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 (National Institute of Optics), Via Branze 45, Brescia, 25123, Italy; Department of Information Engineering, University of Brescia, Via Branze 38, Brescia, 25123, Italy; Laboratory of Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, Leuven, B-3001, Belgium; Dipartimento di Matematica e Fisica, Universita Cattolica Del Sacro Cuore, Via Musei 41, Brescia, 25121, Italy; Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP), Via Musei 41, Brescia, 25121, Italy; VITO, Boeretang 200, Mol, 2400, VITO, Boeretang 200, Mol 2400, Belgium; EnergyVille, Energyville i, Thor Park 3800, Genk, 3600, Belgium; FemtoNanoOptics Group, University de Lyon, CNRS, University Claude Bernard Lyon 1, Institut Lumiire Matiire, Villeurbanne, F-69622, 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.


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