Plasmon excitations in carbon onions: Model vs. measurements

©1998 American Institute of PhysicsNon-relativistic local dielectric response theory has proven successful in the interpretation of Electron Energy Loss data of nanometer-size isotropic particles of different geometries. In previous work, we have adapted this model to take into account anisotropy as encountered in the case of carbon onions. We have shown that this anisotropy needs to be taken into account since important deviations with respect to an isotropic model can be observed. In this contribution, we report on the first energy filtered images of carbon onions and compare intensity profiles across the spheres to our calculations

Plasmon excitations in graphitic carbon spheres

©1998 The American Physical Society. The electronic version of this article is the complete one and can be found online at: http://link.aps.org/doi/10.1103/PhysRevB.57.15599DOI: 10.1103/PhysRevB.57.15599Electron energy loss spectroscopy in a high-resolution transmission electron microscope has recently been used with success to characterize the electronic properties of closed cage nanometer-size graphitic particles. In the plasmon region, the experimental data reveal interesting size-dependent variations, which are not yet fully understood. The difficulties encountered in the interpretation of the spectra are principally due to the lack of a complete theoretical treatment of the anisotropic dielectric response in nanometer-size particles. In order to obtain a better understanding of the experimental data we propose a model based on nonrelativistic local dielectric response theory for electrons penetrating through a nested concentric-shell fullerene or the so-called ‘‘carbon onion.’’ The anisotropy of the electronic properties of the sphere is taken into account via the frequency-dependent dielectric tensor of graphite. The model can be applied to simulate electron energy loss spectra as well as line scans through energy filtered images and allows thus a direct comparison to experimental data

Collective oscillations in a single-wall carbon nanotube excited by fast electrons

©2001 The American Physical Society. The electronic version of this article is the complete one and can be found online at: http://link.aps.org/doi/10.1103/PhysRevB.64.115424DOI: 10.1103/PhysRevB.64.115424Electron energy loss spectroscopy is a well adapted tool for the investigation of the valence excitations of individual nanometer-size particles. The interpretation of the loss spectra of such small particles, however, relies in most cases on a quantitative comparison with simulated excitation probabilities. Here we present a formalism developed for the interpretation of the energy loss data of single-wall carbon nanotubes based on the hydrodynamic theory of plasmon excitations by high-energy electrons. The nanotubes are modeled as a two-dimensional electron gas confined on the circumference of a cylinder. The plasmon excitation probabilities, directly comparable to measurements, are discussed for various parameters

De nugis curialium, ou quand Jean de Salisbury et Gautier Map suivent la voie des exempla

Les « De nugis curialium » que sont l’ouvrage éponyme de Gautier Map et le Policraticus de Jean de Salisbury sont souvent cités comme témoins d’une certaine forme d’écriture exemplaire. Or, alors que l’expression nugae curialium impose régulièrement à la critique de rapprocher les deux ouvrages, les différences d’intentions et d’usages de l’exemplum chez les deux auteurs méritent d’être soulignées. L’étude des lignes programmatiques de Gautier Map, ainsi que de sa pratique exemplaire, en comparaison avec le prologue et un chapitre du Policraticus, permet de définir selon quels principes et pour quelles raisons l’auteur du De nugis curialium entendait prendre le contre-pied de l’écriture exemplaire de Jean de Salisbury.The « De nugis curialium » which constitute the eponymous work of Gautier Map and John of Salisbury’s Policraticus are often cited as representative of a certain type of exemplary writing. Although the phrase nugae curialium often encourages critics to note the similarities between the two works, their diverging intentions and the differing ways each one appropriates exempla deserve to be mentioned. In order to understand how and for what reason the author of the De nugis curialium intended to contradict Jean de Salisbury’s exemplary writing, this article compares Gautier Map’s guiding principles and use of exempla with the prologue and a chapter of the Polycraticus

De nugis curialium, ou quand Jean de Salisbury et Gautier Map suivent la voie des exempla

Les « De nugis curialium » que sont l’ouvrage éponyme de Gautier Map et le Policraticus de Jean de Salisbury sont souvent cités comme témoins d’une certaine forme d’écriture exemplaire. Or, alors que l’expression nugae curialium impose régulièrement à la critique de rapprocher les deux ouvrages, les différences d’intentions et d’usages de l’exemplum chez les deux auteurs méritent d’être soulignées. L’étude des lignes programmatiques de Gautier Map, ainsi que de sa pratique exemplaire, en comparaison avec le prologue et un chapitre du Policraticus, permet de définir selon quels principes et pour quelles raisons l’auteur du De nugis curialium entendait prendre le contre-pied de l’écriture exemplaire de Jean de Salisbury.The « De nugis curialium » which constitute the eponymous work of Gautier Map and John of Salisbury’s Policraticus are often cited as representative of a certain type of exemplary writing. Although the phrase nugae curialium often encourages critics to note the similarities between the two works, their diverging intentions and the differing ways each one appropriates exempla deserve to be mentioned. In order to understand how and for what reason the author of the De nugis curialium intended to contradict Jean de Salisbury’s exemplary writing, this article compares Gautier Map’s guiding principles and use of exempla with the prologue and a chapter of the Polycraticus