Hyperfine Splitting in Hydrogen

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. 

Eides et al. Theory of Light Hydrogenic Bound States, STMP 222, 217-232 (2007) 

Despite the difference between the two cases, discussion of the proton size and structure corrections to HFS in hydrogen below is in many respects parallel to the discussion of the respective corrections to the Lamb shift in Chap. 6. 

1 Nuclear Size, Recoil and Structure Corrections of Orders Z x)Ef and ZcxYEp 

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

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)... 

Recently there has been considerable progress in measurement and calculation of the hyperfine splitting of the ground state and the 2si/2 state in the hydrogen atom. The 2.s-, /2 hyperfine splitting in hydrogen was determined to be [6]... 

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

Being a purely electrodynamic bound state, muonium is the best system for comparison between the hyperfine splitting theory and experiment. Unlike the case of hydrogen the theory of hyperfine splitting in muonium is free from uncertainties generated by the hadronic nature of the proton, and is thus much more precise. The scale of hyperfine splitting is determined by the Fermi energy in (8.2)... 

Abstract. The usefulness of study of hyperfine splitting in the hydrogen atom is limited on a level of 10 ppm by our knowledge of the proton structure. One way to go beyond 10 ppm is to study a specific difference of the hyperfine structure intervals 8Au2 — Avi. Nuclear effects for axe not important this difference and it is of use to study higher-order QED corrections. 

The magnetic interaction of the Is electron in the nucleus causes a hyperfine splitting in the ground state of hydrogen and heavier isotopes. In particular, the 1.4 GHz splitting frequency in hydrogen, corresponding to a transition... 

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