High order vibrational matrix elements for diatomic molecules; dipole moment function and transition moments of CO

Abstract

The fifth and sixth-order contributions to the vibrational matrix elements are obtained for the transitions v→ v'( v'⩽ v+4) using an eight power internuclear Dunham potential and a quartic power series expansion of the dipole moment function. The results for the dipole moment coefficients M 0 to M 4 of CO and the transition moments R v v' (with v=5, 10, 20) deduced from a calculation including succesively third, fourth, fifth and sixth-order perturbation theory are compared. The validity of these results is discussed. Using a quintic dipole moment function, general expressions for the vibrational matrix elements corresponding to the transitions v→ v'( v'⩽ v+5) are also presented and the influence of these contributions on the calculation of the dipole moment coefficients as well as the hot band transition moments of CO is shown.