Tunable vacuum ultraviolet laser spectroscopy of XeAr and XeNe near 68 000 cm−1: Interatomic potentials mediated by a 6s Rydberg electron

The laser induced fluorescence spectra of XeAr and XeNe have been measured near the Xe 6s[3/2]°1−1S0 transition at 68 045.663 cm−1. In XeAr, nine discrete peaks were observed, attributed to excitation to vibrational levels of the excited Ω=0+ electronic state, merging into a continuum. From a Franck–Condon analysis, the potential for the excited Ω=0+ state of XeAr was determined. It was found that this potential has a shallow minimum at long range [De′=28(1) cm−1, re′=5.44(7) Å] with a shallow repulsive wall. The shallow repulsive wall is attributed to the influence of the XeAr+ ion core at short range. The role of the 6s Rydberg electron of Xe in determining the shape of the interatomic potentials of excited XeRg (Rg=a rare gas atom) is discussed on the basis of a simple model potential, in which the interatomic potential is described as the sum of a diatomic ion core (XeRg+) potential term and a term representing the exchange repulsion between the Rydberg electron and the rare gas moiety. For XeNe, only continuum spectra were observed, indicating that the upper states are not bound.