Desorption of large organic molecules induced by keV projectiles

In order to understand the emission of organic molecules in sputtering, cla ssical molecular dynamics (MD) is used to model the 5 keV Ar atom bombardme nt of polystyrene oligomers adsorbed on Ag(1 1 1). The analysis of the resu lts shows that a significant fraction of the trajectories generates high ac tion events in the sample. These events are characterized by the simultaneo us motion of several hundreds of substrate atoms and, oftentimes, by high e mission yields of substrate atoms, clusters and polystyrene molecules. Coll ision trees representing the energetic part of the cascades confirm that hi gh sputtering yields of molecules occur when a large portion of the primary particle energy is quickly dissipated in the upper layers of the silver su bstrate. This class of events where high action occurs in the surface regio n might explain the ejection of organic species with a mass of several kilo daltons such as biomolecules and synthetic polymers. In the simulation, the se events are capable of desorbing polystyrene molecules of similar to2 kDa . (C) 2001 Published by Elsevier Science B.V.