# Recovery of high-energy photoelectron circular dichroism through Fano interference

## TL;DR

This paper demonstrates a significant high-energy photoelectron circular dichroism (PECD) effect caused by Fano interference in methyloxirane, revealing new insights into chiral asymmetry detection at high energies.

## Contribution

It introduces a novel PECD mechanism at high energies via Fano interference, expanding understanding of chiral asymmetry in photoelectron spectroscopy.

## Key findings

- PECD observed above 500 eV in methyloxirane
- Fano interference causes sign change in dichroic parameter
- High-energy PECD is linked to resonant Auger decay

## Abstract

It is commonly accepted that the magnitude of a photoelectron circular dichroism (PECD) is governed by the ability of an outgoing photoelectron wave packet to probe the chiral asymmetry of a molecule. To be able to accumulate this characteristic asymmetry while escaping the chiral ion, photoelectrons need to have relatively small kinetic energies of up to a few tens of electron volts. Here, we demonstrate a substantial PECD for very fast photoelectrons above 500 eV kinetic energy released from methyloxirane by a participator resonant Auger decay of its lowermost O $1s$-excitation. This effect emerges as a result of the Fano interference between the direct and resonant photoionization pathways, notwithstanding that their individual effects are negligibly small. The resulting dichroic parameter has an anomalous dispersion, i.e. it changes its sign across the resonance, which can be considered as an analogue of the Cotton effect in the X-ray regime.