Quantum Dynamics Study Of The F^- + CH₃Cl And OD + CH₃/CHD₂ Reaction Systems

In this paper,we applied a reduced dimensionality,time-dependent quantum reaction dynamics method to study the F^– + CH₃ Cl ? FCH₃ + Cl^–and OD + CH₃/CHD₂ ? O + CH₃D/CHD3 reaction systems.We studied the influence of the ro-vibrational states of the reactant molecule on the reaction cross section.Also we explore the energy efficiency based on the equal amount of total energy in surmounting the reaction energy barrier.The rate constants of the two reactions were also calculated in our quantum study.The energy efficiency on reactivity of the Polanyi rules is summarized solely from the locations of energy barriers on the potential energy surfaces.Here our quantum dynamics study for the F^– + CH₃ Cl ? FCH₃ + Cl^– reaction shows that the two potential energy minima in the entrance channel on the potential energy surface play an essential role in energy efficiency on reactivity.The reactivity of this reaction is dominated by the relative low collision energies where two distinctive reaction mechanisms involve the two minima in the entrance channel.Overall,the Cl-CH₃ stretching motion and C-H₃ umbrella motion both are more efficient than the translational motion in promoting this reaction.Although this reaction has a negative energy barrier,our study shows that it is the minima in the entrance channel,together with the energy barrier relative to these minima,that determine the energy efficacy on reactivity.At the same time,our study shows the rotational excited states inhibit the occurrence of the reaction,as well as our calculated rate constants are excellent agree with the experimental results.A quantum reactive dynamics,six degree-of-freedom,time-dependent wave packet method is applied to study the OD + CH₃/CHD₂ ? O + CH₃D/CHD3 reaction using the ab initio potential energy surface.We study the effects of different ro-vibrational state on the reaction`s integral scattering cross section and energy efficiency based on the equal amount of total energy in surmounting the reaction energy barrier.Our calculations show the vibrational excitations of the reactant OD promote the reaction by reducing the reaction threshold;the vibrational excitations of the reactant CHD₂?C-X?have a certain inhibitory effect on the reaction.Based on the equal amount of total energy,the ratios of the first vibrational excitation state and ground state shows that for the most part of the energy,the vibrational excitation energy of OD is more effective than the translational energy,and for most part of the energy,the translational energy plays a more important role than the vibrational excitation energy of CHD₂.The Polanyi rules are summarized by A + BC reactions.Either the translational energy or the vibrational energy is more effective on surmounting the energy barrier.The polyatomic reactions usually include a variety of vibration modes.Our study of the OD + CHD₂ reaction shows that different vibration modes have a great impact on the energy efficiency.