A comparison of the electronic structure and optical plasmons in Cs$_{x}$ clusters, Cs$_{x}$ shells and C$_{60}$ coated with a Cs$_{x}$ shell

We present calculations of the electronic structure and collective excitations in Cs clusters, Cs shells and C$_{60}$ coated with a shell of Cs atoms. The ground state properties of these systems are described using the Local Density Approximation and the electronic excitations by the Random Phase Approximation. The jellium shell approximation underlying our calculations correctly predicts the magic numbers. The optical excitation spectra in Cs clusters and Cs coated C$_{60}$ are found to be in agreement with available experimental data.