ATMOSPHERIC CHEMISTRY OF FCOX RADICALS - UV SPECTRA AND SELF-REACTION KINETICS OF FCO AND FC(O)O-2 AND KINETICS OF SOME REACTIONS OF FCOX WITH O-2, O-3, AND NO AT 296 K

A pulse radiolysis technique has been used to measure the UV spectra of FCO and FC(O)O-2 radicals over the ranges 265-275 and 220-290 nm, respectively. At 269.6 nm, sigma(FCO) = (1.7 +/- 0.2) X 10(-18) cm(2) molecule(-1); at 250 nm, sigma(FC(O)O2) = (2.1 +/- 0.2) X 10(-18) cm(2) molecule(-1). The decay of UV absorption was used to study the kinetics of the self-reactions of FCO and FC(O)OI radicals at 296 +/- 2 K. Observed self-reaction rate constants, defined as -d[FCO]/dt = 2k(7)[FCO](2) and -d[FC(O)O-2]/dt = 2k(8obs)[FC(O)O-2](2), were k(7) = (1.6 +/- 0.2) x 10(-11) and k(8obs) = (6.0 +/- 0.7) X 10(-12) cm(3) molecule(-1) s(-1). A rate constant, k(l) = (1.2 +/- 0.2) x 10(-12) cm(3) molecule(-1) s(-1), was derived for the addition reaction FCO + O-2 --> FC(O)O-2 in 1000 mbar of SF6 diluent. Rate constants for the reactions of FCO, FC(O)O, and FC(O)O-2 radicals with NO were determined to be (1.0 +/- 0.2) x 10(-12), (1.3 +/- 0.7) x 10(-10), and (2.5 +/- 0.8) x 10(-11), cm(3) molecule(-1) s(-1), respectively. An upper limit of k(3) < 6 x 10(-14) cm(3) molecule(-1) s(-1) was measured for the reaction of FC(O)O radicals with O-3. Finally, a rate constant of (5.5 +/- 0.7) x 10(-12) cm(3) molecule(-1) s(-1) was measured for the association reaction of F atoms to NO in 1000 mbar of SF6 diluent. All experiments were performed at 296 +/- 2 K. Results are discussed with respect to the atmospheric chemistry of hydrofluorocarbons.