On the rovibrational spectra of the excimer HeH and its isotopes. A multistate close-coupling treatment

Abstract

By applying a recently published multistate approach (MSA) to the calculation of partial and total predissociation rates, a series of systematic ab initio computations of resonance positions and widths of rovibrational levels of the and electronic states up to the third dissociation continuum of the prototypical excimer and its isotopes , and have been carried out. The resulting resonance landscape, unique for each isotope, clearly displays all near degeneracies and crossings of levels, effects that account for the erratic phenomena observed in the spectra, such as anomalous line intensities, missing lines and band break-offs. Dipole transition probabilities for a number of bands have also been calculated, allowing predictions of observable emission lines to be made. The results demonstrate the validity of the MSA and show that this type of theoretical spectroscopy requires as input potential energies and coupling matrix elements of high accuracy.