Hyperfine coupling
From Wikipedia, the free encyclopedia
Hyperfine coupling refers to the interaction between an electron in an atom or molecule and one or more atomic nuclei.
Every electron has an intrinsic magnetic moment and a spin quantum number s = ½. For hyperfine coupling to occur, an electron must interact with an atomic nucleus having a spin quantum number I 
0.
Hyperfine interactions can be measured, among other ways, in atomic and molecular spectra and in electron paramagnetic resonance spectra of free radicals and transition-metal ions.
[edit] Terminology
The following terminology has evolved to describe spectra:
- Fine structure refers to that part of a spectrum caused by the splitting of energy levels, and spectral lines, due to interactions among electrons in a single atom or molecule. The interactions originate in the s = 1/2 quantum number for electrons.
- Hyperfine structure refers to that part of a spectrum caused by the splitting of energy levels, and spectral lines, due to an unpaired electron interacting with a nucleus having I 0. The electron and nucleus (nuclei) are on the same atom or within the same molecule.
- Superhyperfine structure refers to that part of a spectrum caused by the splitting of energy levels, and spectral lines, due to an unpaired electron interacting with a nucleus having I 0. The electron and nucleus (nuclei) are on different atoms or different molecules.
- Spin-spin structure refers to that part of a spectrum caused by the splitting of energy levels, and spectral lines, due to interactions among nuclei having I 0. This phenomenon is especially important in NMR spectra
[edit] References
- G. Herzberg, Atomic Spectra and Atomic Structure. Dover, New York, 1944. See especially chapter 5.
- M. Symons, Chemical and Biochemical Aspects of Electron-Spin Resonance Spectroscopy. Wiley, New York, 1978
- J. A. Weil, J. R. Bolton, and J. E. Wertz, Electron Paramagnetic Resonance: Elementary Theory and Practical Applications. Wiley-Interscience, New York, 2001
