A sensitive broadband high-frequency electron spin resonance/electron nuclear double resonance spectrometer operating at 5–7.5 mm wavelength

Seck, M.; Wyder, P.

doi:10.1063/1.1148847

Cited by 18 publications

(9 citation statements)

References 20 publications

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“…2) the EPR intensity depended on the orientation of the sample quadrants with respect to this distribution. With the sample sectors closest to the poles of the magnet the intensity was maximal (37.4% according to eqn (30) integrated twice over the interval 2p/4 to p/4 ) while rotation over 90 degrees afforded minimal intensity (12.6%). A complete Figure 16.…”

Section: Intensity Dependence On Cell Geometrymentioning

confidence: 99%

Broadband Transmission EPR Spectroscopy

Hagen

2013

PLoS ONE

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EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9–10 GHz range. Most (bio)molecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin – nuclear spin interactions and electron spin – electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8–2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed.

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Section: Intensity Dependence On Cell Geometrymentioning

confidence: 99%

Broadband Transmission EPR Spectroscopy

Hagen

2013

PLoS ONE

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“…For the measurements of CR of SE on liquid helium, we used a microwave (MW) spectrometer working in the range of 40-60 GHz, originally built for electron spin resonance measurements [10]. The low-temperature part consists of a cavity in the form of an upright cylinder resonating in the TE 011 mode, and operated in reflection.…”

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confidence: 99%

Coulomb Narrowing of the Quantum Cyclotron Resonance in a Nondegenerate Two-Dimensional Electron Liquid

et al. 1999

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We have observed a narrowing of the linear cyclotron resonance linewidth with an increase in the density of surface electrons on liquid helium in the electron-vapor atom scattering regime. The effect changes sign at densities n s . 1.7 3 10 8 cm 22 . The data are interpreted as a Coulombic effect on the Landau level width produced by a strong fluctuating electric field. [S0031-9007(99) PACS numbers: 73.20. Dx, 73.25. + i, 76.40. + b Cyclotron resonance (CR) studies in two-dimensional (2D) electron systems such as inversion layers on semiconductor surfaces and electrons bound at the free surface of liquid helium have been of great interest for many years [1,2]. Cyclotron resonance serves as a powerful probe for the effects of quantization of both out-of-plane and in-plane (orbital) motions on electron transport phenomena [3,4]. Two-dimensional electrons on a liquid helium surface are usually under extremely strong coupling conditions with respect to mutual Coulomb interaction: e 2 p pn s ͞k B T ¿ 1 (here n s is the electron density). At such conditions a strong influence of electron-electron interaction on the CR linewidth and line shape is expected. In the ultraquantum limit for short-ranged scatterers, according to [1] , the linewidth is determined by the Landau level width itself. Therefore the CR may also serve as a probe for Coulombic effects on the Landau level width.Experimental studies of the Coulomb effect on the static magnetoconductivity of surface electrons (SE) on liquid helium extensively carried out over the years [5,6] were shown to be in agreement with the theoretical concept of a quasiuniform many-electron fluctuating field E f . However, the only direct study of the many-electron effect on the CR of SE [7] showed mysteriously a density dependence of the linewidth that is opposite to the theoretical predictions [8,9], putting in question the applicability of this concept.The intriguing decrease of the CR linewidth with the electron density was predicted nearly two decades ago [8]. This effect caused by the many-electron fluctuating electric field E f is expected to be quite universal: From a theoretical point of view, it does not depend much on a particular scattering mechanism and remains valid for the Wigner solid [9]. The CR data reported by that time [4] showed a slight decrease of the CR linewidth with the increase of the holding electric field E Ќ 2pen s at low temperatures T , 0.8 K, where electrons are scattered by capillary wave quanta (ripplons). Under these conditions the electron-ripplon coupling is also dependent on E Ќ which interferes with the many-electron effect. At T ϳ 1.3 K, where the main scatterers are helium vapor atoms, the opposite behavior was reported: The linewidth increases linearly with E Ќ [4]. Later, a more detailed exploration of the low temperature regime with the electron density n s being varied independently of the holding electric field E Ќ showed no sign of the linewidth narrowing with n s for the Wigner solid phase [7]. Additionally, the onset of the ele...

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“…28 Using a coupling loop located in the fixed top plate, the radiation is fed into the cavity and excites the TE 011 mode. It consists of a fixed upper plate and a movable outer part, the latter consisting of the body of the resonator and the bottom plate ͑Fig.…”

Section: A Cavitymentioning

confidence: 99%

Broadband electron spin resonance at 4–40 GHz and magnetic fields up to 10 T

Schlegel

Dressel

Slageren

2010

Review of Scientific Instruments

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A broadband electron spin resonance spectrometer is described which operates at frequencies between 4 and 40 GHz and can be used in superconducting magnets. A tunable cylindrical cavity is connected to a vector network analyzer via coaxial cables, and the radiation is fed into the cavity by a coupling loop. No field modulation is employed. Resonance frequencies below 14 GHz are obtained by inserting dielectrics with different permittivities into the cavity. The setup allows for measurements with the microwave magnetic field either parallel or perpendicular to the external field.

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A sensitive broadband high-frequency electron spin resonance/electron nuclear double resonance spectrometer operating at 5–7.5 mm wavelength

Cited by 18 publications

References 20 publications

Broadband Transmission EPR Spectroscopy

Broadband Transmission EPR Spectroscopy

Coulomb Narrowing of the Quantum Cyclotron Resonance in a Nondegenerate Two-Dimensional Electron Liquid

Broadband electron spin resonance at 4–40 GHz and magnetic fields up to 10 T

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