Diatomic molecules as perturbed Morse oscillators. II. Extension to higher-order parameters

Energy levels are calculated for a rotating, vibrating diatomic molecule with perturbed-Morse-oscillator potential energy, V (r) =Ve [y2+b4y4+b5y5+⋅⋅⋅], where y=1−exp [−a (r−re)]. Formulas are presented which permit the determination of model parameters up through b12 from spectral data. Formulas are applied to analyses of electronic ground states of CO, HF, and HCl, and to the B (3Π0u+) state of I2. Results for CO and HF are compared with RKR calculations. While the analyses are mathematically precise for all cases, physical accuracy is greatest for states with many bound vibrational levels.