Spin-resolved rotational energy transfer for the CH B 2Sigma-(v=0, N, F) state by collisions with Ar.

An experimental and theoretical investigation of rotational energy transfers (RET) of CH involving the B (2)Sigma(-) (v=0, 0</=N</=5, F) state by collisions with Ar is undertaken, using the photolysis-probe technique. Time-resolved laser-induced fluorescence resulting from an initially prepared fine-structure label is dispersed using a step-scan Fourier transform spectrometer. The spin-resolved RET rate constants are evaluated with the simulation of a kinetic model. The quantum-scattering method is used for the calculation of the fine-structure-resolved cross sections and rate constants in the rotationally inelastic collisions. The theoretical values are generally consistent with our experimental findings, both in the order of magnitude and trend of N and DeltaN dependence. The propensity rules obtained from the experiments are essentially obeyed by theoretical calculations, and are also in accordance with those reported by Kind and Stuhl. The RET rate constants obtained for the v=0 level are smaller than those obtained previously for v=1. The discrepancy in the RET behavior may be caused by an anisotropy difference of the interaction potential resulting from vibrational excitation.