A Rectangular Loop–Gap Resonator for EPR Studies of Aqueous Samples

Authors: Piasecki W.¹; Froncisz W.¹; Hubbell W.L.²

Source: Journal of Magnetic Resonance, Volume 134, Number 1, September 1998 , pp. 36-43(8)

Publisher: Academic Press

Abstract:

A new rectangular geometry of the loop–gap resonator for the use with a flat cell has been developed. Maxwell's equations for the resonators with two, four, six, and eight gaps have been solved assuming the existence of only the magnetic z-component. The formulas obtained were numerically solved for the electric and magnetic field distributions over the cross-sections of the resonators. The presence of a nodal plane for the electric field in the center of the resonator allows the use of a flat cell instead of a capillary for EPR measurements. Using the field distributions obtained, the quality factor and EPR signal amplitude for various shapes and gap numbers for the resonators containing a flat cell filled with water were examined numerically. This allowed finding the geometry that yields the maximum EPR signal intensity. Several X-band resonators were built in order to verify the results obtained theoretically. The experiments confirmed the ability of a novel resonant structure to accommodate a flat cell filled with an aqueous sample. It has been found that the optimum aqueous sample volume for the X-band rectangular loop–gap resonator equals 16 mm³. For a saturable aqueous sample this gives a fourfold improvement in the S/N ratio over the circular 1 mm i.d. loop–gap resonator equipped with 0.6 mm i.d. capillary. Copyright 1998 Academic Press.

Language: English

Document Type: Research article

Affiliations: 1: Department of Biophysics, Jagiellonian University, Al. Mickiewicza 3, Kraków, 31-120, Poland 2: Jules Stein Eye Institute and Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California, 90024

Publication date: 1998-09-01

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