Relaxation Dynamics in Photoexcited Chiral Molecules Studied by Time-Resolved Photoelectron Circular Dichroism: Toward Chiral Femtochemistry

TL;DR

This study demonstrates that time-resolved photoelectron circular dichroism (TR-PECD) can sensitively track ultrafast relaxation dynamics in photoexcited chiral molecules, providing new insights into chiral recognition processes at femtosecond timescales.

Contribution

It introduces TR-PECD as a novel, sensitive method to observe ultrafast dynamics in chiral molecules, surpassing traditional techniques in temporal resolution.

Findings

TR-PECD reveals ultrafast relaxation dynamics in chiral molecules.

A large forward/backward asymmetry in photoelectron emission is observed.

TR-PECD provides access to dynamics inaccessible by angle-integrated spectra or beta parameters.

Abstract

Unravelling the main initial dynamics responsible for chiral recognition is a key stepin the understanding of many biological processes. However this challenging task requires a sensitive enantiospecic probe to investigate molecular dynamics on their natural femtosecond timescale. Here we show that, in the gas phase, the ultrafast relaxationdynamics of photoexcited chiral molecules can be tracked by recording Time-ResolvedPhotoElectron Circular Dichroism (TR-PECD) resulting from the photoionisation bya circularly polarized probe pulse. A large forward/backward asymmetry along theprobe propagation axis is observed in the photoelectron angular distribution. Its evolution with pump-probe delay reveals ultrafast dynamics that are inaccessible in theangle-integrated photoelectron spectrum nor via the usual electron emission anisotropyparameter ($\beta$). PECD, which originates from the electron scattering in the chiral molecular potential, appears as a new sensitive observable for ultrafast molecular dynamicsin chiral systems.