Nucleus magnetization, distribution

From these considerations, we conclude that the differences in the magnetization distribution must give relatively large positive contribution to corresponding to a magnetization distribution closer to the nucleus for Cs, than for Cs. 

We only briefly mention that a similar modification, i.e., a change from a Dirac delta distribution to an extended distribution, would be required for the spin-dependent electron-nucleus contact term, known as Fermi contact term, if the usual point-like nuclear magnetization distribution (the pointlike nuclear magnetic dipole approximation) is replaced by an extended nuclear magnetization distribution. 

In contrast, soft magnetic solids and paramagnetic systems with weak anisotropy may be completely polarized by an applied field, that is, the effective field at the Mossbauer nucleus is along the direction of the applied field, whereas the EFG is powder-distributed as in the case of crystallites or molecules. In this case, first-order quadrupole shifts cannot be observed in the magnetic Mossbauer spectra because they are symmetrically smeared out around the unperturbed positions of hyperfine fines, as given by the powder average of EQ mj, d, in (4.51). The result is a symmetric broadening of all hyperfine fines (however, distinct asymmetries arise if the first-order condition is violated). 

Quadrupolar nuclei Those nuclei, which because of their spin quantum number (which is always >1/2), have asymmetric charge distribution and thus posses an electric quadrupole as well as a magnetic dipole. This feature of the nucleus provides an extremely efficient relaxation mechanism for the nuclei themselves and for their close neighbors. This can give rise to broader than expected signals. 

A magnetic moment Is the tendency of a nucleus or electronic. oibitol with an unequal distribution of charge to align itself in a magnetic field. 

ENDOR experiments can be performed in liquid solution, in which only the isotropic hfc s (Ajso) are detected. They are proportional to the spin density at the respective nucleus. Erom the assigned isotropic hfc s a map of the spin density distribution over the molecule can be obtained. In frozen solutions and powders the anisotropic hf interactions can also be determined. Eurthermore, the method allows the detection of nuclear quadrupole couplings for nuclei with 1 1. For dominant g anisotropy as found in many metal complexes the external magnetic field can be set to several specific g values in the EPR, thereby selecting only those molecules that have their g tensor axis along the chosen field direction. In such orientation-selected spectra only those hf components are selected that correspond to this molecular orientation ( single crystal-like ENDOR ). 

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