The molecular dynamics method is used to simulate Coulomb explosion of fast C60 ion clusters in an Al target, taking into account dynamical screening of interionic interactions by the electron gas of the target. It is found that the wake forces in the medium are strong enough, depending on cluster speed, to stabilize the whole cluster against Coulomb explosion, or to compress the trailing part of the cluster, for prolonged times of penetration through the target. This is encouraging news for such cluster-ion beams applications where massive energy depositions in small volumes of targets are desired.

A hybrid theoretical model, capable of describing the characteristics of a collisional sheath driven by a sinusoidal current source and determining the energy and angular distributions of ions incident onto the substrate, is proposed. The model consists of one-dimensional time-dependent fluid equations coupled with the Poisson equation determining spatiotemporal evolution of the sheath and the Monte Carlo simulation predicting the energy and angular distributions of ions striking the electrode, in which charge-exchange collisions between ions and neutrals are included. Additionally, an equivalent circuit model in conjunction with the fluid equations is adopted to self-consistently determine the relationship between the instantaneous potential at a rf-biased electrode and the sheath thickness. It is found that the collisional effects would influence the height of the energy peaks in the ion energy distributions and the ion angular distributions.

The angle-resolved energy spectra of the electrons emitted from a metal surface during specular reflection of heavy ions have been studied by means of the first-order, time-dependent perturbation theory, with the electron states obtained from a finite step-barrier potential model. The surface response has been described by the dielectric formalism within the specular reflection model, where the local-field correction and the plasmon-pole approximation have been used for the dielectric function in the cases of low and high ion velocities, respectively. The ion trajectory has been evaluated based on the surface continuum potential and the ion image potential, whereas the screening of the ion by the bound electrons has been taken into account by means of the Brandt-Kitagawa model. It has been found that the electron spectra are dominated by the decay of surface plasmons for fast incident ions, whereas the electron emission is dominated by the single-electron excitation mechanism for slow incident ions.

A theoretical model is developed to study the energy loss of heavy ions specularly reflected on a solid surface at a glancing angle using the dielectric response theory and the specular reflection model. A local-field correction and a plasmon-pole approximation for dielectric function are employed in the low- and highvelocity regimes, respectively. Also, the Brandt-Kitagawa model is used to express the distribution of the electrons bound to the projectiles. We obtain analytical expressions for the position-dependent stopping power and the surface image potential. The energy losses, dependent on the charge state of the ions and the incident angles, are calculated and compared with the corresponding experimental results.

The dielectric response formalism is used to evaluate the dynamically screened interaction potential among the ions in a fast C20 cluster passing through a solid target. This potential is further used to calculate the individual ion charge states in the cluster by means of a statistical–variational theorywhich takes into account the effects of the vicinity of the neighbouring ions. Coulomb explosion and the energy losses of the cluster are simulated by solving equations ofmotion for individual ions while taking into account, in a self-consistent manner, the variation of ion charges in the course of explosion. Moreover, a Monte Carlo method is used to simulate the effects ofmultiple scattering of cluster constituent ions on target atoms. It is found that, owing to the wake-like asymmetry of the inter-ionic potential, both the distribution of ion charges in the cluster and the Coulomb explosion patterns exhibit strong spatial asymmetries in the direction of motion. It is also shown that the cluster energy losses exhibit characteristic interferences due to the vicinity effects, which diminish after long dwell times. (Some figures in this article are in colour only in the electronic version)