Time-dependent theory of Auger decay induced by ultra-short pulses in a strong laser field

A quantum mechanical theory of a laser-assisted Auger process in atoms excited by an ultra-short (attosecond) electromagnetic pulse in the field of a few-cycle strong laser pulse is presented. It is based on the non-stationary Schrodinger equation, which describes the photoionization of an inner atomic shell and the decay of the created vacancy, while the Auger electron is treated in the strong field approximation. As an example, the photoionization of the Ne 1s shell with the subsequent KLL Auger transition is considered. The spectra and angular distributions of photoelectrons and Auger electrons are calculated and discussed. The photoelectron spectra show a typical picture of streaking in the laser field. In contrast, the Auger electron spectrum contains sideband structure, which is however, different from the conventional equidistant sideband structure, which had been discussed for longer pulses and smaller Auger electron energies. The predicted sideband structure strongly depends on the delay time between the laser pulse and the x-ray pulse. It is sensitive to the carrier-envelope phase as well. A simplified description of the Auger electron spectra in laser-assisted Auger decay, which gives the sideband structure in close agreement with the results of the exact theory, is suggested.