Photoexcitation Circular Dichroism in Chiral Molecules

TL;DR

This paper introduces a highly sensitive form of circular dichroism, called photoexcitation circular dichroism, which leverages coherent electron motion to detect chirality in molecules more effectively than traditional magnetic-based methods.

Contribution

It presents a novel, ultrafast chiral detection technique that does not depend on magnetic effects, enabling better control and observation of chiral dynamics in molecules.

Findings

Demonstrated orders of magnitude increase in sensitivity over traditional methods

Achieved ultrafast detection of chiral electron motion

Enabled monitoring of chiral chemical changes in real-time

Abstract

Chirality is ubiquitous in nature and fundamental in science, from particle physics to metamaterials.The most established technique of chiral discrimination - photoabsorption circular dichroism - relies on the magnetic properties of a chiral medium and yields an extremely weak chiral response. We propose and demonstrate a new, orders of magnitude more sensitive type of circular dichroism in neutral molecules: photoexitation circular dichroism. It does not rely on weak magnetic effects, but takes advantage of the coherent helical motion of bound electrons excited by ultrashort circularly polarized light. It results in an ultrafast chiral response and the efficient excitation of a macroscopic chiral density in an initially isotropic ensemble of randomly oriented chiral molecules. We probe this excitation without the aid of further chiral interactions using linearly polarized laser pulses. Our time-resolved study of vibronic chiral dynamics opens a way to the efficient initiation, control and monitoring of chiral chemical change in neutral molecules at the level of electrons.