Determination of opacity data bases for TiO and H2O

Abstract

Current ab initio methods for determining potential energy surfaces are discussed in relation to the TiO and H2O molecules, both of which make important contributions to the opacity of M-type stars. For the TiO molecule we discuss the determination of the radiative lifetimes of the excited states and band oscillator strengths for both the triplet and singlet band systems. While the theoretical radiative lifetimes for TiO agree well with recent measurements, the band oscillator strengths differ significantly from those currently employed in opacity calculations. For the H2O molecule we discuss the current results for the ground state potential energy and dipole moment surfaces generated at NASA Ames. We show that it is necessary to account for such effects as core-valence correlation to generate a potential energy surface of near spectroscopic accuracy. The current status of our effort to establish opacity data bases for both TiO and H2O is described.