Structure Property Relationships For Third-Order Organic Non-Linear Optical Materials.
Final rept. 1 Mar 92-28 Feb 95,
CALIFORNIA INST OF TECH PASADENA
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The dependance of the second and third order polarizabilities on ground state polarization was measured for a series of donor acceptor polyenes using electric field induced second harmonic generation and third harmonic generation, respectively. The changes in ground state polarization, associated with the donoracceptor strength or solvent polarity, were probed by x ray crystallography, nuclear magnetic resonance, electronic absorption and Raman spectroscopies. Tile observed behavior of the second and third order polarizabilities as a function of ground state polarization agrees well with theoretical predictors. In particular, positive and negative peaks, as well as sign changes, were observed for both the second and third order polarizabilities. The dependences for the second and third order polarizabilities are consistent with a derivative relationship between them. In addition, the third order polarizability of a series of molecules possessing zero bond length alternation was found to be negative, in agreement with predictions based on the relationship between the polarizabilities and ground state geometry.