Temperature dependence of the O+I(P21/2)→O+I(P23/2) quenching rate constant

Abstract

The rate constant for quenching of I(P21/2) by O(P3) has been measured for the temperature range 295–360 K. Pulsed laser photolysis of mixtures N2O and I2 was used to examine the kinetics. O(P3) atoms were produced by the photoinitiated reaction sequences N2O+hν→O(D1)+N2 and O(D1)+M→O(P3)+M, while singlet oxygen was generated by the secondary reaction O(D1)+N2O→O2(a 1Δ)+N2. Iodine atoms were produced by I2 photodissociation and from the secondary reactions of I2 with O(P3) atoms. Subsequent excitation of I by O2(a Δ1) led to I(P21/2) formation, with I(P21/2) 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 cm3 s−1. The room 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.

O2(a1Δ) quenching in the O/O2/O3 system

“…The photolysis radiation was provided by an excimer laser (Lambda Physik Compex Pro 102, 10 ns pulse duration) operating at 248 nm (KrF). The photolysis cell has been described in recent publications [16][17][18][19]. It was constructed from a solid brass block with 1 cm diameter channels for the flow of gases, the passage of the photolysis laser beam, and the observation of emission from the photolysis zone.…”

Kinetics of oxygen species in an electrically driven singlet oxygen generator

“…The most active processes involving electrons and ions in the discharge zone that can contribute to the kinetics of these species are listed in Table 1 (processes [13][14][15][16][17][18]. For the typical electric discharge O 2 (a 1 ∆) generator conditions [30] .…”

“…as phase processes involving the reactive oxygen species O 2 (a 1 ∆), O( 3 P) and O 3 have been studied extensively due to their importance in the terrestrial atmosphere [1][2][3][4][5][6], oxygencontaining plasmas [7][8][9][10], the oxygen-iodine laser [11][12][13][14] and combustion [15][16]. There has been a long standing interest in the possibility of developing a discharge driven oxygen iodine laser (DOIL), where O 2 (a 1 ∆) is produced via electric discharge [7][8][9][10][11][12][13].…”

Recent advances in the development of discharge‐pumped oxygen‐iodine lasers

“…I is then rapidly dissociated by the sequence (14) (15) By this means O atoms are removed and I is dissociated without depletion of the energy stored by O (a). However, if the O atoms are not consumed in this process their presence becomes detrimental due to the quenching reaction [31,32] …”

“…Initial attempts to determine this rate constant in a pulsed photochemistry experiment produced a much lower estimate, but subsequent measurements have provided results that are consistent with the modeling estimates. Most recently, Mikheyev et al [32] used photolysis of N O/I mixtures to investigate the quenching rate constant for the temperature range from 293 to 360 K. O( P) atoms were produced by the photo-initiated reaction sequence (24) (25) while singlet oxygen was generated by the secondary reaction (26) Iodine atoms were produced by I photodissociation and from the secondary reactions of I with O( P) atoms. Subsequent excitation of I by O (a) led to I( P formation, with I( P concentrations monitored using timeresolved 1315 nm emission.…”