Vibrational energy transfer processes in dye molecules after ultrafast excitation of skeletal modes

Skeletal modes of dye molecules in liquid solutions at frequencies below 1700 cm(-1) are vibrationally excited via resonant absorption of ultrashort IR pulses. The vibrational relaxation and energy transfer processes are monitored via electronic transitions to the S-1 state. The depopulation times of initially excited modes increase from less than or similar to 1 ps around 1600 cm(-l) to values of similar to 2 ps at 1200 cm(-1). The subsequent intermolecular energy transfer within several ps to the surrounding is dependent on the solvent. Polarization sensitive measurements are used to determine the direction of vibrational transition dipole moments. (C) 1998 Elsevier Science B.V. All rights reserved.