Toward preresonant impulsive Raman preparation of large amplitude vibrational motion

This article investigates a new approach to the optical generation of large-amplitude coherent molecular vibrations in condensed media. On the basis of analytical results using pulse propagators in the classical Franck approximation, we are led to investigate the efficacy of driving vibrational motion in the electronic ground state by impulsive stimulated Raman scattering with a timed sequence of electronically preresonant femtosecond laser pulses, Numerically exact computations are performed on a model system of dilute molecular Iodine in a low-temperature host crystal. Vibrational relaxation is incorporated via Redfield theory, The results indicate that under a variety of conditions, chemically significant (greater than 0.1 Angstrom) displacements can be produced in a Raman active mode with a fair measure of control over wave packet spreading, and without substantial population loss due to electronic absorption. (C) 1996 American Institute of Physics.