RESONANT-RAMAN-SCATTERING STUDIES OF DISORDER IN SOLUTION-CAST POLYDIACETYLENE FILMS

The disorder in polydiacetylene films cast from solution is studied by Raman scattering under preresonance and resonance conditions in both Stokes and anti-Stokes configurations. The disorder-induced inhomogeneities in the exciton energy levels and the strongly coupled vibrations cause strong dispersion of the C?C and C?C stretching frequencies with the laser excitation photon energy, surprisingly similar to that of trans-polyacetylene. We show, however, that the complete inhomogeneously broadened phonon distribution is revealed when the excitation is not in resonance. In addition to the excitation resonance, resonances associated with the Stokes and anti-Stokes emission beams strongly affect the measured Raman profiles. © 1990 The American Physical Society.