Information from local perturbations in the spectra of diatomic molecules: the A3Π -b1Σ+perturbation in OH+

Abstract

The problems connected with extracting useful information from the local perturbations which are often observed in the spectra of diatomic molecules is briefly discussed. The interest is in particular focused on the cases for which the perturbing state cannot be observed through transitions to other states. It is shown that the most important parameters of the unobserved perturbing state can be evaluated from an exact numerical diagonalization of the appropriate secular matrix combined with a least squares fitting procedure. The usefulness of the method is exemplified for the case of OH⁺ which has strong perturbations in the A³ Pi , v=1 sublevels. The Lambda doubling parameters of the A³ Pi , v=1 sublevels (A³ Pi -x³ Sigma ^- interaction) are recalculated and brought into agreement with those of the unperturbed A³ Pi , v=0 levels.