POLARIZATION OF LIGHT EMITTED AFTER POSITRON IMPACT EXCITATION OF ALKALI ATOMS

Recent two-state and five-state close-coupling calculations for positron-alkali scattering are used to predict the linear polarization of the resonance line (np)2po --> (ns)2S emitted by the alkali atoms Li, Na, K and Rb after positron impact excitation. The collision energies considered range from threshold (almost-equal-to 2 eV) to 40 eV. The results are interpreted in terms of elementary collision theory, including depolarization of the line radiation through fine- and hyperfine-structure effects. Given the size of the polarizations predicted and the recent developments in positron physics, an experimental test of our results should be possible. This should provide an independent test of the theoretical model, in addition to the cross sections considered so far.