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Femtosecond energy relaxation in pi -conjugated polymers.

Ultrafast relaxation processes in poly(p-phenylenevinylene) and its oligomers are investigated using femtosecond luminescence spectroscopy. A quasi-instantaneous luminescence rise and the absence of luminescence near the excitation energy indicate very rapid vibronic relaxation. The subsequent transient redshift of the spectra is attributed to ultrafast energy relaxation of optical excitations within an inhomogeneously broadened density of states