Quantum non-adiabatic study of the quasi-molecular satellites of the Lyman α line perturbed by H

Abstract

In the so-called one-perturber approach, free–bound and free–free transitions contribute to absorption in the wings of atomic lines perturbed by collisions. Perturbation theory for the interaction of light with a binary collisional complex is applied to the calculation of the absorption coefficient. The initial and final wavefunctions of the binary complex are quite general, taking into account non-adiabatic effects between the adiabatic electronic states. Application to the calculation of the Lyman α quasi-molecular satellite due to H–H collisions is presented. We compare the results that include rotational coupling between the upper B1Σ+u and C1Πu states with the results obtained in an adiabatic approach. It is shown that no significant difference between these results is obtained so that the total absorption coefficient may be calculated by summing up the contributions of the different electronic transitions calculated in the Born–Oppenheimer approximation. As expected, discrepancies between quantal and semi-classical results appear at low temperatures, which are slowly reduced as the temperature increases.