QUENCHING OF I(2P1/2) BY O3

The quenching of the spin-orbit excited state of iodine atoms (I*) by ozone was measured in a flash photolysis system monitoring the resonant absorption of I* at 206.2 nm. A quenching rate constant of (1.1 +/- 0.1) . 10(-11) cm3 s-1 was obtained at 300 K. This high value implies a reactive channel leading to the production of IO + O2. Indirect experimental observations confirm the presence of the latter species after the flash. A comparison of the present results with the reaction involving the fundamental state of atomic iodine is made. A strong spin-orbit effect is found. The rate constant for the quenching by O2 was also measured yielding a value of (2.7 +/- 0.3) . 10(-11) cm3 s-1.