Analytical global potential energy surfaces of the two lowest (2)A ' states of NO2

We report two new global analytical potential energy surfaces (PESs) corres ponding to the lowest adiabatic 1 (2)A' and 2 (2)A' states of NO2. High qua lity ab initio calculations were performed at a MRCI (multi-reference confi guration interaction) level using a polarised triple-zeta basis set. Energi es were computed on a grid of 650 and 595 energies for the 1 (2)A' and 2 (2 )A' states respectively. These were used to construct global analytic PESs with the DMBE (double many-body expansion) method, paying special attention to the O(P-3) + NO((2)Pi) channel. Additionally, a SEC correction (scaled external correction) was applied in order to obtain the correct dissociatio n energy in this channel for the ground 1 (2)A' state. Particular attention was paid to the inclusion of an anisotropic long-range description of the potential, which was absent in the previously available global PESs. Geomet ries and energies of the main stationary points of these (2)A' surfaces com pare very well with other theoretical and experimental data.