CHEMICAL KINETIC-STUDIES USING ULTRAVIOLET CAVITY RING-DOWN SPECTROSCOPIC DETECTION - SELF-REACTION OF ETHYL AND ETHYLPEROXY RADICALS AND THE REACTION O-2-]C2H5O2(C2H5)

A laser photolysis reactor that uses cavity ring-down spectroscopic (C RDS) detection was characterized and used to measure the rate coeffici ents of three benchmark reactions of known importance to ethane oxidat ion. At 295 K and approximately 700 Pa (5.5 Torr) total pressure, we o btained the self-reaction rate coefficients of k = (1.99 +/- 0.44) x 1 0(-11) cm(3) molecule(-1) s(-1) for C2H5 + C2H5 and k = (7.26 +/- 2.4) x 10(-14) cm(3) molecule(-1) s(-1) for C2H5O2 + C2H5O2 We obtained k = (2.7 +/- 0.3) x 10(-12) cm(3) molecule(-1) s(-1) for the pseudo-firs t-order association reaction O-2 + C2H5 + AT We also measured the abso rption cross sections of the ethyl radical, sigma(220) = (252 +/- 42) x 10(-20) cm(2) molecule(-1) and sigma(222) 2 (206 +/- 42) x 10(-20) c m(2) molecule(-1) Stated uncertainties are 2 sigma. The new rate coeff icients agree with those obtained previously by other methods. The agr eement confirms that ultraviolet CRDS detection is a viable tool for e xperimental determinations of gas-phase radical-radical and radical-mo lecule reaction late coefficients.