Inelastic Collision Processes for Formation of Spectral Line Shapes in Stellar Atmospheres. Reprojection method

Abstract

Modeling of formation of spectral lines in stellar atmospheres requires accurate data on inelastic collision processes. The only source of this information is theoretical calculations mainly performed within the standard adiabatic Born-Oppenheimer approach. It is shown that the conventional application of this approach encounters severe difficulties, in particular, due to nonzero couplings in the asymptotic region. This results in the fact that the conventional applications do not provide convergences, which are necessary for calculations of inelastic cross sections, giving infinite cross sections. The proposed remedy is the quantum reprojection method within the standard adiabatic Born-Oppenheimer approach. The method takes nonvanishing asymptotic nonadiabatic couplings into account and distinguishes asymptotic currents in molecular-state channels and in atomic-state channels. The method is demonstrated for the example of low-energy inelastic Li + Na collisions for which the conventional application of the Born-Oppenheimer approach fails.