Velocity correlated (precursor mediated) multifragmentation in sub-keV fullerene-surface impact: Evidence from both positive and negative Cn± (n = 7, 9, 11) fragments and molecular dynamics simulations

We have investigated the multifragmentation event of sub-keV C60- impacting a gold surface using kinetic energy measurements of both positively and negatively charged outgoing fragments and molecular dynamics simulations. We have found that the energy losses are practically independent of fragment charge and that all emitted ions, irrespective of mass and charge, have the same peak velocity. These observations establish the validity of the precursor mediated multifragmentation model, previously demonstrated only for outgoing negative ions, also for the formation of positive fragment ions. The actual disintegration of the superhot precursor and resulting formation of the fragment ion occurs 'post-collision' after leaving the surface. Molecular dynamics simulations carried out using the relevant experimental parameters provide further insight into the microscopic dynamics of the process and nature of the superhot precursor.