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

Abstract

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.