Desorption of molecules by cluster impact: A preliminary molecular dynamics study

Abstract

A preliminary molecular dynamics computer simulation has been performed to look at the use of large cluster ions in the desorption of large intact molecules from surfaces. It is found that impacts of large clusters on graphite can produce pronounced acoustic waves and that it is possible that these waves can be used to desorb large molecules from the surface. By using the acoustic wave generated by the impact of a large cluster the molecule being desorbed is gently lifted from the surface in a co-ordinated fashion. This is in contrast to trying to utilise the collision cascade generated by a single ion impact. In the latter case, it is an infrequent event that produces a co-ordinated collision cascade which enables the intact ejection of a large molecule. In the former case, it is the most frequent occurrence, particularly if the energy of the bombarding cluster is low. In this case also very little fragmentation of the surface or molecules occurs.