1. Clean and Adsorbed Surfaces.- Theory of phonons on clean and adsorbed surfaces.- Desorption by... more 1. Clean and Adsorbed Surfaces.- Theory of phonons on clean and adsorbed surfaces.- Desorption by resonant multiphoton excitation of internal adsorbate vibration.- Face centered cubic transition metal surface vibrations.- Atom motion at model crystal surfaces.- Infrared reflection absorption and emission study of methyl alcohol adsorption on MoO3 films.- Rotational accommodation at surfaces via Rayleigh phonons.- Arrangement of CO molecules adsorbed on low index metal surfaces: a comparison between LEED and HREELS or IRS.- Effects of many body forces on the adsorbate induced phonon structure.- Vibrational lifetimes for molecules adsorbed on metal surfaces.- Surface modes of a spherical void at the proximity of a surface.- Theoretical study of the vibrational properties of a (117)F. C. C. surface.- The chemisorption of CO on Cu: an ab initio cluster model study.- Librational modes of molecules on metals.- Vibrations of neutrally adsorbed atoms on transition metal surfaces.- 2. Electr...
André Jean-Marie, Lucas Amand A., Lambert Dominique. La crise mondiale des sciences. Colloque de ... more André Jean-Marie, Lucas Amand A., Lambert Dominique. La crise mondiale des sciences. Colloque de Lille des 28-29 novembre 2005 . In: Bulletin de la Classe des sciences, tome 16, n°7-12, 2005. pp. 217-218
Proceedings of the 17th International Conference on the Physics of Semiconductors, 1985
In recent years, Electron Energy Loss Spectroscopy (EELS) has emerged as a highly reliable tool f... more In recent years, Electron Energy Loss Spectroscopy (EELS) has emerged as a highly reliable tool for the study of clean or contaminated surfaces. In these experiments a beam of monoenergetic electrons is scattered by a surface and analyzed in energy to detect losses characteristic of surface electronic or vibrational excitations. In spite of numerous successes on other materials, these experiments could not easily be carried out on insulators or poorly conducting materials mainly because of surface charging effects. Recently, however, the state of the art drastically evolved as it was discovered that these undesirable potential instabilities could be avoided by an adequate experimental setup1. The new procedure requires an auxiliary gun delivering electrons in the keV energy range to continuously flood the surface as the monoenergetic electron beam is operated. The resolution obtained in these experiments is quite impressive (sometimes as good as 2.5 meV) and an extremely broad range of materials can now be studied by EELS.
Lucas Amand A. Le confinement physique en catalyse hétérogène et autres applications. In: Bulleti... more Lucas Amand A. Le confinement physique en catalyse hétérogène et autres applications. In: Bulletin de la Classe des sciences, tome 19, 2008. pp. 219-228
The celebrated X-ray fiber diagram obtained by Rosalind Franklin for the paracrystalline phase of... more The celebrated X-ray fiber diagram obtained by Rosalind Franklin for the paracrystalline phase of B-DNA is examined at a non technical level. The most prominent features of the intensity distribution in the diagram are reviewed in relation to the corresponding structural properties of the molecule. Optical diffraction experiments (optical trans¬ forms) are performed to reproduce each of several features separately, namely the layer-lines, the maltese cross, the diamond repeats and the missing 4th layer-line. These experiments make use of a single slide (available from the authors on demand) containing a photographic film reduction of four simplified planar models of the DNA backbone which serve as diffraction gratings for the coherent red light of a He-Ne laser or a solid-state laser pointer. No special optics is required. The simulations bring out all of the crucial geometrical parameters of the Watson-Crick double helix. The paper then gives a simple derivation of the formula esta...
The novel application of vacuum ultra-violet absorption spectroscopy and electron energy loss spe... more The novel application of vacuum ultra-violet absorption spectroscopy and electron energy loss spectroscopy to helium bubbles in metals is presented. These measurements, carried out on thin aluminium films containing different concentrations of helium and various bubble size distributions, were aimed at determining the density (and thus pressure) of helium in bubbles by observing the shift and broadening of the IS-2P transition in the helium. The data coupled with a theoretical model developed by the authors (see following paper) indicate densities as high as 10 He cm for specimens containing small bubbles. Data are also presented on the effect that annealing and cooling have on these spectra. The annealing experiments give rise to fairly complex changes in absorption peak structure but with a general shift towards the unperturbed resonance line. The cooling experiment gives rise to a further shift and a narrowing of the absorption spectrum on cooling to 77 K which is tentatively identified as the liquid/solid transition in the helium. Finally, fluorescence spectrum of an Al/He specimen excited with low energy electrons is presented.
Journal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena, 1986
High resolution electron energy loss spectra have been measured on a GaAs–Al0.3Ga0.7As superlatti... more High resolution electron energy loss spectra have been measured on a GaAs–Al0.3Ga0.7As superlattice. Fuchs–Kliewer-like surface and interface optical phonons were observed with frequencies and intensities in excellent agreement with calculations based on the dielectric theory. The spectra obtained after sputter erosion of the superlattice are discussed in terms of induced defects or segregation of Al at the interface.
Journal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena, 1985
By using high resolution electron energy loss spectroscopy (HREELS) the surface phonon spectra of... more By using high resolution electron energy loss spectroscopy (HREELS) the surface phonon spectra of SiO2(0001) and of thick amorphous SiO2 layers have been measured. The spectra recorded on the crystalline surface are characterized by three first order peaks at 498, 798, and 1176 cm−1. The HREELS data could be interpreted by the dielectric theory applied to anisotropic material, and the optical constants were compared to infrared spectroscopy values. HREELS spectra as a function of oxide thickness could be obtained from oxidized Si(100) wafers by sputter erosion. Peak positions shifted to lower frequencies and intensities decreased regularly with decreasing oxide thickness. At the interface a transition layer of about 25 Å was observed and carbon contamination was identified. The dielectric theory applied to a thin homogeneous supported film cannot account for the observed frequency shift.
1. Clean and Adsorbed Surfaces.- Theory of phonons on clean and adsorbed surfaces.- Desorption by... more 1. Clean and Adsorbed Surfaces.- Theory of phonons on clean and adsorbed surfaces.- Desorption by resonant multiphoton excitation of internal adsorbate vibration.- Face centered cubic transition metal surface vibrations.- Atom motion at model crystal surfaces.- Infrared reflection absorption and emission study of methyl alcohol adsorption on MoO3 films.- Rotational accommodation at surfaces via Rayleigh phonons.- Arrangement of CO molecules adsorbed on low index metal surfaces: a comparison between LEED and HREELS or IRS.- Effects of many body forces on the adsorbate induced phonon structure.- Vibrational lifetimes for molecules adsorbed on metal surfaces.- Surface modes of a spherical void at the proximity of a surface.- Theoretical study of the vibrational properties of a (117)F. C. C. surface.- The chemisorption of CO on Cu: an ab initio cluster model study.- Librational modes of molecules on metals.- Vibrations of neutrally adsorbed atoms on transition metal surfaces.- 2. Electr...
André Jean-Marie, Lucas Amand A., Lambert Dominique. La crise mondiale des sciences. Colloque de ... more André Jean-Marie, Lucas Amand A., Lambert Dominique. La crise mondiale des sciences. Colloque de Lille des 28-29 novembre 2005 . In: Bulletin de la Classe des sciences, tome 16, n°7-12, 2005. pp. 217-218
Proceedings of the 17th International Conference on the Physics of Semiconductors, 1985
In recent years, Electron Energy Loss Spectroscopy (EELS) has emerged as a highly reliable tool f... more In recent years, Electron Energy Loss Spectroscopy (EELS) has emerged as a highly reliable tool for the study of clean or contaminated surfaces. In these experiments a beam of monoenergetic electrons is scattered by a surface and analyzed in energy to detect losses characteristic of surface electronic or vibrational excitations. In spite of numerous successes on other materials, these experiments could not easily be carried out on insulators or poorly conducting materials mainly because of surface charging effects. Recently, however, the state of the art drastically evolved as it was discovered that these undesirable potential instabilities could be avoided by an adequate experimental setup1. The new procedure requires an auxiliary gun delivering electrons in the keV energy range to continuously flood the surface as the monoenergetic electron beam is operated. The resolution obtained in these experiments is quite impressive (sometimes as good as 2.5 meV) and an extremely broad range of materials can now be studied by EELS.
Lucas Amand A. Le confinement physique en catalyse hétérogène et autres applications. In: Bulleti... more Lucas Amand A. Le confinement physique en catalyse hétérogène et autres applications. In: Bulletin de la Classe des sciences, tome 19, 2008. pp. 219-228
The celebrated X-ray fiber diagram obtained by Rosalind Franklin for the paracrystalline phase of... more The celebrated X-ray fiber diagram obtained by Rosalind Franklin for the paracrystalline phase of B-DNA is examined at a non technical level. The most prominent features of the intensity distribution in the diagram are reviewed in relation to the corresponding structural properties of the molecule. Optical diffraction experiments (optical trans¬ forms) are performed to reproduce each of several features separately, namely the layer-lines, the maltese cross, the diamond repeats and the missing 4th layer-line. These experiments make use of a single slide (available from the authors on demand) containing a photographic film reduction of four simplified planar models of the DNA backbone which serve as diffraction gratings for the coherent red light of a He-Ne laser or a solid-state laser pointer. No special optics is required. The simulations bring out all of the crucial geometrical parameters of the Watson-Crick double helix. The paper then gives a simple derivation of the formula esta...
The novel application of vacuum ultra-violet absorption spectroscopy and electron energy loss spe... more The novel application of vacuum ultra-violet absorption spectroscopy and electron energy loss spectroscopy to helium bubbles in metals is presented. These measurements, carried out on thin aluminium films containing different concentrations of helium and various bubble size distributions, were aimed at determining the density (and thus pressure) of helium in bubbles by observing the shift and broadening of the IS-2P transition in the helium. The data coupled with a theoretical model developed by the authors (see following paper) indicate densities as high as 10 He cm for specimens containing small bubbles. Data are also presented on the effect that annealing and cooling have on these spectra. The annealing experiments give rise to fairly complex changes in absorption peak structure but with a general shift towards the unperturbed resonance line. The cooling experiment gives rise to a further shift and a narrowing of the absorption spectrum on cooling to 77 K which is tentatively identified as the liquid/solid transition in the helium. Finally, fluorescence spectrum of an Al/He specimen excited with low energy electrons is presented.
Journal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena, 1986
High resolution electron energy loss spectra have been measured on a GaAs–Al0.3Ga0.7As superlatti... more High resolution electron energy loss spectra have been measured on a GaAs–Al0.3Ga0.7As superlattice. Fuchs–Kliewer-like surface and interface optical phonons were observed with frequencies and intensities in excellent agreement with calculations based on the dielectric theory. The spectra obtained after sputter erosion of the superlattice are discussed in terms of induced defects or segregation of Al at the interface.
Journal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena, 1985
By using high resolution electron energy loss spectroscopy (HREELS) the surface phonon spectra of... more By using high resolution electron energy loss spectroscopy (HREELS) the surface phonon spectra of SiO2(0001) and of thick amorphous SiO2 layers have been measured. The spectra recorded on the crystalline surface are characterized by three first order peaks at 498, 798, and 1176 cm−1. The HREELS data could be interpreted by the dielectric theory applied to anisotropic material, and the optical constants were compared to infrared spectroscopy values. HREELS spectra as a function of oxide thickness could be obtained from oxidized Si(100) wafers by sputter erosion. Peak positions shifted to lower frequencies and intensities decreased regularly with decreasing oxide thickness. At the interface a transition layer of about 25 Å was observed and carbon contamination was identified. The dielectric theory applied to a thin homogeneous supported film cannot account for the observed frequency shift.
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