Time-dependent quantum dynamics study of the F + C₂H₆ → HF + C₂H₅ reaction

The reaction probabilities, integral cross sections, energy efficiency and rate constants are investigated for the F + C₂H₆ reaction using the quantum reaction dynamics, wave packet method. The ground-state integral cross section calculated using a six-degree-of-freedom approach is in very good agreement with the quasi-classical trajectory results. We find that the H-CH₂CH₃ stretching motion has the largest enhancement to reactivity, followed by the H-CH₂-CH₃ bending motion. However, the stretching motion between CH₂ and CH₃ slightly hinders the reactivity. The energy-form efficacy based on an equal amount of total energy shows that translational energy is more effective in enhancing the reactivity than vibrational energy of the H-CH₂CH₃ stretching motion at a relatively lower translational energy, while the reverse is true at a relatively high translational energy. An energy-shifting method is employed to calculate the full-dimensional rate constants. The quantum rate constants agree well with one of the two main experimental measurements, and the activation energy has an excellent agreement with the one calculated using canonical variational transition-state theory.