On the problem of the existence of collective oscillations in atoms

The existence of collective oscillations in the electron shells of atoms is discussed. By solving numerically the equations for the effective interaction in the random phase approximation with exchange, it is shown that, at least for atoms of the noble gases, there are no collective levels in the excitation spectrum. Nevertheless, the many-electron correlations play an important role, so that there is a significant difference between the effective and the Coulomb interaction.