Abstract: Much of what is known about the electronic excitations of PDAs has been learned from optical and resonance Raman (RR) spectroscopy (1, 2). In addition to measurements on single crystals the polymer has been studied in solutions, precipitates and thin films. This paper will attempt to review the experimental evidence for the nature of the electronic excited states in PDAs which are accessible by these spectroscopic techniques. Starting from the optical spectra for single crystals the effect of changing environment and conformation on the dominan...
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