A modified projection approach to line mixing

Abstract

This paper presents a simple approach to combine the high-resolution narrowband features of some desired isolated line models with the projection based strong collision (SC) method to line mixing which was introduced by Bulanin, Dokuchaev, Tonkov and Filippov. The method can be viewed in terms of a small diagonal perturbation of the SC relaxation matrix providing the required narrowband accuracy and resolution close to the line centers, at the same time as the SC line coupling transfer rates can be fine tuned to accurately match some given far wing absorption data. The method can conveniently be placed in the framework of the Boltzmann-Liouville transport equation where a rigorous diagonalization of the line mixing problem requires that molecular phase and velocity changes are assumed to be uncorrelated. Exact solutions and numerical examples are provided for the case with pure pressure broadening and velocity independent parameters. A detailed analysis for the general Doppler case is given based on the first order Rosenkranz approximation, including the possibility to incorporate quadratically speed dependent parameters such as with the Hartmann-Tran (HT) profile in the case with uncorrelated collisions