Trajectory modeling of organic chemiionization reactions

Abstract

We have used a Monte Carlo trajectory calculation to model the chemiionization reaction, HI+B→I−+HB+. B is, in our experiments, a polyatomic amine, but the model treats it as a single atom. The reaction occurs on two potential energy surfaces, one covalent dissociating to the reactants, and one ionic corresponding to the products. Several restrictions were included in the model to account for the fact that B is really a molecule. Classical trajectories were then run at a range of energies and for several variations of potential parameters. The model showed that the reactive cross section rises rapidly as a function of translational energy and that the dynamic threshold energy is 0.38 eV higher than the minimum energy required to form the products. Product angular distributions at low energies show a peak in the forward direction but give a large amount of scattering at and behind the center of mass, in qualitative agreement with the experiments. As the energy increases, the distribution shifts to smaller angles. The Coulomb interaction in the ionic surface introduces some novel features not seen in most reactions.