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  Deuteron magnetic resonance studies of anhydrous caffeine

Nowaczyk, A., Nath, R. C., Zimmermann, H., & Böhmer, R. (2012). Deuteron magnetic resonance studies of anhydrous caffeine. Zeitschrift für physikalische Chemie, 226(11), 1115-1124. doi:10.1524/zpch.2012.0333.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0024-1EA7-8 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-0024-1EA8-6
Genre: Journal Article
Alternative Title : Deuteron magnetic resonance studies of anhydrous caffeine

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ZsPhysChem_226_2012_1115.pdf (Any fulltext), 11MB
 
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 Creators:
Nowaczyk, Andre, Author
Nath, Ramesh Chandra, Author
Zimmermann, Herbert1, Author              
Böhmer, Roland, Author
Affiliations:
1Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Max Planck Society, ou_1497700              

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Free keywords: Phase Transitions, Spin−Lattice Relaxation, Echo Spectroscopy
 Abstract: Methyl deuterated caffeine powder was studied using 2H−NMR relaxometry and line shape analysis. In caffeine's low−temperature phase the spin−lattice relaxation times indicate a thermally activated CD3 reorientation (activation energy ≈4 kJ/mol). Below the T1 minimum near 35 K the quadrupolar echo spectra develop features indicative for quantum mechanical tunneling. Dielectric measurements indicate the presence of dipole moment fluctuations with times scales that follow an Arrhenius law (energy barrier ≈107 kJ/mol). It is argued that the underlying motion involves small−angle molecular excursions and therefore remains undetected via stimulated−echo spectroscopy. The hysteresis accompanying the order/disorder transition taking place above 400 K was monitored using solid−echo line shapes as well as via spin relaxation times. In the high−temperature phase indications for the onset of anisotropic large−angle motions were obtained

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Language(s): eng - English
 Dates: 2012-07-302012-09-242012-10-292012-11-01
 Publication Status: Published in print
 Pages: -
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 Table of Contents: -
 Rev. Method: Peer
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Title: Zeitschrift für physikalische Chemie
  Other : International Journal of Research in Physical Chemistry and Chemical Physics
Source Genre: Journal
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Publ. Info: Frankfurt am Main : Akademische Verlagsgesellschaft
Pages: - Volume / Issue: 226 (11) Sequence Number: - Start / End Page: 1115 - 1124 Identifier: ISSN: 0942-9352
CoNE: https://pure.mpg.de/cone/journals/resource/954925572905_1