THEORETICAL CHARACTERIZATION OF THE POTENTIAL-ENERGY SURFACE FOR NH+NO

The potential energy surface (PES) for NH + NO has been characterized using complete active space self-consistent field (CASSCF) gradient calculations to determine the stationary point geometries and frequencies followed by CASSCF/internally contracted configuration interaction (CCI) calculations to refine the energetics. The present results are in qualitative accord with the BAC-MP4 calculations of Melius and Binkley, but there are differences as large as 8 kcal/mol in the detailed energetics. Addition of NH to NO on a 2A' surface, which correlates with N2+OH or H+N2O products, involves barriers of 3.2 kcal/mol (trans) and 6.3 kcal/mol (cis). Experimental evidence for these barriers is found in the work of Bohmer et al. The 2A'' surface has no barrier to addition, but does not correlate with ground state products. Surface crossings between the barrierless 2A'' sur-face and the 2A' surface may be important. Production of N2+OH products is predicted to occur via a planar saddle point of 2A' symmetry. This is in accord with the preferential formation of PI(A') A doublet levels of OH in the experiments of Patel-Misra and Dagdigian. Addition of NH 1DELTA to NO is found to occur on an excited state surface and is predicted to lead to N2O product as observed by Yamasaki et al