I*(5 2<i>P</i>1/2) quenching kinetics

Abstract

Rate constants for the quenching of excited I(5 2P1/2) atoms by I2, O2, ICl, and Cl2 have been measured using time resolved I(2P1/2→2P3/2) 1.315 μm fluorescence from iodine atoms produced by the UV laser induced photodissociation of either CF3I or i-C3F7I. Using the pulsed photodissociation of CF3I at 248 nm as an I(5 2P1/2) source the measured rates (cm3/molecule s) were (3.0±0.1)×10−11, (2.1±0.1)×10−11, (3.3±0.4)×10−11, and (2.0±0.1)×10−14 for I2, O2, ICl, and Cl2, respectively. Using the pulsed photodissociation of i-C3F7I at 308 nm as an I(5 2P1/2) source, similar rates were measured for I* quenching by I2 and ICl, but the I(5 2P1/2)+Cl2 quenching rate increased strongly with increasing amounts of Cl2 photodissociation. For approximately 1.8% Cl2 dissociation at 308 nm the measured rate constant for I(5 2P1/2)+Cl2 quenching was (4.3±0.1)×10−13 cm3/molecule s. This increase in the I*+Cl2 rate is attributed to the two body quenching reaction I*+Cl→I+Cl with a rate constant on the order of 1.5×10−11 cm3/molecule s.