Multiple ionization of rare gas dimers by slow highly charged ions: screening effect during a collision

Abstract

Multiple ionization dynamics of rare gas dimers by slow highly charged ions has been investigated using the three-center Coulombic over-barrier model. The outermost electrons at two atomic sites in the dimer are sequentially removed by forming a quasi-molecule with a projectile, where partial screening is taken into account in the non-active site ionized during a collision. It is found that the fragment ion pair (Q,Q′) distribution is remarkably sensitive to the screening effect, which enhances the population of highly charge-asymmetric pairs such as (2,0) and (3,1). Recent measurement of the ion pair distribution in Ar9+ + Ar2 collisions is best reproduced with the present model by taking a screening parameter of s = 0.4.