Two dimensional time delay approach to femtosecond wavepacket dynamics and population transfer

Summary form only given. A method based on two separate time delays is demonstrated for the selective femtosecond excitation and observation of different vibrations in the electronic ground state of molecules. The first pulse creates the initial wavepacket in the excited electronic state. Normally, the second (Stokes) pulse would induce transitions back to the ground state, populating the states favorably coupled by a good overlap with the initial wavepacket. Instead, we introduce a variable evolution delay between the first two pulses, thus allowing better overlap of the wavepacket with selected vibrational levels in the ground state. Matching the Stokes frequency is also crucial for efficient population transfer.