Impulsive stimulated scattering: General importance in femtosecond laser pulse interactions with matter, and spectroscopic applications

It is shown that ‘‘impulsive’’ stimulated Raman scattering (ISRS) should occur, with no laser intensity threshold, when a sufficiently short laser pulse passes through many types of matter. ISRS excitation of coherent optic phonons, molecular vibrations, and other excitations (including rotational, electronic, and spin) may play important roles in femtosecond pulse interactions with molecules, crystals, glasses (including optical fibers), semiconductors, and metals. Spectroscopic applications of ISRS, including time-resolved spectroscopy of vibrationally distorted molecules and crystals, are discussed.