Quenching effect in below-threshold high harmonic generation

TL;DR

This paper demonstrates how multi-electron interactions cause suppression of certain harmonic orders in below-threshold high harmonic generation, revealing a new electron-electron energy transfer mechanism similar to fluorescence quenching.

Contribution

It introduces a theoretical demonstration of the quenching effect in below-threshold HHG caused by multi-electron dynamics, highlighting the role of energy transfer between electrons.

Findings

HHG is suppressed at specific harmonic orders due to multi-electron effects

The suppression position relates to the energy gap between orbitals

Multi-electron dynamics involve electron-electron energy transfer similar to fluorescence quenching

Abstract

We theoretically demonstrate the quenching effect in below-threshold high harmonic generation (HHG) by using the time-dependent density-functional theory (TDDFT) and solving the time-dependent Schr\"{o}dinger equation (TDSE). It is shown that the HHG is substantially suppressed in particular harmonic orders in the below-threshold region when multi-electron interaction comes into play. The position of the suppression is determined by the energy gap between the highest occupied orbital and the higher-lying orbital of the target. We show that the quenching effect is due to a new class of multi-electron dynamics involving electron-electron energy transfer, which is analog to the fluorescence quenching owing to the energy transfer between molecules in fluorescent material. This work reveals the important role of the multi-electron interaction on HHG especially in the below-threshold region.