Rotationally inelastic collisions of OH(X (2)Pi)+Ar. I. State-to-state cross sections

Inelastic collisions of OH(X (2)Pi) + Ar at an energy of 746 cm(-1) have be en studied in a crossed molecular beam experiment. The OH(X (2)Pi) radicals were prepared in the v = 0, Omega = 3/2, J = 3/2, f state by hexapole stat e selection. Parity-resolved integral state-to-state cross sections for rot ational excitation have been determined up to the Omega = 3/2, J = 9/2 and Omega = 1/2, J = 5/2 states. A strong preference is found for spin-orbit ma nifold conserving transitions to final states of e symmetry. The experiment al results are compared to quantum scattering calculations on ab initio pot ential energy surfaces developed by Degli-Esposti and Werner [J. Chem. Phys . 93, 3351 (1990)] and by Klos [J. Chem. Phys. 112, 4952 (2000)]. The overa ll agreement between experiment and theory is very good; however, the calcu lated cross sections for spin-orbit changing transitions are a bit larger t han the experimental values. The results are also compared to previous expe riments at a collision energy of 451 cm(-1). (C) 2000 American Institute of Physics. [S0021-9606(00)01726-8].