MOLECULAR DESORPTION IN BOMBARDMENT MASS SPECTROMETRIES

Molecular dynamics simulations have been performed to gain microscopic insight into those factors which influence the ejection due to ion bo mbardment of molecules adsorbed on solid substrates. The specific syst em modeled is a pentylidyne (C5H9) film adsorbed on Pt{111} and C{111} . Lowering the binding energy of the film to the substrate from 2.7 to 0.6 eV increases the total yield of ejected particles. The bombardmen t of the film bound by 2.7 eV results in considerable fragmentation of the C5H9 adsorbate while the bombardment of the film bound by 0.6 eV results in the desorption of the intact molecular adsorbate.