O(³P<i>_J</i>) Alignment from the Photodissociation of SO₂ at 193 nm

Abstract

The 193-nm photodissociation of SO 2 has been studied using the resonantly enhanced multiphoton ionization of ground-state O( 3 P J ), coupled with velocity-map ion imaging. The dependence of the ion images on the linear polarization of pump and probe radiation has been used to determine the electronic angular momentum alignment of the recoiling, state-selected atoms, together with their speed distribution and translational anisotropy. The polarization data for J = 1 and 2 have been used to estimate the state multipole moments of the O-atom electron spin and orbital angular momenta. The data suggest that both sources of O-atom electronic angular momentum are polarized. It is shown that the spin polarization could either arise from exit-channel couplings or be a manifestation of the participation of triplet states in the dissociation. The angular dependence of the potential energy in the exit channel is examined using long-range quadrupole−dipole and quadrupole−quadrupole interaction terms, from which molecular-frame multipole moments of the orbital angular momentum of the recoiling O atoms have been calculated. Comparison with the experimentally derived multipole moments is used to help provide insight into the dissociation mechanism. The results are also discussed in light of similar experimental data from the photodissociation of N 2 O.