Collective vibrational coherence in sexithiophenes films

Coherent molecular Vibrations are detected in sexithiophene thin films. The excitation source is a newly developed optical parametric amplifier that p rovides 10-12 fs pulses in the visible wavelength range. Five modes that co uple strongly with the lowest electronic transition, at omega(1) =112 cm(-1 ), omega(2) = 299 cm(-1), omega(3) = 702 cm(-1), omega(4) = 1040 cm(-1), om ega(5) = 1454 cm(-1), are identified. Their assignment is discussed based o n the comparison with high-resolution absorption and emission spectra and t heoretical predictions. (C) 1999 Elsevier Science B.V. All rights reserved.