BRANCHING RATIO OF THE REACTION NH2-TEMPERATURES(NO AT ELEVATED)

The branching ratios into the OH and H2O producing channels in the rea ction of NH2 with NO have been measured at four temperatures ranging f rom.room temperature to 900-degrees-C. The reaction was initiated by p roduction of NH2 by excimer laser photolysis of ammonia at 193 nm in t he presence of nitric oxide and was probed using a color center laser in conjunction with fast IR detectors. Upon photolysis, the NH3 infrar ed absorption decreases with consequent appearance of NH2 infrared abs orption lines. The magnitude of the decrease in the NH3 infrared absor ption is compared with infrared absorbance of OH and H2O produced by t he reaction. Measurement of room temperature peak absorption cross sec tions for NH3, NH2, and H2O combined with the literature value of the OH cross section permits the determination of the branching ratios. Fo r elevated temperatures, the appropriate Boltzmann factors and partiti on functions were used to calculate the required cross sections from t he room temperature values. The branching ratio into the OH channel wa s observed to increase from 10% at room temperature to 17% at 900-degr ees-C. However, the total contribution of the two channels decreased f rom almost-equal-to 94% at 26-degrees-C to almost-equal-to 70% at 900- degrees-C, possibly indicating the onset of an additional reaction cha nnel. The possibility that the OH signal might arise from an artifact source was investigated.