排序方式: 共有35条查询结果,搜索用时 15 毫秒
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Hassan Chataoui Hasna Choukri Mohamed Maatallah Driss Cherqaoui Abdellah Jarid 《Current Applied Physics》2017,17(10):1310-1315
Bending of the A = A (A of the group IVA) double bond neighboring is rationalized by the hyperconjugation phenomenon analysis. The bending is also observed for the high sized linear, cyclic or graphene-like compounds that imply the conjugated double bonds. The electronic delocalization takes place between occupied σ(π) and unoccupied π*(σ*) orbitals especially for compound implying Si and Ge atoms. Leading to rippled structure, this phenomenon affects the silicene and germane thickness sheets and probably would have some consequences on the properties of such compounds when they will be involved in the industries in the future. However we introduce a new parameter to assess the thickness of graphenic structures when the hyperconjugation takes place in the bonding framework. The study has been undertaken at high levels of theory like B3LYP/6-311 + G(3df,2p). 相似文献
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Chafia Bennaceur Carlos Afonso Sandra Alves Anne Bossée Jean-Claude Tabet 《Journal of the American Society for Mass Spectrometry》2013,24(8):1260-1270
Structural elucidation and distinction of isomeric neurotoxic agents remain a challenge. Tandem mass spectrometry can be used for this purpose in particular if a “diagnostic” product ion is observed. Different vibrational activation methods were investigated to enhance formation of diagnostic ions through consecutive processes from O,O-dialkyl alkylphosphonates. Resonant and non-resonant collisional activation and infrared multiphoton dissociation (IRMPD) were used with different mass spectrometers: a hybrid quadrupole Fourier transform ion cyclotron resonance (Qh-FTICR) and a hybrid linear ion trap-Orbitrap (LTQ/Orbitrap). Double resonance (DR) experiments, in ion cyclotron resonance (ICR) cell, were used for unambiguous determination of direct intermediate yielding diagnostic ions. From protonated n-propyl and isopropyl O-O-dialkyl-phosphonates, a diagnostic m/z 83 ion characterizes the isopropyl isomer. This ion is produced through consecutive dissociation processes. Conditions to favor its formation and observation using different activation methods were investigated. It was shown that with the LTQ, consecutive experimental steps of isolation/activation with modified trapping conditions limiting the low mass cut off (LMCO) effect were required, whereas with FT-ICR by CID and IRMPD the diagnostic ion detection was provided only by one activation step. Among the different investigated activation methods it was shown that by using low-pressure conditions or using non-resonant methods, efficient and fast differentiation of isomeric neurotoxic agents was obtained. This work constitutes a unique comparison of different activation modes for distinction of isomers showing the instrumental dependence characteristic of the consecutive processes. New insights in the dissociation pathways were obtained based on double-resonance IRMPD experiments using a FT-ICR instrument with limitation at low mass values.
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Haddad S Charfi-Kaddour S Nickel C Héritier M Bennaceur R 《Physical review letters》2002,89(8):087001
A model is presented for the high field phase diagram of (TMTSF)(2)ClO(4), taking into account the anion ordering, which splits the Fermi surface into two bands. For strong enough field, the largest metal spin density wave critical temperature corresponds to the N=0 phase, which originates from two intraband nesting processes. At lower temperature, the competition between these processes puts at disadvantage the N=0 phase vs the N=1 phase, which is due to interband nesting. A first order transition then takes place from the N=0 to N=1 phase. We ascribe to this effect the experimentally observed phase diagrams. 相似文献
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M. Triki D. Elmaghraoui S. Jaziri R. Bennaceur 《Solid State Communications》2010,150(43-44):2197-2200
Using a numerical method via the electron effective mass theory, a model of a quantum ring (QR) with a shape very close to the real one and taken from an experimental work, we investigate the electron states in a semi-conductor QR, studying the influence of the ring’s geometrical parameters on the electron spectrum and on the optical transitions. Our hetero structure evolves from a single quantum dot (QD) to a QR. We find that the one-electron ground state presents an absolute minimum when studied as a function of the ring radius. The reliability of the calculations is checked with experimental data. 相似文献
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From a quantum collective approach, the momentum relaxation time, through both electron-electron and electron-ion interactions, is obtained based on electron wave functions interacting with the continuum oscillations (plasma waves). The theoretical model presented gives a consistent and complete set of transport coefficients for a dense magnetized plasma. This unified scheme of long- and short-range interactions gives conductivity formulas which are free from the usual Debye length, which loses its physical meaning as an upper impact parameter for relatively high-density, coupled plasma. 相似文献
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Y. Turki-Ben Ali G. Bastard R. Bennaceur 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):222
The aim of this work is to analyze theoretically the correlation energies, for neutral, positive and negative excitons and bi-excitons in the III–V nitride InxGa1−xN/GaN quantum dot; where x=17.5% denotes the indium concentration. So, we propose a model consistent with experimental observations that is small InxGa1−xN truncated pyramids with circular base lying on wetting layer, both buried into GaN matrix. The correlation energies of many-body complexes X, X−, X+ and XX are investigated as a function of the quantum dot radius rc and the intrinsic electric field. 相似文献
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J. Bennaceur R. Mechiakh F. Bousbih M. Jaouadi R. Chtourou 《Journal of Sol-Gel Science and Technology》2012,61(1):69-76
Titanium dioxide doped with iron (III) was prepared by sol–gel Spin Coating method. The phase structures, morphologies, particle
size of the doped TiO2 have been characterized by X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM) and ultraviolet–visible
(UV–Vis) spectrophotometer. The XRD and Raman results show that the 10% Fe3+-doped TiO2 thin films crystallize in anatase phase between 600 and 800 °C, and into the anatase–rutile phase at 1,000 °C, and further
into the rutile phase when the content of Fe3+ increases (20%). The grain size calculated from XRD patterns shows that the crystallinity of the obtained anatase particles
increased from 39.4 to 43.4 nm as the temperature of annealing increase, whereas the size of rutile crystallites increases,
with increasing Fe3+ concentrations from 36.9 to 38.1 nm. The AFM surface morphology results confirmed that the particle size increases by increasing
the annealing temperature and also with an increasing of Fe3+ content. The optical band gap (E
g) of the films was determined by the UV–Vis spectrophotometer. We have found that the optical band gap decreased with an increasing
of annealing temperatures and also with an increasing of Fe3+ content. 相似文献
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We investigate theoretically the optical properties of composite organic–inorganic semiconductor quantum wells. These properties are dominated by hybrid Frenkel (or charge-transfer) and Wannier–Mott excitonic states. An important effect is the possibility of using the Stark shift to tune the resonance between Frenkel and Wannier–Mott excitons. This fact is very important from a practical point of view because it may be difficult to grow such a structure exactly at resonance. We also discussed the coupling of Frenkel or charge transfer and Wannier–Mott exciton through a microcavity photon. We evaluate the hybrid exciton-polariton Rabi splitting. In the strong coupling regime the Rabi splitting depends essentially on the oscillator strength of the Frenkel or charge-transfer exciton. 相似文献