AAS 195th Meeting, January 2000 Session 50. This technique is based on the superlevel formalism. The usage of superlevels reduces the size of the rate equations and the number of rates dramatically and, thereby, makes the problem computationally feasible. We implemented this method in our current model atmospheres for cool dwarfs.
Cool dwarfs have low electron densities and a radiation field that is far from a black body.
Both properties invalidate the conditions for the common LTE approximation. As a case study we applied our method on carbon monoxide. We find that our method gives accurate results since the conditions for the superlevel method are very well met for molecules. The test molecule CO shows significant deviations from LTE in the outer regions of cool photospheres.