共查询到20条相似文献,搜索用时 31 毫秒
1.
S. Nie C.D. Lee R.M. Feenstra Y. Ke R.P. Devaty W.J. Choyke C.K. Inoki T.S. Kuan Gong Gu 《Surface science》2008,602(17):2936-2942
The formation of step bunches and/or facets on hydrogen-etched 6H-SiC(0 0 0 1) and () surfaces has been studied, using both nominally on-axis and intentionally miscut (i.e. vicinal) substrates. It is found that small miscuts on the (0 0 0 1) surface produce full unit-cell high steps, while half unit-cell high steps are observed on the () surface. The observed step normal direction is found to be for both surfaces. Hence, for intentionally miscut material, a miscut oriented towards this direction produces much better order in the step array compared to a miscut oriented towards a direction. For (0 0 0 1) vicinal surfaces that are miscut towards the direction, the formation of surface ripples is observed for 3° miscut and the development of small facets (nanofacets) is found for higher miscut angles. Much less faceting is observed on miscut () surfaces. Additionally, the (0 0 01) surface is found to have a much larger spatial anisotropy in step energies than the () surface. 相似文献
2.
M. Wanke M. Franz M. Vetterlein G. Pruskil B. Hpfner C. Prohl I. Engelhardt P. Stojanov E. Huwald J.D. Riley M. Dhne 《Surface science》2009,603(17):2808-2814
We report on angle-resolved photoelectron spectroscopy results of thin dysprosium-silicide layers formed on Si(1 1 1), taken with a toroidal analyzer allowing to image the energy surfaces in k||-space. At monolayer dysprosium coverages, where hexagonal DySi2 grows with a 1×1 superstructure, electron pockets are observed at the points with highly anisotropic effective masses, and around a hole pocket at the point also an anisotropic dispersion is found. The band filling of these two bands amounts to one, indicating an even number of electrons assigned to the surface unit cell. Similar features are found for multilayer coverages, where hexagonal Dy3Si5 layers are formed with a superstructure. Here, the influence of zone folding effects due to the reconstructed layers in the bulk silicide is only weak because of the high surface sensitivity of the experiments. 相似文献
3.
Theoretical study of optical recording with a solid immersion lens illuminated by focused double-ring-shaped radially-polarized beam 总被引:1,自引:0,他引:1
Based on the Richards–Wolf vector diffraction theory, the intensity distributions in the recording sample near a solid immersion lens are calculated for two different radially-polarized beams ( and modes). Numerical results show that a double-ring-shaped mode focusing has some excellent features in near-field optical storage, compared with a single-ring-shaped mode focusing. The recording density is markedly improved, the focal depth of the near-field recording system is substantially increased, and a subsurface recording is effectively obtained using the mode focusing. 相似文献
4.
First-principles study of benzene on noble metal surfaces: Adsorption states and vacuum level shifts
Kenji Toyoda Yosuke Nakano Ikutaro Hamada Kyuho Lee Susumu Yanagisawa Yoshitada Morikawa 《Surface science》2009,603(18):2912-2922
We have studied the interaction of benzene with Cu(1 1 1), Ag(1 1 1) and Au(1 1 1) surfaces using density functional theory (DFT) within a generalized gradient approximation (GGA) and the van der Waals density functional [vdW-DF; M. Dion, H. Rydberg, E. Schröder, D.C. Langreth, B.I. Lundqvist, Phys. Rev. Lett. 92 (2004) 246401]. The adsorption energies using vdW-DF are significantly more accurate than those using GGA, while the equilibrium adsorption distances between benzene and metal substrates () calculated by both GGA and vdW-DF are almost identical. The work function changes induced by the adsorption of benzene are significantly underestimated compared with the experimental values, as a result of the overestimation of by both GGA and vdW-DF. Instead of determining the values from first-principles calculations, we deduced the most probable adsorption distances in such a way as to reproduce the experimentally-observed work function changes. The deduced adsorption distance () is shortest on Cu(1 1 1) while it is longest on Ag(1 1 1), reflecting the strength of the interactions between benzene and the metal surfaces. It turns out that the substrate dependence of the work function change is mainly ascribed to the difference in the benzene–metal distance (ZC). Charge transfer and work function changes by the adsorption of benzene were analyzed by means of the induced density of interface states (IDIS) model [H. Vázquez, R. Qszwaldowski, P. Pou, J. Ortega, R. Pérez, F. Flores, A. Kahn, Europhys. Lett. 65 (2004) 802], and compared with the self-consistent GGA calculations. The vacuum level shifts estimated by the IDIS model agree with the GGA results for . On the other hand, the discrepancy between the two methods becomes larger for , where the back donation from the metal substrates to the adsorbate becomes significant. We show that the IDIS model reasonably works well for benzene on Cu(1 1 1), Ag(1 1 1) and Au(1 1 1) surfaces because on all surfaces. However, our analysis reveals that the actual charge density redistribution induced by the adsorption of benzene is more complicated than that assumed in the IDIS model. 相似文献
5.
M.J. Dick P.M. Sheridan J.-G. Wang S. Yu P.F. Bernath 《Journal of Molecular Spectroscopy》2006,240(2):238-243
The state of CaOH was investigated using optical–optical double resonance spectroscopy. A combined least-squares fit of the double resonance transition data along with optical transition data and the millimeter-wave pure rotational data of the state was performed using an effective Hamiltonian. The spin–rotation constant was determined for the state for the first time. An analysis of these constants showed that the Ca–O bond length and spin–rotation parameter of the state have the smallest values of all the observed 2Σ+ states of CaOH. This evidence suggests the assignment of the state as arising from a Ca+ atomic orbital of mainly 5sσ character. This atomic orbital assignment was shown to be consistent with both previous work on CaF and recent theoretical calculations on CaOH. 相似文献
6.
The structure of light hypernuclei with strangeness S=−1 and −2 is investigated with the microscopic cluster model and the Gaussian expansion method (GEM). We emphasize that the cluster picture as well as the mean-field picture is invaluable to understand the structure of Λ hypernuclei, Σ hypernuclei and double Λ hypernuclei. A variety of aspects of Λ hypernuclei is demonstrated through a systematic study of p-shell hypernuclei (,, , , , , ) and sd-shell ones (, ): for example, the appearance of genuine hypernuclear states with new spatial symmetry which cannot be seen in ordinary nuclei, the glue-like role of the Λ particle which shrinks the size of nuclear core and thus reduces the B(E2) value, and the halo and skin structures in and etc. The typical light hypernucleus is thoroughly investigated, including its production, structure and decay. Precise three-body and four-body calculations of , and using GEM provide important information on the spin structure of the underlying ΛN interaction, by comparing with recent experimental data from γ-ray hypernuclear spectroscopy. The Λ–Σ coupling effect is studied in and . The binding mechanism of is discussed together with the possible existence of , emphasizing the fact that the study of is useful for extracting information on the ΣN interaction differing from that from . A systematic study of double-Λ hypernuclei, constrained by the NAGARA data () within a four-body cluster model indicates that the recently observed Demachi–Yanagi event can be interpreted as the 2+ state of . The effect of hyperon mixing in and is investigated using one-boson-exchange potentials and quark-cluster-model interactions for the S=−2 sector. A close relation between nuclear deep hole states and hypernuclei is discussed, emphasizing the selection rule for fragmentation of the s-hole in light nuclei, which is promising for understanding the production mechanism of double-Λ and twin-Λ hypernuclei via Ξ-atomic capture. 相似文献
7.
We report the observation of levels in the state of CH2 via optical–optical double resonance spectroscopy. Direct transitions between the lowest singlet state and the state are allowed by symmetry, but weak because they correspond to a two electron excitation in the single configuration approximation to the electronic wavefunction. The observed transitions involve sequential single photon absorptions at visible and near infrared wavelengths using state intermediate levels. Recent ab initio results (S.N. Yurchenko et al., J. Mol. Spectrosc. 208 (2001), 136) predicted the positions of some of the levels which are confirmed by the present results. The new spectra provide accurate energies for rotational levels in the , l = 0 level of the state. 相似文献
8.
We propose a new realization of the elliptic quantum group equipped with the H-Hopf algebroid structure on the basis of the elliptic algebra . The algebra has a constructive definition in terms of the Drinfeld generators of the quantum affine algebra and a Heisenberg algebra. This yields a systematic construction of both finite- and infinite-dimensional dynamical representations and their parallel structures to . In particular we give a classification theorem of the finite-dimensional irreducible pseudo-highest weight representations stated in terms of an elliptic analogue of the Drinfeld polynomials. We also investigate a structure of the tensor product of two evaluation representations and derive an elliptic analogue of the Clebsch–Gordan coefficients. We show that it is expressed by using the very-well-poised balanced elliptic hypergeometric series . 相似文献
9.
The Einstein model to consider thermal effect in universal equations of state (UEOS) is modified. It is proposed that the zero-point vibration term should be deleted in a thermal UEOS, and the parameters cannot be directly taken as experimental data at a reference temperature, VR, BR, and , but their values at absolute zero temperature, V0, B0, and . An approach is proposed to solve V0, B0, and from VR, BR, and . The approaches are applied to three typical universal EOSs, including the Baonza, mGLJ and Morse EOSs. The numerical results show that the solved values of parameters are almost identical for different EOSs. And the thermo-physical properties predicted through different EOSs are almost identical at zero- and low-pressure conditions, once the same approach and input experimental data are used to solve the parameters. It is concluded that the prediction of thermo-physical properties at zero- and low-pressure conditions cannot be taken as the criteria to judge the applicability of a universal EOS. 相似文献
10.
Dilepton production in pp and Au+Au nucleus–nucleus collisions at as well as in In+In and Pb+Au at is studied within the microscopic HSD transport approach. A comparison to the data from the PHENIX Collaboration at RHIC shows that standard in-medium effects of the ρ,ω vector mesons—compatible with the NA60 data for In+In at and the CERES data for Pb+Au at —do not explain the large enhancement observed in the invariant mass regime from 0.2 to 0.5 GeV in Au+Au collisions at relative to pp collisions. 相似文献
11.
M. Kato Y. Morishita M. Oura H. Yamaoka Y. Tamenori K. Okada T. Matsudo T. Gejo I.H. Suzuki N. Saito 《Journal of Electron Spectroscopy and Related Phenomena》2007,160(1-3):39-48
The high-resolution absolute photoionization cross sections for Ar, Kr, Xe and N2 in the inner-shell ionization region have been measured using a multi-electrode ion chamber and monochromatized synchrotron radiation. The energy ranges of the incident photons for the target gases were as follows: Ar: 242–252 eV (2p Rydberg excitation), Kr: 1650–1770 eV (near the 2p ionization thresholds), Xe: 665–720 eV (near the 3d ionization thresholds) and 880–1010 eV (near the 3p ionization thresholds), N2: 400–425 eV (N 1s excitation and ionization). It is the first time to measure the absolute ionization cross sections of Ar, Kr, Xe and N2 over the present energy ranges with the energy resolution of over 10,000. The natural lifetime widths of , , and resonances for Ar, resonance for Xe, and resonance for N2 have been obtained based on the cross sections determined. The ionization energies into the Ar+ (), Ar+ () and Xe+ () ionic states are also determined using the Rydberg formula. 相似文献
12.
We theoretically investigate the generation of vector Bessel beams of the order m using a phase shifted superposition of TE and TM electromagnetic Bessel beams. Such Bessel beams are characterized by the intensity profile described by the superposition of squared Bessel functions of the orders (m-1) and (m+1). We derive the conditions for creating the special distributions of the intensity, which are determined by only one Bessel function, or . We offer the approach of intensity transformation based on the Bessel beam transmission through a multilayer system. Finally, we reveal the perfect intensity transformation transferring the whole energy from - to -profile of intensity distribution. 相似文献
13.
Based on the recent formulation of a general scheme to construct boundary Lax pairs, we develop this systematic construction for the affine Toda field theories (ATFT). We work out explicitly the first two models of the hierarchy, i.e. the sine-Gordon () and the models. The Toda theory is the first non-trivial example of the hierarchy that exhibits two distinct types of boundary conditions. We provide here novel expressions of boundary Lax pairs associated to both types of boundary conditions. 相似文献
14.
Type A -fold supercharge admits a one-parameter family of factorizations into product of first-order linear differential operators due to an underlying symmetry. As a consequence, a type A -fold supersymmetric system can have different intermediate Hamiltonians corresponding to different factorizations. We derive the necessary and sufficient conditions for the latter system to possess intermediate Hamiltonians for the case. We then show that whenever it has (at least) one intermediate Hamiltonian, it can admit second-order parasupersymmetry and a generalized 2-fold superalgebra. As an illustration, we construct a set of generalized Pöschl–Teller potentials of this kind. 相似文献
15.
This paper deals with the problem of discrete time option pricing by the fractional Black–Scholes model with transaction costs. By a mean self-financing delta-hedging argument in a discrete time setting, a European call option pricing formula is obtained. The minimal price of an option under transaction costs is obtained as timestep , which can be used as the actual price of an option. In fact, is an adjustment to the volatility in the Black–Scholes formula by using the modified volatility to replace the volatility σ, where is the Hurst exponent, and k is a proportional transaction cost parameter. In addition, we also show that timestep and long-range dependence have a significant impact on option pricing. 相似文献
16.
Nonparabolic effective mass of conduction subbands in InGaAs/InAlAs quantum wells (QWs), lattice-matched to InP, was quantitatively obtained by analyzing interband-optical transition spectra. Thickness of InGaAs well was 5.3, 9.4, and . Thickness of InAlAs barrier was about , and each QW was independent. Excellent agreement was obtained between experimental mass and theoretical mass predicted by Kane's three-level band theory on bulk InGaAs, in a wide energy range of from the bandedge. Method of experimental analysis on a relation between eigen energy and effective mass was described. 相似文献
17.
R. Seguin A. Schliwa S. Rodt K. Ptschke U.W. Pohl D. Bimberg 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):101
A systematic variation of the exciton fine-structure splitting with quantum dot size in single MOCVD-grown self-organized InAs/GaAs quantum dots is observed, ranging from several tens to as much as , thus covering more than one order of magnitude. Piezoelectricity is identified to be the dominant factor governing the observed trend. A change in sign of the fine-structure splitting is reported for the first time, originating from quantum dots with confinement potentials elongated in the and crystal direction, respectively. 相似文献
18.
The multi-Higgs models having spontaneous CP violation (SPCPV) and natural flavor conservation (NFC) lead to a real CKM matrix V contradicting current evidence in favour of a complex V. This contradiction can be removed by using a generalized μ–τ (called 23) symmetry in place of the discrete symmetry conventionally used to obtain NFC. If the 23 symmetry is exact then the Higgs induced flavour changing neutral currents (FCNC) vanish as in the case of NFC. 23 breaking introduces SPCPV, a phase in V and suppressed FCNC among quarks. The FCNC couplings between i and j generations show a hierarchy with the result that the FCNC can have observable consequences in B mixing without conflicting with the mixing. Detailed fits to the quark masses and the CKM matrix are used to obtain the (complex) couplings and . Combined constraints from flavour and CP violations in the K, Bd, Bs, D mesons are analyzed within the model. They allow (i) relatively light Higgs, 100–150 GeV (ii) measurable extra contributions to the magnitudes and phases of the mixing amplitudes and (iii) the mixing at the current sensitivity level. 相似文献
19.
The local Hurst exponent of the financial time series in the vicinity of crashes on the Polish stock exchange market 总被引:3,自引:0,他引:3
We investigate the local fractal properties of the financial time series based on the whole history evolution (1991–2007) of the Warsaw Stock Exchange Index (WIG), connected with the largest developing financial market in Europe. Calculating the so-called local time-dependent Hurst exponent for the WIG time series we find the dependence between the behavior of the local fractal properties of the WIG time series and the crashes’ appearance on the financial market. We formulate the necessary conditions based on the behavior which have to be satisfied if the rupture or crash point is expected soon. As a result we show that the signal to sell or the signal to buy on the stock exchange market can be translated into evolution pattern. We also find a relation between the rate of the drop and the total correction the WIG index gains after the crash. The current situation on the market, particularly related to the recent Fed intervention in September ’07, is also discussed. 相似文献
20.
Yukihide Tsuji Toshimitsu Mochizuki andTohru Okamoto 《Physica E: Low-dimensional Systems and Nanostructures》2006,34(1-2):156
We have performed the in-plane magnetotransport measurements on the two-dimensional electron gas at the cleaved p-InAs (1 1 0) surface by deposition of Ag. The surface electron density Ns is determined from the Hall coefficient at . The coverage dependence of Ns is well explained by the assumption that each adsorbed Ag atom denotes one electron into InAs until the surface Fermi level reaches the adsorbate-induced donor level. The electron mobility μ is about and does not show a clear dependence on the coverage over . In the high-magnetic field regime of B>1/μ, Shubnikov–de Hass oscillations were observed. A beating pattern due to the strong spin–orbit interaction appears for high Ns. For lower Ns of , an apparent quantum Hall plateau for ν=4 and vanishing of the longitudinal resistivity were observed around . 相似文献