Excitation of solid electrons and energy deposition induced by cluster ions

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This research is devoted to the theoretical study of interaction of cluster ions a and solids. First, we calculated the energy loss ratio R=ΔE(Bn)/(4ΔE(B)), for boron cluster ions Bn+ (n=2-4) with the kinetic energy 0.8 MeV/atom in carbon foil. The experimental data by Narumi et al. Showed the cluster effect, R>1, for any cluster size. The calculated results showed that only the perpendicular-orientation case (I. E., the atomic plane of a cluster is normal to the direction of motion) could nearly reproduce the data well, and that other cases (the randomly-oriented case and the parallel case) are far from the data. Moreover in the case of B2+, even the perpendicular case failed to get agreement with the data trend. This reason is partly due to the fact that the internuclear distance between two B ions is considerably larger (2.322Å=4.465aィイD20ィエD2) than other clusters (2.95aィイD20ィエD2). Newt, we investigated the influence of the cluster structure (a linear-chained and a rhombic C4+ ion) on the energy loss in carbon foil. At velocities greater than 2(a.u.), the energy-loss ratio, ΔE(C4)/(4ΔE(C)), for the rhombic is larger than for the linear and decreases more steeply with increasing the foil thickness. Regarding the diatomic molecular ions N2+, the energy loss in thin foils will reflect the pre-equilibrium charge state in the reduction of the energy-loss ratio. Finally we proposed the new model which could explain the reduction of the cluster average charge compared with the single-ion charge with the same velocity. Especially the cluster-size dependence and the foil-thickness dependence obtained by Brunelle et al. Could be reproduced well. The key idea is the binding effect of the surrounding ions in the cluster. It is found that the inclusion of the reduction of the average cluster charge still shows the cluster effect in the energy-loss.