Hyperfine splitting 0-Hydrogen

It can be noticed there are two types of hydrogen atoms atoms 1-5 lying in the molecular plane and atoms 6 and 7 lying out of the plane. Thus, the hyperfine splitting constants (an) cannot be interpreted by means of one relationship, but the expressions... 

A Ni-bound H H species in the Ni-C form has been considered to be unlikely based on the very small hyperfine splitting observed due to exchangeable 78). It has been argued, however, that the observed small values could arise from an equatorially bound Ni hydride (79). It has also been postulated that the photolyzed hydrogen species contained in the Ni-C state is the proton of a thiol group bound to the Ni ion 80). 

For instance, nitration of naphthalene, azulene, biphenylene, and triphenylene proceeds preferentially in positions with the greatest constant of hyperfine splitting at the hydrogen atom in ESR spectra of corresponding cation-radicals. The constant is known to be proportional to the spin density on the carbon atom bearing the mentioned hydrogen. It is important, however, that the same orientation is also observed at classical mechanism of nitration in cases of naphthalene, azulene, and biphenylene, but not triphenylene (see Todres 1985). 

The hyperfine splitting in the ground state of hydrogen is one of the most precisely measured quantities in modern physics [1, 2] (see for more details Subsect. 12.2.1 below), and to describe it theoretically we need to consider additional contributions to HFS connected with the bound state nature of the proton. 

The weak interaction contribution to hyperfine splitting in hydrogen is easily obtained by generalization of the muonium result in (10.38)... 

Hyperfine splitting in the ground state of hydrogen was measured precisely more than thirty years ago [65, 66]... 

The theoretical situation for the hyperfine splitting in hydrogen always remained less satisfactory due to the uncertainties connected with the proton structure. 

The scale of hyperfine splitting in hydrogen is determined by the Fermi energy in (8.2)... 

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