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 meas ured near the Xe 6s[3/2](1) degrees - S-1(0) transition at 68 045.663 cm(-1). In XeAr, nine discrete peaks were observed, attributed to exci tation to vibrational levels of the excited Omega=0(+) electronic stat e, merging into a continuum. From a Franck-Condon analysis, the potent ial for the excited Omega=0(+) state of XeAr was determined. It was fo und that this potential has a shallow minimum at long range [D-e' = 28 (1) cm(-1), r(e)' = 5.44(7) Angstrom] with a shallow repulsive wall. T he shallow repulsive wall is attributed to the influence of the XeArion core at short range. The role of the 6s Rydberg electron of Xe in determining the shape of the interatomic potentials of excited XeRg (R g = a ran gas atom) is discussed on the basis of a simple model potent ial, in which the interatomic potential is described as the sum of a d iatomic ion core (XeRg(+)) potential term and a term representing the exchange repulsion between the Rydberg electron and the rare gas moiet y. For XeNe, only continuum spectra were observed, indicating that the upper states are not bound. (C) 1996 American Institute of Physics.