Controlling core hole relaxation dynamics via intense optical fields

The influence of an intense optical laser on the electronic relaxation of the 3d–5p resonance in atomic Kr has been studied experimentally and theoretically. The resonance profile undergoes a strong modification, observed as a shift and a broadening of the excitation spectrum, as a function of the optical intensity. The theoretical treatment of the process demonstrates the importance of strongly time-dependent dynamics as the origin of the observed phenomena resulting in the ponderomotive shift of the resonance position as well as a competition between resonant and normal Auger decay. The ionization of the excited 5p electron by the optical laser provides the possibility to change the ratio between singly and doubly charged final states by controlling the relaxation of the resonant core hole state via resonant or normal Auger decay.