  Tunneling of electrons traversing a few-electron quantum dot is strongly
influenced by the Coulomb interaction leading to Coulomb blockade effects and
single-electron tunneling. We present calculations which demonstrate that
correlations between the electrons cause a strong suppression of most of the
energetically allowed tunneling processes involving excited dot states. The
excitation of center-of-mass modes, in contrast, is unaffected by the Coulomb
interaction. Therefore, channels connected to these modes dominate the
excitation spectra in transport measurements.
