A PHOTOCHEMICAL, THERMODYNAMIC, AND KINETIC-STUDY OF CLOO

The relative absorption cross sections for the ClOO radical were measured in the region 220-280 nm. The absolute UV absorption cross section at 246.0 nm, the peak of the absorption, was determined to be (2.98 +/- 0.23) x 10(-17) cm2 molecule-1. Using this value, the cross sections in the 220-280-nm range were calculated. The equilibrium constant for the Cl + O2 reversible ClOO reaction was measured at six temperatures between 191 and 250 K. A third law analysis of these measured equilibrium constants yields a value of -5.1 kcal mol-1 for DELTA-degrees-H(r233) or -4.6 kcal mol-1 for DELTA-degrees-H(r0) The removal of ClOO in the above temperature range was found to occur via the reaction Cl + ClOO --> products. The rate coefficient for this reaction was measured to be (2.15 +/- 0.13) x 10(-10) cm3 molecule-1 s-1, independent of temperature.