Time dependent theory of two-step absorption of two pulses

The time dependent theory of two step-absorption of two different light pulses with arbitrary duration in the electronic three-level model is proposed. The probability that the third level is excited at the moment t is found in depending on the time delay between pulses, the spectral widths of the pulses and the energy relaxation constants of the excited electronic levels. The time dependent perturbation theory is applied without using “doorway-window” approach. The time and spectral behavior of the spectrum using in calculations as simple as possible model is analyzed.