Vibrational calculations for the HD2 first-excited state using a coordinate-transformation technique

The calculations of the vibrational spectrum of HD2 in its first-excited electronic state are reported by using a coordinate-transformation technique. The implications of the geometric phase effect in the spectrum are investigated. The results show that the lowest 45 vibrational levels calculated using the traditional Longuet-Higgins phase are in good agreement with those obtained using a single-surface generalized Born-Oppenheimer equation.