title: A spinning thermometer to monitor microwave heating and glass transitions in dynamic nuclear polarization.
abstract: 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.
authors: Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne, Batochime, Lausanne, Switzerland. pascal.mieville@epfl.ch
authors: Pascal
authors: P
authors: Miéville
authors: Veronika
authors: V
authors: Vitzthum
authors: Marc A
authors: MA
authors: Caporini
authors: Sami
authors: S
authors: Jannin
authors: Sandrine
authors: S
authors: Gerber-Lemaire
authors: Geoffrey
authors: G
authors: Bodenhausen
mesh_terms: D001965:Bromides / Q000737:chemistry; D002138:Calibration; D005898:Glass / Q000737:chemistry*; D006358:Hot Temperature; D009682:Magnetic Resonance Spectroscopy; D008872:Microwaves; D044367:Phase Transition; D010984:Platinum / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D013821:Thermometers
chemical_list: D001965:Bromides; D017680:Potassium Compounds; D010984:Platinum; C039004:potassium bromide