Formalism of collective electron excitations in fullerenes

We present a detailed formalism for the description of collective electron excitations in fullerenes in the process of the electron inelastic scattering. Considering the system as a spherical shell of a finite width, we show that the differential cross section is defined by three plasmon excitations, namely two coupled modes of the surface plasmon and the volume plasmon. The interplay of the three plasmons appears due to the electron diffraction of the fullerene shell. Plasmon modes of different angular momenta provide dominating contributions to the differential cross section depending on the transferred momentum.Comment: 11 pages, 2 figures; submitted to the special issue "Atomic Cluster Collisions: Structure and Dynamics from the Nuclear to the Biological Scale" of Eur. Phys. J.

On the response function of simple metal clusters

We analyse the response function of simple metal clusters considering several theoretical approaches and exploring a large class of momenta and energies. The study is performed on a wide range of cluster sizes to explore the relative weight of the various dominant contributions to the response. We work with Sodium clusters in jellium approximation. The comparison between the various theoretical approaches shows altogether a remarkable consistency. The simple Boson approximation to the response function is furthermore shown to perform remarkably well in spite of its simplicity

Collective excitations in the electron energy loss spectra of C60

The results of a joint experimental and theoretical investigation of the collective excitations in the energy loss spectra of the C60 fullerene are presented. A variation of the shape of the electron energy loss spectrum has been observed experimentally as the scattering angle increases. This variation is described within the frame of a new theoretical model which treats the fullerene as a spherical shell of a finite width and accounts for the two modes of the surface plasmon and for the volume plasmon as well. It is shown that at small angles the inelastic scattering cross section is determined mostly by the excitation of the symmetric mode of the surface plasmon, while at larger angles the excitation of the antisymmetric surface and volume plasmons becomes prominent

Valence photoionization of small alkaline earth atoms endohedrally confined in C60\mathrm{C_{60}}

A theoretical study of photoionization from the outermost orbitals of Be, Mg and Ca atoms endohedrally confined in C60 is reported. The fullerene ion core, comprised of sixty C4+, is smudged into a continuous jellium charge distribution, while the delocalized cloud of carbon valence electrons plus the encaged atom are treated in the time-dependent local density approximation (TDLDA). Systematic evolution of the mixing of outer atomic level with states of the C60 valence band is found along the sequence. This is found to influence the plasmonic enhancement of atomic photoionization at low energies and the geometry-revealing confinement oscillations at high energies in significantly different ways: (a) the extent of enhancement is mainly determined by the strength of atomic ionization, giving the strongest enhancement for Be even though Ca suffers the largest mixing. But (b) strongest collateral oscillations are uncovered for Ca, since, relative to Be and Mg, the mixing causes the highest photoelectron production at confining boundaries of Ca. The study paints the first comparative picture of the atomic valence photospectra for alkaline earth metallofullerenes in a dynamical many-electron framework