Coupling tensor Fermi contact term

The spin-density p") obtained in KSCED calculations is used to derive the hyperfine interaction tensor employing the conventional formulas for the isotropic coupling constant (Fermi contact term, Aiao) and the magnetic dipolar tensor (Ay) ... 

In these expressions the index i runs over electrons and a runs over nuclei. The Fermi contact term describes the magnetic interaction between the electron spin and nuclear spin magnetic moments when there is electron spin density at the nucleus. This condition is imposed by the presence of the Dirac delta function S(rai) in the expression. The dipole-dipole coupling term describes the classical interaction between the magnetic dipole moments associated with the electron and nuclear spins. It depends on the relative orientations of the two moments described in equation (7.145) and falls off as the inverse cube of the separations of the two dipoles. The cartesian form of the dipole-dipole interaction to some extent masks the simplicity of this term. Using the results of spherical tensor algebra from the previous chapter, we can bring this into the open as... 

These four contributions la, lb, 2, and 3 are called the diamagnetic, orbital, dipole, and Fermi contact terms, respectively. For the anisotropic part of the spin-spin coupling tensor, a dipolar-contact cross term was obtained. The gauge origin for Ayy was here placed on the nucleus N. Numerical values were estimated for J in HD using the closure approximation and an effective energy denominator, AE, for and Again, Eqs. (12)-(16) remain exact at the non-relativistic limit. 

Concerning the Hesns Hamiltonian, the quantities that need to be computed are the isotropic and anisotropic spin-spin coupling tensor. The isotropic contribution, the so-called Fermi contact term, is related to the spin density at the nucleus K under consideration [139],... 

In addition to the isomer shift and the quadrupole splitting, it is possible to obtain the hyperfine coupling tensor from a Mossbauer experiment if a magnetic field is applied. This additional parameter describes the interactions between impaired electrons and the nuclear magnetic moment. Three terms contribute to the hyperfine coupling (i) the isotropic Fermi contact, (ii) the spin—dipole... 

The hyperfine coupling tensor (A) describes the interaction between the electronic spin density and the nuclear magnetic momentum, and can be split into two terms. The first term, usually referred to as Fermi contact interaction, is an isotropic contribution also known as hyperfine coupling constant (HCC), and is related to the spin density at the corresponding nucleus n by [25]... 

Using an AMI ground-state wavefunction, the anisotropy A J of the J(X,Y) tensor was calculated for compounds of type MesX—Y (X = C, Si, Sn, Pb Y = F, Cl) at the RPA level and Eq. (36) was used to perform a bond contribution analysis of the Fermi contact-spin dipolar cross term, which was calculated as the main contribution to A J(X,Y) in the whole series except for X = Pb. The role played by the X—Y bond, its antibond and the Y lone pairs in determining the cross term as the dominant one was discussed. The RPA-AMl approach was used to study the /(Sn,Sn) coupling through the... 

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