Computational investigation of energy transfer and line broadening for Ar^* + He collisions

Potential energy curves for all states arising from the interaction of He with the 3p⁶, 3p⁵4s, and 3p⁵4p configurations of Ar have been determined using high-level electronic structure calculations. The results have been used to examine collisional energy transfer probabilities and spectral line shape parameters (shifting and broadening rate coefficients). The main focus has been on states and transitions that are of relevance to optically pumped He/Ar^* laser systems. The line shape predictions were found to be in good agreement with experimental data, while there is notable disagreement for the energy transfer probabilities. The experimental data are found to be at variance with the predictions of standard two-state curve crossing models for energy transfer.