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Chemical Kinetic Studies Using
Ultraviolet Cavity Ring-Down Spectroscopic Detection: Self-Reaction of Ethyl and
Ethylperoxy Radicals and the Reaction,
O2 + C2H5  C2H5O2
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A laser-photolysis reactor that uses cavity ring-down spectroscopic (CRDS) detection
was characterized and used to measure the rate coefficients of three benchmark reactions
of known importance to ethane oxidation. At 295 K and approximately 700 Pa (5.5 torr)
total pressure we obtained the self-reaction rate coefficients of
k = 1.99(0.44)x10-11 cm3s-1 for C2H5
+ C2H5 and k = 7.26(2.4)x10-14 cm3s-1
for C2H5O2 + C2H5O2..
We obtained k = 2.7(0.3)x10-12 cm3s-1 for
the pseudo-first order association reaction, O2 + C2H5 + Ar. We also measured the absorption cross-sections of the ethyl
radical, s 220 = 252(42)x10-20
cm2 and s222 =
206(42) x 10-20 cm2. Stated
uncertainties are two sigma. The new rate coefficients agree with those obtained
previously by other methods. The agreement confirms that ultraviolet CRDS detection is a
viable tool for experimental determinations of gas-phase radical-radical and
radical-molecule reaction rate coefficients.
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*National Research Council postdoctoral
associate/NIST. |