Rate Constants for the Reactions of NH2 and HNO with Atomic Oxygen at Temperatures between 242 and 473 K

A pulsed laser photolysis−discharge flow−photoionization mass spectrometer system has been employed to investigate the kinetics of the reactions NH2 + O(3P) (atomic oxygen) and HNO + O(3P) over the temperature range 242−473 K in 2−7.5 Torr of He. O(3P) was generated in a microwave discharge of an oxygen−helium mixture, while NH2 was produced by 193 nm ArF laser photolysis of NH3. HNO was formed as a reaction product of NH2 + O. Both NH2 and HNO were photoionized by an Ar resonance lamp and detected as parent ions in a quadrupole mass spectrometer. From the analysis of the time profiles of ion signals for various O-atom concentrations, the overall rate constants are best represented by the pressure and temperature-independent values of k1 = (1.2 ± 0.3) × 10-10 and k2 = (3.8 ± 1.3) × 10-11 in the units of cm3 molecule-1 s-1 for the NH2 + O and HNO + O reactions, respectively. The value of k1 is 30−80% larger than values reported previously.