DIRECT DETERMINATION OF PRODUCT BRANCHING FOR THE NH2+NO REACTION AT TEMPERATURES BETWEEN 302 AND 1060 K

The branching ratio of the two product channels of the NH2 + NO reacti on, alpha and beta for the formation of N2H + OH and N-2 + H2O, respec tively, have been determined independently at temperatures between 302 and 1060 K by mass spectrometry. For beta determination, the concentr ation of H2O was measured directly, whereas for a, the yield of OH was monitored by the CO2 formed by its reaction with added Cd. Both [H2O] and [CO2] were carefully calibrated with different standard mixtures before each measurement. a was found to increase gradually from 0.11 /- 0.02 at 302 K to 0.30 + 0.02 at 1060 K, with the concomitant decrea se of beta from 0.89 +/- 0.04 to 0.70 +/- 0.03. The two independent me asurements indicate for the first time that the relationship alpha + b eta = 1 holds quantitatively throughout the temperature range studied.