Molecular-dynamics simulations are performed to investigate the ejection into the gas phase of large molecules in an amorphous van der Waals solid due to a rapid expansion of a cylindrical "track" of material. Such an excitation geometry may be caused by a fast ion penetrating a solid. The ejection yield, the angular distribution of ejected particles, and the crater size are investigated as a function of the expansion rate and energy, sample thickness, and angle of incidence. Comparisons are made with results from an analytic continuum mechanical model which estimates the ejection from the transiently pressurized region. Although the model is described for point particles and is independent of excitation mechanism, it is able to describe many aspects of the simulation.

Using silicon photodiodes with an ultrathin passivation layer, the average total energy lost to silicon target electrons (electronic stopping) by incident low energy ions and the recoil target atoms they generate is directly measured. We find that the total electronic energy deposition and the ratio of the total nuclear to electronic stopping powers for the incident ions and their recoils each follow a simple, universal representation, thus enabling systematic prediction of ion-induced effects in silicon. We also observe a velocity threshold at 0.05 a.u. for the onset of electronic stopping.

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