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Broadband W-band Rapid Frequency Sweep Considerations for Fourier Transform EPR. Cell Biochem Biophys 2017 Dec;75(3-4):259-273

Date

05/31/2017

Pubmed ID

28555359

Pubmed Central ID

PMC5693649

DOI

10.1007/s12013-017-0804-7

Scopus ID

2-s2.0-85019687030   5 Citations

Abstract

A multi-arm W-band (94 GHz) electron paramagnetic resonance spectrometer that incorporates a loop-gap resonator with high bandwidth is described. A goal of the instrumental development is detection of free induction decay following rapid sweep of the microwave frequency across the spectrum of a nitroxide radical at physiological temperature, which is expected to lead to a capability for Fourier transform electron paramagnetic resonance. Progress toward this goal is a theme of the paper. Because of the low Q-value of the loop-gap resonator, it was found necessary to develop a new type of automatic frequency control, which is described in an appendix. Path-length equalization, which is accomplished at the intermediate frequency of 59 GHz, is analyzed. A directional coupler is favored for separation of incident and reflected power between the bridge and the loop-gap resonator. Microwave leakage of this coupler is analyzed. An oversize waveguide with hyperbolic-cosine tapers couples the bridge to the loop-gap resonator, which results in reduced microwave power and signal loss. Benchmark sensitivity data are provided. The most extensive application of the instrument to date has been the measurement of T1 values using pulse saturation recovery. An overview of that work is provided.

Author List

Strangeway RA, Hyde JS, Camenisch TG, Sidabras JW, Mett RR, Anderson JR, Ratke JJ, Subczynski WK

Authors

Richard R. Mett PhD Adjunct Professor in the Biophysics department at Medical College of Wisconsin
Jason W. Sidabras PhD Assistant Professor in the Biophysics department at Medical College of Wisconsin
Witold K. Subczynski PhD Professor in the Biophysics department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Electron Spin Resonance Spectroscopy
Fourier Analysis
Microwaves
Signal-To-Noise Ratio