Abstract
We study theoretically x-ray absorption and ionization spectra of an atom or molecule by two coherent x-ray pulses that show a relative phase shift resulting in a time delay of the pulse envelopes. We demonstrate that the phase modulation of the spectra is shifted with respect to the phase oscillation comb of the x-ray double pulse. The reason for this shift is the dynamics of the process defined by the interplay of the delay time, the pulse width, the detuning, and the lifetime of the core-excited state.
Highlights
Coherent steering of a quantum system by light enabling manipulation by populations and interfering pathways is one of the attractive areas of study in optical physics [1,2,3,4,5] and photochemistry [3]
We have shown that an additional dynamic phase shift is induced in x-ray absorption and have studied its dependence on the pulse parameters
With the help of analytical analysis and numerical simulations we see clearly two distinct phase shifts: (i) a “conventional” phase shift related to the delay time between the coherent pulse replicas, which is equal to ωτ, and (ii) an additional—dynamic—phase shift δ arising from the interference of the two x-ray pulses with the two-level quantum system
Summary
Coherent steering of a quantum system by light enabling manipulation by populations and interfering pathways is one of the attractive areas of study in optical physics [1,2,3,4,5] and photochemistry [3]. The role of the phase is studied in the case of a polychromatic short-wavelength field Good examples of such kind of phenomena are interference of one- and two-photon ionization channels controlled by the the phase shift [8,12] and the coherent control of the population of the Rydberg states by the time delay of the light wave packet pair with the broad spectral bandwidth [7]. Revealed such a phase shift of the x-ray response relative to the phase of the incoming coherent pulse replicas for Auger decay accompanied by shake-up excitation, while no shift was observed for the x-ray photoelectron spectroscopy (XPS) and participator Auger processes This behavior was assigned to the correlated electronic dynamics.
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