Molecular dynamics simulations of keV particle bombardment. Correlation of intact molecular ejection with adsorbate size

Molecular dynamics simulations employing a reactive many-body potential of the keV particle bombardment of small hydrocarbon molecules adsorbed on a metal surface have been performed. The simulations predict the occurrence of considerable lateral motion of particles in the region right above the surface. For adsorbates such as CH_x, dominant ejected species are an H atom or the intact adsorbate as there are only two unique bonds to sever. Molecules that extend further above the surfaces are exposed to more collisions from laterally moving particles and consequently there is more fragmentation and the dominant ejected species is usually not the original adsorbate.