The non-Markovian master equation for stochastically perturbed systems: Effect on spectral lineshape

Based on the system-reservoir model in which the intermediate states of the system are perturbed by stochastic interaction with the surroundings, we have generalized the master equation for the description of quantum dissipative processes and applied it to a three-level system to calculate transient optical response in pump-probe spectroscopy. We have shown that while the two damping processes act independently in the Markovian description, the interference of stochastic and system-reservoir interactions and the resulting non-lorentzian structure of the band-shape function appear as the essential non-Markovian features in the dissipative dynamics.