Molecular-scale modeling of light emission by combustion: An ab initio study

Area of Science:

• Chemical Physics
• Combustion Science
• Theoretical Chemistry

Background:

• Combustion processes are well-understood, but light emission mechanisms remain under-explored.
• Light emission during oxidation is often linked to electronic excitation events.

Purpose of the Study:

• To model light emission as electronic excitation during oxidation reactions.
• To investigate the dynamics of oxygen molecule collisions with various target molecules.

Main Methods:

• Simulated collisions between oxygen molecules (O2) and target molecules (Mg2, SiH4, CH4) at varying kinetic energies (4, 6, 10 eV).
• Utilized time-dependent density functional theory (TD-DFT) to track electronic excitation.
• Employed complete active space self-consistent field (CASSCF) method for qualitative analysis.

Main Results:

• Oxygen-magnesium dimer collisions showed increased electronic excitation with higher kinetic energy.
• Substantial electronic excitation occurred in oxygen-silane collisions only at 10 eV.
• Oxygen-methane collisions resulted in molecular reflection, with no observed oxidation or electronic excitation.

Conclusions:

• The study provides a foundational model for understanding light emission in combustion.
• Collision energy significantly influences electronic excitation and oxidation potential.
• Molecular mass and structure play a critical role in determining reaction outcomes.