The efficient generation of accurate molecular potential energy surfaces (PESs) is a perpetual challenge for theoretical chemistry. It is particularly difficult to reliably determine excited state PESs, which typically exhibit intersecting adiabatic surfaces. The accurate description of these electronic surfaces, as well as the reproduction of seams of conical intersection, 1 are a requirement for dynamical studies of photo-initiated nonadiabatic processes. Generally, the required excited state PESs are generated using quantum chemistry methods, either via the parameterization of model potential functions or 'on-the-fly', as is common in trajectory simulations. The accuracy of these surfaces is strongly dependent on the level of electronic structure theory employed, and even different high levels of ab initio theory may yield qualitatively different excited state PESs. Electronic structure methods that are capable of furnishing accurate PESs over the range of electronic characters and nuclear configurations encountered in, e.g., organic photochemistry are typically characterized by an ability to describe electronic states for which a good zeroth-order description involves multiple electronic configurations. That is, those that are multi-reference in nature. Electronic structure methods that can simultaneously meet these requirements are generally based on restricted and complete active space self consistent field (RASSCF/CASSCF) methods. Dynamic correlation may then be included by employing perturbation theory (as in the complete active space second-order perturbation theory, [CASPT2]) or configuration interaction (multi-reference configuration interaction, [MRCI]). 9,10 A consequence of the generality of active space methods is that they are typically computationally expensive. Furthermore, they generally require significant user input into the selection of the relevant active spaces, and the quality of the results is strongly dependent on how these spaces are chosen.