# Real-time probing of chirality during a chemical reaction

## TL;DR

This paper introduces a novel laser-based technique to observe the ultrafast evolution of molecular chirality during a chemical reaction, revealing dynamic changes in chiral response on femtosecond timescales.

## Contribution

It presents a general experimental method using high-harmonic generation to probe real-time chirality changes during photodissociation, enabling new insights into chiral reaction pathways.

## Key findings

- Chiral response changes sign within 100 fs
- Chiral response magnitude increases then decays within 500 fs
- Reveals chirality evolution during molecular dissociation

## Abstract

Chiral molecules interact and react differently with other chiral objects, depending on their handedness. Therefore, it is essential to understand and ultimately control the evolution of molecular chirality during chemical reactions. Although highly sophisticated techniques for the controlled synthesis of chiral molecules have been developed, the observation of chirality on the natural femtosecond time scale of a chemical reaction has so far remained out of reach for isolated molecules. Here, we demonstrate a general experimental technique, based on high-harmonic generation in tailored laser fields, and apply it to probe the time evolution of molecular chirality during the photodissociation of 2-iodobutane. These measurements show a change in sign and a pronounced increase in the magnitude of the chiral response over the first 100 fs, followed by its decay within less than 500 fs, revealing the photodissociation to achiral products. The observed time evolution is explained in terms of the variation of the electric and magnetic transition-dipole moments between the lowest electronic states of the cation as a function of the reaction coordinate. These results open the path to investigations of the chirality of molecular reaction pathways, light-induced chirality in chemical processes and the control of molecular chirality through tailored laser pulses.