Channel coupling and relativistic effects in electron-impact excitation of rubidium

Electron-impact excitation of the 5s → 5p resonance transition in rubidium is investigated using a semi-relativistic Breit–Pauli R-matrix with pseudo-states (close-coupling) approach. For the example of 20 eV incident energy, we illustrate the importance of channel coupling and relativistic effects in the computational model. Similar to the case of e–Cs collisions discussed by Andersen and Bartschat (2002 J. Phys. B: At. Mol. Opt. Phys. 35 4507), relativistic effects exhibit themselves only on selected parameters, such as the spin-asymmetry function for the scattering of a spin-polarized electron beam from an unpolarized target beam, while they are almost invisible in the (pseudo-) Stokes parameters that can be measured either in an electron–photon coincidence setup or via 'time-reversed' superelastic collisions. The overall agreement with the available experimental data is satisfactory.