Highlights of the Science and Life of Peter Varga (1946—2018)

Peter Varga has passed on October 27, 2018. His pioneering discoveries of chemical resolution at the atomic scale on surface alloys, atomic resolution of ultrathin alkali halides, nucleation of bcc iron in ultrathin films, and the microscopic structure of ultrathin alumina films stimulated worldwide research. In recognition of his outstanding scientific contributions, in December 2017 the Japanese Society for the Promotion of Science (JSPS) awarded him a prize for his distinguished contribution on the clarification of surface phenomena by atomic level investigations and the development of novel functional materials. This contribution highlights the life of Peter Varga as a scientist and as a person. With his elegance, his energy, his wit, and his generosity he was a close friend and role model to many of us, and showed us how to combine scientific curiosity and creativity with the lightness of being

A novel method for unambiguous ion identification in mixed ion beams extracted from an EBIT

A novel technique to identify small fluxes of mixed highly charged ion beams extracted from an Electron Beam Ion Trap (EBIT) is presented and practically demonstrated. The method exploits projectile charge state dependent potential emission of electrons as induced by ion impact on a metal surface to separate ions with identical or very similar mass-to-charge ratio.Comment: 8 pages, 5 figure

Analytical model for the sputtering of rough surfaces

The sputtering yields of solids under ion bombardment are highly sensitive to the roughness of their surfaces. Understanding how sputtering is exactly affected by different surface morphologies is relevant especially for plasma-wall interaction in fusion reactors and space weathering of planetary surfaces. We present an analytical model that allows to calculate sputtering yields of random gaussian rough surfaces under arbitrary angles of incidence, taking into account local incidence angles, shadowing and redeposition of sputtered materials. Sputtering yields of a rough surface can then be calculated with the sputtering yield’s dependence on the ion incidence angle for a flat surface and a single statistical parameter, which characterizes the surface roughness. The model supports previous findings that the mean surface inclination angle is a well-suited parameter to describe the sputtering behavior of rough surfaces. Comparisons of the results to previous experiments and numerical simulations for various cases are presented, showing that the model allows to quantitatively reproduce sputtering yields of different samples over a wide range of roughness regimes

A classical Over Barrier Model to compute charge exchange between ions and one-optical-electron atoms

In this paper we study theoretically the process of electron capture between one-optical-electron atoms (e.g. hydrogenlike or alkali atoms) and ions at low-to-medium impact velocities (v/v_e <= 1) working on a modification of an already developed classical Over Barrier Model (OBM) [V. Ostrovsky, J. Phys. B: At. Mol. Opt. Phys. {\bf 28} 3901 (1995)], which allows to give a semianalytical formula for the cross sections. The model is discussed and then applied to a number of test cases including experimental data as well as data coming from other sophisticated numerical simulations. It is found that the accuracy of the model, with the suggested corrections and applied to quite different situations, is rather high.Comment: 12 pages REVTEX, 5 EPSF figures, submitted to Phys Rev