Kinetic and Dynamic Studies of the F(²P) + ND₃ → DF + ND₂ Reaction

The fast F reaction with NH₃ poses a big challenge to experimental studies because of secondary chemical and collisional reactions. The quasi-classical trajectory method is utilized to investigate the mode specificity, product energy disposal, and temperature dependence of the thermal rate coefficient of F + ND₃ → DF + ND₂ on a recently developed potential energy surface. The effect of isotopic substitution is explored by comparing the F + ND₃ reaction with the F + NH₃ reaction. The computed results permit a better understanding of the F + ammonia reaction. The DF vibrational state has a Λ-type distribution, in accordance with the experimental measurement by the fast flow reactor technique. The product ND₂ is dominantly populated in the ground state, and a considerable amount of ND₂ is produced in the fundamental states of the bending mode. The similar vibrational state distributions of HF and NH₂ in the F + NH₃ reaction indicate a weak isotopic substitution effect on the product energy disposal. Exciting the umbrella mode of ND₃ suppresses the reaction at low energies below 5 kcal mol^-1, in sharp contrast to the observation in the F + NH₃ reaction. These dynamical behaviors can be partially explained by the sudden vector projection model. In addition, the thermal rate coefficient of F + ND₃ shows no temperature dependence in the range between 150 and 2000 K. There exists an inverse kinetic isotope effect at temperatures from 150 to 1500 K.