3-ethyl-2-[3-(3-ethyl-2(3H)-benzoxazolylidene)-1-propenyl]benzoxazolium iodide (dye I) and pseudoisocyanine bromide are employed to form H aggregates as donors and J aggregates as acceptors. The energy of an H band of the H aggregates is higher than that of a J band of the J aggregates. It was confirmed that excitation of the H band does not emit fluorescence by comparison of excitation spectra of dye I H aggregates with that of dye I monomer. Absorption, fluorescence, and excitation spectra of spin-coated films of H aggregates mixed with various quantities of J aggregates have been observed. Excitation spectra probed at the J band are found to have a component of the H band. Fluorescence spectra originated from excitation of the H band are extracted and qualitatively analyzed. It is confirmed that excitation of the H band causes to emit fluorescence of a J band of the J aggregates. These phenomena show that exciton energy can transfer from the lowest energy in electronic states of the H aggregate, which state is optically forbidden, to electronic state of the J aggregate.
Simultaneous modulations of both frequencies and amplitudes of C-C and C = C stretching vibration modes, due to dynamical coupling to a breather soliton, in trans-polyacetylene was successfully time resolved. The frequency shifts of both modes were in good agreement with a simulation based on the Su-Schrieffer-Heeger model. It was found that the intensities of transition dipoles changed due to the breather, whereas transition energies were dominantly modulated by C = C stretching mode as recent theoretical work predicted.
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