Intermolecular energy transfer after vibrational excitation of a perylene dye in solution, in polymer binder, and in a side-chain copolymer

Skeletal modes between 1550 cm(-1) and 1750 cm(-1) of the perylene chromophor are vibrationally excited in different surroundings via resonant absorption of ultrashort IR pulses. The vibrational energy transfer is monitored via electronic transitions to the S-1 state with the help of a second, delayed visible pulse. In liquid chloroform solution of the dye an intermolecular energy transfer time of tau (e)=(15 +/-1) ps was determined. In the solid dye/PMMA blend the intermolecular energy transfer time was with tau (e)=(10,5 +/-1) ps substantially smaller. In the copolymer a similar time constant of tau (e)=(9 +/-1) ps is found. Obviously the spacer decouples in the copolymer not only the electronic systems but also the vibrational manifolds. (C) 2001 American Institute of Physics.