Mechanisms of Organic Molecule Ejection in SIMS and FABMS Experiments

A classical dynamics model is used to investigate nuclear motion in solids due to bombardment by energetic atoms and ions. Of interest are the mechanisms of ejection and cluster formation of molecular species where we have predicted intact ejection of benzene-C₆H₆, pyridine-C₅H₅N, napthalene-C₁₀H₈, bipheny1-C₁₂H₁₀ and coronene-C₂₄H₁₂. The results presented here show that the energy distributions of the parent molecular species, e.g., benzene, are narrower than those of atomic species, even though the ejection processes in both cases arise from energetic nuclear collisions. The bonding geometry also influences the ejection yield and angular distribution. The specific case of π-bonded and σ-bonded pyridine on a metal surface is discussed with comparisons between the calculated results and experimental data. These calculations provide a means of interpreting SIMS, FABMS and possibly even PDMS experimental data.