Direct Dynamics Simulations of Collision- and Surface-Induced Dissociation of N-Protonated Glycine. Shattering Fragmentation

Abstract

Direct dynamics classical trajectory simulations are used to study energy transfer and unimolecular dissociation in collisions of N-protonated glycine, (gly-H)+, with an argon atom and a hydrogenated diamond {111} surface. The (gly-H)+ potential is represented by the AM1 semiempirical electronic structure theory and analytic potentials developed previously are used for the diamond surface and the (gly-H)+/Ar and (gly-H)+/diamond intermolecular potentials. The AM1 potential for (gly-H)+ gives the same collisional energy transfer distributions as does the AMBER empirical force field. For (gly-H)+ + diamond {111} at a collision energy and angle of 70 eV and 45°, the average percent energy transfer to (gly-H)+ vibration/rotation, to the surface, and to final ion translation are 12, 38, and 50, respectively. A distribution of (gly-H)+ dissociation products are observed in these collisions, with ∼55% of the dissociations occurring while (gly-H)+ collides with the surface, i.e., shattering fragmentation. Shatter...