Nuclear magnetic moments determination

Electron spin resonance studies of silver(II) pyridine complexes have proved to be extremely useful in determining the nature of the spedes in solution. Since natural silver has two isotopes, 107Ag and 109Ag, in approximately the same abundance, both of spin / = J, and since their nuclear magnetic moments differ by less than 15%, interpretation of spectra is often considered in terms of a single nucleus. The forms of the hyperfine splitting patterns for IN, cis and trans 2N, 3N and 4N, would be expected to be quite different and hence the number of pyridines can be readily assessed from well-resolved spectra. Spin Hamilton parameters obtained from both solid and frozen solution spectra are collected in Table 64.497 499 501-510... 

Also it would be possible to determine experimentally the influence of the electron shell to the nuclear wave function (nuclear polarizability). The 1S-electrons in heavy atoms admix excited states to the ground state of the nucleus in the order of 10 3 [24]. This leads additionally to the diamagnetic shielding to observable differences in the order of 10 3 of the nuclear magnetic moments for different charge states. 

When we now speak of nuclear magnetic resonance, we are discussing the kind of NMR discovered by Bloch and Purcell, that is, nuclear magnetic resonance in bulk materials. The early work in NMR was concentrated on the elucidation of the basic phenomena (much of which we cover in Chapters 2 and 8) and on the accurate determination of nuclear magnetic moments, which were of interest in elucidating aspects of the structure of the atomic nucleus. 

Precise determination of hyperfine constants for the halogen atoms was beyond the scope of the present investigation and, indeed, presents a problem of some magnitude (1,4,8). However, the major splitting in the spectra of CF , CF, Br , and Br i roughly parallels the values of the nuclear magnetic moments. 

The magnet generates the magnetic field which polarizes the nuclear magnetic moments. Its strength determines the degree of polarization and thus enters the sensitivity of the measurement. Furthermore, it determines the measurement frequency as well as... 

The Zeeman Hamiltonian Hz describes the interaction between the nuclear magnetic moment, and the external magnetic field Bq. It determines the Larmor frequency coq of deuterium, which is, for example, 76.8 MHz at 11.7 T (corresponding to a 500-MHz spectrometer). 

Molecular beam resonance experiments performed on CsBr and LiBr resulted in a coarse determination of the Br nuclear magnetic moments. Pound subsequently used solution-state Br NMR experiments (a negative solid-state experiment was attempted on a single crystal of KBr) to improve the precision of both magnetic moments by nearly an order of magnitude. The first bromine SSNMR spectrum ( Br) was acquired by Pound using a single crystal of NaBr. Relative to far fewer liferature reporfs confain Br SSNMR experi-... 

Because the longest-lived oxygen radioisotope, 0, has a half-life of only 124 s, the separated isotopes 0 and are valuable in tracer experiments. The nuclear magnetic moment of 0 gives it application in determining molecular structure by nuclear magnetic resonance measurements. 

Excited-state g-factors and nuclear magnetic moments are usually determinable with high accuracy because the ground-state values or alternatively the internal magnetic fields are known from other measurements. The excited-state moments have been determined for nearly all Mossbauer transitions by this method. Both the quadrupole and the magnetic moments provide highly significant tests of nuclear models. 

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