Multi-Sideband RABBIT in Argon

TL;DR

This paper introduces a three-sideband RABBIT method in argon to analyze atomic phase interference, revealing phase and delay behaviors across different energy levels and angular momentum channels through combined experimental and theoretical approaches.

Contribution

It develops and validates a novel 3-SB RABBIT scheme that isolates atomic phases and explores phase variations with energy and angle, advancing attosecond measurement techniques.

Findings

Phases in three sidebands become similar at higher electron energies.

Angular dependence of phases varies due to different quantum channels.

Qualitative agreement between experiment and R-matrix calculations.

Abstract

We report a joint experimental and theoretical study of a three-sideband (3-SB) modification of the "reconstruction of attosecond beating by interference of two-photon transitions" (RABBIT) setup. The 3-SB RABBIT scheme makes it possible to investigate phases resulting from interference between transitions of different orders in the continuum. Furthermore, the strength of this method is its ability to focus on the atomic phases only, independent of a chirp in the harmonics, by comparing the RABBIT phases extracted from specific SB groups formed by two adjacent harmonics. We verify earlier predictions that the phases and the corresponding time delays in the three SBs extracted from angle-integrated measurements become similar with increasing photon electron energy. A variation in the angle dependence of the RABBIT phases in the three SBs results from the distinct Wigner and continuum-continuum coupling phases associated with the individual angular momentum channels. A qualitative explanation of this dependence is attempted by invoking a propensity rule. Comparison between the experimental data and predictions from an R-matrix (close-coupling) with time dependence calculation shows qualitative agreement in the observed trends.