Vibrational Calculations for the HD2 First-Excited Electronic State Using a Coordinate-Transformation Technique

We report calculations of the vibrational spectrum of HD 2 in its first-excited electronic state by using a coordinate-transformation technique. The implications of the geometric phase (GP) effect in the spectrum have been investigated. The results show that the lowest 45 vibrational levels calculated using the traditional Longuet−Higgins phase (φ/2, where φ is the pseudorotation angle) are in good agreement with those obtained by using a single-surface generalized Born−Oppenheimer equation previously reported by the authors.