Knowledge Bank

Bands of TiO are conspicuous in normal red giant stars, ZrO bands are the defining spectral feature of S stars, and bands of CaCl are present in the spectra of some carbon stars. Stellar evolution theories predict that the S stars and the carbon stars are evolved stars in which core hydrogen and helium have been exhausted. In order to understand better the evolution of these stars, more accurate models for their atmospheres require inclusion of these molecules for comparison with observed spectra. We have used high resolution FTS spectra of these molecules produced by a high temperature furnace to determine experimentally the electronic dipole moment matrix elements for some transitions of these molecules. We have fitted profiles to absorption and emission spectra of these molecules and/or constructed synthetic spectra to arrive at experimental values of their dipole moments from previous lifetime measurements of one or a few levels. We describe our techniques and present results.