  The many-particle ground state and excitations of self-assembled InAs quantum
dots are investigated using far-infrared (FIR) and capacitance spectroscopy.
The contributions of quantization and charging energies to the $n$--electron
energy spectrum are determined. For $n = 1$, 2, we find good agreement with a
parabolic model; for higher filling, the Coulomb interaction reveals itself not
only in the capacitance, but also in the FIR excitations
