Electron spin resonance spectrometer

In an electron spin resonance spectrometer, transitions between the two states are brought about by the application of the quantum of energy hv which is equal to g H. The resonance condition is defined when hv = g H and this is achieved experimentally by varying H keeping the frequency (v) constant. Esr spectroscopy is used extensively in chemistry in the identification and elucidation of structures of radicals. 

T.H. Wilmshurst, Electron Spin Resonance Spectrometers, Plenum Press, New York, 1967. 

Wilmshurst, T. H., Electron Spin Resonance Spectrometers. Hilger, London, 1967. 

Instrumentation. Two electron spin resonance spectrometers have been used in the course of the work. The Southampton instrument was built in the laboratory, using a Varian magnet, and operated at 3 cm. wavelength. It employed an Hon rectangular cavity and obtained high sensitivity by magnetic field modulation at 100 kc.p.s. with a crystal detector phase sensitive detection... 

Electron spin traps Diamagnetic chemicals (e.g., nitrones) that can react with unstable free radicals to form more stable free radicals. These stable free radicals can then be detected in an electron spin resonance spectrometer. 

A5. Amity, I., Fabry-Perot cavity for millimetre and sub-millimetre electron spin resonance spectrometers. Rev. Sci. Imtrum. 41, 1492-1494 (1970). 

The measurements of ESR spectra were made by use of Electron Spin Resonance Spectrometer Model JES-ME-3X made by Japan Electron Optics Laboratory Co. Ltd. with X band and magnetic field... 

Detection of hydroxyl radical. For detection of hydroxyl radicals, a spin trapping agent, DMPO was obtained from Sigma-Aldrich.4 The water containing 500 pM DMPO was circulated for 30 min in exPCAW-l,and the water was sampled at 0, 1, 5, 10, 15, 20, 30 min of circulation and exposure to UV, USW and elevated 02. The samples in a flat-shaped quartz ESR cell were analyzed with an electron spin resonance spectrometer (JEOL-TE200, X-band). DMPO-OH signal were collected with a sweep width of 5 mM, a 100 kHz modulation frequency, 60 s sweep time, a time constant of 0.1 s and microwave power of 10 mW, at room temperature of 20-25°C. 

A somewhat different experimental approach is to convert the resonant absorption spectrum into its first derivative [38]. This can be done by a similar modulation procedure to that used in electron-spin resonance spectrometers. The major complication is that two modulating velocity terms are... 

Electron spin resonance spectrometers are available commercially, and typical operating conditions are a frequency/of 10 ° cps (x band), and a magnetic field H of 3600 gauss. Sometimes the measurements are made at other frequencies such as 2.4 X 10 cps (k band). The samples may be examined as a function of the microwave power, the microwave frequency, the modulation conditions, and the temperature. 

Poole CP (1967) Electron spin resonance a comprehensive treatise on experimental techniques. Interscience Publishers, a division of John WUey, New York WUmshurst TH (1967) Electron spin resonance spectrometers. Hilger, London Weckhuysen BM,Van DerVoort P,CatanaG (eds) (2000) Spectroscopy of transition metal ions on surfaces. Leuven University Press, Leuven... 

The esr spectrum of the paramagnetic component coincident to the metal-metal axis was observed at 4 K through the coupling of a single-crystal dielectric resonator of K2Pt(CN)4Bro.3o(H20)3 with an electron spin resonance spectrometer. Preliminary results include a line at g w 2 with a complex hyperfine structure (208). An impurity center associated with the presence of a copper(II) complex of Z>4a symmetry has recently been detected by esr (466). 

The g-factor of an aromatic radical determines the magnetic field at which the unpaired electron will resonate with the fixed frequency microwaves of a conventional electron spin resonance spectrometer. Thus we have the familiar resonance eqn. 4.15.4... 

A simple electron spin resonance spectrometer (Fig. 1.4) consists in principle of a microwave generator G that transmits electromagnetic energy via a waveguide W through a cavity C containing the sample to a detector D. The cavity is located between the poles N and S of a magnet. 

The fluorescence detector (ED) is one of the most sensitive detectors in use, and can record both excitation and emission spectra. The excitation spectra are identical to the UV-visible absorption spectra however, emission spectra can provide additional information. Detectors that are used to detect isotope-labeled molecules measure the radioactivity present. Other analytical instruments, such as IR spectrometers, mass spectrometers, NMR spectrometers, electron spin resonance spectrometers, plasma emission and plasma absorption spectrometers can be connected to HPLCs for use as detectors, to provide further information on molecular structure. 

Radical concentrations were then calculated from the light intensity differences using a calibration curve obtained from direct determination of PS radical concentration using an electron spin resonance spectrometer vs light absorbance at 412 nm (Fig. 2.3.13). 

Perhaps the most convincing argument in favor of a direct role of copper in the cytochrome oxidase reaction comes from studies done with the electron spin resonance spectrometer. Such studies demonstrate that some of the copper ions undergo valency changes during the oxidation-reduction process. The site of action of the copper in the electron transport chain would then be as follows ... 

Electron spin resonance spectrometer Varian Instruments... 

F ure 8.43 Basic components of an electron spin resonance spectrometer... 

A technique which is similar to radioimmunoassay, the difference being that the antigen is labelled with a free radical such as nitroxide. When the antibody combines with the labelled antigen, the free radical is immobilized and broad spectral peaks are observed on an electron spin resonance spectrometer. When the labelled antigen is displaced by unlabelled antigen from the test sample, a sharp peak is produced. In this way, the amount of antigen in the patient s sample can be measured. 

Wilmshurst,T.Hi Electron Spin Resonance Spectrometers (Adam Hilger, London 1967). 

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