Experimental and theoretical results are presented for the A2 spin asymmetry for elastic and inelastic scattering of spin-polarized electrons from rubidium, at incident electron energies of 15, 20, 30, 50 and 80 eV. Theoretical calculations are performed within a semi-relativistic Breit-Pauli R-matrix (close-coupling) model. The experimental data reveal significant asymmetries at all energies. The experimental results are reasonably well described by the present theoretical calculations and by other calculations using a relativistic distorted-wave approach, and provide a clear relativistic signature. Recently published measurements (Hall etal2004) of 'standard' collision parameters for 5s

Abstract. The search for relativistic effects in electron-alkali scattering is currently a topic of considerable interest. The A 2 spin asymmetry parameter is a direct measure of relativistic effects in the electron-atom collision process, as it is entirely dependent on the spin-orbit effect. We present measurements of the A 2 spin asymmetry for the 5S → 5P transition in rubidium at incident energies of 15, 20, 30 and 50 eV and for elastic scattering at 15, 20, 30, 50 and 80eV. Our results indicate that under these collision conditions, relativistic effects are measurable, in qualitative agreement with the available theory.

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