This is a section about Hyperfine structure!
Hyperfine structure is a very important subject about which there is a lot to say.
For example, this sentence. And then another one.

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This is a section about Hyperfine structure!
Hyperfine structure is a very important subject about which there is a lot to say.
For example, this sentence. And then another one.
Small splits present in all levels due to interaction between the electron spin and the nuclear spin if it is present, i.e. the nucleus has an even number of nucleons.
As the name suggests, this energy split is very small, since the influence of the nucleus spin on the electron spin is relatively small compared to other fine structure.
TODO confirm: does it need quantum electrodynamics or is the Dirac equation enough?
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