Nuclides, magnetically active

Table 1 lists some of the important properties of several commonly observed nuclides in the study of pharmaceuticals. Notice that some elements such as hydrogen, have several magnetically active isotopes with very different properties. Interestingly, has the highest sensitivity to detection of any nucleus, but its use is limited by the added complexity of working with a radioactive isotope. The absolute sensitivity listed in the table takes into account the natural abundance of the isotope. Sensitivity can be improved in some studies by the chemical incorporation of magnetically active isotopes such as and... 

The nuclear Overhauser effect or NOE is a spatial phenomenon involving two magnetically active nuclides in close proximity. Generally, we think of these experiments in terms of interactions, but heteronucHde pairs also exhibit these... 

The use of NMR spectroscopy to characterize diamagnetic transition metal and posttransition metal complexes has increased tremendously in the past decade (111, 129). Mercury has two NMR-active isotopes, Hg (natural abundance = 13.22%) and (natural abundance = 16.84%). The former is quadrupolar (nuclear spin, / = ), and consequently, much more difficult to observe, due to line broadening. The latter, on the other hand, is one of approximately 20 nuclides in the periodic table with the preferred spin I = i. Its receptivity, a measure of relative signal strength, is five times that of C for comparison, " Cd, the most widely studied of the posttransition nuclei, has a receptivity of only 8 relative to C. Magnetic resonance frequencies are intimately connected with the quantity and dis-... 

All y-ray spectra were collected on 7-track magnetic tape, and the spectra analyzed by FOURIER, a computer program for computing nuclide activities, elemental concentrations and statistical parameters of the analytical results. Corrections for the Se interference in the ° Hg 280 KeV y-ray were made as described by Filby, et The Cu... 

From Equations 1.1 and 1.2 we can calculate the NMR frequency of any NMR-active nuclide on the basis of the strength of the applied magnetic field alone (Equations 1.3a and 1.3b). In practice, the gyromagnetic ratio we look up will already have the factor of Planck s constant included thus the imits of y will be in radians per tesla per second. For hydrogen, y is 2.675 X 10 radians/tesla/second (radians are used... 

If a large ensemble of an NMR-active nuclide (e.g., H) experience the same chemical environment, solvent, temperature, pressure, concentration, and field(s), they form a single net magnetization that, when excited with RF, generates a resonance (peak) in the spectrum with a particular chemical shift. For example, all the H s in chloroform generate a resonance with a shift of 7.27 ppm relative to the resonance of the H s in TMS. 

Magnetically equivalent.Two nuclei are magnetically equivalent when they are of the same nuclide and when both have exactly the same geometrical relationship to every other NMR-active nucleus in a molecule. 

Properties of Nuclear Magnetic Resonance (NMR)-Active Nuclides of (Current or Potential) Interest for the Study of Carbon Materials... 

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