Attosecond photoionization dynamics with stimulated core-valence transitions

We investigate ionization of neon atoms by an isolated attosecond pump pulse in the presence of two coherent extreme ultraviolet or x-ray probe fields. The probe fields are tuned to a core-valence transition in the residual ion and induce spectral shearing of the photoelectron distributions. We show that the photoelectron-ion coincidence signal contains an interference pattern that depends on the temporal structure of the attosecond pump pulse and the stimulated core-valence transition. Many-body perturbation theory is used to compute atomic response times for the processes and we find strikingly different behavior for stimulation to the outer-core hole (2p <-> 2s) and stimulation to the inner-core hole (2p <-> 1s). The response time of the inner-core transition is found to be comparable to that of state-of-the-art laser-based characterization techniques for attosecond pulses.