Solid-state dynamic nuclear polarization at 263 GHz: spectrometer design and experimental results.
Dynamic Nuclear Polarization (DNP) experiments transfer polarization from electron spins to nuclear spins with microwave irradiation of the electron spins for enhanced sensitivity in nuclear magnetic resonance (NMR) spectroscopy. Design and testing of a spectrometer for magic angle spinning (MAS) DNP experiments at 263 GHz microwave frequency, 400 MHz (1)H frequency is described. Microwaves are generated by a novel continuous-wave gyrotron, transmitted to the NMR probe via a transmission line, and irradiated on a 3.2 mm rotor for MAS DNP experiments. DNP signal enhancements of up to 80 have been measured at 95 K on urea and proline in water-glycerol with the biradical polarizing agent TOTAPOL. We characterize the experimental parameters affecting the DNP efficiency: the magnetic field dependence, temperature dependence and polarization build-up times, microwave power dependence, sample heating effects, and spinning frequency dependence of the DNP signal enhancement. Stable system operation, including DNP performance, is also demonstrated over a 36 h period.
Rosay
Melanie
M
Bruker BioSpin Corporation, 15 Fortune Drive, Billerica, MA 01821, USA. melanie.rosay@bruker-biospin.com
Tometich
Leo
L
Pawsey
Shane
S
Bader
Reto
R
Schauwecker
Robert
R
Blank
Monica
M
Borchard
Philipp M
PM
Cauffman
Stephen R
SR
Felch
Kevin L
KL
Weber
Ralph T
RT
Temkin
Richard J
RJ
Griffin
Robert G
RG
Maas
Werner E
WE
D003497:Cyclic N-Oxides / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D008872:Microwaves; D011392:Proline / Q000737:chemistry; D020005:Propanols / Q000737:chemistry; D013696:Temperature; D014508:Urea / Q000737:chemistry
C521769:1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol; D003497:Cyclic N-Oxides; D020005:Propanols; D014508:Urea; D011392:Proline
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