Two Electron Photoemission in Solids

Abstract

We observed the emission of correlated electron pairs from the valence band of solids following the absorption of single photons in the vacuum ultraviolet range. Applying a time-of-flight technique, we measured the energy distributions of correlated electron pairs emitted from clean Cu(001) and Ni(001) crystals. Significant differences between both metals were found. For the interpretation we suggest a single step two-electron-photoionization process and a competing two step mechanism involving a single photoionization and a subsequent electron-electron collision in the valence band.