Far-infrared absorption of a confined two-dimensional electron gas with an imbedded Coulomb impurity

We study the far-infrared response of a confined two-dimensional electron gas (2DEG) with an imbedded simple Coulomb impurity. The system is subject to a quantizing perpendicular magnetic field at low temperature. The electron-electron interaction is treated in the Hartree or the Hartree-Fock approximation. In large enough systems we observe both bulk and edge effects in addition to single particle excitations due to the impurity. The structure of the excitations depends on the filling of the Landau bands and thus the screening properties of the 2DEG.