  We present a detailed analysis of the spin-flip excitations induced by a
periodic time-dependent electric field in the Rashba prototype Au(111) noble
metal surface. Our calculations incorporate the full spinor structure of the
spin-polarized surface states and employ a Wannier-based scheme for the
spin-flip matrix elements. We find that the spin-flip excitations associated
with the surface states exhibit an important angular modulation which is
completely absent in the standard Rashba model \cite{rashba}. Furthermore, we
demonstrate that the maximum of the calculated spin-flip absorption rate is
about twice the model prediction. These results show that although the Rashba
model accurately describes the spectrum and spin polarization, it does not
fully account for the dynamical properties of the surface states.
