Probing of the 2A(g) state in nanopolyacetylene on the time scale from femtoseconds to milliseconds

The dynamic properties of the 2A(g) stare in films of nanopolyacetylene hav e been measured using photoinduced spectroscopy and photoinduced polarimetr y methods both in the transient and cw regime. The excitation density per p olyacetylene nanoparticle was no more than one absorbed pump photon. Using femtosecond pulses, we evaluated the rise time (less than or equal to0.2 ps ) and the decay time (approximate to1 ps) of the photoinduced response from the 2A(g) state of ruans-nanopolyacetylene. The longest relaxation time ap proximate to7 mus was measured at room temperature. Using picosecond pulses and a novel photoinduced polarimetry method, we have done the first measur ements of the transient polarization response of a conjugated material. The observed polarization signal is associated with a small photoinduced dichr oism and birefringence in the 2A(g) state. The decay time of the polarizati on signal was approximate to0.3 ns. (C) 2001 Elsevier Science B.V. All righ ts reserved.