Dynamic screening and charge state of fast ions in plasma and solids

Abstract

This paper addresses the effect of target plasma electrons on the charge state of energetic ions, penetrating a target composed of bound as well as plasma electrons. Dynamic screening of the projectile Coulomb potential by the plasma electrons brings about a depression in the ionization energy of the ionic projectiles, as has been verified experimentally. This in turn makes the ionization cross-sections larger, while making the recombination cross-section smaller, thereby causing an increase in the ion charge state compared to the case of a gas target. The effect of the plasma environment, where the valence electrons are treated as plasma, is illustrated here for a 2 MeV carbon beam penetrating amorphous carbon targets of varying densities.

Influence of laser beam intensity profile on propagation dynamics of laser-blow-off plasma plume

“…It can play a crucial role in the development of extreme ultraviolet lithography source, thin film deposition, synthesis of nanoparticles, metallic atomic beam source for accelerators, and probing neutral atomic beam in plasma environment (Chrisey & Hubler, 1994;Geohegan et al, 1998;Doria et al, 2004;Fazio et al, 2009;Hoffman, 2009;Huber et al, 2005;Masnavi et al, 2006;Nardi et al, 2009;Sizyuk et al, 2007;Wolowski et al, 2007;Wang et al, 2007). Several attempts have been made to optimize the expanding laser produced plasma plume by varying experimental factors like, ambient gas, focal spot size, laser pulse width, irradiance, and wavelength of ablating laser (Key et al, 1983;Bulgakova et al, 2000;Amoruso et al, 2003;Harilal, 2007;Beilis, 2007;Laska et al, 2008;Rafique et al, 2008).…”

Theory and simulation of heavy ion stopping in plasma

“…Next, one is concerned with the projectile -plasma interaction itself in mainly two respects: First, the energy loss of the projectile in elastic collisions with free target electrons and target ions and in inelastic collisions due to ionization and excitation of target ions, and the related collective effects like the target polarization with the resulting dynamic screening and the excitations of plasma waves. And second, the changes in the electronic configuration of the projectile ion by various processes like recombination of free electrons, collisional ionization and excitation, and the charge transfer by bound -bound transitions between target ions and projectile, see e.g., the recent investigations by Eisenbarth et al (2007) and Nardi et al (2009).…”

High Energy Density Physics with Heavy Ion Beams and related Interaction Phenomena

“…Thereby an increase in the ion charge state compared to the case of a gas target is caused. This important effect of the plasma environment can experimentally be investigated by studying the difference in angular-and energy straggling of electrons and ions penetrating amorphous carbon targets and plasma of varying densities [10].…”