The Impact of Multichannel and Multipole Effects on the Cooper Minimum in the High-Harmonics Spectrum of Argon

TL;DR

This study demonstrates that multichannel and multipole effects significantly influence the shape, position, and yield of the Cooper minimum in argon's high-harmonic spectrum, emphasizing the importance of detailed electron-ion interaction modeling.

Contribution

It introduces a detailed TDCIS approach to analyze how interchannel and multipole effects alter the HHG spectrum, especially the Cooper minimum in argon.

Findings

The Cooper minimum's shape and position are highly sensitive to interchannel interactions.

Ignoring multiple-orbital effects can underestimate HHG yield by up to 100 times.

HHG yield is affected by the nonspherical multipole character of the electron-ion interaction.

Abstract

We investigate the relevance of multiple-orbital and multipole effects during high-harmonic generation (HHG). The time-dependent configuration-interaction singles (TDCIS) approach is used to study the impact of the detailed description of the residual electron-ion interaction on the HHG spectrum. We find that the shape and position of the Cooper minimum in the HHG spectrum of argon changes significantly whether or not interchannel interactions are taken into account. The HHG yield can be underestimated by up to 2 orders of magnitude in the energy regio of 30-50 eV. We show that the argument of low ionization probability is not sufficient to justify ignoring multiple-orbital contributions. Additionally, we find the HHG yield is sensitive to the nonspherical multipole character of the electron-ion interaction.