Global potential energy surface, vibrational spectrum, and reaction dynamics of the first excited, ((A)over-tilde2A′) state of HO2

The authors report extensive high-level ab initio studies of the first excited ((A) over tilde (2)A') state of HO2. A global potential energy surface (PES) was developed by spline-fitting 17 000 ab initio points at the internal contracted multireference configuration interaction (icMRCI) level with the AVQZ basis set. To ascertain the spectroscopic accuracy of the PES, the near-equilibrium region of the molecule was also investigated using three interpolating moving least-squares-based PESs employing dynamically weighted icMRCI methods in the complete basis set limit. Vibrational energy levels on all four surfaces agree well with each other and a new assignment of some vibrational features is proposed. In addition, the dynamics of both the forward and reverse directions of the H+O-2((a) over tilde (1)Delta(g))<-> OH + O reaction (J=0) were studied using an exact wave packet method. The reactions are found to be dominated by sharp resonances. (C) 2010 American Institute of Physics. [doi:10.1063/1.3490642]