Temperature and Pressure Dependence of the Reaction between Ethyl Radical and Molecular Oxygen: Experiments and Master Equation Simulations.

Abstract

We have used laser-photolysis - photoionization mass-spectrometry to measure the rate coefficient for the reaction between ethyl radical and molecular oxygen as a function of temperature (190-801 K) and pressure (0.2-6 Torr) under pseudo-first-order conditions ([He] ≫ [O2] ≫ [C2H5•]). Multiple ethyl precursor, photolysis wavelength, reactor material, and coating combinations were used. We reinvestigated the temperature dependence of the title reaction's rate coefficient to resolve inconsistencies in existing data. The current results indicate that some literature values for the rate coefficient may indeed be slightly too large. The experimental work was complemented with master equation simulations. We used the current and some previous rate coefficient measurements to optimize the values of key parameters in the master equation model. After optimization, the model was able to reproduce experimental falloff curves and C2H4 + HO2• yields. We then used the model to perform simulations over wide temperature (200-1500 K) and pressure (10-4-102 bar) ranges and provide the results in PLOG format to facilitate their use in atmospheric and combustion models.