All-optical coherent control of chiral electronic transitions for highly enantioselective photochemistry

TL;DR

This paper presents a novel all-optical quantum control method using shaped laser pulses to achieve highly enantioselective electronic excitation in chiral molecules, surpassing traditional circularly polarized light methods.

Contribution

It introduces a new laser-based control strategy that does not require chiral sensitisers or cold molecules, enabling practical enantioselective photochemistry in liquid samples.

Findings

Achieves ~30% enantioselectivity in electronic excitation populations.

Surpasses circularly polarized light by three orders of magnitude in selectivity.

Demonstrates effectiveness in liquid-phase, randomly oriented samples.

Abstract

Enantioselective photochemistry provides access to unique molecular structures and functions, with deep implications for fundamental science and industrial applications. Current methods for highly enantioselective photochemistry critically rely on chiral sensitisers, as circularly polarised light on its own yields vanishingly weak enantioselectivity. Here, we introduce a quantum control strategy to drive highly enantioselective electronic excitations in randomly oriented samples using a pulsed ($\sim$22 fs) IR laser and two of its harmonics, in the absence of intermediate resonances. Our approach addresses electronic transitions, does not require chiral sensitisers, or cold molecules, or long electronic coherence times, is relevant for liquid-phase samples, and remains effective over interaction regions extending across many laser wavelengths, even in the presence of dispersion. We show how, by 3D shaping the field's polarisation over the interaction region, we can achieve enantioselective coherent control over electronic population transfer. Our ab-initio simulations in the chiral molecule carvone yield a selectivity of $\sim$30 % in the populations of the first excited electronic state, three orders-of-magnitude higher than what is possible with circularly polarised light ($\sim$0.01 %). These results bring all-optical enantioselective photochemistry into the realm of practical applications.