Measurement of energy and angular distributions of secondary ions in the sputtering of gold by swift Au-n clusters: Study of emission mechanisms

Energy and angular distributions of negative ions (Au–, Au2-, Au3-, and Au5-) emitted from gold target bombarded by Au, Au4, and Au9 projectiles at 200 keV/atom were measured with a multipixel position sensitive detector. The angular distributions are symmetrical with respect to the normal to the target surface and forward peaked. They depend on the type of emitted ions, on the emission energy, and on the projectile size. More forward directed emission is observed with Au9 projectiles. The secondary ion energy distributions obtained with Au and Au4 projectiles are well reproduced by a sum of linear collision cascades and thermal spike processes. However, in the case of Au9 projectiles the energy distributions are better described by using a simple spike model with two different average temperature regimes: the first one corresponds to high emission energy occurring in the early stage of the whole process, and the second to the low energy component

Yves Bouvier, Connexions électriques. Technologies, hommes et marchés dans les relations entre la Compagnie générale d’électricité et l’État

Yves Bouvier a su mettre à profit une bonne décennie pour transformer une thèse remarquée, La Compagnie générale d’électricité : un grand groupe industriel et l’État. Technologies, hommes et marchés, 1898-1992, soutenue en Sorbonne en décembre 2005, en un ouvrage remarquable, resserré, remanié, mis à jour, en quelque sorte maturé comme un produit scientifique beaucoup plus large que le titre académique initial. Connexions électriques offre bien un kaléidoscope de la trajectoire des réseaux d’..

Simulation of MeV/atom cluster correlations in matter

We present an efficient algorithm able to predict the trajectories of individual cluster constituents as they penetrate relatively thick amorphous targets. Our algorithm properly treats both the intracluster Coulomb repulsion and the collisions between cluster constituents and target atoms. We have compared our simulation predictions to experimental measurements of the distribution of lateral exit velocities, and demonstrated that the in-target Coulomb explosion of 2MeV/atom carbon clusters in carbon foils must be shielded with a screening length of less than 2.5 Å. We also present a simple phenomenological model for the suppression of the exit-side charge of ions in clusters which depends on the enhanced ionization potential that an electron near an ion feels due to the ion’s charged comoving neighbors. By using our simulation algorithm we have predicted the exit correlations of the cluster constituents and verified that the charge suppression model fits the observed charge suppression of ions in clusters to within the experimental uncertainties

Cluster-induced crater formation

Using molecular-dynamics simulation, we study the crater volumes induced by energetic impacts ($v= 1- 250$ km/s) of projectiles containing up to N=1000 atoms. We find that for Lennard-Jones bonded material the crater volume depends solely on the total impact energy $E$. Above a threshold \Eth, the volume rises linearly with $E$. Similar results are obtained for metallic materials. By scaling the impact energy $E$ to the target cohesive energy $U$, the crater volumes become independent of the target material. To a first approximation, the crater volume increases in proportion with the available scaled energy, $V=aE/U$. The proportionality factor $a$ is termed the cratering efficiency and assumes values of around 0.5.Comment: 9 page

Heavy gold cluster beams production and identification

NIM ACCIt is shown that beams of very heavy gold clusters can be produced by a liquid metal ion source (LMIS). An experimental method is described for defining the LMIS source and the Wien filter parameters that must be set to extract and select large Aun clusters. This method is based on the acceleration of the clusters to high energy (MeV) and on the measurement, after their passage through a thin foil, of their number of constituents and velocity. Only an average mass over charge value is obtained for a given set of source and Wien filter parameters. These parameters can then be used to select heavy Aun cluster beams for applications at low energy (keV) in mass spectrometry

Energy loss and angular distributions of gold cluster constituents

Heavy gold cluster beams are accelerated to high energy (hundreds of keV/atom) and break up when going through a thin foil. The energy and angular distributions of the constituents are then measured and very well reproduced by a SRIM code calculation, which takes into account atomic interactions only. These distributions do not depend on the number of constituents in the cluster and are found to be the same as those of single gold atoms at the same velocity, in the studied energy range

Towards curating personalized art exhibitions in Virtual Reality with multimodal Brain-Computer-Interfaces

International audienceToday, we live in an age of 'Like' where appreciation of digital content is expressed constantly by interacting with feedback icons. In contrast, Brain-Computer-Interfaces (BCIs) can decode cognitive states from neural signals without explicit user feedback that interrupts aesthetic experiences (AEs). This recently started project will elucidate the neuro-cognitive mechanisms behind art appreciation and implement an Electroencephalography (EEG)-based BCI to detect physiological correlates of artwork preference in order to curate personalized art exhibitions in Virtual Reality. Most EEG recordings in visual neuroaesthetics focused on Event-Related Potentials, often using paradigms with unatural viewing conditions. On the other hand, the neural dynamics during visual art appreciation remain obscure and previous studies reported conflicting results. Furthermore, the liking of visual artworks was mostly investigated from the perspective of beauty or pleasantness, concepts which are not applicable to all aesthetic pleasures. We hypothesize instead that art preferences in general depend on rewarding AEs. Therefore, we will develop novel algorithms to decode and discriminate EEG neuromarkers of hedonic AEs. In a first step, we conceptualized neuro-cognitive components of AE, such as attention, emotion and intrinsic reward, as well as their established EEG neuromarkers. In the future, we will record EEG and other physiological measures, e.g. eye-tracking and heart rate, in naturalistic single trial experiments, use advanced Machine Learning to detect artwork preference and recommend further objects based on this multimodal information. Finally, we embrace open science and will make subject data and BCI algorithms publicly accessible

Very large gold and silver sputtering yields induced by keV to MeV energy Aun_n clusters (n = 1-13)

CAS, BIA

Quadrupole deformations of neutron-drip-line nuclei studied within the Skyrme Hartree-Fock-Bogolyubov approach

We introduce a local-scaling point transformation to allow for modifying the asymptotic properties of the deformed three-dimensional Cartesian harmonic oscillator wave functions. The resulting single-particle bases are very well suited for solving the Hartree-Fock-Bogoliubov equations for deformed drip-line nuclei. We then present results of self-consistent calculations performed for the Mg isotopes and for light nuclei located near the two-neutron drip line. The results suggest that for all even-even elements with $Z$=10--18 the most weakly-bound nucleus has an oblate ground-state shape.Comment: 20 pages, 7 figure