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11.
Linear and nonlinear optical susceptibilities in a laterally coupled quantum-dot–quantum-ring system
Linear and nonlinear optical susceptibilities in a laterally coupled quantum-dot–quantum-ring system have been theoretically studied. In general, we find that the structure parameters of the coupled system significantly affect the optical susceptibilities. The enhancement of the coupling effects between the dot and ring is found to increase considerably the optical susceptibilities and redshift drastically the transition energies. Comparing to the linear susceptibility, the nonlinear optical susceptibility is found to be more sensitive to the variation of the structure parameters. A comprehensive analysis of the electron probability density movement with respect to the modification of the structure parameters is provided, which offers a unique perspective of the ground-state localization. 相似文献
12.
It is well-known that nano-systems can have properties which are distinctly different from macroscopic systems. In this study we point out the following specific behaviour: if the particle number is decreased so that the size of the system is in the nanometer-realm, new effects emerge which reflect certain features of biological systems although the system is inorganic in nature. This behaviour is shown by realistic molecular dynamics calculations in connection with aluminum-nanoclusters at various temperatures. The clusters can transform without external influence from a metastable into a stable state, and there can be more than one stable state, that is, we observe a bifurcation in the sense of chaos-theory. The stable states can differ in both the atomic structure and the outer shape. 相似文献
13.
Sotirios A. Hadjiagapiou 《Zeitschrift für Physik B Condensed Matter》1992,86(3):465-468
The competition between one- and two-photon processes is studied in a four wave mixing process. Using the flipper operatorsS
+,S
– for atoms, the propagator of the system is calculated. With the help of the propagator correlation functions of radiation fields are evaluated. 相似文献
14.
An existence and uniqueness theorem for a class of stochastic delay differential equations is presented, and the convergence of Euler approximations for these equations is proved under general conditions. Moreover, the rate of almost sure convergence is obtained under local Lipschitz and also under monotonicity conditions. 相似文献
15.
Sotirios E. Notaris. 《Mathematics of Computation》2006,75(255):1217-1231
We evaluate explicitly the integrals , with the being any one of the four Chebyshev polynomials of degree . These integrals are subsequently used in order to obtain error bounds for interpolatory quadrature formulae with Chebyshev abscissae, when the function to be integrated is analytic in a domain containing in its interior.
16.
Kotsiris SG Vasil'ev YV Streletskii AV Han M Mark LP Boltalina OV Chronakis N Orfanopoulos M Hungerbühler H Drewello T 《European journal of mass spectrometry (Chichester, England)》2006,12(6):397-408
A variety of derivatized fullerenes have been studied by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Of particular emphasis has been the evaluation of a recently introduced solvent-free sample/target preparation method. Solvent-free MALDI is particularly valuable in overcoming adverse solvent-related effects, such as insolubility and/or degradation of the sample. The method was applied to fullerene derivatives susceptible to decomposition under insufficiently "soft" MALDI conditions. Analytes included the hydrofullerene: C(60)H(36), fluorofullerenes: C(60)F(x) where x = 18, 36, 46, 48 and C(70)F(x) where x = 54, 56, methano-bridged amphiphilic ligand adducts to C(60) and the [4 + 2] cycloadduct of tetracene to C(60). The new solvent-free sample preparation is established as an exceedingly valuable addition to the repertoire of preparation protocols within MALDI. The MALDI mass spectra were of very high quality throughout, providing a testimony that "soft" MALDI conditions could be achieved. Using the [4 + 2] cycloadduct of tetracene to C(60) as the model analyte for direct comparison with solvent-based MALDI, the solvent-free approach led to less fragmentation and more abundant analyte ions. Applying solvent-free sample preparation, different matrix compounds have been examined for use in the MALDI of derivatized fullerenes, including sulfur, tetracyanoquinodimethane (TCNQ), 9-nitroanthracene (9-NA) and trans-2-[3-(4-tert-butylphenyl)-2-methyl-2- propenylidene]malononitrile (DCTB). DCTB was confirmed as the best performing matrix, reducing unwanted decomposition and suppression effects. 相似文献
17.
Sotirios M. Totokotsopoulos 《Tetrahedron》2008,64(18):3998-4003
A new synthetic approach toward 6a-carba-β-d-fructopyranose, a non-nutritive sweetener related to topiramate, is described. This scheme uses 2-C-hydroxymethyl-l-erythrose acetonide as starting material and efficiently delivers the target compound applying an RCM protocol for the construction of the carbocycle ring. 相似文献
18.
Vasil'ev YV Kotsiris SG Bashkin IO Antonov VE Moravsky AP Drewello T 《The journal of physical chemistry. B》2005,109(24):11875-11879
The high-pressure treatment of C60 in an H2 atmosphere at high temperatures leads to the efficient formation of a covalently bound dimer and some oligomeric species. The resulting hydrogenated C120 is an example of the bulk production of covalently bound derivatized fullerene cores. Matrix-assisted laser desorption/ionization in conjunction with reflectron time-of-flight mass spectrometry has been applied to the product analysis. The dissociation pattern of selected C120H(2x)+ ions (x > 30) indicates the dimeric structure of (C60H(x))2, as opposed to a giant hydrofullerene species possessing a fused C120 core. However, the results also clearly indicate a much stronger bonding (multiple sigma bonding) between the C60H(x) units than present in cycloaddition products. Evidence of a covalently linked dimer was obtained in labeling experiments, on the basis of which any laser-induced gas-phase aggregation of the C60H(x) monomer during the analysis is discounted. 相似文献
19.
20.
Streletskii AV Ioffe IN Kotsiris SG Barrow MP Drewello T Strauss SH Boltalina OV 《The journal of physical chemistry. A》2005,109(4):714-719
The mechanism of formation of fluorofullerene (FF) negative ions derived from the compounds C(60)F(18), C(60)F(36), and C(60)F(48) was studied by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (ToF) mass spectrometry (MS). A combined experimental/theoretical approach provides compelling evidence of nondissociative, thermodynamically controlled electron transfer from matrix-derived negative ions to the FF analyte as the main secondary-ionization process. Consistent with this thermochemical model, analyte parent molecular ion yield and degree of fragmentation for a particular MALDI experiment was found to depend on the nature of the matrix material (the five matrices investigated were sulfur, trans-2-[3-{4-tert-butylphenyl}-2-methyl-2-propenylidene]malononitrile, 9-nitroanthracene, 2,6-bis((furan-2-yl)methylene)cyclohexanone, and 2,6-bis((thiophen-2-yl)methylene)cyclohexanone). For mixtures of C(60)F(n) compounds with different n values and therefore different electron affinitites, unwanted electron-transfer reactions, which can lead to the suppression of C(60)F(n)(-) ions with low n values, were successfully blocked for the first time by judicious choice of the matrix. Therefore, reliable qualitative MS analysis of FF mixtures with wide ranges of composition is now possible. 相似文献