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

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.