Kinetic excitation of solids: The concept of electronic friction

The energy dissipation into electron-hole pairs has been simulated ab initio within time-dependent density-functional theory for hydrogen atoms with a low kinetic energy in the range below 10 eV impinging on an Al(1 1 1) surface. The H-atoms penetrate into the crystal via the fcc-hollow site and are backscattered by the third atomic layer. The energy dissipation rate due to electronic friction fits well to known bulk data. The electron-hole pair excitation spectra are characterized by an approximately exponentially decaying tail of the electron energy distribution, with a fictitious temperature describing the slope of the spectra in the range of 2000-3000 K, depending on the initial kinetic energy of the incident H-atom