TY - JOUR
T1 - Effect of electron spectral diffusion on static dynamic nuclear polarization at 7 Tesla
AU - Leavesley, Alisa
AU - Shimon, Daphna
AU - Siaw, Ting Ann
AU - Feintuch, Akiva
AU - Goldfarb, Daniella
AU - Vega, Shimon
AU - Kaminker, Ilia
AU - Han, Songi
N1 - Funding Information:
This work is supported by grants of the National Science Foundation (CHE #1505038) and the Binational Science Foundation (Grant #2014149). IK acknowledges the support of the long-term postdoctoral fellowship by the Human Frontier Science Foundation. We would also like to thank Shamon Walker and Arvid Niem-eller for their help in the early efforts to build and establish dual DNP and EPR hardware capabilities at 7 Telsa, which ultimately has led to the measurement of ELDOR data presented here.
Publisher Copyright:
© 2017 the Owner Societies.
PY - 2017
Y1 - 2017
N2 - Here, we present an integrated experimental and theoretical study of 1H dynamic nuclear polarization (DNP) of a frozen aqueous glass containing free radicals at 7 T, under static conditions and at temperatures ranging between 4 and 20 K. The DNP studies were performed with a home-built 200 GHz quasi-optics microwave bridge, powered by a tunable solid-state diode source. DNP using monochromatic and continuous wave (cw) irradiation applied to the electron paramagnetic resonance (EPR) spectrum of the radicals induces the transfer of polarization from the electron spins to the surrounding nuclei of the solvent and solutes in the frozen aqueous glass. In our systematic experimental study, the DNP enhanced 1H signals are monitored as a function of microwave frequency, microwave power, radical concentration, and temperature, and are interpreted with the help of electron spin-lattice relaxation times, experimental MW irradiation parameters, and the electron spectral diffusion (eSD) model introduced previously. This comprehensive experimental DNP study with mono-nitroxide radical spin probes was accompanied with theoretical calculations. Our results consistently demonstrate that eSD effects can be significant at 7 T under static DNP conditions, and can be systematically modulated by experimental conditions.
AB - Here, we present an integrated experimental and theoretical study of 1H dynamic nuclear polarization (DNP) of a frozen aqueous glass containing free radicals at 7 T, under static conditions and at temperatures ranging between 4 and 20 K. The DNP studies were performed with a home-built 200 GHz quasi-optics microwave bridge, powered by a tunable solid-state diode source. DNP using monochromatic and continuous wave (cw) irradiation applied to the electron paramagnetic resonance (EPR) spectrum of the radicals induces the transfer of polarization from the electron spins to the surrounding nuclei of the solvent and solutes in the frozen aqueous glass. In our systematic experimental study, the DNP enhanced 1H signals are monitored as a function of microwave frequency, microwave power, radical concentration, and temperature, and are interpreted with the help of electron spin-lattice relaxation times, experimental MW irradiation parameters, and the electron spectral diffusion (eSD) model introduced previously. This comprehensive experimental DNP study with mono-nitroxide radical spin probes was accompanied with theoretical calculations. Our results consistently demonstrate that eSD effects can be significant at 7 T under static DNP conditions, and can be systematically modulated by experimental conditions.
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U2 - 10.1039/c6cp06893f
DO - 10.1039/c6cp06893f
M3 - Article
C2 - 28094364
AN - SCOPUS:85024403287
SN - 1463-9076
VL - 19
SP - 3596
EP - 3605
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 5
ER -