Effects of the close approach of potential curves in photoabsorption by diatomic molecules-IV. The near-diabatic and near-adiabatic cases

The suitability of the Fano-Mies type theory for the case of the close approach of two weakly-coupled diatomic potential curves, one of which supports bound vibrational states and the other continuum dissociation states, is explored. For both the near-diabatic and near-adiabatic limits, the isolated resonance approximation to the Fano theory agrees accurately with solutions of associated coupled equations only for the case of very small deviations from the corresponding limit. Calculations with the full Fano-Mies theory are so involved and time consuming as to be computationally unattractive. We conclude that the Fano-Mies approach is valuable for qualitative physical insight but not for quantitative analysis of high accuracy data. © 1990.