Energy loss of ions and ion clusters in a disordered electron gas.

The various aspects of the correlated stopping power of pointlike and extended ions moving in a disordered degenerate electron gas have been analytically and numerically studied. Within the linear response theory we have made a systematic and comprehensive investigation of correlated stopping power, vicinage function, and related quantities for protons and extended ions, as well as for their clusters. The disorder, which leads to a damping of plasmons and quasiparticles in the electron gas, is taken into account through a relaxation time approximation in the linear response function. The stopping power for an arbitrary extended ion with a single bound electron is calculated in both the low- and high velocity limits. Our analytical results show that in a high velocity limit the main logarithmic contribution to the stopping power for an extended ion is significantly modified and for instance, in the case of He+, Li2+, and Be3+ ions must behave as ln ( A v(5) ), ln ( A v(3.25) ), and ln ( A v(2.77) ), respectively where v is the ion velocity. This behavior may be contrasted with the usual ln ( v(2) ) dependence for a point ion projectile. It is shown that the factor A which depends on the damping can be significantly reduced by increasing the latter. In order to highlight the effects of damping we present a comparison of our analytical and numerical results, in the case of both pointlike and extended ions, obtained for a nonzero damping with those for a vanishing damping.