ATMOSPHERIC CHEMISTRY OF CF3COX RADICALS - FATE OF CF3CO RADICALS, THE UV ABSORPTION-SPECTRUM OF CF3C(O)O-2 RADICALS, AND KINETICS OF THE REACTION CF3C(O)O-2-]CF3C(O)O+NO2(NO)

The atmospheric fate of CF3CO radicals has been studied using a pulse radiolysis technique to provide kinetic data and FTIR-smog chamber sys tem to provide product data. In 1 atm of SF6 at 296 +/- 2 K, CF3CO rad icals decompose to give CF3 radicals and CO with a rate of (1.2 +/- 0. 8) x 10(5) s(-1) and react with O-2 to form CF3C(O)O-2 radicals with a rate constant of (7.3 +/- 1.1) x 10(-13) cm(3) molecule(-1) s(-1). In 1 atm of N-2 at 296 +/- 2 K, the rate constant ratio k(CF3CO + O-2 -- > CF3C(O)O-2)/k(CF3CO --> CF3 + CO) (7.4 +/- 0.6) X 10(-18) cm(3) mole cule(-1). Reaction with O-2 accounts for 99.5% of the loss of CF3CO ra dicals in the atmosphere. The ultraviolet absorption spectrum of CF3C( O)O-2 radicals has been studied over the wavelength range 220-300 nm, and at 230 nm, sigma(CF3C(O)O2)) = (3.78 +/- 0.43) X 10(-18) cm(2) mol ecule(-1). Monitoring the rate of NO2 formation at 400 nm allowed a lo wer limit of k(4) > 9.9 X 10(-12) cm(3) molecule(-1) s(-1) to be deriv ed for the rate constant of the reaction of CF3C(O)O-2 radicals with N O. Reaction of CF3C(O)O-2 radicals with NO produces the alkoxy radical CF3C(O)O, which undergoes C-C bond scission rapidly with a rate great er than 6 x 10(4) s(-1), Results are discussed with respect to the atm ospheric chemistry of CF3COx radicals. As part of the present work, a rate constant k(6) = (2.3 +/- 0.4) X 10(-11) cm(3) molecule(-1) s(-1) was determined for the reaction of F atoms with CF3CHO.