Quantum mechanical scattering of asymmetric molecules. III Calculations or total molecular beam cross sections for the systems He–D2 and He–HT

Abstract

Exact quantum mechanical coupled channels calculations including closed channels have been performed for the systems He–D2 as an example of an interaction potential with electronic anisotropy, and for the system He–HT in order to compare for the effect of the shift of the center of interaction from the center of mass. Total integrated collision cross sections have been evaluated for an energy range which is experimentally accessible. The effects of elastic and inelastic rotational contributions necessitate a reconsideration of the law of conservation of cross section. Feshbach resonances, undulating structures due to metastable orbiting resonances, and Newton-Fonda anomalies at thresholds for rotational excitation are discussed. The magnitude of the deviations for asymmetric molecules in different rotational states forbid the use of the customary approximation calculations. These deviations will be responsible for systematic errors in experiments if one tries to analyze the data with spherical symmetric potentials. The influence of the source temperature is mentioned. The determination of the ratio of polarized beam cross sections yields interesting results about alignment of spins. Whereas the determination of the repulsive anisotropy in the high energy limit appears to be possible within 20% error with the shift approximation, the attractive anisotropy is only accessible with exact coupled channels calculations because of the presence of metastable orbiting influence in the intermediate energe range.