A photoionization mass spectrometric study of HNCO yields the ionization potential (I.P.) (HNCO)=11.595±0.005 eV and the appearance potential (A.P.) (NCO+/HNCO)≤16.532±0.011 eV at 0 K. A similar study of NCO (generated by F+HNCO) gives I.P. (NCO)=11.759±0.006 eV. These observations lead to D0 (H–NCO)≤110.1±0.3 kcal/mol. Additional analysis enables one to infer 28.4±0.5 kcal/mol ≤ ΔHf00 (NCO)≤32.8±0.7 kcal/mol. The implication of these results for kinetic modeling of the processes for reduction of NOx is discussed.

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