VIBRATIONAL RAMAN-SPECTROSCOPY OF POLYCONJUGATED ORGANIC OLIGOMERS AND POLYMERS

New classes of polymers and oligomers whose backbone consists of a net work of delocalized pi electrons have recently been synthesized and sh ow electrical and non-linear optical properties of great interest for new technologies. The vibrational spectra of these materials show pecu liar features which, if properly interpreted, can provide unique struc tural information. The interpretation of the spectra requires the deve lopment of new theoretical tools. The theoretical and experimental asp ects of the problem are presented. It is also shown that the nuclear r elaxation following the excitation of the electrons by an intense elec tromagnetic field can be described in terms of the vibrational modes a nd can be related to the nuclear contributions to the non-linear optic al responses of the material. In this case Raman intensities play a de termining role.