Precise potential-energy function for the X1Σ+state of hydrogen chloride

Abstract

Data for frequencies and wavenumbers of 896 rotational and vibrational–rotational transitions of gaseous hydrogen chloride, ¹H³⁵ Cl, ¹H³⁷ Cl, ²H³⁵ Cl, ²H³⁷ Cl, in the ground electronic state X¹Σ⁺ have been analysed according to a method of stepwise merging in order to generate a precise potential-energy function essentially free of mass dependence, up to 0.52 of the dissociation limit. This dependence of the Born–Oppenheimer potential energy upon internuclear separation is given both in numerical form (R.K.R. method) and analytically according to the Dunham series expansion. Seven mass coefficients and 24 energy coefficients in mass-reduced form suffice to reproduce satisfactorily not only the fitted 896 frequencies and wavenumbers but also other data of ³HCl and ¹H³⁷ Cl not included in the fitting procedure.