Search results for " Clusters"
showing 10 items of 1091 documents
Plasmonic Silver Nanorod Sensitivity: Experiment and Simple Theoretical Treatment
2013
We compare the plasmonic sensitivity of silver and gold nanorods with similar resonance wavelengths by monitoring the plasmon resonance shift of single noble metal nanorods upon changing the environment from water to sucrose solution. We find that silver nanorods have 1.2 to 2 times higher sensitivity than gold in good agreement with simulations based on the boundary-elements-method (BEM). To exclude the effect of particle volume on sensitivity, we test gold rods with increasing particle width at a given resonance wavelength. Using the Drude-model of optical properties of metal together with the quasi-static approximation (QSA) for localized surface plas-mons, we show that the dominant cont…
Nonlinear Structural Mechanics Based Modeling of Carbon Nanotube Deformation
2003
A nonlinear structural mechanics based approach for modeling the structure and the deformation of single-wall and multiwall carbon nanotubes (CNTs) is presented. Individual tubes are modeled using shell finite elements, where a specific pairing of elastic properties and mechanical thickness of the tube wall is identified to enable successful modeling with shell theory. The effects of van der Waals forces are simulated with special interaction elements. This new CNT modeling approach is verified by comparison with molecular dynamics simulations and high-resolution micrographs available in the literature. The mechanics of wrinkling of multiwall CNTs are studied, demonstrating the role of the …
Electronic polarizability of small sodium clusters.
1986
Abstract : Small sodium clusters consisting of 1 to 40 atoms are described as spheres of interacting homogeneous electron gas (jellium model). The static electronic polarizability is calculated using self consistent density functional methods. An excellent agreement with recent experimental results is observed.
Resonance laser ionization spectroscopy of tellurium
2019
Abstract Resonance ionization schemes for tellurium are investigated with a resonance ionization laser ion source and Ti:Sapphire lasers for fundamental research applications. We present the first three-step resonance ionization spectra of atomic Te. Several autoionizing Rydberg series converging to the first excited state of Te+ are observed and assigned to 5p3 (2Do3/2) ns and nd configurations. Our results include confirmation and significant expansion of the Rydberg series previously reported as well as observation of three new series. From the series convergence limits the ionization potential of tellurium is revised to be 72,669.006(42)stat(20)sys cm−1.
Periodic unmixing of a binary metallic vapor
2005
We report on a type of surface structuring after short pulse laser ablation of a binary alloy. We observe the emergence of a concentric ring structure with changing elemental composition. The composition changes are interpreted by condensation of the ambient ablation vapor due to stress wave excitations in the ablation spot.
Optical and electronic properties of graphene nanoribbons upon adsorption of ligand-protected aluminum clusters
2014
We have carried out first-principles calculations to investigate how the electronic and optical features of graphene nanoribbons are affected by the presence of atomic clusters. Aluminum clusters of different sizes and stabilized by organic ligands were deposited on graphene nanoribbons from which the energetic features of the adsorption plus electronic structure were treated within density-functional theory. Our results point out that, depending on their size and structure shape, the clusters perturb distinctively the electronic properties of the ribbons. We suggest that such selective response can be measured through optical means revealing that graphene nanoribbons can work as an efficie…
Background-Free Second-Harmonic Generation Microscopy of Individual Carbon Nanotubes
2015
We use polarized second-harmonic generation (SHG) microscopy to investigate pristine air-suspended carbon nanotubes (CNT). We show that SHG originates from CNT chirality, allowing also different response for the two circular polarizations of fundamental light.
Production of negative osmium ions by laser desorption and ionization.
2010
The interest to produce negative osmium ions is manifold in the realm of high-accuracy ion trap experiments: high-resolution nearly Doppler-free laser spectroscopy, antihydrogen formation in its ground state, and contributions to neutrino mass spectrometry. Production of these ions is generally accomplished by sputtering an Os sample with Cs(+) ions at tens of keV. Though this is a well-established method commonly used at accelerators, these kind of sources are quite demanding and tricky to operate. Therefore, the development of a more straightforward and cost effective production scheme will be of benefit for ion trap and other experiments. Such a scheme makes use of desorption and ionizat…
The Influence of Business Ecosystems on Innovation-Based Industries: A Research on the Mechanical Sector in Italy
2018
The business ecosystem perspective can be considered as a more advanced point of view for interpreting the development of local economic systems, if compared to more traditional concepts such as clusters, industrial districts, local or regional systems, and local networks. The business ecosystem perspective allows to better highlight the adaptive and evolutionary nature of local systems in front of the changing external environment and dynamics on national and international markets. The aim of the research was to analyze the key characteristics of firms belonging to a local business ecosystem specialized on an innovation-driven industry – the mechanical sector – in order to verify which kin…
IONIC TRANSPORT ACROSS POROUS CHARGED MEMBRANES AND THE GOLDMAN CONSTANT FIELD ASSUMPTION
1986
Starting from a simple theoretical model based on Nernst-Planck flux equations and the Donnan equilibrium relationship, the ionic transport across a porous, charged membrane is analysed and conditions are given which make exact the so-called “constant field assumption”. The validity of the reported results is later verified in the case of a well-known problem: the ionic transport across a cation-exchange membrane under bi-ionic conditions.