AUGER, RESONANT, AND PLASMON-ASSISTED CHARGE-TRANSFER PROCESSES IN ATOM-SURFACE COLLISIONS

The Keldysh Green's-function formalism is used to evaluate the atomic occupation number of a projectile colliding with a metal surface. This formalism has an advantage that allows us to handle simultaneously Au ger, resonant, and plasmon-assisted exchange processes along;with the interference between them. A time-dependent Hamiltonian containing Ang er-like and resonant like terms, and the electron-electron Coulomb pot ential in the solid, is proposed. The atomic self-energies are calcula ted up to a second order in the interaction potential. An effective re sonant amplitude is defined, and Auger self-energies are presented whe re the plasmon-assisted processes are included through a surface respo nse function. Finally, some numerical results for a proton colliding w ith an Al surface by using a simplified description of the solid respo nse function are presented, where an analysis in terms of the incidenc e angle and the energy level is shown.