almost equal at 217 nm. The determined alignment and anisotropy parameters further indicate that the slow channel follows an incoherent excitation, while the fast channel follows a coherent excitation to A(1A′) and B(1A″) states with a phase difference of π/2.