Revisiting impulsive stimulated thermal scattering in supercooled liquids: Relaxation of specific heat and thermal expansion

Year: 2021

Authors: Gandolfi M., Liu L., Zhang P., Kouyate M., Salenbien R., Banfi F., Glorieux C.

Autors Affiliation: CNR, INO, Natl Inst Opt, Via Branze 45, I-25123 Brescia, Italy; Univ Brescia, Dept Informat Engn, Via Branze 38, I-25123 Brescia, Italy; Katholieke Univ Leuven, Dept Phys & Astron, Lab Soft Matter & Biophys, Celestijnenlaan 200D, B-3001 Leuven, Belgium; Univ Cattolica Sacro Cuore, Dipartimento Matemat & Fis, Via Musei 41, I-25121 Brescia, Italy; Interdisciplinary Labs Adv Mat Phys I LAMP, Via Musei 41, I-25121 Brescia, Italy; VITO, Boeretang 200, B-2400 Mol, Belgium; Energyville I, EnergyVille, Thor Pk 3800, B-3600 Genk, Belgium; Univ Claude Bernard Lyon 1, Univ Lyon, CNRS, FemtoNanoOpt Grp,Inst Lumiere Matiere, Villeurbanne, France.

Abstract: Impulsive stimulated thermal scattering (ISTS) allows one to access the structural relaxation dynamics in supercooled molecular liquids on a time scale ranging from nanoseconds to milliseconds. Till now, a heuristic semi-empirical model has been commonly adopted to account for the ISTS signals. This model implicitly assumes that the relaxation of specific heat, C, and thermal expansion coefficient, ?, occur on the same time scale and accounts for them via a single stretched exponential. This work proposes two models that assume disentangled relaxations, respectively, based on the Debye and Havriliak-Negami assumptions for the relaxation spectrum and explicitly accounting for the relaxation of C and ? separately in the ISTS response. A theoretical analysis was conducted to test and compare the disentangled relaxation models against the stretched exponential. The former models were applied to rationalize the experimental ISTS signals acquired on supercooled glycerol. This allows us to simultaneously retrieve the frequency-dependent specific heat and thermal expansion up to the sub-100 MHz frequency range and further to compare the fragility and time scale probed by thermal, mechanical, and dielectric susceptibilities.

Journal/Review: JOURNAL OF CHEMICAL PHYSICS

Volume: 155 (16)      Pages from: 164501-1  to: 164501-16

More Information: C.G. and M.G. acknowledge financial support from the KU Leuven Research Council (Grant No. C14/16/063) (OPTIPROBE). M.G. acknowledges financial support from the CNR Joint Laboratories program 2019-2021, Project No. SAC.AD002.026 (OMEN). L.L. acknowledges financial support from the FWO (Research Foundation-Flanders) postdoctoral research fellowship (Grant Nos. 12V4419N and 12V4422N). P.Z. acknowledges the support of the Chinese Scholarship Council (CSC). F.B. acknowledges financial support from the Universite de Lyon in the frame of the IDEXLYON Project (Grant No. ANR-16-IDEX-0005) and from Universite Claude Bernard Lyon 1 through the BQR Accueil EC 2019 grant.
KeyWords: glass-forming liquids; light-scattering; orientational relaxation; heterodyne-detection; propylene-glycol
DOI: 10.1063/5.0063805

Citations: 2
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