Coherently-controlled two-dimensional spectroscopy: evidence for phase induced long-lived memory effects

Using low-intensity phase-shaped excitation pulses we used two-dimensional (2D) electronic spectroscopy to follow the time dependence of the coherent correlations imposed on a solvated organic dye (Rhodamine 101 in methanol) at room temperature. Shaping of the excitation pulses strongly affects both the real and imaginary parts of the 2D-spectra, especially at small waiting times. In particular, the periodic phase modulation of the excitation pulses appears as a two-dimensional grid-like modulation in the correlation spectrum corresponding to the waiting time T = 0. By increasing the waiting time, this modulation quickly disappears in omega(t) space. However, it is still present in w, space even at very long waiting times (> or = 80 ps) where the inhomogeneous broadening is significantly reduced, and reaches its stationary value of approximately 16%. The resonant nature of this induced modulation at long waiting time allows us to conclude that phase shaping of the excitation induces a long-lived memory in solvated organic dyes that is associated with coherent population transfer.