Epr at Varian: 1954-1974

Hyde, James S.

doi:10.1142/9789812816764_0056

Cited by 8 publications

(2 citation statements)

References 12 publications

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“…The high magnetic field induces strong Lorentz forces on the modulation coil, which cause vibrations in the probe head at the modulation frequency or its harmonics. This is called microphonics [9,23,24]. This interference tends to be in phase with the modulated EPR signal and can seriously deteriorate the signal-to-noise ratio.…”

Section: Introductionmentioning

confidence: 99%

Continuous-wave EPR at 275GHz: Application to high-spin Fe3+ systems

Mathies

Blok

Disselhorst

et al. 2011

Journal of Magnetic Resonance

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Section: Introductionmentioning

confidence: 99%

Continuous-wave EPR at 275GHz: Application to high-spin Fe3+ systems

Mathies

Blok

Disselhorst

et al. 2011

Journal of Magnetic Resonance

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“…Pulse, continuous wave (CW), and rapid scan EPR measurements often have significant contributions from background signals due to a wide range of environmental interferences such as extraneous RF signals, temperature variations, vibrations and instrumental artifacts such as switching transients, eddy currents, reflections, ground loops, spins in materials of the resonator and sample holder, and many others. For example, Hyde [1] pointed out that magnetic field modulation introduces background problems due to forces on the wires and due to eddy currents induced in the cavity body. Pulsed EPR suffers deadtime after the pulse due to resonator ring-down, reflections, and switching transients.…”

Section: Introductionmentioning

confidence: 99%

Background correction in rapid scan EPR spectroscopy

Buchanan

Woodcock

Quine

et al. 2018

Journal of Magnetic Resonance

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In rapid scan EPR the rapidly-changing magnetic field induces a background signal that may be larger than the EPR signal. A method has been developed to correct for that background signal by acquiring two sets of data, denoted as scan 1 and scan 2. In scan 2 the external field B is reversed and the data acquisition trigger is offset by one half cycle of the scan field relative to the settings used in scan 1. For data acquired with a cross-loop resonator subtraction of scan 2 from scan 1 cancels the background and enhances the EPR signal. Experiments were performed at an EPR frequency of about 258 MHz, which is in the range that is commonly used for in vivo imaging. Samples include nitroxide radicals, a trityl radical, a dinitroxide, and a nitroxide in the presence of a magnetic field gradient. This method has the advantage that no assumption is made about the shape of the background signal, and it provides an approach to automating the background correction.

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Pulsed saturation recovery 250 MHz electron paramagnetic resonance spectrometer

Quine

2005

Concepts Magn. Reson.

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Pulsed saturation recovery capability has been added to the pulsed 250 MHz EPR spectrometer previously described. The design of the spectrometer is sufficiently flexible so that the only change needed was an interchangeable plug-in card that directed the VHF pulses and the low-power CW VHF to monitor the spin recovery following saturation. The plug-in module converts the ESE spectrometer to a SR spectrometer. The switch in the plug-in module for pulsed ESE or FID operation with the crossed-loop resonator (CLR) is replaced by a directional coupler. The effect of the directional coupler is to cause the low-level CW observe power to always be incident on the CLR and to direct the high-power RF pulses to the excitation side of the CLR. The pump and observe RF paths do not need to be coherent. The phase differences between the pump and observe RF paths do not have a detectable effect on the observed recovery signal because, unlike an FID or echo measurement, the SR measurement is not sensitive to phase coherence other than in the double-balanced mixer signal detector. The circuit on the plug-in card also provides signal paths for tuning both resonators of the CLR. The SR experiments are described and examples are presented of T 1 measurements made possible by this new 250 MHz saturation recovery capability.

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Epr at Varian: 1954-1974

Cited by 8 publications

References 12 publications

Continuous-wave EPR at 275GHz: Application to high-spin Fe3+ systems

Continuous-wave EPR at 275GHz: Application to high-spin Fe3+ systems

Background correction in rapid scan EPR spectroscopy

Pulsed saturation recovery 250 MHz electron paramagnetic resonance spectrometer

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