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有机共轭分子由于其非定域的π电子体系常呈现大的非线性光学响应。共轭链长是影响其非线性光学系数的重要因素。 本文用量子化学方法研究了共轭链长对一系列有机分子二阶非线性光学系数的影响,所选的分子为:NEPEA—nn’(n+n’=0,1,2)和NPEPA—m(m=1,2,3),其化学结构如图1所示。在这2个系列中把苯环的贡献看作2个乙烯π键,则在胺基和硝基之间的π键数N_π从2变化到7。
Organic conjugated molecules often exhibit large nonlinear optical responses due to their non-localized π-electron system. Conjugate chain length is an important factor affecting the nonlinear optical coefficient. In this paper, the influence of conjugate chain length on the second-order nonlinear optical constants of a series of organic molecules has been investigated by using quantum chemistry method. The selected molecules are NEPEA-nn ’(n + n’ = 0,1,2) and NPEPA- m (m = 1,2,3), the chemical structure shown in Figure 1. In these two series, the contribution of the benzene ring is taken as two ethylene π bonds, then the π bond number N_π between the amine group and the nitro group changes from 2 to 7.