TRIPLET EXCITON GENERATION AND DECAY IN A RED POLYDIACETYLENE STUDIED BY FEMTOSECOND SPECTROSCOPY

Results from femtosecondrpicosecond transient absorption spectra measurements in the near-infraredrvisible spectral region of the red form of a soluble polycarbazolyldiacetylene in a polyethylene matrix are reported. Intrachain singlet and triplet excitons are identified by the different dynamics of the photoinduced bands. The results are consistent with the ultrafast generation -200 fs. of triplet pairs by fission of a singlet state located below the first optically allowed electronic state. In the picosecond time domain, triplet pairs undergo a random walk in a one-dimensional path with statistically distributed traps and partially dissociate into long-lived (150 micros. localized triplets