Multiphoton interaction phase shifts in attosecond science

TL;DR

This paper investigates how multiphoton phase shifts influence interferometric experiments in attosecond science, providing a simple rule for understanding phase effects and clarifying experimental differences.

Contribution

It introduces a straightforward rule of thumb for interaction phase shifts, explaining experimental observations and resolving interpretative issues in attosecond and free-electron laser experiments.

Findings

Interferometric above-threshold ionization experiments are shifted by π/4 relative to RABBIT.

No RABBIT-term appears in laser-assisted photoionization with mixed harmonics.

Derived rules explain phase shift effects and experimental differences.

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.