Interpretation of the structures observed for excitation cross-sections in C ^{2 +} / He ^{2 +}-Li collisions

Abstract:

The existence of oscillatory or plateau like structures in the low energy dependence of the excitation cross-sections in ion-atom collisions has recently been subject of different interpretations based on model calculations. We report atomic-state close-coupling calculations for the description of Li (2 s → 2 p ) excitation by He²⁺ and C²⁺ impact where the appearance of such structures is very different and previously documented in experimental studies. A system specific interpretation based on dynamic adiabatic energy curves is given and the interplay between high-energy direct and low-energy molecular mechanisms in the two systems are discussed.