A coupled-channel approach based on the Arthurs and Dalgarno formalism is presented to describe the scattering of a Rydberg atom and a rare-gas atom. The method permits the calculation of cross sections for changes in the electronic orbital angular momentum of the Rydberg atom. The theory explicitly relates the scattering behavior of the Rydberg state to the electron-rare-gas scattering length. Preliminary results for ${\mathrm{Na}}^{*}\mathrm{}\left(\mathrm{nd}\right)\mathrm{}$+He and ${\mathrm{Na}}^{*}\mathrm{}\left(\mathrm{nf}\right)\mathrm{}$+He are in good agreement with experiment.

• Received 27 March 1978

DOI:https://doi.org/10.1103/PhysRevA.18.1339