Stopping power of fast, partially stripped molecules and clusters: Vicinage effects in charge states

Abstract

We present a consistent variational approach to the vicinage effect on ion charges in a cluster made of partially stripped ions, based on the Brandt--Kitagawa theory for isolated ions, supplemented by dynamically screened interionic interactions. Interferences in cluster stopping power are shown to be strongly influenced by the ion-charge dependence on internuclear separations, and may give rise to energy loss enhancement or deenhancement, when compared to the case when the ion charges are frozen at the value corresponding to isolated ions at the same speed. In addition, the ion charge reduction is shown to be responsible for softening the interionic interactions responsible for Coulomb explosion. Calculations of the vicinage effect on ion charges are performed for a fast ${\mathrm{N}}_{2}$ molecule moving through a carbon target, and the roles of Coulomb explosion and multiple scattering in energy loss are discussed.