Time-dependent simulations: acceleration and deceleration of convoy electrons in grazing-ion-surface collisions

DARIO M. MITNIK, A. ARNAU, I. ALDAZABAL AND V.H. PONCE

Creta, Grecia

Conferencia; XX International Symposium on Ion-Atom Collisons; 2007

ISIAC

Spectra of electrons emitted in grazing ion-surface collisions provide information about the structure of the surface, and has been the subject of intense research in the past years. In particular, it is interesting to study the electron distribution around the direction of the specular reflection of the projectile, where the spectrum displays a sharp peak, known as the "convoy" peak. However, the shape and position of the convoy peak are affected by surface potential produced by the ionization of the target (the "track potential"). In this work, we developed a numerical method for treating the surface track potential, expanding it in spherical coordinates around the colliding ion. We assume that the ion capture an electron from the surfaces, leaving it in a particular continuum state. The formation of a charge distribution in the surface behind the projectile, breaks up the spherical symmetry of the captured electron distribution, producing an electron emission spectra that is not necessarily centered around the ion. We use the techniques developed for the time dependent calculations of atomic collisions to propagate an initial configuration along the projectile trajectory. By analyzing the final electron distribution around the incident ion, we can understand the mechanisms responsibles for the acceleration or deceleration of the convoy electrons. In particular, the relationship between the position of the maximum of the electron distribution with the electron-capture processes, and with the track potential form.