Resonantly Enhanced Multiphoton Ionization under XUV FEL radiation: A case study of the role of harmonics

TL;DR

This study investigates how small amounts of harmonic contamination in XUV FEL radiation can significantly influence resonant two-photon ionization, revealing the importance of harmonic effects in experimental setups.

Contribution

It provides a detailed quantitative analysis of harmonic effects on resonant two-photon ionization, including dependence on intensity, harmonic percentage, and detuning, with generalizable results.

Findings

Harmonics can significantly affect ionic yields even in small amounts.

The study reveals the dependence of ionization on harmonic percentage and detuning.

Results are applicable to a wide range of resonant ionization scenarios.

Abstract

We provide a detailed quantitative study of the possible role of a small admixture of harmonics on resonant two-photon ionization. The motivation comes from the occasional presence of 2nd and 3rd harmonics in FEL radiation. We obtain the dependence of ionic yields on the intensity of the fundamental, the percentage of 2nd harmonic and the detuning of the fundamental from resonance. Having examined the cases of one and two intermediate resonances, we arrive at results of general validity and global behavior, showing that even a small amount of harmonic may seem deceptively innocuous.