Breit-interaction correction to the hyperfine constant of an external s electron in a many-electron atom - art. no. 042504

Correction to the hyperfine constant A of an external s-electron in many-el ectron atom caused by the Breit interaction is calculated analytically: del taA/A = 0.68Z alpha (2). The physical mechanism for this correction is pola rization of the internal electronic shells (mainly 1s(2) shell) by the magn etic field of the external electron. This mechanism is similar to the polar ization of vacuum considered by Karplus and Klein [Phys. Rev. 85, 972 (1952 )] long time ago. The similarity is the reason why in both cases (Dirac sea polarization and internal atomic shells polarization) the corrections have the same dependence on the nuclear charge and fine-structure constant. In conclusion we also discuss Z alpha (2) corrections to the parity violation effects in atoms.