The electronic excitations of potassium clusters embedded in a MgO matrix have been investigated as a function of cluster size and momentum transfer by means of electron-energy-loss spectroscopy. The experimental results show deviations from predictions of classical electrodynamics but they are in qualitative agreement with a calculation for excitations of a jellium sphere made with use of the time-dependent local-density approximation.

• Received 14 June 1988

DOI:https://doi.org/10.1103/PhysRevLett.61.2249