  The role of the exchange-correlation potential and the exchange-correlation
kernel in the calculation of excitation energues from time-dependent density
functional theory is studied. Excitation energies of the He and Be atoms are
calculated, both from the exact ground-state Kohn-Sham potential, and from two
orbital-dependent approximations. These are exact exchange and self-interaction
corrected local density approximation (SIC-LDA), both calculated using the
Krieger-Li-Iafrate (KLI) approximation. For the exchange-correlation kernela,
three adiabatic approximations were tested: The local density approximation,
exact exchange, and SIC-LDA. The choice of the ground-state
exchange-correlation potential has the largest impact on the absolute position
of most excitation energies. In particular, orbital-dependent approximate
potentials result in a uniform shift of the transition energies to the Rydberg
states.
