A novel approach to evaluate non linear optical response in organic conjugated molecules from vibrational spectra

Summary form only given. The experimental and theoretical hyperpolarizabilities (/spl szlig/ and /spl gamma/) of several low band gap organic molecules are studied. These data are compared with the relaxation contributions (/spl szlig//sup r/ and /spl gamma///sup r/) calculated from vibrational observables (i.e. from infrared and Raman frequencies and intensities) on the basis of a model previously proposed by us. In all the cases studied the striking observation is made that the experimental and theoretical /spl szlig/ and (/spl szlig//sup r/ or, /spl gamma/ and /spl gamma//sup r/ are practically identical. These findings suggest that the evaluation of (/spl szlig//sup r/ and /spl gamma//sup r/ from vibrational data of low band gap molecules becomes an alternative way to measure molecular hyperpolarizabilities. The physical basis for this idea and its relevance will be presented and discussed.