THEORETICAL-STUDIES OF HE(S-1)-PI-2) .2. FULLY AB-INITIO CROSS-SECTIONS FOR THE INELASTIC-SCATTERING AND COMPARISON WITH EXPERIMENT(CH(CHI)

We report a series of full close-coupling calculations of integral cro ss sections for fine structure resolved, rotationally inelastic transi tions of CH induced by collisions with He. These calculations use the necessary two CH(X(2) Pi)+He potential energy surfaces as determined b y a variety of ab initio techniques described in the preceeding paper. The calculated N=1-->N=2-7 cross sections confirm a previous predicti on of preferential population of final state levels in which the elect ronic wave function of the CH molecule is antisymmetric with respect t o reflection in the plane of rotation of the molecule. A generally goo d overall agreement is found between the energy-dependent cross sectio ns determined in earlier experiments of Macdonald and Liu and appropri ate averages of the calculated cross sections. However, small, systema tic, qualitative discrepancies persist between theory and experiment D iagnostic calculations were carried out to identify the cause of these discrepancies. These calculations explored the influence of restricti ons in basis set, configuration interaction, and functional forms used in fitting the potential energy surfaces. They also explored the cons equences of the dynamical approximations of CH as a rigid rotor and th e independence of the CH spin-orbit constant on the approach of the He partner. All these diagnostic calculations generally confirm the anti cipated marginal influence of these approximations.