Temperature dependence of rotational excitation rate coefficients of OH(X2Π) in collision with He

We report fully-quantum, close-coupling (CC) calculations of inelastic integral cross sections of hydroxyl radical collisions with He, based on a recent RCCSD(T) potential energy surface. We compare with experimental calculated integral cross sections for a collision energy of 394 cm−1. The excellent agreement confirms the accuracy of the potential energy surfaces. Scattering calculations, which take into account the fine-structure of the OH radical, are done on a grid of collision energies large enough to ensure converged state-to-state rate coefficients for temperatures ranging from 1 K up to 500 K. The calculated cross sections and rate coefficients exhibit sizeable, parity-dependent propensities.