Vibrational frequencies of modes involving intermolecular motions in liquids are relatively small, in the Raman scattering close to the excitation frequency, and the bands may merge into a diverging uninterpretable signal. Raman optical activity (ROA) spectral shapes in this region, however, are structured more and may better reflect the nature of the studied systems. To understand the origin of the signal and its relation to the molecules, ROA spectra of six chiral neat liquids are recorded and analyzed on the basis of molecular dynamics and density functional theory computations. The theory of Raman scattering of liquids is discussed and adapted for modeling based on clusters and periodic boundary conditions. A plain cluster approach is compared to a crystal-like model. The results show that the low-frequency optical activity can be reliably modeled and related to the structure. However, momentary arrangement of molecules leads to large variations of optical activity, and a relatively large number of geometries need to be averaged for accurate simulations. The intermolecular modes are intertwined with intramolecular ones and start to dominate as the frequency goes down. The low-frequency ROA signal thus reflects the chemical composition and coupled with the modeling it provides a welcome means to study the structure and interactions of chiral liquids.

Department of Analytical Chemistry University of Chemistry and Technology Technická 5 16628 Prague Czech Republic

Department of Optics Palacký University Olomouc 17 listopadu 12 77146 Olomouc Czech Republic

Institute of Organic Chemistry and Biochemistry Academy of Sciences Flemingovo náměstí 2 16610 Prague Czech Republic

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