The energy curve of XeF, X ²Σ⁺

Abstract

The energy curve of the ground state of XeF is obtained theoretically assuming that the energy is represented by the sum of the "first order energy" and the dispersion energy. Since the inverse power expansion of the dispersion energy is not valid when the atoms overlap significantly, the dispersion energy is estimated in the overlap region by noting that the Coulomb integrals now vary exponentially with internuclear distance. The onset of overlap was chosen to occur over a range of distances which then permits a range of well depths to be determined. Comparison with recent experimental results indicates that the σ of the analogous van der Waals well provides agreement with the well depth. The energy curve has an unusual shape which suggests that the region around the minimum is determined by a small mixing of charge transfer into the ground state. Since this study is intended to determine the qualitative electronic basis of the binding in molecules like XeF, no attempt was made to calculate the vibrational spectrum but it is clear from the curve shape that the spectrum could be fit only with a large anharmonicity coefficient. © 1976.