| We explore the properties of quantum chemical approximations to the excited states of model chromophores of the green fluorescent protein of A. victoria. We calculate several low-lying states by several methods of quantum chemical calculation, including state-averaged complete active space SCF (CASSCF) methods, time dependent density functional theory (TDDFT), equation-of motion coupled cluster (EOM-CCSD) and multireference perturbation theory (MRPT). Amongst the low-lying states we identify the optically bright pipi* state of the molecules and examine its properties. We demonstrate that the state is dominated by a single configuration function. We calculate zero-time approximations to the resonance Raman spectrum of GFP chromophore models, and assign published spectra based upon these. |
