Slow dynamics in glycerol: collective de gennes narrowing and independent angstrom motion
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Slow dynamics in glycerol: collective de gennes narrowing and independent angstrom motion Makina Saito1 · Yasuhiro Kobayashi1 · Ryo Masuda1 · Masayuki Kurokuzu1 · Shinji Kitao1 · Yoshitaka Yoda2 · Makoto Seto1
© Springer International Publishing Switzerland 2016
Abstract The slow dynamics of microscopic density correlations in supercooled glycerol was studied by time-domain interferometry using 57 Fe-nuclear resonant scattering gamma rays of synchrotron radiation. The dependence of the relaxation time at 250 K on the momentum transfer q is maximum near the first peak of the static structure factor S(q) at q ∼ 15 nm−1 . The q-dependent behavior of the relaxation time known as de Gennes narrowing was confirmed in glycerol. Conversely, de Gennes narrowing around the second and third peaks of S(q) at q ∼ 26 nm−1 and 54 nm−1 was not detected. The q dependence of the relaxation time was found to follow a power-law equation with power-law index of 1.9(2) in the q region well above the first peak of S(q) up to ∼ 60 nm−1 , which corresponds to angstrom scale, within experimental error. This suggests that in the angstrom-scale dynamics of supercooled glycerol, independent motions dominate over collective motion. Keywords De Gennes narrowing · Glycerol · Nuclear resonant scattering · Time-domain interferometry
1 Introduction The study of microscopic dynamics of supercooled glass formers is critical to understanding the nature of glass transition [1, 2]. In particular, the diffusional relaxation process known
This article is part of the Topical Collection on Proceedings of the International Conference on the Applications of the M¨ossbauer Effect (ICAME 2015), Hamburg, Germany, 13-18 September 2015 Makina Saito
[email protected] 1
Research Reactor Institute, Kyoto University, Osaka 590-0494, Japan
2
Japan Synchrotron Radiation Research Institute, Sayo, Hyogo, 679-5198, Japan
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Hyperfine Interact (2016) 237:22
as α process has been considered to be closely related to the glass transition. In fragile glass formers, the α-relaxation time increases with cooling following the Vogel–Fulcher– Tammann law. This divergence is attributed to the growth of the cooperative rearrangement region (CRR), where molecules move cooperatively. Therefore, it is expected that the motional collectivity of the α process is developed with decreasing temperature. Conversely, another process known as the slow β process (Johari–Goldstein process) seems to branch from the α process with cooling in the relaxation map and can be observed even in the glass state [3]. The slow β process seems to be a local activation process; however, the origin is not fully understood. Understanding the hierarchy dynamics with structural assignment of the origin is a key to understand the glass transition mechanism. Quasi-elastic scattering measurements give the relaxation time of the microscopic structures specifying the spatial scale of the structure to be studied. The spatial scale is selected by setting the detection angle of the scattere
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