EFFECTS OF CHALCOGEN ATOMS ON THE 3RD-ORDER HYPERPOLARIZABILITY OF XANTHONE HOMOLOGS

The third-order nonlinear hyperpolarizabilities (gamma) of anthrone (A TN), xanthone (O-XTN), thioxanthen-9-one (S-XTN), and selenoxanthen-9- one (Se-XTN) have been measured in tetrahydrofuran (THF) solution by d egenerate four-wave mixing (DFWM) using 7 ns and 40 ps pulses with a w avelength of 532 nm. The obtained gamma of these four compounds using 7 ns pulses are 6.9 X 10(-34) 0.9 X 10(-34), 87 X 10(-34) and 12 X 10( -34) esu and those using 40 ps pubes are 3.9 X 10(-35) 19 x 10(-35), 1 5 x 10(-35) and 8.2 X 10(-35) esu. These results indicate that the gam ma of xanthone homologues depend largely upon the element at the 10-po sition especially when 7 ns pubes were used. It is proposed that a ver y large gamma of S-XTN obtained using a 7 ns pulse may arise from ther mal mechanisms.