Charge cloud orientation in excitation or deexcitation of Na*(3p) in Na-He collisions

The direct excitation and deexcitation probabilities of Na(3p) are calculated in an 8-state model using the Projected Valence Bond potential energies of NaHe, the impact parameter method is used in the 0.5 keV < ECM < 100 keV energy range. A 3-state model predicts propensity rules which are confirmed by the present more elaborate model in the energy range of the maximum of the 3s-3p transition, but a discrepancy attributed to ionisation of Na occurs at energies beyond the excitation probability maximum (ECM > 2 keV). (orig.)