  We present a detailed study of different exchange-correlation (xc)
functionals in describing the dynamical properties of finite systems. For that
purpose, we calculated the static polarizabilities, ionization potentials and
optical absorption spectrum of four small clusters, Na_2, Na_4, SiH_4 and
Si_2H_6, using a real-space, real-time technique. The computed static
polarizabilities and ionization potentials seem to be in rather good agreement
with the available experimental data, once the proper asymptotics of the
potential are taken into account. The same conclusion holds for the absorption
spectra, although the xc kernels in use do not provide a sufficiently strong
attractive interaction between electrons and holes, leading to spectra slightly
shifted towards higher energies. This deficiency is traced back to the
insufficient description of dynamical effects in the correlation functional.
Furthermore, it is shown that the xc potential used to obtain the ground state
is the key factor to get reasonable spectra, whereas the choice of the xc
kernel just amounts to small, although important, quantitative changes.
