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

In this paper,we have calculated the second-order non-linear optical polarizabilities β_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.