ATMOSPHERIC CHEMISTRY OF HFC-143A - SPECTROKINETIC INVESTIGATION OF THE CF3CH2O2-CENTER-DOT RADICAL, ITS REACTIONS WITH NO AND NO2, AND THE FATE OF CF3CH2O

The ultraviolet absorption spectrum of CF3CH2O2 radicals, the kinetics of their self-reaction, and their reactions with NO and NO2 have been studied in the gas phase at 296 K using a pulse radiolysis technique. A long path-length Fourier transform infrared technique was used to study the fate of CF3CH2O radicals. Absorption cross sections were quantified over the wavelength range 220-300 nm. At 250 nm, sigma(CF3CH2O2) = (2.73 +/- 0.31) x 10(-18) molecule(-1). By monitoring the rate of NO2 formation, k(4) = (1.2 +/- 0.3) x 10(-11) cm(3) molecule(-1) s(-1) was found for the reaction of CF3CH2O2 radical with NO. The reaction of CF3CH2O2 radicals with NO gives CF3CH2O radicals. in the atmosphere, >99.3% of the CF3CH2O radicals react with O-2 to give CF3CHO. By monitoring the rate of NO2 decay, k(5) = (5.8 +/- 1.1) x 10(-12) cm(3) molecule(-1) s(-1) was found for the reaction of CF3CH2O2 radical with NO2. The results are discussed with respect to the atmospheric chemistry of CF3CH3 (HFC-143a). As a part of the present work, relative rate techniques were used to measure the following rate constants: (2.6 +/- 0.7) x 10(-12) and (2.0 +/- 0.5) x 10(-12) for the reaction of F atoms with CF3CH3, (5.5 +/- 0.3) x 10(-11) for the reaction of F atoms with CF3CH2OH, and (3.6 +/- 0.2) x 10(-17) for the reaction with Cl atoms with CF3CH3 (units of cm(3) molecule(-1) s(-1)).