Kinetic studies for advanced iodine laser concepts

Singlet oxygen-generators for COIL devices that involve discharge or optical excitation are currently being investigated. These generators deliver relatively high yields O-2(b(1)Sigma(+)) as the flows do not contain water vapor. In addition, discharge generators provide high concentrations of O atoms. Dissociation of I-2 by the reagent streams from these generators will follow different kinetic pathways than those that are most important when the flow from a chemical generator is used. To provide a basis for understanding the dissociation kinetics that will be relevant for discharge and optically driven COIL devices we have examined the quenching of O-2(b) and O-2(a) by I-2. Dissociation of I-2 by atomic oxygen and I*+O quenching have also been investigated. The primary findings are: (1) Quenching of O-2(b) by I-2 is fast (5.8x10(-11) cm(3) s(-1)) with a branching fraction of 0.4 for the channel O-2(b)+I-2-->O-2(a)+I-2. (2) Quenching of O-2(a) by I-2 is too slow (k<5x10(-16) cm(3) s(-1)) to be the initiation step in the I-2 dissociation process. (3) O-2(a) is generated when I-2 is dissociated by O atoms. (4) The upper bound for the rate constant for quenching of I* by O atoms is k<5x10(-12) cm(3) s(-1).