Search results for "Excitation"
showing 10 items of 1290 documents
Electromagnetic properties of low-lying states in neutron-deficient Hg isotopes: Coulomb excitation of Hg-182, Hg-184, Hg-186 and Hg-188
2019
The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass 182-188 Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of $ 0^{+}_{1,2}$01,2+, $ 2^{+}_{1,2}$21,2+and $ 4^{+}_{1}$41+states was observed in all nuclei under study. Reduced E2 matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate…
Single-molecule optical switching of terrylene in p-terphenyl
1997
The controlled manipulation and switching of single atoms and molecules raise the prospect of ultra-high-density data storage. Switching by motion of a single atom has been reported1, and techniques of single-molecule optical detection and spectroscopy2 in the condensed phase have been refined to a degree that allows the modification of the absorption properties of a single chromophore3. Light-induced jumps in single-molecule excitation frequencies have been reported3,4,5, but in none of these cases could the process be controlled: the jumps varied from molecule to molecule, they were interrupted by spontaneous jumps, and the new excitation frequencies could not be identified unambiguously.…
Measurements of ultrafast spin-profiles and spin-diffusion properties in the domain wall area at a metal/ferromagnetic film interface
2017
AbstractExciting a ferromagnetic material with an ultrashort IR laser pulse is known to induce spin dynamics by heating the spin system and by ultrafast spin diffusion processes. Here, we report on measurements of spin-profiles and spin diffusion properties in the vicinity of domain walls in the interface region between a metallic Al layer and a ferromagnetic Co/Pd thin film upon IR excitation. We followed the ultrafast temporal evolution by means of an ultrafast resonant magnetic scattering experiment in surface scattering geometry, which enables us to exploit the evolution of the domain network within a 1/e distance of 3 nm to 5 nm from the Al/FM film interface. We observe a magnetization…
Dynamics of exciton creation and decay processes in composition – disordered InGaN thin films
2011
In the GaN-based ternary alloys, InGaN crystals have been recognized as key materials for e-h plasmas-exciton dynamics, because of large exciton binding energies (24.8 meV in GaN). We report investigations of creating and recombination dynamics of excitons in commercially important InxGa1-xN composition range from x = 0.1 to 0.18 in which nanoscale indium composition fluctuation occurs and formation of indium rich clusters acting as quantum dots (QD) can be expected. Three MOCVD grown samples having x = 0.1; 0.14 and 0.18 have been investigated using 3D picosecond transient PL spectroscopy. It has been found that the band to band photo excitation at 15 K in whole composition range results i…
Probing Surface Quantum Flows in Deformed Pygmy Dipole Modes
2017
In order to explore the nature of collective modes in weakly bound nuclei, we have investigated deformation effects and surface flow patterns of isovector dipole modes in a shape-coexisting nucleus $^{40}$Mg. The calculations were done in a fully self-consistent continuum finite-amplitude Quasiparticle Random Phase Approximation (QRPA) in a large deformed spatial mesh. An unexpected result of pygmy and giant dipole modes having disproportionate deformation splittings in strength functions was obtained. Furthermore, the transition current densities demonstrate that the long-sought core-halo oscillation in pygmy resonances is collective and compressional, corresponding to the lowest excitatio…
Role of Ge nanoclusters in the performance of photodetectors compatible with Si technology
2013
In this work, we investigate the spectral response of metal-oxide- semiconductor photodetectors based on Ge nanoclusters (NCs) embedded in a silicon dioxide (SiO2) matrix. The role of Ge NC size and density on the spectral response was evaluated by comparing the performance of PDs based on either densely packed arrays of 2 nm-diameter NCs or a more sparse array of 8 nm-diameter Ge NCs. Our Ge NC photodetectors exhibit a high spectral responsivity in the 500-1000 nm range with internal quantum efficiency of ~ 700% at - 10 V, and with NC array parameters such as NC density and size playing a crucial role in the photoconductive gain and response time. We find that the configuration with a more…
Spectral characterization of bulk and nanostructured aluminum nitride
2009
Spectral characteristics including photoluminescence (PL) spectra and its excitation spectra for different AlN materials (AlN ceramics, macro size powder and nanostructured forms such as nanopowder, nanorods and nanotips) were investigated at room temperature. Besides the well known UV-blue (around 400 nm) and red (600 nm) luminescence, the 480 nm band was also observed as an asymmetric long-wavelength shoulder of the UV-blue PL band. This band can be related to the luminescence of some kind of surface defects, probably also including the oxygen-related defects. The mechanisms of recombination luminescence and excitation of the UV-blue luminescence caused by the oxygen-related defects were …
Launching propagating surface plasmon polaritons by a single carbon nanotube dipolar emitter.
2011
International audience; We report on the excitation of propagating surface plasmon polaritons in thin metal films by a single emitter. Upon excitation in the visible regime, individual semiconducting single-walled carbon nanotubes are shown to act as directional near-infrared point dipole sources launching propagating surface plasmons mainly along the direction of the nanotube axis. Plasmon excitation and propagation is monitored in Fourier and real space by leakage radiation microscopy and is modeled by rigorous theoretical calculations. Coupling to plasmons almost completely reshapes the emission of nanotubes both spatially and with respect to polarization as compared to photoluminescence…
Photoluminescence excitation spectroscopy in boron nitride nanotubes compared to microcrystalline h‐BN and c‐BN
2005
Photoluminescence spectra and photoluminescence excitation spectra have been measured on samples of hexagonal boron nitride microcrystalline powder, cubic boron nitride single crystal, and boron nitride nanotubes (mixture of single-walled and multi-walled with some h-BN precursor). The reason for studying these 3 samples in a comparative fashion is that nanotube BN, while based on a rolled hexagonal-BN (sp2-bonded) sheet, is expected to take on more sp3 bond-character reminiscent of cubic-BN as the curvature becomes tighter. With some simplicity of statement, this study was planned to view spectroscopy of nanotube BN with respect to its two limiting cases of bond character, all measured in …
Strongly directional scattering from dielectric nanowires
2017
It has been experimentally demonstrated only recently that a simultaneous excitation of interfering electric and magnetic resonances can lead to uni-directional scattering of visible light in zero-dimensional dielectric nanoparticles. We show both theoretically and experimentally, that strongly anisotropic scattering also occurs in individual dielectric nanowires. The effect occurs even under either pure transverse electric or pure transverse magnetic polarized normal illumination. This allows for instance to toggle the scattering direction by a simple rotation of the incident polarization. Finally, we demonstrate that directional scattering is not limited to cylindrical cross-sections, but…