Preparation and monitoring of high-ground-state vibrational wavepackets by femtosecond coherent anti-Stokes Raman scattering

Femtosecond time-delayed coherent anti-Stokes Raman scattering is presented not only as a tool for monitoring but also as a viable method for the preparation of vibrational wavepackets with very high quantum numbers in the ground electronic state of molecules. We experimentally demonstrate a particularly useful approach of using two separate time delays between the pulses for preparing vibrational wavepackets as high as v″=38 [ΔEv=7000 cm−1] in bulk gas-phase molecular iodine. By means of an ultrashort laser pulse, we prepare a wavepacket in an electronic excited state, optimize the frequency and timing of a second pulse to efficiently generate the targeted ground-state vibrational wavepacket, and monitor the wavepacket by coherent scattering from a third pulse. The method is further used to probe interference effects in femtosecond four-wave-mixing signals generated by molecular wavepackets.