Generation of Preferential Lambda-Doublet Populations in the CollisionalRelaxation of Highly Rotationally Excited CH(X(2) Pi)

摘要

By means of full quantum close-coupling and coupled-states calculations based onan ab initio potential energy surface for the Ar-CH system, we confirm a propensity seen experimentally by Hancock, Stuhl, and their co-workers. During the rotational relaxation of high rotational levels of the CH(X(2) Pi) radical, produced by photolysis of a suitable precursor, there appears a clear population imbalance in favor of the Lambda doublet levels of Pi(A') symmetry. A full kinetic simulation, based on the calculated cross sections, reproduces nearly quantitatively the experimental observations of both the temporal evolution and the pressure dependence of this Lambda doublet asymmetry. This asymmetry is a consequence of both an enhanced depletion of high N Pi(A') levels and the