Lamb Shift
A small energy difference between the 2s1/2 and 2p1/2 states of hydrogen caused by quantum vacuum fluctuations.
Governing formula
ΔE_Lamb ≈ 1057 MHz (for Hydrogen 2s1/2 and 2p1/2)
SI unit
MHz or eV
In depth
Discovered by Willis Lamb in 1947, classical Dirac theory predicted these two states were exactly degenerate. The shift arises because vacuum virtual photon fluctuations cause the electron to jiggle, slightly altering its effective potential.
Examples in the real world
Providing crucial early experimental verification of Quantum Electrodynamics (QED).