We report an ($e,2e$) binding energy spectrum of Xe obtained at an impact energy of 2.1 keV, which covers the binding energy range up to 220 eV. The result is directly compared with data from high-energy photoelectron spectroscopy. It is found that an ($e,2e$)-specific, very broad band appears at around 120 eV, although in other energy regions the binding energy spectra by the two methods are in good agreement. The presence of such a band is revealed for the first time, which can be attributed to the second-order effects of the electron-target interaction that involves giant resonance phenomena of the Xe $4d$ electron.

• Received 12 July 2006

DOI:https://doi.org/10.1103/PhysRevLett.98.013201