SPECTRAL DIFFUSION IN 1D SYSTEMS - SIMULATION AND EXPERIMENTAL RESULTS FOR MATRIX-ISOLATED POLYDIACETYLENE AND POLY-ISOPROPENYLNAPHTHALENE

Spectral diffusion in 1 D systems with enenetic disorder has been studied employing Monte Carlo simulation and low temperature site-selective fluorescence (SSF) spectroscopy. By keeping track of the energy of an excitation started at specified sites within a one-dimensional array of hopping sites with Gaussian energy profile the temporal evolution of the occupational density of states has been determined. It allows the establishment of criteria for analysing SSF spectra parametric in excitation energy. Experimental results are presented for two prototypical systems: (i) a matrix-isolated polydiacetylene (PDA-9PA) chain as an example of an exchange-coupled 1 D system where disorder results from local chain distortion and (ii) poly-isopropenylnaphthalene as an example of a pendant group polymer with multipolar coupling among the chromophoies whose disorder results from the statistics of their environment. They provide insight to excitation dynamics in 1 D systems and illustrate the usefulness of SSF spectroscopy to disentangle the effects of energy migration and chromophore relaxation due to electron-phonon coupling on fluorescence spectra. © 1990.