Relaxation, incubation, and dissociation in CO2

Area of Science:

• Physical Chemistry
• Chemical Kinetics
• Spectroscopy

Background:

• Understanding the dissociation and relaxation rates of carbon dioxide (CO2) is crucial for various chemical processes.
• Previous studies have provided data, but discrepancies and theoretical inconsistencies remain.
• Accurate kinetic data are essential for modeling high-temperature gas dynamics and combustion.

Purpose of the Study:

• To accurately determine the rate and incubation time for CO2 dissociation and relaxation.
• To investigate the pressure dependence of CO2 reaction rates.
• To compare experimental findings with existing literature and theoretical models like RRKM calculations.

Main Methods:

• Utilized the laser-schlieren technique in incident shock wave experiments.
• Covered a wide range of temperatures (1377-6478 K) and pressures (42-750 Torr).
• Employed improved experimental setups for precise measurements of rate and incubation times.

Main Results:

• Steady rate measurements generally agree with recent determinations.
• Observed non-second-order rate behavior, with rates varying significantly with pressure (70-600 Torr).
• Found incubation time to relaxation time ratios consistent with other molecules but smaller than reported in some reflected-shock experiments.

Conclusions:

• Experimental results highlight a pressure-dependent anomaly in CO2 reaction rates not fully explained by current RRKM calculations.
• The observed incubation to relaxation time ratios are consistent with other molecules, suggesting a potential issue with previous reflected-shock data.
• Further theoretical and experimental work is needed to reconcile the observed rate anomalies and refine kinetic models for CO2.