Sudden Approximation Applied to Rotational Excitation of Molecules by Atoms. III. Angular Distribution and Energy Dependence of the Inelastic Scattering

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Abstract
The sudden approximation for rotational excitation of diatomic polar molecules by atomic impact is applied, yielding semiclassical angular distributions of rotational transition cross sections and their energy dependence. The results for a model system (intended to approximate TlF–Ar) are not inconsistent with the experimental findings of Toennies. The dominant excitations are those allowed by first‐order time‐dependent perturbation theory, but the strong coupling (due principally to the large long‐range anisotropy in the potential) produces extensive excitation to remote open channels, i.e., those forbidden by low‐order perturbation theory. The main prediction of the present work is the presence of a single major peak in each of the various differential polar inelastic cross sections; with increasing collision energy, these maxima trend to smaller angles and increase in peak intensity.