Test of accuracy of diatomic potential energy function calculated by inversion of spectroscopic data

Abstract

The method of direct numerical inversion of a spectrum to the generalized potential energy function (GPEF) with correct long-range part is proposed. The reliability of the method was tested by its application to the X 1 Σ + state of HeH +: the GPEF was calculated from vibrational-rotational transitions belonging to the fundamental v = 1 ← 0 band. The obtained GPEF reproduces the wavenumbers of transitions used in the fit with experimental accuracy (0.002 cm −1) and predicts the wavenumbers of transitions belonging to the v = 2 ← 1 and v = 3 ← 2 bands with a mean absolute error of 0.065 cm −1. The maximum difference between the GPEF and accurate ab initio potential of HeH + in the attractive branch is 30 cm −1 (0.2% of dissociation energy). The advantages of the proposed method are discussed.