Pierre Longe

Excitations in a spherical two-dimensional electron gas — Application to the C60 molecule

The dielectric function of a spherical two-dimensional electron gas (2DEG) is calculated in the framework of the random phase approximation. The whole spectrum of electron-hole and plasmon excitations is then calculated numerically, along with the electron energy loss function. The dispersion and strength of the plasmon mode as functions of the angular momenta are also obtained. The results are compared with those of a planar 2DEG with the same areal density.

The effect of the core hole on the shape of soft X-ray spectra in metals

Abstract The importance of using a pseudopotential to calculate the contribution of the core hole potential to the intensity of the emission and absorption X-ray spectra in metals is emphasized.

Photoemission loss spectra of metals with emergence parallel to the surface

Abstract A theory is presented for the energy loss spectra of photoelectrons emitted from atoms located outside a metal sample at a distance z0 from the surface. These electrons travelling along trajectories parallel to the surface, loss energy mostly by surface plasmon excitation, the losses by bulk plasmon or pair excitations being negligible. The intensity of losses by surface plasmon excitations is found to be proportional to the logarithm of the length l of the trip of the photoelectrons along the surface, a length which extends from the emitting atom to the surface edge. But this intensity does not depend on the distance z0 as long as z0/l small. Considering only the high energy photoemission where the initial energy ϵ0 of the electrons is much larger than the surface plasmon energy ωs, we find that these l-dependent losses only occur when the angle of emergence is smaller than (ω s /ϵ 0 ) 1 2 and peak strongly when this angle is smaller than ωs/2ϵ0. An experiment with appropriate parameters is proposed to verify the principal results of our theory. Further investigation will yield interesting information on the surface plasmon structure, e.g. the dispersion rule.

Strength of plasmon satellites in the valence band photoemission spectra of metals

Abstract The strength of the first bulk plasmon satellite in the valence band photo-emission spectra of simple metals has been calculated for the dispersionless plasmon model. It is found that due to the mobility of the final state hole in the valence band, the strength of the plasmon satellite is lowered compared to that of the core state. This conclusion is qualitatively confirmed by an independent experiment of Van Attekum and Trooster.

Possible observation of Aharonov-Bohm effect in a graphene tubule

Recent discovery of metal encapsulated graphene tubules with radii of several nanometers has provided the possibility of observing the proper Aharonov-Bohm (AB) effect in bound states. A calculation is presented for the AB effect in a graphene tubule due to the introduction of a magnetized whisker completely inside the tubule such that the tubule itself experiences no magnetic field. The resulting AB current and AB magnetic flux in the graphene tubule should be detectable with the presently available experimental techniques.

Effect of Hole Mobility on Valence Band Photoemission Spectra of Metals

In recent years, there have been extensive experimental and theoretical investigations of the core level photoemission spectra (XPS) of simple metals.1 However, no such systematic study of valence band XPS of metals has been carried out. In this paper we present a calculation of the strength of the first plasmon satellite of the valence band x-ray photoelectron spectra (XPS) of simple metals. We find that due to the mobility of the final state hole in the conduction band, the strength of the plasmon satellite is lowered from that of the core state photoemission; a conclusion which is in qualitative agreement with an independent experimental observation of Van Attekum and Trooster.