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 Title: Epr of CH3 radicals in SIO2 clathrate Author(s): Dmitriev, Yurij Contributor(s): Benetis, Nikolas Ploutarch; Buscarino, Gianpiero Subject(s): Matrix isolation (and droplets) Abstract: EPR lineshape simulations of CH$_{3}$/SiO$_{2}$ clathrates reveal the motional conditions of the CH$_{3}$ radical up to the unusual regime of its stability, the high temperature diffusional regime. This was obvious by the isotropic magnetic interaction at the highest experimental temperatures over 140 K. Special motional and thermodynamics conditions for methyl radical may however prevail for the CH$_{3}$/SiO$_{2}$ clathrates system due to the limited space of the host voids, compared to solid gas isolation. The lowest temperature in the experiment was 4.1 K, while the highest one was 300 K. The EPR parameters of the radical revealed non-monotonic temperature dependence. The extremely wide temperature range of the radical stability may be attributed to the solidity of the clathrate voids and the small diameter of their channels that do not allow molecular collisions between the radical species. At the lowest sample temperatures, a portion of the radicals stopped to rotate thus indicating their attachment to specific matrix sites with large radical-host interaction. The unusual increase of the width of the CH$_{3}$/SiO$_{2}$ clathrate spectra with the temperature at high sample temperatures indicates resemblance to the spin-rotation interaction relaxation mechanism known only in the case of small species in non-viscous fluids, and is contrasted to the normal difussional decrease of the width in the CH$_{3}$ hosted in a series of solid. The effect was explained by adopting extremely frequent radical collisions with the clathrate void walls leading to repeated angular momentum alterations, a kind of “reorientation”.\footnote{Yu. A. D. acknowledges support by the Russian Foundation for Basic Research (RFBR), research project 16-02-00127a.} Issue Date: 2016-06-20 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper/Presentation Type: Text Language: En URI: http://hdl.handle.net/2142/91192 Rights Information: Copyright 2016 by the authors Date Available in IDEALS: 2016-08-22
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