2-PHOTON ABSORPTION AND EXCITED-STATE REFRACTIONS IN ANTHRAQUINONE DYES

We examine the nonlinear optical properties of solutions of 9,10-anthr aquinone, 1,4-dihydroxy-anthraquinone, 5,8-dichloro-1,4-dihydroxy-anth raquinone and 1,4-bisethyl amino-anthraquinone by means of the intensi ty-dependent transmission and the Z-scan method with 532 nm 8 ns pulse s. The results demonstrated that the 9,10-anthraquinone displayed a tw o-photon absorption (TPA) character. The molecular TPA cross section o f this compound is estimated as sigma(2) = 7.22 x 10(-19) cm(4)/GW or sigma(2) = 26.96 x 10(-48) cm(4)/photon/s, respectively, and an essent ial state of 'm(1)A(g)', which should be located near the 2 omega virt ual transition state, is predicted. On the other hand, the effective e xcited-state nonlinear refractive coefficients n(2)(eff) these anthraq uinones are found to be similar to 10(-10) esu, which are comparable w ith those highly conjugated planar molecules of tetrabenzporphyrins an d phthalocyanines.