Postcollision multifragmentation in fullerene-surface impact: Microscopic insights via molecular dynamics simulations.

Abstract

Postcollision multifragmentation which we have recently observed experimentally in C60 (-)-surface impact is the phenomenon of a delayed multiparticle breakup of a highly collisionally vibrationally excited large molecule/cluster (the precursor species) into several polyatomic fragments, after leaving the surface. In this paper, we show that the molecular dynamics simulations of near-grazing C60 collisions with a gold surface at 300 eV impact energy (very similar to the experimental conditions) successfully reproduce the experimentally observed characteristics of the postcollision multifragmentation process. The calculated mass resolved kinetic energy distributions and the time dependent yield curves of the Cn fragments revealed a precursor mediated, velocity correlated, delayed fragmentation event along the outgoing trajectory, far away from the surface. Most of the large fragments (n ≥ 5) are formed within a time window of 2-20 ps after leaving the surface, corresponding to the vertical distances of 3-30 nm from the surface. Analysis of delay times and actual time duration for multifragmentation reveal that a large part can be described as simultaneous postcollision (delayed) multifragmentation events. The delayed nature of the event seems to be due to an early sequence of structural transformations of the precursor.