  The resonant interaction of laser light with atoms is analyzed from the
time-dependent density functional theory perspective using a model Helium atom
which can be solved exactly. It is found that in exact-exchange approximation
the time-dependent dipole shows Rabi-type oscillations of its amplitude.
However, the time-dependent density itself is not well described. These
seemingly contradictory findings are analyzed. The Rabi-type oscillations are
found to be essentially of classical origin. The incompatibility of
time-dependent density functional theory with few-level approximations for the
description of resonant dynamics is discussed.
