Fluorescence spectra of all trans 1,4-diphenylbutadiene obtained by the two-photon excitation into the 2(1)Ag state

The fluorescence spectra obtained by the two-photon excitation into the 2(1)Ag state of diphenylbutadiene (DPB) have been measured in room temperature solutions, along with the one- and two-photon absorption spectra. It is shown that DPB molecule excited into the two-photon allowed 2(1)Ag state through the two-photon process exhibits the fluorescence from the two-photon forbidden 1(1)Bu state irrespective of the solvent polarizability. Relaxation processes followed by the two-photon excitation into the 2(1)Ag state, and the shape of the two-photon absorption spectra measured when the 2(1)Ag origin is located below the 1(1)Bu origin are discussed