Capturing electron-driven chiral dynamics in UV-excited molecules

TL;DR

This study uses ultrafast time-resolved photoelectron circular dichroism to directly observe electron-driven chiral dynamics in neutral molecules, revealing femtosecond-scale modulations of chiroptical response and potential for enantioselective control.

Contribution

It demonstrates the first direct imaging of electron-driven chiral dynamics at their intrinsic timescale in neutral molecules using TR-PECD with 2.9 fs resolution.

Findings

Electronic beatings cause periodic chiroptical modulations on femtosecond timescales.

Sign inversion of chiroptical response occurs in less than 10 fs.

Photoinduced chiral currents enable enantio-selective molecular orientation filtering.

Abstract

Molecular chirality is a key design property for many technologies including bioresponsive imaging, circularly polarized light detection and emission, molecular motors and switches. Imaging and manipulating the primary steps of transient chirality is therefore central for controlling numerous physical, chemical and biological properties that arise from chiral molecules in response to external stimuli. So far, the manifestation of electron-driven chiral dynamics in neutral molecules has not been demonstrated at their intrinsic timescale. Here, we use time-resolved photoelectron circular dichroism (TR-PECD) with an unprecedented instrument response function of 2.9 fs to image the dynamics of coherent electronic motion activated by prompt UV-excitation in neutral chiral molecules, disclosing its impact on the molecular chiral response. We find that electronic beatings between Rydberg states lead to periodic modulations of the chiroptical response on the few-femtosecond timescale, showing a sign inversion in less than 10 fs. Calculations including both the molecular UV-excitation and subsequent photoionization confirm this interpretation and provide further evidence that the combination of the resulting photoinduced chiral current with a circularly polarized probe pulse realizes an enantio-selective filter of molecular orientations upon photoionization, opening up a route towards enantio-selective charge-directed reactivity.