Modernization of the x-band epr spectrometer bruker elexsys e580 for dynamic nuclear polarization

Abstract

To study the effects of dynamic nuclear polarization (DNP) in the X-band (microwave frequency of 9 GHz), using the capabilities provided by commercial EPR equipment, a part of the EPR spectrometer associated with the excitation and detection of double electron-nuclear resonance signals (ENDOR) has been modernized. Using the developed preamplifier of NMR signals, a homemade “Kazan Nova II”NMR spectrometer was implemented into the radio frequency path of the EPR spectrometer. The tuning and matching circuits made it possible to observe the NMR and DNP signals on protons in the frequency range 14.5–15.2 MHz. The performance of the DNP equipment was tested for a solution of the stable nitroxyl radical TEMPOL in benzene and a crude oil sample. The DNP effects caused by the Overhauser and solid effects were observed. The modernization of the existing EPR equipment creates a basis for further expanding its capabilities to study DNP effects in various systems at different conditions (in the pulsed mode of saturation of the EPR lines, with the temperature lowering, under the action of optical excitation, etc).