Femtosecond vibrational-electronic four-wave-mixing spectroscopy

Two novel two-dimensional vibrational-electronic spectroscopies are theoretically proposed. The first method uses electronically off-resonant fields to create a vibrational coherence state in the ground electronic state and then thus created transient grating is probed by using a time-delayed electronically resonant field. The second method is to use an infrared pulse to create a vibrational coherence state and an electronically two-photon resonant field is used to probe the IR-induced vibrational grating in time. These two methods are found to be useful in selectively studying vibronic coupling of the solvent intermolecular vibrational modes to the electronic transition of a chromophore dissolved in an isotropic medium. (C) 2001 American Institute of Physics.