Statistical energy distribution model for the decay of hollow atoms formed in collisions of slow(v<1a.u.)highly charged ions andC60

Abstract

It is now well known that electron-capture processes in high impact parameter collisions between slow highly charged ions and clusters (as ${\mathrm{C}}_{60}$ for instance) or surfaces populate high Rydberg levels of the projectile forming a so-called ``hollow atom.'' We present in this paper a statistical energy distribution (SED) model for the analysis of the decay of such hollow atoms. The overbarrier model is employed to estimate the initial binding energy of captured electrons and total geometrical cross sections. We show that although the model firstly derived by Russek was incomplete, a simple modification to it that accounts for hollow atom specifications leads to a better agreement with experimental cross sections over a wide range of projectile ions of different atomic numbers (Ar, Kr, Xe) and different charge states $(q=16--30).$ We present also a quantum-mechanics-based formulation of a SED model that allows us to reproduce rather nicely experimental cross sections too. The presented model applied better for high projectile charge states allowing the capture of a great number of electrons that populate a quasicontinuum of Rydberg states for which we do not have to take into account individual Auger transitions.