Coherent control of excited state vibrational coherences of a molecule in solution

We demonstrate control of excited state wave packets in the laser dye LD690 by spectral and phase shaping of the pump pulses. Excitation by blue detuned, positively chirped pulses slows the dephasing of the excited state vibrational coherences compared to a transform-limited pulse. Negative chirp suppresses the onset of coherent oscillations in the ground state. The high electronic state selectivity achieved with spectral shaping enables us to probe the characteristics of the excited state potential energy surface. We find that the frequency of the dominant vibrational mode is 573 wavenumbers in the excited state, shifted from 586 wavenumbers in the ground state.