Tensor cross sections and collisional depolarization of OH(X 2Pi) in collisions with helium

Tensor cross sections for collisions of OH(X (2)Pi) with helium are computed using accurate ab initio potential energy surfaces computed by Lee et al. We use these cross sections to predict rate constants for collisional depolarization of specific rotational fine-structure levels of OH(X (2)Pi) in collisions with helium. Good agreement is found with the results of the two-color polarization spectroscopy experiments of Paterson et al. [J. Chem. Phys. 129, 074304 (2008)]. By examination of partial cross sections, the range of impact parameters at which collisional depolarization occurs is shown to be similar to that for rotationally inelastic collisions.