Effects of chalcogen atoms on the third-order hyperpolarizability of xanthone homologues

The third-order nonlinear hyperpolarizabilities (γ) of anthrone (ATN), xanthone (O-XTN), thioxanthen-9-one (S-XTN), and selenoxanthen-9-one (Se-XTN) have been measured in tetrahydrofuran (THF) solution by degenerate four-wave mixing (DFWM) using 7 ns and 40 ps pulses with a wavelength of 532 nm. The obtained γ of these four compouns using 7 ns pulses are 6.9×10−34, 0.9×10−34, 87×10−34 and 12×10−34 esu and those using 40 ps pulses are 3.9×10−35, 19×10−35, 15×10−35, and 8.2×10−35 esu. These results indicate that the γ of xanthone homologues depend largely upon the element at the 10-position especially when 7 ns pulses were used. It is proposed that a very large γ of S-XTN obtained using a 7 ns pulse may arise from thermal mechanisms.