Magnetogyric ratio of the nuclei

Spin coupling constants between different combinations of nuclear species can be meaningfully compared only when signs and magnitudes of the magnetogyric ratios of the nuclei are accounted for. Thus it is useful to consider a reduced coupling constant K g which... 

Other Nuclei. Although most nmr experiments continue to involve H, or both, many other nuclei may also be utilized Several factors, including the value of I for the nucleus, the magnitude of the quadmpolar moment, the natural abundance and magnetogyric ratio of the isotope, or the possibihty of preparing enriched samples, need to be considered. The product of the isotopic parameters can be compared to the corresponding value for providing a measure of relative sensitivity or receptivity. Table 1 summarizes these factors for a number of isotopes. More complete information may... 

Fig. 42a-c Spectra of tetramethyltin in CDC13. a Proton decoupled, b proton coupled (2JsncH 54.3 Hz), c proton spectrum. The satellite signals are due to coupling to tin-117 (inner lines) and tin-119 (outer lines). The ratio of the coupling with tin-119 to that with tin-117 is 1.046 1 (the ratio of the magnetogyric ratios of the two nuclei)... 

Here, h denotes Planck s constant h divided by 27i, and /zq is the permeability of vacuum. I and 5 are the nuclear spins of the resonating spins I and non-resonating spins S, respectively. Ni and Ns denote the numbers of resonating and nonresonating nuclei in the sample, respectively ys the magnetogyric ratio of the nonresonating spins S, and and ryj- the internuclear distances. 

We described the nuclear Overhauser effect (NOE) among protons in Section 3.16 we now discuss the het-eronuclear NOE, which results from broadband proton decoupling in 13C NMR spectra (see Figure 4.1b). The net effect of NOE on 13C spectra is the enhancement of peaks whose carbon atoms have attached protons. This enhancement is due to the reversal of spin populations from the predicted Boltzmann distribution. The total amount of enhancement depends on the theoretical maximum and the mode of relaxation. The maximum possible enhancement is equal to one-half the ratio of the nuclei s magnetogyric ratios (y s) while the... 

The occurrence of a negative NOE when both nuclei have magnetogyric ratios of the same sign can be attributed to a breakdown of the extreme narrowing condition so that equation (16) is no longer valid. (222-227)... 

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