Abstract :
A large body of work to calculate nonrelativistic energies, relativistic corrections, and quantum electrodynamic (QED) energy shifts in helium is reviewed and compared with experiment. Of particular significance are measurements of the QED (Lamb) shift for the low-lying S-states of helium, where the accuracy rivals the best measurements in the corresponding He+ hydrogenic ion. Applications of high precision spectroscopy to measurements of the fine structure constant α, and to measurements of the nuclear charge radius from the isotope shift are discussed.
