High-temperature non-equilibrium atom-diatom collisional energy transfer

Area of Science:

• Chemical Physics
• Molecular Dynamics
• Gas Kinetics

Background:

• Molecular collisions drive internal energy redistribution and gas relaxation towards equilibrium.
• Understanding vibrational energy transfer is key to predicting gas behavior under various conditions.

Purpose of the Study:

• Investigate translational-vibrational energy transfer during atom-diatom collisions.
• Analyze energy transfer dynamics at high translational gas temperatures.
• Develop a model for vibrational state-to-state transition rates.

Main Methods:

• Utilized quasi-classical trajectory simulations for the N + N2 system.
• Employed ab initio potential energy surfaces for accurate interaction modeling.
• Developed a simplified model to describe transition probability dependence on collisional energy.

Main Results:

• Observed an "activation-saturation" behavior in transition probabilities with increasing collisional energy.
• The proposed model successfully describes this behavior and allows rate coefficient evaluation.
• Simulations of vibrational energy relaxation in N + N2 under hypersonic flow conditions showed good agreement with existing data.

Conclusions:

• The developed model accurately captures vibrational energy transfer dynamics in atom-diatom collisions.
• This work provides a method to predict vibrational energy distribution evolution using the master equation approach.
• The findings are relevant for modeling high-temperature gas phenomena, such as in hypersonic flows.