Investigation of steric effects in inelastic collisions of NO(X (2)Pi) with Ar

Cross sections were determined for collisions of Ar with oriented NO(X (2)P i), based on full close-coupled calculations and new ab initio potential en ergy surfaces (PESs). Collisions in which the NO molecules are initially or iented so that the O end preferentially points toward the Ar atom are more effective in promoting spin-orbit changing transitions. The magnitude of th e steric asymmetry is consistent with earlier calculations based on a previ ous PES, and agrees well with experiment. Various modifications of the full PESs were used to explore the origin of the observed features in the steri c asymmetries, in particular the striking oscillatory pattern seen in the v ariation of the steric asymmetry with final state. (C) 2000 American Instit ute of Physics. [S0021-9606(00)01017-5].