A high magnetic field EPR spectrometer

Müller, Frank; Hopkins, M. A.; Coron, N.; Grynberg, M.; Brunel, Louis Claude; Martinez, G.

doi:10.1063/1.1140474

Cited by 159 publications

(107 citation statements)

References 15 publications

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“…Electron paramagnetic resonance (EPR) experiments have realized new opportunities as magnetic fields have been increased 1,2,3,4,5,6,7 and pulsed capabilities have been added 8,9,10,11,12,13,14 .…”

Section: Introductionmentioning

confidence: 99%

A multifrequency high-field pulsed electron paramagnetic resonance/electron-nuclear double resonance spectrometer

Morley

Brunel

Tol

2008

Review of Scientific Instruments

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We describe a pulsed multi-frequency electron paramagnetic resonance spectrometer operating at several frequencies in the range of 110-336 GHz. The microwave source at all frequencies consists of a multiplier chain starting from a solid state synthesizer in the 12-15 GHz range. A fast PIN-switch at the base frequency creates the pulses. At all frequencies a FabryPérot resonator is employed and the π/2 pulse length ranges from ~100 ns at 110 GHz to ~600 ns at 334 GHz. Measurements of a single crystal containing dilute Mn 2+ impurities at 12 T illustrate the effects of large electron spin polarizations. The capabilities also allow for pulsed electron nuclear double resonance experiments as demonstrated by Mims ENDOR of 39 K nuclei in Cr:K 3 NbO 8 .

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Section: Introductionmentioning

confidence: 99%

A multifrequency high-field pulsed electron paramagnetic resonance/electron-nuclear double resonance spectrometer

Morley

Brunel

Tol

2008

Review of Scientific Instruments

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“…The spectrometer used for these experiments has been described (19). The 245-GHz (A = 1.22 mm) methanol-d (CH302H) emission from the far-infrared laser was used for these experiments.…”

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confidence: 99%

Angular orientation of the stable tyrosyl radical within photosystem II by high-field 245-GHz electron paramagnetic resonance.

Brunel

Brill

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

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The 4 K 245-GHz/8.7-T electron paramagnetic resonance spectrum of the stable tyrosyl radical in photosystem I, known as TyrD, has been measured. Illumination at 200 K enhances the signal Intensity of TyrD" by a factor of >40 compared to the signal obtained from darkadapted samples. This signal ehncement and the unusual ine shape of the TyrD' resonance result from the magnetic dipolar coupling of the radical to the manganese duster involved in oxygen evolution. The relative alar orientation of the m _ cluster with respect to TyrD-has been determined from line-shape analysis. The resonance arising from TyrD' in Tris-washed nsfree photosystem U sample is also distorted. This effect probably originates from the influence of the nonheme iron on the spin aon of the tyrosyl radical.The relative angular orientation of the nonheme iron has also been determined. Oriented samples were used to determine the angular orientation of TyrD with respect to the membrane plane. Combining angular data with pubilshed distances, we have constructed a three-dimensional picture of the relative positions of TyrD', the manganese cluster, and the noneme iron. The data suggest a more symmetrical placement of the manganese relative to TyrD-and TyrZ, the tyrosine involved in eleco transfer, than is usually assumed in current models of photosystem H.At low temperatures, the electron paramagnetic resonance (EPR) signal of the stable tyrosyl radical, known as TyrD- (1, 2), from plant photosystem II (PSIT) is known to be "relaxation enhanced" when the sample is illuminated at 200 K (3, 4). This enhancement has been attributed to the presence of a second paramagnetic species that is capable of increasing the relaxation rates of the tyrosyl radical through a dipolar interaction. The second paramagnet is thought to be the manganese cluster that is involved in charge storage and probably acts as the active site for oxygen evolution (5, 6). The dipolar spin-relaxation mechanism has been thoroughly studied (7-9). The strength of the dipolar interaction is determined by the distance between the two spins and the angle between the interspin vector and the applied magnetic field. Previous work on PSII has concentrated on the determination of the interspin distance (10-13). No attempts have been made to obtain the angular orientation of the two spins.At magnetic field strengths used in conventional EPR spectroscopy, the spectrum of the tyrosyl radical is dominated by the hyperfine interactions between the electron spin and its neighboring protons. The inhomogeneous line width of the spectrum is determined by the anisotropic parts of these hyperfine interactions and the g anisotropy, each of which has its own particular orientation dependence relative to the molecular frame. A good approximation is that all possible orientations ofthe radical with respect to the applied magnetic field contribute to a given field position on the TyrD spectrum. Thus, the determination ofthe orientation of an external relaxer is difficult. However, at magnetic fields m...

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“…Most of the early quasioptical EPR spectrometers (10,11,33) were based on the simple transmission cavity arrangement shown in Fig. 5, with cylindrical waveguide or lens trains used to conduct the radiation between the sample in the magnet and source or detector.…”

Section: Transmission Spectrometermentioning

confidence: 99%

“…For transmission through the optical bore between the optical bridge and the sample, a number of methods have been used, including oversized smoothwalled cylindrical wave guide (33,35), lens trains (10,11,13), and the method that has become most commonly used, corrugated cylindrical waveguide (36). Typically the corrugations in such a waveguide are rectangular, about /4 and spaced at a distance of about /2 where is the wavelength (or center of the wavelength range) of interest.…”

Section: Power Transmissionmentioning

confidence: 99%

Engineering and design concepts for quasioptical high‐field electron paramagnetic resonance

Gullá

Budil

2004

Concepts Magn Reson

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ABSTRACT:In recent years, electron paramagnetic resonance (EPR) has been extended to high magnetic fields requiring superconducting magnets, by analogy with similar extensions in NMR some decades earlier. One major difference between high-field EPR and NMR is that the corresponding increase in applied resonant frequency has required a significantly different technology in the case of EPR. In contrast to the waveguide-based systems used in conventional EPR fields, high-field EPR has required quasioptical technology that is more commonly used in radioastronomy and communications. This article presents an overview of quasioptical methods as they have been applied in high-field EPR systems. Two matrix methods for designing and engineering quasioptical circuits are presented, and their application illustrated with practical examples. Methods for evaluating the performance of the magnet and sensitivity of the quasioptics are also surveyed.

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A high magnetic field EPR spectrometer

Cited by 159 publications

References 15 publications

A multifrequency high-field pulsed electron paramagnetic resonance/electron-nuclear double resonance spectrometer

A multifrequency high-field pulsed electron paramagnetic resonance/electron-nuclear double resonance spectrometer

Angular orientation of the stable tyrosyl radical within photosystem II by high-field 245-GHz electron paramagnetic resonance.

Engineering and design concepts for quasioptical high‐field electron paramagnetic resonance

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