Intermediate species manipulations by vibrational excitations in a flame

Resonant vibrational excitation of C₂H₄ molecules by a tunable CO₂ laser can enhance the growth of high-quality, {100}-oriented diamond films in combustion flames by increasing the population of key intermediate oxide species. However, the molecular dynamic mechanisms behind this process are not well understood, particularly how the resonant excitation contributes to the formation of these specific intermediate species.

To investigate these phenomena, we performed molecular dynamics simulations using the Reaxff interatomic potential. Our approach microscopically mimicked the vibrational excitation of C₂H₄ by adding kinetic energy to chosen ionic sites of the molecules. The results demonstrate that this microscopic, site-specific energy addition is more effective at manipulating the formation of intermediate oxides relevant to diamond growth than macroscopic parameters like temperature or initial C₂H₄/C₂H₂ and C₂H₄/O₂ ratios.

This study provides new insights into how a wavelength-tunable CO₂ laser can steer chemical reactions in a flame through resonant vibrational excitation of ethylene molecules. Our findings could pave the way for more precise control over chemical vapor deposition processes and the synthesis of high-quality diamond materials.