Photoelectron spectrum of Xe2 and potential energy curves for Xe+2

Abstract

The photoelectron spectrum of the Xe2 van der Waals molecule was determined at 584 Å with a resolution of 20 meV, using an apparatus which combines a supersonic molecular beam source with a hemispherical photoelectron spectrometer. This experiment gives new information on the potential energy curve for the bound Xe+2 ground state at large internuclear separation. An optimum potential was determined for this state by fitting the observed photoelectron peak to a calculated Franck–Condon distribution. The calculations show specifically that the Morse function is not an adequate approximation to the potential at large internuclear distances. This experiment also gives new information on the potential energy curves for the weakly bound Xe+2 excited states in the region of their potential minima, thus complementing Xe–Xe+ scattering experiments which probe these potentials in the region of their repulsive walls. Potential energy curves for all of the Xe+2 states dissociating to Xe(1S0)+Xe+(2P3/2 or 2P1/2) are constructed primarily from experimental results and are compared with recent theoretical calculations by Wadt. Photoelectron spectra of heavier xenon clusters were also determined and are discussed briefly.