Stark-Induced Electric Dipole Amplitudes for Hyperfine Transitions
  Stark-induced electric dipole amplitudes between states of the same nominal parity can be important in experiments to observe parity nonconservation in atoms. The Stark-induced E1 amplitudes are expressed in terms of an irreducible spherical-tensor decomposition. This formalism is applied to the specific case of transitions between hyperfine sublevels of a single atomic state. It is shown that in the ground states of alkali atoms, such transitions are suppressed by many orders of magnitude relative to naive expectations. 
David DeMille (Amherst College, Amherst) and Mikhail Kozlov   (Petersburg Nuclear Physics Institute, Russia)