Studies on two-photon absorption cross-sections of different type stilbenederivatives

The geometry, electronic structures and electronic spectra of different typ e stilbene derivatives (D - pi - D, A - pi - A, D - pi - A) are systematica lly studied by AM1 and ENDO/CI methods. On the basis of correct UV - vis sp ectra, the position and strength of the two - photon absorption can be pred icted. Nonlinear third - order optical susceptibilities and two - photon ab sorption cross - sections was calculated using a program of Sum - over - st ates expression compiled by the present authors. The influence of various s ubstituents on two-photon absorption cross - sections are discussed microme chanically.