Monte Carlo trajectories: Dynamics of the reaction F+D2 on a semiempirical valence-bond potential energy surface

Abstract

A semiempirical valence‐bond calculation was carried out for the potential energy surface of H₂F treating explicitly seven valence electrons ${\text{(2p}}_{\mathrm{F}}^5{\text{1s}}_{{\mathrm{H}}_a}{\text{1s}}_{{\mathrm{H}}_b})$ . The integrals were evaluated from diatomic potential energy curves using the Cashion‐Herschbach method. Using this potential energy surface, the chemical reaction $\mathrm{F}+{\mathrm{D}}_2\to \mathrm{FD}+\mathrm{D}$ was studied by Monte Carlo calculations of quasiclassical trajectories. Cross‐section calculations were carried out for initial conditions in these ranges: relative translational energy, 1.56–19.3 kcal/mole; rotational angular momentum (in units of $\hslash$ ), 0–5; vibrational quantum number, 0–1. In addition, distributions of internal energy and scattering angles for the molecular product were calculated. The results were compared with those of previous theoretical studies and the comparison indicates that subtle features (not well understood) of the potential surface may be important for obtaining correct results. The results were also compared with molecular beam, chemical laser, and infrared chemiluminescence results. The angular distributions are not accurate but the product internal energy distributions are in fairly good agreement with experiment. For the reaction $\mathrm{F}+{\mathrm{H}}_2\to \mathrm{FH}+\mathrm{H}$ , a limited number of trajectories were carried out for initial vibrational quantum numbers 0–3.