Infrared Cathodoluminescence of Xe2 Excimers in Xe-He and Xe-N2 Dense Gas Mixtures

Multiple scattering effects influence the transport properties of excess electrons in gaseous and fluid dielectrics but also affect the energy levels of electrons in delocalized molecular orbitals and can be investigated by carrying out spectroscopic observations. We have measured the infrared cathodoluminescence of the Xe ₂ excimer in dense Xe gas, and in Xe-He, and Xe-N ₂ mixtures. The large orbital characterizing the weakly bound, optically active electron of Xe ₂ encompasses several surrounding atoms and allows us to study their effects on the electron energy. In particular, the Coulomb force screening on the electron due to the atoms polarizability and the mutiple scattering effects described by the quantum scattering length are discussed and a gas density dependence of the Xe ₂ energy levels is predicted. A good agreement with the experimental density dependent wavelength shift of the infrared Xe ₂ excimer band is found.