RESONANCE RAMAN-SPECTROSCOPY AS A TEST OF AB-INITIO METHODS FOR THE COMPUTATION OF MOLECULAR-POTENTIAL ENERGY SURFACES

The use of ab initio quantum chemical methods to aid in the interpreta tion of resonance Raman spectra is illustrated with examples where the resonant electronic absorption spectra are unstructured. In such case s only the gradient of the excited electronic state potential energy s urface at the ground electronic state geometry is important in determi ning the upper state dynamics that are relevant to the Raman scatterin g process, The use of ab initio methods for which analytic gradients a re available permits application to large molecular systems and to clu ster models of molecules in solution. This procedure eliminates possib le ambiguities in the empirical interpretation of resonance Raman spec tra. These same ab initio methods may be used to provide descriptions of the groundstate normal modes and the effect of isotopic substitutio n on the form of the normal modes. (C) 1998 John Wiley & Sons Ltd.