Quantum scattering calculations on the NH3+OH→NH2+H2O reaction

Abstract

Quantum scattering calculations on the NH3+OH→NH2+H2O reaction have been performed at energies up to 0.8 eV. The rotating bond approximation is used, treating NH2 as a pseudoatom. The OH rotation and a reactive N–H stretch of NH3 are treated explicitly as well as the bending motion and one OH local stretch vibration of H2O. A reduced dimensionality potential energy surface is developed. It has accurate reactant and product rovibrational energy levels for the modes explicitly treated in the scattering calculations and incorporates the zero point energy of the other modes. Quantized transition states gating the flux are found and mode selectivity is observed. Reactants in their ground rovibrational states produce mainly ground state H2O and vibrationally excited NH3 produces mainly vibrationally excited H2O. Rate constants are obtained using an adiabatic approach to account for all degrees of freedom not explicitly treated in the scattering calculations. Tunneling makes a dominant contribution to the rate constants, which are in reasonable agreement with previous theoretical and experimental work.