Quantum defect description of non-Rydberg molecules

Abstract

Quantum defect theory, combined with the frame transformation method, is applied to analyze non-Born–Oppenheimer effects in the hydrogen molecular ion and its isotopes by calculating low-lying vibrational energy levels of the ground electronic states. The calculation, based purely on the 1sσg Born–Oppenheimer potential of H+2, shows improvement over Born–Oppenheimer results despite the fact that the hydrogen molecular ion cannot be regarded as a Rydberg molecule.