SYSTEMATIC CHARACTERIZATION OF EXCITED-STATES IN PI-CONJUGATED POLYMERS

Exact finite chain calculations within a diagrammatic exciton basis gi ve pictorial descriptions of all excited states of pi-conjugated polym ers. In linear chain polymers the 1B(u) is an exciton, and the fundame ntal two-photon states can be broadly classified into triplet-triplet, charge-transfer and singlet-singlet excitations. The mA(g), a two-pho ton state that plays a strong role in nonlinear optics, is a correlate d charge-transfer state. The singlet-singlet states occur higher in en ergy and split into bound biexcitons and a continuum of free two-excit on states. (C) 1997 Elsevier Science B.V.