Chemical kinetics of discharge-driven oxygen-iodine lasers

Oxygen-iodine lasers that utilize electrical discharges to produce O-2(a(1)Delta) are currently being developed. The discharge generators differ from those used in chemical oxygen-iodine lasers in that they produce significant amounts of atomic oxygen and traces of ozone. As a consequence of these differences, the chemical kinetics of the discharge laser are markedly different from those of a conventional chemical oxygen-iodine laser (COIL). The reactions of O with iodine include channels that are both beneficial and detrimental to the laser. The beneficial reactions result in the dissociation of I-2 while the detrimental processes cause direct and indirect removal of I(P-2(1/2)) (denoted I*, the upper level of the laser). We have examined kinetic processes relevant to the laser through studies of photo-initiated reactions in N2O/CO2/I-2 mixtures. The reactions have been monitored using absorption spectroscopy, laser induced fluorescence and time-resolved emission spectroscopy. It has been established that deactivation of I* by O atoms is a critical energy loss process. We have determined a rate constant of (1.2 +/- 0.1)x10(-11) cm(3) S-1 for this reaction. As part of this effort the branching fraction for the formation of O-2(a) from the reaction of O(D-1) with N2O was determined to be 0.38. This result has implications for lasers based on photolysis of O-3/N2O/I-2 mixtures and the formation of O-2(a) in the upper atmosphere.