Revisiting impulsive stimulated thermal scattering in supercooled liquids: Relaxation of specific heat and thermal expansion - Université Claude Bernard Lyon 1 Accéder directement au contenu
Article Dans Une Revue Journal of Chemical Physics Année : 2021

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

Résumé

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, γ, 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 γ 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.

Dates et versions

hal-03438855 , version 1 (22-11-2021)

Identifiants

Citer

Marco Gandolfi, Liwang Liu, Pengfei Zhang, Mansour Kouyaté, Robbe Salenbien, et al.. Revisiting impulsive stimulated thermal scattering in supercooled liquids: Relaxation of specific heat and thermal expansion. Journal of Chemical Physics, 2021, 155 (16), pp.164501. ⟨10.1063/5.0063805⟩. ⟨hal-03438855⟩
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