Impact-parameter dependence of Na(3s→3p) excitation in Na-Ne collisions

A combined experimental and theoretical investigation of the impact-parameter dependence of Na(3s to 3p) excitation in 1-10 keV Na-Ne collisions is presented. Two different mechanisms are shown to account for the features observed in the Na(3p) excitation. At low collision energies, the excitation takes place at well localised molecular curve crossings. At high energies, direct excitation at larger impact parameters dominates