Theory of laser-assisted Auger processes generated by ultrashort XUV pulses in atoms

A non-stationary quantum mechanical theory of the laser-assisted Auger process in atoms excited by an ultrashort (attosecond) electromagnetic pulse in the field of a few-cycle strong optical laser pulse is considered. The theory is based on numerically solving the time-dependent Schrodinger equation describing Auger decay. An approach is suggested which can be applied for the case of low-energy Auger electrons when it is necessary to take accurately into account the electron interaction with both the laser field and the field of the residual ion. We show that the amplitude of the process can be presented as a coherent sum of contributions from the corresponding Auger decays at consecutive moments of time. This presentation saves considerable computer time in numerical calculations of the Auger spectrogram. It also demonstrates that the Auger electrons emitted at different moments are coherent. As an example, the electron spectra for laser-assisted Auger decay are calculated for the MNN transition in Kr. The variation of the Auger spectra with time delay between the two pulses is discussed. The results are compared with those obtained within the strong-field approximation.