Dynamics of singlet excitons in 1D conjugated polydiacetylene chains:: a femtosecond fluorescence study

The B-1(u) exciton lifetime has been measured in isolated polydiacetylene chains, using fluorescence up-conversion. It is found to be 130-135 fs at 20 K, and corresponds to the non-radiative internal conversion to a lower-lying excited A, state, as in polyenes. At low temperature, the absorption linewidth is almost lifetime-limited: inhomogeneous broadening is small (less than or equal to 30 cm(-1)). The lineshape remains Lorentzian up to 150 K, but with a three-fold increase in width, whereas the lifetime is merely constant. The broadening is most probably due to a reduction of the coherence time. (C) 1999 Elsevier Science B.V. All rights reserved.