THE UV ABSORPTION-SPECTRUM OF THE ETHYLPEROXY RADICAL AND ITS SELF-REACTION KINETICS BETWEEN 218 AND 333 K

The UV absorption spectrum of the C2H5O2 radical between 215 and 295 nm, and the kinetics of its self-reaction in the temperature range 218-333 K were measured using the molecular modulation technique in conjunction with both single wavelength and diode array UV spectroscopy. The UV spectrum of C2H5O2 is a broad absorption with a sigma(max) of 4.36 X 10(-18) cm2 molecule-1 at 240 nm. Analysis of decay profiles of C2H5O2 at 250 nm enabled an overall removal rate constant k(obs) for C2H5O2 of (1.1 +/- 0.1) X 10(-13) cm3 molecule-1 s-1 at 298 K to be determined. Between 250 and 330 K, k(obs) may be represented by k(obs)(250-330 K) = (1.85 +/- 0.2) X 10(-13) exp{-[(147 +/- 30)/T]} cm3 molecule-1 s-1. A further expression is presented for lower temperatures where curvature in the Arrhenius plot is observed. Comparisons with previous measurements of sigma(C2H5O2) and the temperature dependence of k(obs) are presented.