  We consider the dynamical atom-surface Casimir-Polder force in the
non-equilibrium configuration of an atom near a perfectly conducting wall,
initially prepared in an excited state with the field in its vacuum state. We
evaluate the time-dependent Casimir-Polder force on the atom, and find that it
shows an oscillatory behavior from attractive to repulsive both in time and in
space. We also investigate the asymptotic behavior in time of the dynamical
force and of related local field quantities, showing that the static value of
the force, as obtained by a time-independent approach, is recovered for times
much larger than the timescale of the atomic self-dressing, but smaller than
the atomic decay time. We then discuss the evolution of global quantities such
as atomic and field energies, and their asymptotic behavior. We also compare
our results for the dynamical force on the excited atom with analogous results
recently obtained for an initially bare ground-state atom. We show that new
relevant features are obtained in the case of an initially excited atom, for
example much larger values of the dynamical force with respect to the static
one, allowing for an easier way to single-out and observe the dynamical
Casimir-Polder effect.
