Quasi-Classical Trajectory Study of NH(³∑^-) + NH(³∑^-) Reactive Collisions

Area of Science:

• Chemical Kinetics
• Theoretical Chemistry
• Computational Chemistry

Background:

• Understanding the formation of nitrogen molecules (N₂) is crucial in various chemical processes.
• The reaction mechanism of NH radical collisions has been a subject of theoretical interest.

Purpose of the Study:

• To investigate the dynamics of collisions between two NH radicals using a full-dimension quasi-classical trajectory study.
• To elucidate the microscopic reaction mechanisms for N₂ formation from NH + NH collisions.
• To analyze the influence of reactant energy states on the reaction pathways and rates.

Main Methods:

• Utilized a global six-dimensional potential energy surface for the singlet electronic state of the N₂H₂ system.
• Employed quasi-classical trajectory calculations to simulate NH radical collisions.
• Applied a variant of the vibrational energy quantum mechanical threshold method to correct for zero-point energy leakage.
• Performed state-specific calculations to examine the impact of rotational and vibrational excitation.

Main Results:

• Identified two potential reaction mechanisms for N₂ formation: a one-step (NH + NH → N₂ + H + H) and a two-step pathway (NH + NH → N₂H + H → N₂ + H + H).
• Observed rapid vibrational energy redistribution within the four-body complex in the two-step mechanism.
• Presented and discussed excitation functions.
• Investigated the effect of reactant rotational and vibrational energy on reactivity.
• Reported reaction rate constants for ground and rotationally excited states.

Conclusions:

• The collision of two NH radicals can lead to N₂ formation through distinct one-step or two-step mechanisms.
• Reactant energy states significantly influence the observed reaction dynamics and rates.
• The study provides valuable insights into the kinetics and mechanisms of N₂ formation from NH radicals.