Knowledge Bank

Ab initio potential energy surface calculations have been carried out for the ground and several excited states of the $NO2$ molecule and $H2O+$ ion. These surfaces have been calculated by SCF and limited-CI methods using contracted Gaussian-lobe basis sets of double-zeta quality. Results of these calculations will be presented and discussed for potential surfaces which intersect at $C2v$ molecular conformations, but interact and undergo avoided crossings when the molecule is distorted to $Cs$ conformations. An example of such a pair of surfaces is the $12A\prime -22A\prime$ set of $NO2$ electronic states that at $C2v$ conformations are designated $l2A1$ and $l2B2$.