Diatomic molecules as perturbed Morse oscillators. I. Energy levels

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Abstract
A formula is obtained for the rotational–vibrational energy levels of a diatomic molecule using a perturbed Morse potential V (r) =V e [(1−e −a q )2+b 4(1−e −a q )4 +b 5(1−e −a q )5+⋅⋅⋅], along with additional perturbations describing rotational energy. Results are equivalent to Dunham’s formulas, but have superior convergence properties for analyzing spectra. How to choose the ’’best’’ unperturbed Morse potential and how to evaluate perturbation parameters are briefly discussed. Formulas are applied to the ground state of CO, and results are compared with those for RKR and other potentials.