FEMTOSECOND OPTICAL PROCESSES IN DURHAM POLYACETYLENE AND NORBORNYLENE POLYACETYLENE COPOLYMER

The femtosecond non-linear optical response of polyacetylene and a norbornylene-polyacetylene copolymer, synthesized by the ''Durham'' route, has been measured using a variety of resonant four-wave mixing and transient absorption experiments. The source, magnitude and sign of the ground and excited state contributions to the third-order non-linearity have been resolved temporally and by polarization. The kinetics of excited state absorption is modelled on the basis of carrier recombination by one-dimensional diffusion. Photon echo measurements put an upper limit of 30 fs on the pure dephasing time.