THE QUANTUM-YIELD OF FORMATION OF CF2O IN THE GAS-PHASE PHOTOOXIDATION OF CF3I AT 253.7-NM

The quantum-yield of formation of CF2O in the gas-phase photo-oxidatio n of CF3I at 253.7 nm, Phi(CH2O)(253.7) has been measured for the firs t time. The value obtained, 1.05 +/- 0.11 (+/- sigma), was determined using Fourier transform infrared (FTIR) spectroscopy. CF2O concentrati ons were measured by performing a Beer's Law analysis on the P and R b ranches of the nu(2) absorption of CF2O at 1956.1 and 1943.1 cm(-1), r espectively. Actinometry at 253.7 nm was carried out using the trifluo roaceticanhydride, (CF3CO)(2)O, (TFAA) system recommended previously ( G.A. Chamberlain and E. Whittle, J. Chem. Sec. Faraday Trans. I, 71 (1 975) 1978), and was based on comparison of the intensities of eight P and R vibration-rotation lines of the CO photoproduct with those of CO recorded for calibration mixtures composed of CO and TFAA. A quantum- yield of I-2 formation of 0.47 +/- 0.04 was also measured by optical a bsorption techniques. It is suggested that CF2O and I-2 are formed via the decomposition of CF3OOI, trifluoromethylperoxyhypoiodite. This sp ecies is produced in the reaction of CF3O2. radicals with atomic I, wh ich acts as a chaperone for the observed chemistry.