Electronic Structures and Nonlinear Optical Properties for Cross-Conjugated Polyene

Abstract

ABSTRACTFor several cross-conjugated molecules, molecular excited states and third-order nonlinear susceptibilities γ are calculated by semi-empirical molecular orbital method. The calculated γ are compared with each other and the reason for the differences are discussed in terms of the orbital shapes which contribute mainly to γ. The reason that long polyene chains have large γ, is ascribed to the large transition moment which is explained by the signs of the LCAO coefficients. On the other hand, it is found that the cross-conjugated molecules in which two similar-length chain cross at the center is not good for large third-order susceptibility.