共轭链长及羰基位置对分子二阶极化率的影响

Carbonyl Location and Conjugated System Dependence of the Second Order Nonlinear Polarizablity

采用引入外场微扰的ＣＮＤＯ／Ｓ－ＣＩ方法，计算了一系列二苯基烯酮类化合物的分子二阶极化率（或二阶非线性光学系数）βｖｅｃ值。选取了苯不上含不同取代基团的化合物，从羰基在共轭链中的位置及共轭链长度方面，控讨了其微观二阶非线性光学效应的变化规律。结果表明：共轭链中羰基位置对βｖｅｃ值有重要的影响，并且呈现出一定的规律性；对于苯环上取代相同基团的化合物，其分子二阶非线性光学系数随共轭链长度的变化成指数关系，ｌｎβｖｅｃ对于Ｃ＝Ｃ双键数目ｎ的变化斜率为０．４～０．６。

In this paper,we have calculated the second-order non-linear optical polarizabilitiesβ vec of a series of unsaterated carbonyl compounds using the CNDO/S-CI quantum chemical calculation program,and studied the β vec calues while the carbonyl location and the lenght of the conjugated chain change in the conjugated molecules.The results receal that the carbonyl location and the conjugated system can affect the β vec of the carbonyl compounds greatly.Moreover,there are certain laws in their changes.The change ratio of lnβ vec to n(the number of C=C in the conjugated molecule) is about 0.4～0.6.