Dissociation cross sections for N₂ + N → 3N and O₂ + O → 3O using the QCT method.

Area of Science:

• Chemical Physics
• Atmospheric Chemistry
• Computational Chemistry

Background:

• Previous studies on collision-induced dissociations (CIDs) often relied on less accurate potential energy surfaces (PESs).
• Limited CID cross-section data was available for N2 + N and O2 + O reactions, hindering accurate modeling.
• Accurate modeling of hypersonic re-entry flows requires precise chemical reaction data.

Purpose of the Study:

• To calculate accurate cross sections for N2 + N and O2 + O collision-induced dissociations (CIDs).
• To provide a comprehensive dataset of CID cross sections up to 30 eV.
• To develop an interpolating scheme for fitting CID cross sections across the entire ro-vibrational spectrum.

Main Methods:

• Employed the Quasi-Classical Trajectory (QCT) method for calculating CID cross sections.
• Utilized highly accurate ab initio Potential Energy Surfaces (PESs), specifically CASSCF-CASPT2 for N3 and a new global PES for O3.
• Developed an interpolating scheme based on spectroscopic data to extend QCT results to all ro-vibrational levels.

Main Results:

• Generated and published CID cross-section data for N2 + N and O2 + O reactions up to 30 eV.
• The calculated rate coefficients showed satisfactory agreement with existing experimental and theoretical results.
• An effective interpolating scheme was introduced to cover the entire ro-vibrational spectrum.

Conclusions:

• The generated CID cross-section data is vital for enhancing the accuracy of chemical reaction models.
• This data will be directly applicable to Direct Simulation Monte Carlo (DSMC) codes used for hypersonic re-entry flow simulations.
• The study provides a more precise foundation for understanding and modeling high-energy atmospheric entry phenomena.