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Low-frequency (gigahertz to terahertz) depolarized Raman scattering off n-alkanes, cycloalkanes, and six-membered rings: a physical interpretation

preprint
submitted on 28.04.2020 and posted on 13.05.2020 by Andrew J. Farrell, Mario González Jiménez, Gopakumar Ramakrishnan, Klaas Wynne
Molecular liquids have long been known to undergo various distinct and simple intermolecular motions, from fast librations and cage rattling oscillations to slow orientational and translational diffusion. However, their resultant gigahertz to terahertz spectra are far from simple, appearing as broad shapeless bands that span many orders of magnitude of frequency making meaningful interpretation troublesome. Ad hoc spectral lineshape fitting has become a notoriously fine art in the field; a unified approach to handling such spectra is long overdue. Here we apply ultrafast optical Kerr-effect (OKE) spectroscopy to study the intermolecular dynamics of room temperature n-alkanes, cycloalkanes, and six-carbon rings, as well as liquid methane and propane. This work provides stress-tests and converges upon an experimentally robust model across simple molecular series and temperatures, providing a blueprint for the interpretation of the dynamics of van der Waals liquids. This will enable the interpretation of low frequency spectra of more complex liquids.

Funding

EPSRC EP/K034995/1

EPSRC EP/N508792/1

EPSRC EP/N007417/1

Leverhulme RPG-2018-350

ERC Advanced 832703

History

Email Address of Submitting Author

klaas.wynne@glasgow.ac.uk

Institution

University of Glasgow

Country

UK

ORCID For Submitting Author

0000-0002-5305-5940

Declaration of Conflict of Interest

No conflict of interest

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