  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.

Atomic Physics