Interaction of multiply charged ions with large free silver nanoparticles: Multielectron capture, fragmentation, and sputtering phenomena

We report on the interaction of multiply charged ions at keV energies with free Ag nanoparticles with diameters of similar to 6 nm (containing about 6600 Ag atoms). As the ionization energy increases only very slowly with the degree of ionization, multielectron capture processes are very likely to occur in peripheral collisions with large cluster sizes. However, due to the large particle size, the produced highly charged Ag nanoparticles are mostly stable. For projectile charge states below q = 8 the geometrical cross section overcomes the cross section for peripheral electron transfer, and penetrating collisions become dominant. Therefore, these collisions can be described as ion collision with a nanosurface, where the distribution of small-size fragments with n < 20 is due to sputtering events from the nanoparticle surface. This is in contrast to nanoparticles with a smaller diameter (<2 nm), where small fragments are produced by fission of multiply charged clusters.