High energy bombardment mass spectrometric techniques are becoming ever more important for organic and biological samples. Before the molecule can be detected, though, it must first be ejected. The authors have developed a molecular dynamics prescription for examining the fundamental processes important for the ejection of organic molecules during the particle bombardment event. The major advance here over previous simulations is the use of an empirical many-body potential energy function constructed for studying reactive dynamics. Specifically, bonds can be broken and reformed. For the first time, one can examine the possibility of reactions among the organic molecules. As an initial test system, the authors have investigated the 500 eV Ar bombardment of ethylidyne, C{sub 2}H{sub 3}, on Pt (111). This specific system has been studied experimentally by White and co-workers using SIMS. The authors have modeled both 0.25 and 0.50 monolayer ethylidyne coverage in order to test density effects. They find that approximately 80% of the ejected hydrocarbon species originate from a single C{sub 2}H{sub 3} adsorbate, while the others result from reactions between two C{sub 2}H{sub 3} adsorbates. A study of the internal energies of all of the ejected hydrocarbon aggregates reveals that those originating from a single C{submore » 2}H{sub 3} adsorbate are generally stable to any further fragmentation or rearrangement. Examples of common ejection mechanisms for species which originate from a single adsorbate, such as CH{sub 3}, C{sub 2}H{sub 3}, HCCH, and those which originate from more than one adsorbate, such as CH{sub 4} and H{sub 2} will be discussed.« less