Inelastic Scattering of CO with He: Polarization Dependent Differential State-to-State Cross Sections

A joint theoretical and experimental study of state-to-state rotationally inelastic polarization dependent differential cross sections (PDDCSs) for CO (v = 0, j = 0, 1, 2) molecules colliding with helium is reported for collision energies of 513 and 840 cm–1. In a crossed molecular beam experiment, velocity map imaging (VMI) with state-selective detection by (2 + 1) and (1 + 1′) resonance enhanced multiphoton ionization (REMPI) is used to probe rotational excitation of CO due to scattering. By taking account of the known fractions of the j = 0, 1, and 2 states of CO in the rotationally cold molecular beam (Trot ≈ 3 K), close-coupling theory based on high-quality ab initio potential energy surfaces for the CO–He interaction is used to simulate the differential cross sections for the mixed initial states. With polarization-sensitive 1 + 1′ REMPI detection and a direct analysis procedure described by Suits et al. (J. Phys, Chem. A 2015, 119, 5925), alignment moments are extracted from the images and the latt...