Ultrafast intra- and intermolecular energy transfer in solutions after selective infrared excitation

Abstract

Energy is supplied to the solvent or solute molecules via resonantly absorbed infrared photons. The long wavelength tail of the S 1 absorption band of a probe molecule is monitored on a picosecond time scale. This technique is used to study energy transfer from the solvent to the probe molecule and vice versa. Exciting a vibrational mode of the probe molecules, the energy is rapidly redistributed via intramolecular processes followed by an intermolecular dissipation to the solvent with time constants of ∼10 ps. Intermolecular energy transfer from the solvent to the probe molecules is observed within ≲5 ps, independent of the solvent.