Search results for "Localized"
showing 10 items of 297 documents
A Hirshfeld partitioning of polarizabilities of water clusters
2006
International audience; A new Hirshfeld partitioning of cluster polarizability into intrinsic polarizabilities and charge delocalization contributions is presented. For water clusters, density-functional theory calculations demonstrate that the total polarizability of a water molecule in a cluster depends upon the number and type of hydrogen bonds the molecule makes with its neighbors. The intrinsic contribution to the molecular polarizability is transferable between water molecules displaying the same H-bond scheme in clusters of different sizes, and geometries, while the charge delocalization contribution also depends on the cluster size. These results could be used to improve the existin…
Surface plasmon polaritons on metal cylinders with dielectric core
2001
International audience; Metal-cladded dielectric cylinders with submicron diameters may serve to model coated tips used in nearfield scanning optical microscopy. The signal measured may be greatly influenced by resonance effects due to eigenmodes of the probe. Especially, using a photon scanning tunneling microscope setup, gold-coated tips have been found to detect a signal proportional to the magnetic field distributions [E. Devaux et al.. Phys. Rev. B 62, 10 504 (2000)]. This effect is attributed to cylindrical surface plasmons. We present here fully retarded calculations of the dispersion and field patterns of the nonradiative plasmon modes in cylindrical geometry. We study the effect of…
Near-field observation of surface plasmon polariton propagation on thin metal stripes
2001
International audience; We use a photon scanning tunneling microscope to probe the field of surface plasmon polariton modes excited on finite-width thin metal films (metal stripes). We first investigate the coupling between surface plasmons launched by a focused beam on a homogeneous thin film and the modes sustained by metal stripes of different widths. We show that. if the width of the metal stripe is about a few micrometers, a strong coupling with the stripe modes can be achieved at visible frequencies. A sharp transverse confinement of the field associated with the surface plasmon modes propagating on the metal stripe is unambiguously observed on the constant height photon scanning tunn…
Discontinuity induced angular distribution of photon plasmon coupling
2011
Metal-dielectric transitions are important structures that can display a host of optical characteristics including excitation of plasmons. Metal-dielectric discontinuities can furthermore support plasmon excitation without a severe condition on the incident angle of the exciting photons. Using a semi-infinite thin gold film, we study surface plasmon (SP) excitation and the associated electromagnetic near-field distribution by recording the resulting plasmon interference patterns. In particular, we measure interference periods involving SPs at the scanable metal/air interface and the buried metal/glass one. Supported by optical near-field simulations and experiments, we demonstrate that the …
Pulvérisation ciblée sur les tâches d’adventices détectées par drône en colza
2019
L’idée de cartographier les zones infestées par les adventices pour restreindre la surface traitée, et donc les quantités d’herbicides utilisées, méritait d’être testée. Depuis l’acquisition des données par drone, en passant par le traitement des images, jusqu’à l’exploitation de la carte par le pulvérisateur au champ. C’est pourquoi, Terres Inovia a décidé de collaborer avec AIRINOV pour conduire un essai sur colza en vue de la pulvérisation ciblée sur les tâches d’adventices détectées préalablement par drone. Cette étude exploratoire avait pour objectif de vérifier l’intérêt, la faisabilité, la pertinence et l’efficacité d’une telle technique. Elle s’inscrit dans le projet européen H2020 …
Développement opérationnel en grandes cultures semées en ligne d’une rampe de pulvérisation grande largeur localisée sur le rang
2019
National audience; Pour réduire l’utilisation des herbicides, une des solutions possibles est de ne traiter que le rang en post-levée et de biner l’inter-rang ensuite. Terres Inovia, en collaboration avec la Coopérative Agricole Lorraine, a mis en place des essais au champ sur colza et tournesol avec la rampe localisée Marechal, dans le but de mettre au point cette technique pour des rampes de grande largeur avec une bonne qualité de pulvérisation sur le rang et un type de guidage adapté à des terres à colza, plus irrégulières que les terres à betterave sur lesquelles la rampe avait été développée. L’objectif est également d’évaluer les efficacités de la technique (satisfaction du désherbag…
Surface plasmon interference excited by tightly focused laser beams
2007
International audience; We show that interfering surface plasmon polaritons can be excited with a focused laser beam at normal incidence to a plane metal film. No protrusions or holes are needed in this excitation scheme. Depending on the axial position of the focus, the intensity distribution on the metal surface is either dominated by interferences between counterpropagating plasmons or by a two-lobe pattern characteristic of localized surface plasmon excitation. Our experiments can be accurately explained by use of the angular spectrum representation and provide a simple means for locally exciting standing surface plasmon polaritons.
Helicate Extension as a Route to Molecular Wires
2008
We describe the preparation of a helicate containing four closely spaced, linearly arrayed copper(I) ions. This product may be prepared either directly by mixing copper(I) with a set of precursor amine and aldehyde subcomponents, or indirectly through the dimerization of a dicopper(I) helicate upon addition of 1,2-phenylenediamine. A notable feature of this helicate is that its length is not limited by the lengths of its precursor subcomponents: each of the two ligands wrapped around the four copper(I) centers contains one diamine, two dialdehyde, and two monoamine residues. This work thus paves the way for the preparation of longer oligo- and polymeric structures. DFT calculations and elec…
Dicopper(II) Metallacyclophanes as Multifunctional Magnetic Devices: A Joint Experimental and Computational Study
2015
Metallosupramolecular complexes constitute an important advance in the emerging fields of molecular spintronics and quantum computation and a useful platform in the development of active components of spintronic circuits and quantum computers for applications in information processing and storage. The external control of chemical reactivity (electro- and photochemical) and physical properties (electronic and magnetic) in metallosupramolecular complexes is a current challenge in supramolecular coordination chemistry, which lies at the interface of several other supramolecular disciplines, including electro-, photo-, and magnetochemistry. The specific control of current flow or spin delocaliz…
Light induced processes in thin films of indandione type organic molecules
2007
The optically induced switching of material properties is important for investigations of opto-electronic effects and optomechanical properties. Investigated organic materials contain chromophore dipole consisting of acceptor and donor groups bridged by a delocalized p-electron system. Both calculations and experimental data show a reversible highly dipolar photoinduced intra molecular charge transfer in indandione type molecules (DMABI) accompanied by change of the sign and the value of the dipole moment. Investigations of optical properties of thin host-guest polymer films show that the photoinduced process of DMABI is related to the photoinduced switching between two equally stable state…