Claudio Darío Archubi

Influence of the surface band structure on electron emission spectra from metal surfaces

(Received 22 October 2013; revised manuscript received 25 February 2014; published 21 April 2014)ElectrondistributionsproducedbygrazingimpactoffastprotonsonMg(0001),Cu(111),Ag(111),andAu(111)surfaces are investigated, focusing on the effects of the electronic band structure. The process is described withinthe band-structure-based approximation, which is a perturbative method that includes an accurate representationof the electron-surface interaction, incorporating information of the electronic band structure of the solid. For allthe studied surfaces, the presence of partially occupied surface electronic states produces noticeable structuresin double-differential—energy- and angle-resolved—electron emission probabilities from the valence band. ForMg, Cu, and Ag these structures remain visible in electron emission spectra after adding contributions comingfrom core electrons, which might make possible their experimental detection, but for Au they are hidden byinner-shell emission.DOI: 10.1103/PhysRevB.89.155421 PACS number(s): 34

Channeling effect in electronic spectra produced by grazing impact of fast protons on insulator surfaces

Electron emission due to grazing scattering of fast protons from LiF and KCl surfaces is studied under axial incidence conditions. The differential emission probability is calculated within a distorted-wave formalism, taking into account axial channeled trajectories. For different emission angles, electronic spectra for proton incidence along the two principal crystal axes ([100] and [110]) are compared with those co rresponding to an impact velocity in a random direction, finding effects associated with the channeling conditions.

Multiple scattering of charged particles in a free-electron gas

We study the influence of electron-scattering processes on the angular distributions of point particles moving through a free-electron gas. Previous calculations for slow ions are extended to all (nonrelativistic) velocities. The formulation is based on the extension of the multiple-scattering theory to the case of particles moving through a free-electron gas, using Lindhards dielectric function to separately evaluate the contributions of binary (electron-hole) and collective (plasmon) excitations. We find that the angular spread of the beam of particles is dominated by binary collisions. The results for the width of the angular distribution are compared with an integral expression derived by Lindhard.