Low energy electron induced dissociation in condensed diallyl disulfide

Using a high sensitivity Time of Flight mass analyser we have measured the electron stimulated desorption (ESD) of anions and cations from multilayer thin films of diallyl disulfide (DADS) formed by condensation onto Pt and Kr substrates. Measurements were performed as a function of incident electron energy (E-i), film thickness and effective incident current. For E-i less than or similar to 15 eV the desorption yields of anions are the result of dissociative electron attachment (DEA) via several transient negative ions often associated with electron capture into C-S and S-S sigma* bonds. The minimum incident energies observed for desorption of the anionic fragments H-, S-, CH2CHCH2-, and CH2CHCH2S- are compared to theoretical bond dissociation energies calculated using DFT methods. In comparison to gas-phase electron impact mass spectra, the yield of cationic fragments are dominated by desorption of low mass fragments although similar species are observed in both cases. Electron impact at higher electron energies on thicker films of DADS enhances desorption of larger fragment ions, including those formed by the scission and formation of multiple bonds.