Photoexcitation Circular Dichroism in Chiral Molecules

Samuel Beaulieu (1) , Antoine Comby (1) , Dominique Descamps (1) , Baptiste Fabre (1) , Gustavo Garcia (2) , Romain Géneaux (3) , Alex Harvey (4) , Francois Légaré (5) , Z Mašín (4) , Laurent Nahon (2) , A. Ordonez (4) , Stephane Petit (1) , B Pons (1) , Yann Mairesse (1) , Olga Smirnova (4) , Valérie Blanchet (1)

1 CELIA - Centre d'Etudes Lasers Intenses et Applications
2 SSOLEIL - Synchrotron SOLEIL
3 LIDYL - Laboratoire Interactions, Dynamiques et Lasers (ex SPAM)
4 MBI - Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie
5 INRS - Institut National de la Recherche Scientifique [Québec]

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.

Domaines: Chimie-Physique [physics.chem-ph]

Samuel Beaulieu, Antoine Comby, Dominique Descamps, Baptiste Fabre, Gustavo Garcia, et al.. Photoexcitation Circular Dichroism in Chiral Molecules. 2016. ⟨hal-01417835v1⟩