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Kinetics of the NH Reaction with H2 and Reassessment of HNO Formation from NH + CO2, H2O
RENSSELAER POLYTECHNIC INST TROY NY DEPT OF CHEMICAL AND BIOLOGICAL ENGINEERING
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The reaction of ground-state NH with H2 has been studied in a high-temperature photochemistry HTP reactor. The NHX3sigma radicals were generated by the 2-photon 193 nm photolysis of NH3, following the decay of the originally produced NHA3product radicals. Laser-induced fluorescence on the NHA3product-X3 sigma 0, 0 transition at 336 nm was used to monitor the progress of the reaction. We obtained kappa 833-1432 Kappa 3.5 x 10-11 exp-7758 KappaTau cm3 molecule-1 s -1, with plus or minus 2 sigma precision limits varying from 12 to 33 and corresponding accuracy levels from 23 to 39. This result is in excellent agreement with that of Rohrig and Wagner Proc. Combust. Inst. 25 1994 975 and the data sets can be combined to yield kappa 833-1685 Kappa 4.4 x 10-11 exp-8142 KappaTau. Starting with this agreement, it is argued that their rate coefficients for NH CO2 could not be significantly in error Proc. Combust. Inst. 25 1994 975. This, combined with models of several combustion systems, indicates that HNO CO cannot be the products, contrary to their suggestion Proc. Combust. Inst. 25 1994 975. Ab initio calculations have been performed which confirm this conclusion by showing the barriers leading to these products to be too high compared to the measured activation energies. The calculations indicate the likelihood of formation of adducts, of low stability. These then may undergo further reactions. The NH H2O reaction is briefly discussed and it is similarly argued that HNO H2 cannot be the products, as had been previously suggested.
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