The splitting of spectral lines caused by nucleon-electron spin interaction. A fine structure with fixed angular quantum
number l and total angular momentum quantum number j is split into
hyperfine structure components with f taking the possible values
In particular, the energy separation between the two outermost components and in a hydrogen atom is
where is the electron mass, is the proton mass, Z is the atomic number, is the fine structure constant, g is a dimensionless constant that is positive for some nuclei and negative for others, n is the principal quantum number.
Electron Quantum Numbers, Fine Structure Constant, Lamb Shift
References
Basdevant, J.-L. and Dalibard, J. "Hyperfine Structure in Electron Spin Resonance." Ch. 16 in The Quantum Mechanics Solver: How to Apply Quantum Theory to Modern Physics. Berlin: Springer-Verlag, pp. 119-126, 2000.
Bethe, H. A. and Salpeter, E. "Hyperfine Structure Splitting." §22 in Quantum Mechanics of One- and Two-Electron Atoms. New York: Plenum, pp. 107-114, 1977.
Bjorken, J. D. and Drell, S. D. Relativistic Quantum Mechanics. New York: McGraw-Hill, pp. 57-60, 1964.
Fermi, E. "Über die magnetischen Momente der Atomkerne." Z. Phys. 60, 320-333, 1930.
Griffiths, D. J. "Hyperfine Structure." §5.5 in Introduction to Elementary Particles. New York: Wiley, pp. 156-159, 1987.
