Global modelling of the observed line positions for the spectra of ultraviolet bands: Dunham coefficients for the A²Σ⁺ excited state of the ¹⁶OH molecule

A global treatment of the available experimental data on transition frequencies both in the A²Σ⁺state and in the A²Σ⁺−X²Π, and B²Σ⁺−A²Σ⁺ electronic systems of ¹⁶OH molecule was carried out. In this analysis, a global model with vibrational dependences of the parameters of the effective Hamiltonian for the diatomic molecule in different electronic state was used. As a result of the fit, a set of the ‘Dunham-type’ coefficients for A²Σ⁺ electronic state was obtained. They reproduce the experimental dataset within estimated experimental uncertainties. The determined ‘Dunham-type’ coefficients were employed to generate the potential energy curve in the A²Σ⁺ electronic state using the RKR method.