Virtual photon approach of cathodoluminescence and ion-beam induced luminescence of solids

Constantini, J.-M.*; Ogawa, Tatsuhiko   ; Gourier, D.*

A novel analysis of luminescence is presented on the basis of virtual photon spectra (VPS) produced by charged particles (electrons or ions) passing by luminescent species such as defects or impurities, in wide band-gap ionic-covalent solids. The electron-energy dependence of experimental luminescence spectra of sapphire (-AlO) is discussed in relation to the computed VPS for the primary and secondary electrons. The experimental luminescence spectra of -AlO are also analyzed in this framework for protons and helium ions in the MeV energy range. The variations of stopping power are consistent with the variation of the number of emitted VPs. The decay of luminescence yield versus ion stopping power is discussed on the basis of the variation of the computed VPS, and ionization and excitation induced by primary ions and secondary electrons. This decay is accounted for by a decrease of the yield of low-energy secondary electrons with the subsequent VP emission.