ATMOSPHERIC CHEMICAL-KINETICS OF FC(O)O

Temperature dependent rate constant measurements over the range 233-323 K are reported for the reactions of FC(O)O with NO, NO2, O-3, HO2, C2H5O2, F, and FC(O)O, along with rate constants for the reaction with FCO, FC(O)O-2, and C2H5 at 295 K. FC(O)O is generated by the 193 nm photolysis (FC(O)O)(2). The photolysis yields 67% F atoms and 33% FC(O)O radicals at 295 K. The latter species is formed with extensive internal excitation, principally in the upsilon(3) bending mode, but is collisionally relaxed with an overall rate of (3.5 x 10(-13))P-tot s(-1). An FC(O)O visible absorption cross section of (9.2 +/- 0.8) x 10(-18) cm(2) at 641 nm is determined by three methods: the formation of FNO from FC(O)O, the removal of ethylperoxy radicals by FC(O)O, and comparison to CH3Cl photolysis. Kinetics measurements are made by monitoring the transient change in UV/vis absorption by FC(O)O, C2H5O2, HO2, O-3, and/or FC(O)O-2. The rate constants for the removal of FC(O)O by atmospherically important radicals are k(12) = 3.6 x 10(-11)(T/300)(-0.1) cm(3) s(-1) for NO, k(27) = 7.5 x 10(-12)(T/300)(-3.1) cm(3) s(-1) for NO2, and k(25) = 1.2 x 10(-11)(T/300)(-1.2) cm(3) s(-1) for HO2. In contrast, the rate constant for reaction with ozone is very slow, k(29) < 3 x 10(-15) cm(3) s(-1). This precludes the suggestion that FC(O)O could participate in catalytic ozone depletion cycles.