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A spinning thermometer to monitor microwave heating and glass transitions in dynamic nuclear polarization
Author(s) -
Miéville Pascal,
Vitzthum Veronika,
Caporini Marc A.,
Jannin Sami,
GerberLemaire Sandrine,
Bodenhausen Geoffrey
Publication year - 2011
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2811
Subject(s) - spinning , thermometer , chemistry , magic angle spinning , microwave , polarization (electrochemistry) , atmospheric temperature range , analytical chemistry (journal) , irradiation , optics , thermodynamics , nuclear magnetic resonance spectroscopy , chromatography , nuclear physics , polymer chemistry , physics , organic chemistry , quantum mechanics
As previously demonstrated by Thurber and Tycko, the peak position of 79 Br in potassium bromide (KBr) allows one to determine the temperature of a spinning sample. We propose to adapt the original design by using a compact KBr tablet placed at the bottom of the magic angle spinning rotor, separated from the sample under investigation by a thin disk made of polytetrafluoroethylene (or ‘Teflon’®). This design allows spinning the sample up to at least 16 kHz. The KBr tablet can remain in the rotor when changing the sample under investigation. Calibration in the range of 98 < T < 320 K has been carried out in a static rotor by inserting a platinum thermometer. The accuracy is better than ± 0.9 K, even in the presence of microwave irradiation. Irradiation with 5 W microwaves at 263 GHz leads to a small temperature increase of 3.6 ± 1.4 K in either static or spinning samples. The dynamic nuclear polarization enhancement decreases with increasing temperature, in particular when a frozen glassy sample undergoes a glass transition. Copyright © 2011 John Wiley & Sons, Ltd.