Spectral modulation of femtosecond laser pulse induced by molecular alignment revivals.

We demonstrate experimentally and numerically that the quantum wake of molecular alignment induced by impulsive rotational Raman excitations with femtosecond pump pulses produces observable phase modulations on femtosecond probe pulses. This leads to a spectral red- or blueshift of the probe pulses when they are properly delayed around the rising or falling edge of the half-revival time of the molecular alignment, respectively.