Enantiospecific two-photon electric-dipole selection rule of chiral molecules.

Zou, Fen; Li, Yong; Zhang, Peng · Sci Adv · 2025

basic_science · Level V

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Abstract

Distinguishing between enantiomers is crucial in chemistry and pharmacology. Existing optical methods rely on enantiospecific three-photon electric-dipole transitions, requiring phase locking, three-photon resonance, and precise beam control, limiting their practicality. Here, we propose an optical method that eliminates these constraints by applying a static electric field, which breaks a symmetry combining rotation and time reversal, leading to distinct two-photon selection rules for enantiomers. This enables selective excitation of a target enantiomer using two beams without phase locking or intensity control, greatly improving the feasibility of optical enantiomer differentiation.