Temperature dependence of the O+I(~2P_(1/2))→O+I(~2P_(3/2)) quenching rate constant

摘要

The rate constant for quenching of I(~2P_(1/2)) by O(~3P) has been measured for the temperature range 295-360 K. Pulsed laser photolysis of mixtures N_2O and I_2 was used to examine the kinetics. O(~3P) atoms were produced by the photoinitiated reaction sequences N_2O + hv→O(~1D))+N_2 and O(~1D)) +M→O(~3P)+M, while singlet oxygen was generated by the secondary reaction O(~1D)+N_2O →O_2(a ~1'Δ)+N_2. Iodine atoms were produced by I_2 photodissociation and from the secondary reactions of I_2 with O(~3P) atoms. Subsequent excitation of I by O_2(a ~1Δ) led to I(~2P_(1/2)) formation, with I(~2P_(1/2)) concentrations monitored using time-resolved 1315 nm emission. The rate constant of the quenching process was determined by fitting a kinetic model to the observed emission traces. Special attention was given to the gas flow conditions. A modest temperature dependence of the quenching rate constant was found, and this was well represented by the equation k=(6.5±1) × 10~(-12)(T/300)~(1.76) cm~3 s~(-1). The roomrn temperature rate constant differs from previous experimental determinations but agrees well with the value determined by modeling of the data from discharge driven oxygen-iodine lasers.