Noun
Lamb shift (plural Lamb shifts)
(quantum mechanics, quantum electrodynamics) A small difference between the energy levels 2S½ and 2P½ of the hydrogen atom, not predicted by the Dirac equation, whose detection in the Lamb–Retherford experiment of 1947 foreshadowed the development of quantum electrodynamics (in which the discrepancy is explained to be an effect of the emission and re-absorption of virtual photons); such a difference between otherwise expectedly equal energy levels of hydrogen or any other type of atom.
However, in 2010 an international research team published a proton charge radius measurement via the Lamb shift in muonic hydrogen (an exotic atom made of a proton and a negatively charged muon ). Source: Internet
The 2 contribution is the Breit term; workers rarely go to 4 because at 3 one has the Lamb shift, which requires quantum electrodynamics. Source: Internet
Retrieved 2010-11-7 The Lamb shift in muonic hydrogen was measured by driving the muon from a 2s state up to an excited 2p state using a laser. Source: Internet