Coupled-channel study of halogen (2P) + rare gas (1S) scattering

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Abstract
Quantum mechanical coupled‐channel (CC) scattering calculations are reported using realistic adiabatic potentials for the 2P+1S interaction of F–Ar, F–Xe, and Cl–Xe. Differential cross sections dσ/dω derived from a simple elastic approximation appropriate for large spin orbit interactions accurately reproduce all the gross features computed by the coupled‐channel method. This finding supports the extraction of interaction potentials from laboratory differential cross sections I (ϑ) via an elastic analysis. Integral inter and intramultiplet changing cross sections are expressed conveniently in terms of Grawert’s B(j, j’;g) coefficient. Information on the collision dynamics is extracted by following the partial wave dependence of selected B(j, j’;g). Classical turning point analysis, based on the values of the large l‐waves for which these partial wave contributions Bl(j, j’;g) begin to rise above zero, leads to the conclusion that both intermultiplet and first order forbidden intramultiplet transitions are caused by a single localized nonadiabatic coupling region at the position of complex crossing of the Ω=1/2 adiabatic potentials. Small amplitude oscillations or perturbations in the CC calculated dσ/dω and in the experimental I (ϑ) are thought to be examples of Stükelberg oscillations, though quantitative agreement between these quantities is not obtained. The energy dependence and interference structure of the computed B(j, j;g) are briefly discussed, as is the approximation of the constant spin orbit interaction over the experimentally accessible range of internuclear distances.