Picosecond transient Raman scattering in polydiacetylene 4-BCMU films

Abstract Picosecond transient resonant Raman scattering (TPRRS) measurements at room temperature have been completed on solution-cast thin films of polydiacetylene 4-BCMU. We observed a transient reduction of a few percent in Raman scattering intensity for both C = C and C = C stretching vibrations when pumping at the absorption edge; this is explained by saturation of the RRS cross section caused by photogenerated excitons. At low pump intensities ( 2 ) the TPRRS decay is quite fast (of order 3 ps) and the TPRRS spectra follow the regular Raman lineshape. For high pump intensities (>15 MW/cm 2 ), however, a narrow spectral hole burning in TPRRS is observed and the TPRRS decay becomes considerably longer. The latter effect is explained by a phonon-mediated stark effect which is enhanced under resonance conditions.