Abstract
Ab initio simulations of a range of interferometric experiments are used to identify a strong dependence on multiphoton phase shifts in above-threshold ionization. A simple rule of thumb for interaction phase shifts is derived to explain both the conservation of photoelectron yield and its absolute CEP-dependence. For instance, it is found that interferometric above-threshold ionization experiments are shifted by $\pi/4$ relative to RABBIT experiments, and that there is no RABBIT-term in a laser-assisted photoionization experiment with odd and even harmonics. Thus, our work helps to resolve the issues of interpretation of quantum dynamics in attosecond and free-electron laser sciences.
Highlights
Interference effects have long played a central role in our understanding of both classical and quantum physics
In this article we have studied theoretically the interpretation of quantum dynamics in a range of recent attosecond experiments that rely on weak probe laser beams and introduced the concept of interaction phases that accumulate with each laser interaction
We have found that RABBIT SBs are exceptional, as they are not affected by such interaction phase shifts
Summary
Interference effects have long played a central role in our understanding of both classical and quantum physics. Novel types of nonlinear spectroscopies make use of probe laser beams to change the dynamics in the interferometric arms, making it possible to interfere different energy components of the system [4] Prime examples of such nonlinear arms include perturbed quasiclassical trajectories in HHG in atoms [5,6,7,8], molecules [9], and solids [10]; perturbed photoelectrons in laser-assisted photoionization (LAP) from atoms [11,12,13,14,15] and molecules [16]; resonant two-photon ionization via bound [17] or autoionizing states [18,19,20]; and perturbed photoelectrons in above-threshold ionization (ATI) [21]. This plethora of interferometric arms makes it possible to inherently study nonlinear processes, such as HHG and ATI, but they raise the question of interpretation between unperturbed and perturbed dynamics
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