Home News About Us Contact Contributors Disclaimer Privacy Policy Help FAQ

Home
Search
Quick Search
Advanced
Fulltext
Browse
Collections
Persons
My eDoc
Session History
Login
Name:
Password:
Documentation
Help
Support Wiki
Direct access to
document ID:


          Institute: MPI für medizinische Forschung     Collection: Jahrbuch 2012     Display Documents



ID: 638132.0, MPI für medizinische Forschung / Jahrbuch 2012
Deuteron Magnetic Resonance Studies of Anhydrous Caffeine
Translation of Title:Deuteron Magnetic Resonance Studies of Anhydrous Caffeine
Authors:Nowaczyk, Andre; Nath, Ramesh Chandra; Zimmermann, Herbert; Böhmer, Roland
Language:English
Date of Publication (YYYY-MM-DD):2012-11-01
Title of Journal:Zeitschrift für Physikalische Chemie
Journal Abbrev.:Zeitschrift für Physikalische Chemie
Volume:226
Issue / Number:11
Start Page:1115
End Page:1124
Review Status:Peer-review
Audience:Experts Only
Intended Educational Use:No
Abstract / Description: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
Free Keywords:Phase Transitions, Spin−Lattice Relaxation, Echo Spectroscopy
External Publication Status:published
Document Type:Article
Communicated by:Wulf Kaiser
Affiliations:MPI für medizinische Forschung/Abteilung Biophysik
MPI für medizinische Forschung/Abteilung Biomolekulare Mechanismen
MPI für medizinische Forschung/Arbeitsgruppe Zimmermann
MPI für medizinische Forschung/Abteilung Molekulare Physik
Identifiers:LOCALID:7834
URI:http%3A%2F%2Fwww.oldenbourg-link.com%2Fdoi%2Fabs%2...
DOI:10.1524%2Fzpch.2012.0333
Full Text:
Sorry, no privileges
The scope and number of records on eDoc is subject to the collection policies defined by each institute - see "info" button in the collection browse view.