Coherence and decoherence in a conjugated polymer: waves, dephasing, and stochastic motion

The dynamics of optical relaxations, subsequent to excitation with a femtosecond (fs) laserpulse, were monitored via site-selective time-resolved luminescence spectroscopy. The sample under investigation was the conjugated polymer poly(para-phenylene vinylene) (PPV). The techniques of luminescence up-conversion and luminescence interferometry were applied to investigate the relaxation in the incoherent and the coherent regime, at low temperature (1.4 K). By varying the excitation energy (2.275 eV to 2.583 eV) it was possible to monitor the dispersive excitation energy transfer, the dynamic stokes shift, and electronic coherences in the low energy edge of the S1-states of PPV. (author)