Hyperfine interaction, central atom

Very large hyperfine interactions. A number of paramagnetic fluorides exhibit extremely large central-atom hyperfine interactions, e. g. 1576 G for in AsFa(12), 6200 G for jp,... 

Provided the unshifted centres of the transitions can be located the central-atom hyperfine interaction and value may be determined exactly from an iterative solution of the Breit-Rabi equations. Ligand fluorine hyperfine interactions should be determined from the highest-field transition available where spin-spin decoupling is essentially complete. 

The contribution of central-atom ns character to the semi-occupied orbital gives rise to a distinctive feature in the ESR spectra of many of these radicals, namely a very large central atom hyperfine interaction, often several kiloGauss. On the other hand, the isotropic hyperfine interactions are surprisingly... 

The halogen hexafluorides CIF, BrF and IF, on the other hand, have central atoms whose nuclei havenon-zero nuclear spin. The appearance of their spectra is therefore dominated by the central-atom hyperfine interactions, which (particularly for BrF and IF ) are extremely large and necessitated unusual methods of analysis (22). 

The ESR spectrum exhibited by unpaired spins of electrons bound to donors can provide an identification of the donor species through the interaction of the paramagnetic electrons with the nuclear magnetic moments of the donor atoms. This central hyperfine interaction splits the ESR spectrum into 21+1 lines, where I is the nuclear spin, providing in many cases an identification of the donor. For more details see for example Datareview 2.4. 

As between the isoelectronic radicals PF5", SF5 and AsF5 , SeF5 we conclude that the difference in the 19f hyperfine interactions is essentially Coulombic in origin. The anionic species have less charge on the central atom, and their bonds are therefore slightly weaker and more polarizable than those of the neutral species. The dominant contribution to the hyperfine inter-... 

Based on the Ga quadrupolar interaction and the orientation dependence of the (hyperfine broadened) central linewidth, Koschnick et al argue that their ENDOR signal is due to an interstitial Ga atom which is the residual donor in their film [59], Glaser and co-workers argue that the Ga nuclei observed in their resonance... 

---