Inducing transient enantiomeric excess in a molecular quantum racemic mixture with microwave fields

• Published in: Nature communications Vol. 14; no. 1; pp. 934 - 8
• Main Authors: Sun, Wenhao, Tikhonov, Denis S., Singh, Himanshi, Steber, Amanda L., Pérez, Cristóbal, Schnell, Melanie
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 20.02.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/638/440/94; 639/766/36/1121; Alcohol; Benzyl alcohol; Chemistry; Cryoforming; Cryogenic temperature; Enantiomers; Humanities and Social Sciences; Mixtures; multidisciplinary; Quantum tunnelling; Rotational states; Science; Science (multidisciplinary); Wave packets
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-36653-3

Chiral molecules with low enantiomer interconversion barriers racemize even at cryogenic temperatures due to quantum tunneling, forming a racemic mixture that is impossible to separate using conventional chemical methods. Here we both experimentally and theoretically demonstrate a method to create and probe a state-specific enantiomeric enrichment for such molecular systems. The coherent, non-linear, and resonant approach is based on a microwave six-wave mixing scheme and consists of five phase-controlled microwave pulses. The first three pulses induce a chiral wavepacket in a chosen rotational state, while the consecutive two pulses induce a polarization for a particular rotational transition (listen transition) with a magnitude proportional to the enantiomeric excess created. The experiments are performed with the transiently chiral molecule benzyl alcohol, where a chiral molecular response was successfully obtained. This signal demonstrates that enantiomeric excess can be induced in a quantum racemic mixture of a transiently chiral molecule using the developed microwave six-wave mixing scheme, which is an important step towards controlling non-rigid chiral molecular systems. There is growing interest in controlling and manipulating molecules using external field. Here the authors demonstrate microwave induced transient enantiomeric excess in a state-selective benzyl alcohol using microwave six-wave mixing.