Dynamics of Production and Oxidation of Boranes

Laser induced fluorescence was used to measure time dependent concentrations of Hydroxide resulting from the reaction of oxygen (3P) with diborane and ethane. The oxygen atoms were generated by titrating microwave discharged nitrogen/helium with Nitric oxide to the chemiluminescent endpoint. THe operating pressures in the flow reactor ranged from 5 to 15 torr; the mixtures consisted of He/O(3P)/fuel in the approximate ratios 100/1/0.1 to 100/1/1. Flow conditions were such that in the low pressure experiments the controlled residence time prior to detection were 0.8-17 ms; under the higher pressure conditions, the time interval covered was 2-35 ms. We estimated that the temperature of the reaction region was approx. 350K, based on rotational emission temperatures measured for BO, generated under closely similar conditions. First a complete mechanism was derived for ethane for a specified set of experimental parameters. For ethane, a single set of experimental conditions was selected for ratioing the recorded intensity to the computed OH density; this was cross-checked with other runs for ethane. Finally, a mechanism was developed for B2H6, which quantitatively checked our experimentally determined profiles both in shape and magnitude, for three sets of conditions, and within a factor of two for the concentration runs (100% B2H6 feeding into the reactor at 14 Torr).