Energy-loss calculation of swift Cn+ (n=2–60) clusters through thin foils

Abstract

The energy loss of swift Cn+ (n=2–60) clusters moving with velocity 1≲v≲4 a.u. (0.3≲E≲6MeV∕atom) through carbon, aluminum, and silicon thin foils has been calculated. We have considered that the carbon atomic ions resulting from the dissociation of these clusters feel Coulomb explosion, stopping, and wake forces due to the target polarization, as well as nuclear scattering with the target nuclei; the three former interactions depend on the ion charge state, which can change during its travel through the foil, due to electron-capture and -loss processes. Our calculation predicts an enhancement of the average energy loss of each dissociated atomic ion in comparison with the case of the same, but isolated, carbon atomic ion, which is small for velocities v∼1 a.u. and becomes more important for higher velocities (v∼4 a.u.). The energy loss of the dissociated atomic ions generally increases with the size and packing level of the cluster, although in some cases it tends to a saturation value (when the number of constituents of the cluster increases) or it could even decrease with cluster size for certain situations (for projectiles with 1≲v≲2 a.u. in aluminum or silicon targets). The vicinage effects in the energy loss also depend on the target nature, being more important for silicon and aluminum foils than for amorphous carbon foils. Our results show that in most cases the highest enhancement in energy loss should be expected for large clusters with high projectile velocities in aluminum or silicon targets. The experimental energy loss measured in carbon targets is well reproduced by our calculations.