Knowledge Bank

Transmissions giving rise to combination bands in the region $5000-10000cm-1$ are expected to be the most important for calculations of stellar model atmospheres. This contribution will present a detailed study of such bands for the HCN molecule. Using MCSCF and CI methods, the potential energy surface around the equilibrium geometry has been investigated. In addition to frequencies, the dipole intensities have been calculated for all transitions among a total of 150 vibrational states up to about $15000cm-1$. It is found that the numerous weak transitions are as important as the few strong ones in determining the structure of stellar atmospheres.