Selective femtosecond spectroscopy of molecules in the multipulse technique for observing the optical Kerr effect

A method of multipulse coherent pumping by femtosecond laser pulses is proposed to detect optical Kerr effect for studying molecular motions in liquids. The method is analysed theoretically based on a phenomenological model describing the vibrational–rotational motion of organic molecules. It is shown that multipulse pumping can be used to control coherent excitation of molecular vibrations by amplifying or suppressing selectively individual intramolecular modes, which simplifies considerably the interpretation of molecular motions and expands the possibilities of the coherent spectroscopy of molecules in liquids.