  The existence of image states in small clusters is shown, using a
quantum-mechanical many-body approach. We present image state energies and wave
functions for spherical jellium clusters up to 186 atoms, calculated in the GW
approximation, where G is the Green's function, and W the dynamically screened
Coulomb interaction, which by construction contains the dynamic long-range
correlation effects that give rise to image effects. In addition we find that
image states are also subject to quantum confinement. To extrapolate our
investigations to clusters in the mesoscopic size range, we propose a
semiclassical model potential, which we test against our full GW results.
