ATMOSPHERIC CHEMISTRY OF CF3CFHCF3 (HFC-227EA) - SPECTROKINETIC INVESTIGATION OF THE CF3CFO2-CENTER-DOT-CF3 RADICAL, ITS REACTIONS WITH NO AND NO2, AND FATE OF THE CF3CFO-CENTER-DOT-CF3 RADICAL

The ultraviolet absorption spectrum of the (CF3CFO2CF3)-C-. radical, t he kinetics of its self-reaction and reactions with NO and NO2 have be en studied in the gas phase at 296K using a pulse radiolysis technique , A long-path-length Fourier transform infrared technique was used to study the fate of the (CF3CFOCF3)-C-. radical. Absorption cross sectio ns for the (CF3CFO2CF3)-C-. radical were quantified over the wavelengt h range 220-270 nm. At 230 nm, sigma((CF3CFO2CF3)-C-.) = (351 +/- 73) x 10(-20) cm(2) molecule(-1). The observed rate constant for the (CF3C FO2CF3)-C-. self-reaction was (1.8 +/- 0.3) x 10(-12) cm(3) molecule(- 1) s(-1). The rate constants for the reaction of (CF3CFO2CF3)-C-. radi cals with NO and NO2 were k(3) = (2.1 +/- 0.9) x 10(-11) and k(4) = (4 .8 +/- 1.4) x 10(-12) cm(3) molecule(-1) s(-1). The atmospheric fate o f (CF3CFOCF3)-C-. radicals is decomposition via C-C bond scission to g ive CF3 radicals and CF3C(O)F. In 1000 mbar of SF6 at 296 K decomposit ion of (CF3CFOCF3)-C-. radicals proceeds at a rate greater than 1 x 10 (5) s(-1) As part of this work relative rate techniques were used to m easure k(Cl+CF3CFHCF3) = (4.5 +/- 1.2) x 10(-17) and k(F+CF3CFHCF3) = (1.5 +/- 0.5) x 10(-13) cm(3) molecule(-1) s(-1). This compares well w ith the value of k(F+CF3CFHCF3) = (1.9 +/- 0.4) x 10(-13) cm(3) molecu le(-1) s(-1) obtained by pulse radiolysis. The results are discussed i n the context of the atmospheric chemistry of HFC-277ea.