On the nature of the high-frequency relaxation in a molecular glass former: A joint study of glycerol by field cycling NMR, dielectric spectroscopy, and light scattering

Gainaru, C.; Lips, O.; Troshagina, A.; Kahlau, R.; Brodin, A.; Fujara, F.; Rössler, E. A.

doi:10.1063/1.2906122

Cited by 46 publications

(33 citation statements)

References 65 publications

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“…This ratio is known for many processes and is well justified by the difference between vectorial and tensorial characters of the responses probed by dielectric spectroscopy and DLS, respectively [37]. In this respect the low-frequency process appears to be governed by a rotational diffusive mechanisms, while α-process involves a significant amount of large-angle reorientations, as also suggested by previous studies [12].…”

Section: ( )mentioning

confidence: 54%

Identification of Structural Relaxation in the Dielectric Response of Water

et al. 2016

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One century ago pioneering dielectric results obtained for water and n-alcohols triggered the advent of molecular rotation diffusion theory considered by Debye to describe the primary dielectric absorption in these liquids. Comparing dielectric, viscoelastic, and light scattering results we unambiguously demonstrate that the structural relaxation appears only as a high-frequency shoulder in the dielectric spectra of water. In contrast, the main dielectric peak is related to a supramolecular structure, analogous to the Debye-like peak observed in mono-alcohols. PACS: 82.30.Rs, 77.22.Gm, 83.60.Bc, 78.35.+c Being in the focus of intensive research for the last few centuries [1], water still presents many challenging scientific puzzles. They include complex phase diagram [2], possible liquid-liquid transition [3] and significant role of quantum effects [4]. Among them is also the anomalously large dielectric constant that makes water an excellent solvent and is exploited on a daily basis in microwave heating. Not only the amplitude, but also the spectral shape of water's dielectric response is rather peculiar. For most liquids the dominating dielectric relaxation process is the structural α-relaxation that has asymmetric spectral shape corresponding to a stretched exponential relaxation in time domain [5,6]. In contrast, the dielectric spectrum in water is dominated by a Debye-like peak (single exponential process I), and has another less intense relaxation feature (process II) at higher frequencies [7,8]. The microscopic mechanism triggering this response remains highly debated with the focus on the main question: Does the Debye process reflect molecular scale structural relaxation or polarization of intrinsic supramolecular structures mediated by H-bonds?In his seminal dielectric work [9] Debye himself argued in favor of the first scenario, based on hydrodynamic estimates of the rotational time for a single H2O molecule that appears close to the time scale of the process I, τI. Several recent studies also assigned process I to reorientation diffusion of single water molecules [10,11,12]. In contrast, other phenomenological works consider process I related with dynamics of H-bonded network [13,14,15]. One major problem is that dielectric spectroscopy lacks microscopic information [5] and standalone cannot clarify the molecular nature of the processes observed for water. Hence information from other techniques needs to be involved.In many aspects dielectric response of water resemble that known for mono-alcohols (MA) [16]. These liquids (e.g. npropanol [17]), also display a bimodal dielectric spectra with dominating low-frequency Debye-like peak. Although Debye again assigned the main peak of n-propanol to rotational diffusion of single alcohol molecules [9], it is known now that this process has strikingly different microscopic origin [16,18] Inspired by recent developments for MA, we pursue in this work the same strategy of combining dielectric, viscoelastic, and light scattering studies to unravel the nature o...

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Section: ( )mentioning

confidence: 54%

Identification of Structural Relaxation in the Dielectric Response of Water

et al. 2016

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“…To determine the plateau height A 0 ðTÞ, we average over the data points in the range o ¼ 3 Â 10 5 21 Â 10 6 s À1 , where negative influences of other effects are least, see below. Striving for a comparison with results from dielectric spectroscopy, we have to consider that w 00 ðoÞ is a normalized susceptibility so that, according to the fluctuation-dissipation theorem, it needs to be divided by temperature to obtain a standard susceptibility [55]. Therefore, the quantity AðTÞ A 0 ðTÞ=T is displayed in the inset of Fig.…”

Section: Resultsmentioning

confidence: 99%

Combining 7Li NMR field-cycling relaxometry and stimulated-echo experiments: A powerful approach to lithium ion dynamics in solid-state electrolytes

Graf

Kresse

Privalov

et al. 2013

Solid State Nuclear Magnetic Resonance

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“…Various explanations of the microscopic origin of the JG relaxation were suggested, e.g., motions of molecules that are located within "islands of mobility", local regions with higher molecular mobility [62]. Alternatively, the -relaxation or excess wing were ascribed to motions of the molecules on a smaller length scale than the  relaxation via transitions between local energy minima arising from a fine structure of the energy landscape experienced by the molecules [70,71,72]. There are also various other approaches for the explanation of the excess wing and  relaxation, see, e.g., [60,73,74,75].…”

Section: Glassy Dynamics As Revealed By Linear Dielectric Spectroscopymentioning

confidence: 99%

Investigation of nonlinear effects in glassy matter using dielectric methods

Lunkenheimer

Michl

Bauer

et al. 2017

Eur. Phys. J. Spec. Top.

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Abstract. We summarize current developments in the investigation of glassy matter using nonlinear dielectric spectroscopy. This work also provides a brief introduction into the phenomenology of the linear dielectric response of glassforming materials and discusses the main mechanisms that can give rise to nonlinear dielectric response in this material class. Here we mainly concentrate on measurements of the conventional dielectric permittivity at high fields and the higher-order susceptibilities characterizing the 3 and 5 components of the dielectric response as performed in our group. Typical results on canonical glass-forming liquids and orientationally disordered plastic crystals are discussed, also treating the special case of supercooled monohydroxy alcohols.

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On the nature of the high-frequency relaxation in a molecular glass former: A joint study of glycerol by field cycling NMR, dielectric spectroscopy, and light scattering

Cited by 46 publications

References 65 publications

Identification of Structural Relaxation in the Dielectric Response of Water

Identification of Structural Relaxation in the Dielectric Response of Water

Combining 7Li NMR field-cycling relaxometry and stimulated-echo experiments: A powerful approach to lithium ion dynamics in solid-state electrolytes

Investigation of nonlinear effects in glassy matter using dielectric methods

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