Monte Carlo calculations of reaction rates and energy distributions among reaction products. III. H+F2→ HF+F and D+F2→ DF+F

Abstract

A three‐dimensional classical trajectory calculation is made of the collision dynamics of the exothermic reactions $\mathrm{H}+{\mathrm{F}}_2\mathrm{(v,\hspace{0.17em}J)\to }\mathrm{HF}\mathrm{(v\prime ,\hspace{0.17em}J\prime )+}\mathrm{F}$ and $\mathrm{D}+{\mathrm{F}}_2\mathrm{(v,\hspace{0.17em}J)\to }\mathrm{DF}\mathrm{(v\prime ,\hspace{0.17em}J\prime )+}\mathrm{F}$ by means of a modified London‐Eyring‐Polanyi‐Sato (LEPS) potential energy surface. Trajectory calculations are used to establish the anti‐Morse parameters for a modified LEPS potential‐energy surface which produce the best agreement with previous experimental measurements of reaction rates and energy distributions among reaction products. Very good agreement is obtained with the experimental overall rate constant, the experimental prediction that the maximum vibrational level population of HF (v′) is achieved in v′ = 5, and the mean fraction of available energy entering vibration of the newly formed HF bond. The maximum vibrational level population of DF (v′) is achieved in v′ = 8. The mean fractions ${\mathrm{(f̄}}_{\mathrm{v\prime }}{\mathrm{=E}}_{\mathrm{v\prime }}{\mathrm{/E}}_{\mathrm{total}}\hspace{0.17em}\mathrm{and}{\mathrm{\hspace{0.17em}f̄}}_{\mathrm{R\prime }}{\mathrm{=E}}_{\mathrm{J\prime }}{\mathrm{/E}}_{\mathrm{total}})$ of the total available energy entering vibration plus rotation are (1) for $\mathrm{H}+{\mathrm{F}}_2{\mathrm{,\hspace{0.17em}f̄}}_{\mathrm{v\prime }}{\mathrm{+f̄}}_{\mathrm{R\prime }}\text{=(0.54+0.02)=0.56}$ . (2) for $\mathrm{D}+{\mathrm{F}}_2{\mathrm{,\hspace{0.17em}f̄}}_{\mathrm{v\prime }}{\mathrm{+f̄}}_{\mathrm{R\prime }}\text{=(0.56+0.02)=0.58}$ . The relative rate constants for both reactions have a slight temperature dependence. Rate constants are presented for reactions directly into specific vibrational states of HF and DF.