Collective vibrational coherence in sexithiophenes films

Abstract Coherent molecular vibrations are detected in sexithiophene thin films. The excitation source is a newly developed optical parametric amplifier that provides 10–12 fs pulses in the visible wavelength range. Five modes that couple strongly with the lowest electronic transition, at ω 1 =112 cm −1 , ω 2 =299 cm −1 , ω 3 =702 cm −1 , ω 4 =1040 cm −1 , ω 5 =1454 cm −1 , are identified. Their assignment is discussed based on the comparison with high-resolution absorption and emission spectra and theoretical predictions.