Abstract: Electron spin echo (ESE) spectroscopy as applied to nitroxide spin probes in glasses is sensitive to molecular motions of two types. The first type of motion is fast stochastic librations, with correlation times on the scale of nanoseconds. In this work, these librations were found in glassy glycerol above similar to 190 K and in glassy o-terphenyl above similar to 250 K (glass transition temperatures for these two solvents are T-g = 185 K and T-g = 243 K, respectively). Most likely, these librations are of the same origin as anharmonic atomic vibrations, as seen in glasses by neutron scattering above a so-called dynamical transition temperature. The second type of motion is slow millisecond inertial rotations, which are observed in the experimentally accessible microsecond time scale as developing within an angular range of similar to 0.1-2 degrees. Over the temperature range studied, the square of the characteristic rotation rate was found to be proportional to the dielectric alpha-relaxation rate that is known for glycerol and o-terphenyl from literature. This empirical fact probably means that small-angle inertial rotations of spin probes and dielectric alpha-relaxation in the solvent are interrelated phenomena. (C) 2010 Elsevier B.V. All rights reserved.

Cite: Isaev N.P. , Kulik L.V. , Kirilyuk I.A. , Reznikov V.A. , Grigor'ev I.A. , Dzuba S.A.
Fast stochastic librations and slow small-angle rotations of molecules in glasses observed on nitroxide spin probes by stimulated electron spin echo spectroscopy
Journal of Non-Crystalline Solids. 2010. V.356. N20-22. P.1037-1042. DOI: 10.1016/j.jnoncrysol.2010.01.018 WOS Scopus РИНЦ

Dates:

Published print:

May 1, 2010

Identifiers:

Web of science	WOS:000277763600016
Scopus	2-s2.0-77950188637
Elibrary	15315340
OpenAlex	W2067372938

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