Towards the complete experiment: measurement of S(1D2) polarization in correlation with single rotational states of CO(J) from the photodissociation of oriented OCS(v2 = 1|JlM = 111)

Abstract

In this paper we report slice imaging polarization experiments on the state-to-state photodissociation at 42 594 cm⁻¹ of spatially oriented OCS(v₂ = 1|JlM = 111) → CO(J) + S(¹D₂). Slice images were measured of the three-dimensional recoil distribution of the S(¹D₂) photofragment for different polarization geometries of the photolysis and probe laser. The high resolution slice images show well separated velocity rings in the S(¹D₂) velocity distribution. The velocity rings of the S(¹D₂) photofragment correlate with individual rotational states of the CO(J) cofragment in the J_CO = 57–65 region. The angular distribution of the S(¹D₂) velocity rings are extracted and analyzed using two different polarization models. The first model assumes the nonaxial dynamics evolves after excitation to a single potential energy surface of an oriented OCS(v₂ = 1|JlM = 111) molecule. The second model assumes the excitation is to two potential energy surfaces, and the OCS molecule is randomly oriented. In the high J region (J_CO = 62–65) it appears that both models fit the polarization very well, in the region J_CO = 57–61 both models seem to fit the data less well. From the molecular frame alignment moments the m-state distribution of S(¹D₂) is calculated as a function of the CO(J) channel. A comparison is made with the theoretical m-state distribution calculated from the long-range electrostatic dipole–dipole plus quadrupole interaction model. The S(¹D₂) photofragment velocity distribution shows a very pronounced strong peak for S(¹D₂) fragments born in coincidence with CO(J = 61).