NMR magnetic field

NMR magnetic field shift in ppm, potential in electrochemistry, distance in crystallography, etc., and frequency its inverse. 

Structure 1. Under an NMR magnetic field, the axis of the nematic domain tends to align along the applied field, and thus the resulting LC phase is taken to be of a mono-domain texture. 

The frequency of radiation used in NMR depends on the field strength of the magnet used in the instrument. Frequencies range from 60 to 600 MHz for commercial instruments. Modern NMR equipment uses RF pulses in Fourier transform systems. There are no known safety concerns associated with these frequencies of radiation. However NMR magnetic fields can have adverse effects on pacemakers and other medical devices (see below under magnetic fields). 

NMR magnetic field optimization, signal detection and sample handling... 

See also Labelling Studies in Biochemistry Using NMR Laboratory Information Management Systems (LIMS) Macromolecule-ligand Interactions Studied By NMR Magnetic Field Gradients in High Resolution... 

NMR Nuclear magnetic resonance [223, 224] Chemical shift of splitting of nuclear spin states in a magnetic field H [225], C [226, 227], N [228], F [229], 2 Xe [230] Other Techniques Chemical state diffusion of adsorbed species... 

NMR depends on manipulating the collective motions of nuclear spins, held in a magnetic field. As with... 

Figure Bl.l 1.2. Simplified representation of an NMR spectrometer with pulsed RF and superconducting magnet. The main magnetic field Bq is vertical and centred on the sample.

The original method employed was to scan eitiier the frequency of the exciting oscillator or to scan the applied magnetic field until resonant absorption occiined. Flowever, compared to simultaneous excitation of a wide range of frequencies by a short RF pulse, the scanned approach is a very time-inefficient way of recording the spectrum. Flence, with the advent of computers that could be dedicated to spectrometers and efficient Fourier transfomi (FT) algoritluns, pulsed FT NMR became the nomial mode of operation. 

Higher magnetic fields exist tiian those used in NMR but the NMR experiment imposes constraints in addition to just magnitude. An NMR spectroscopy experiment also demands homogeneity and stability of the magnetic... 

Figure Bl.12.13. MAS NMR spectra from kyanite (a) at 17.55 T along with the complete simulation and the individual components, (b) simulation of centreband lineshapes of kyanite as a fiinction of applied magnetic field, and tire satellite transitions showing (c) the complete spiimmg sideband manifold and (d) an expansion of individual sidebands and their simulation.

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