The dissociation of HNO. I. Potential energy surfaces for the X̃1A′, Ã1A′, and ã3A′ states

Abstract

Three-dimensional potential energy surfaces for the X̃1A″, Ã1A″, and ã3A″ states of HNO have been calculated at the multireference configuration interaction (MRCI) level of ab initio theory. Energy points are calculated at 1728 molecular configurations, predominantly sampling the HNO well and the H+NO product channel regions. Energies between grid points are obtained by interpolation with a three-dimensional cubic spline. The well depths are 2.14, 1.27, and 0.38 eV for X̃1A″, ã3A″, and Ã1A″, respectively. Saddle points to inversion, isomerization, and dissociation are reported and their importance discussed to relevant processes. The HNO(X̃1A″) potential energy surface is purely attractive along its minimum energy path to ground-state products, whereas the ã3A″ and Ã1A″ states have barriers of 0.21 and 0.50 eV, respectively. Vibrational term values and rotational constants for HNO and DNO are reported for the fundamental vibrations for all three electronic states. Where comparison with experimental data is possible, the agreement is satisfactory. The three potential energy surfaces are appropriate to study the predissociation dynamics in the Ã1A″ state and the unimolecular dissociation in the X̃1A″ state. © 1997 American Institute of Physics.