Dipole moment functions of the hydrogen halides

Abstract

Experimental intensity data for vibration–rotational transitions and molecular beam data of the hydrogen halide diatomic molecules (HF, HCl, HBr, and HI) have been analyzed, and the coefficients of a power series expansion of the dipole moment functions valid near the equilibrium internuclear separations have been determined. Ab initio quantum chemical computations of the dipole moments have also been carried out over a wide range of internuclear separations for HF, HCl, and HBr, and the factors affecting the accuracy of these results have been critically examined. The long-range values from these computations have been combined with the results near equilibrium in the form of a Padé approximant that embodies the correct asymptotic behavior.