共查询到20条相似文献,搜索用时 18 毫秒
1.
LIU YiMin 《中国科学:物理学 力学 天文学(英文版)》2013,56(11):2122-2127
We propose a potentially practical scheme to generate macroscopic W-type state of N atomic ensembles in cavity QED system consisting of N atomic ensembles trapped in N single-mode cavities connected by(N 1)optical fibers.We show that the N-qubit W-type state of atomic ensembles can be realized with high success probabilities if the coulping strength of the cavity-fiber is much stronger than that of cavity-atom.We also show that both the growth of atomic number in each ensemble and the increase of the number of atomic ensembles can diminish the detrimental influence from dissipative processes.This idea provides a scalable way to an atomic-ensemble-based quantum network,which is plausible with current available technology. 相似文献
2.
For the low ionized anisothermal plasma in a mixture of moleculare nitrogen and molecular hydrogen the isotropic part of the velocity distribution function of the electrons is calculated and compared with the experimentally determined velocity distribution. the calculation of this distribution is performed by the help of the homogeneous and stationary electron Boltzmann-equation and takes into consideration all essential collision processes between the electrons and the N2 and H2 molecules. Furthermore, the calculated results of the mean energy, of the transport coefficients, of the collision frequencies for dissociation and direct ionization of the molecules, of the first Townsend coefficient of the molecules and of the collision rates for the direct ionization of the N- and H-atoms in the mixture are represented for the range 6–100 V/(cm Torr) of the reduced electric field strength and for any composition of the N2-H2 mixture. 相似文献
3.
The N2-H2 plasma gas mixture, generated in a 50?Hz pulsed dc discharge system with active screen cage, is characterized by optical emission spectroscopy (OES), as a function of gas pressure, the fractions of hydrogen and current density. The N2 dissociation degree and N atomic density was measured with actinometery where argon gas is used as actinometer. It was shown that the increase in hydrogen fraction enhances the dissociation of N2, until the maximum of 40%. The excitation temperature is determined from Ar-I emission line intensities by using the simple Boltzmann plot method. The dissociation fraction and excitation temperature is found to increase with hydrogen mixing in nitrogen plasma. 相似文献
4.
V. M. Marchenko L. D. Iskhakova A. V. Kir’yanov V. M. Mashinsky N. M. Karatun E. M. Sholokhov 《Laser Physics》2012,22(1):177-183
Yb2O3 polycrystals with a size of up to 10 mm are synthesized using the sintering and melting of the ultrapure Yb2O3 powders by the CO2-laser radiation with the power P
L ≤ 100 W at the wavelength λ = 10.6 μm at the melting point T
m = 2703 K, forming due to surface tension in melt, and crystallization in air. The analysis of the polycrystal microstructure
using the methods of optical and electron microscopy and X- ray diffractometry shows that perfect oxide crystallites are formed
in the course of crystallization after melting-through. The transformation of the luminescence and selective heat radiation
(SHR) spectra of the Yb2O3 polycrystals is studied under the resonant excitation at λ ≈ 975 nm using a laser diode and the laser heating at the wavelength
λ = 10.6 μm. When the resonant excitation power of the Yb3+ ions increases from 0.15 to 4.5 W, the Stokes luminescence of the Yb2O3 polycrystals is sequentially transformed into SHR and the thermal radiation of the crystal lattice. The transformation of
the emission spectra of the Yb2O3 polycrystals with an increase in the laser heating intensity by about four orders of magnitude can be represented as the
low-temperature heat radiation, spectral burst of the thermodynamically nonequilibrium SHR of the Yb3+ ions, and the high-temperature radiation of the crystal lattice. The temperature dependence of the luminescence spectra and
SHR of the Yb2O3 polycrystals on the intensity of the laser and laser-thermal excitation and the concentration quenching of the Yb3+ luminescence in oxides indicate the key role of the interaction of the f-electron shell of the Yb3+ ions with the natural oscillations of the crystal lattice in the processes of the multiphonon excitation and nonradiative
(multiphonon) and radiative (vibronic) relaxation. 相似文献
5.
N. Thilmann G. Str?mqvist M. C. Pujol V. Pasiskevicius V. Petrov F. Díaz 《Applied physics. B, Lasers and optics》2009,96(2-3):385-392
The linear absorption bandgap in the ultraviolet and the nonlinear index n 2 in near infrared were systematically measured in undoped and Yb3+-doped top-seeded solution-grown monoclinic double-tungstate KRE(WO4)2 (RE=Gd, Y, Yb, Lu) crystals. Anisotropic n 2 nonlinear indices have been determined for E‖N m and E‖N p polarizations with the maximum nonlinear index n 2 observed for the light polarized E‖N m. Moreover, the value of the nonlinear response of particular crystals in this family is proportional to the ionic radius of the RE3+ ion. 相似文献
6.
《Journal of Quantitative Spectroscopy & Radiative Transfer》1986,36(5):445-452
The rototranslational absorption spectrum of N2-H2 gaseous mixtures has been measured at five different temperatures from 298 to 90 K in the frequency range 80–850 cm-1. The absorption spectra due to N2-H2 interactions have been analyzed considering only the quadrupolar induction mechanism. With this assumption, the experimental data are fairly well accounted for, thereby providing a procedure for predicting the N2-H2 spectrum over a wide temperature range. 相似文献
7.
8.
The low-temperature plasticity of solid polycrystalline parahydrogen doped with an isotopic impurity (deuterium) is studied. The dependences of the rate of steady-state creep in p-H2 on the impurity concentration and stress are obtained. The deformation of p-H2 is described with inclusion of the zero-point mean-square displacements 〈x2〉 of particles making up a crystal. The calculated and experimental values of 〈x2〉 are compared for two possible isotope molecules (HD and D2) at three stress levels. A correlation between the 〈x2〉 values and an increase in the force constants of a p-H2 crystal doped with the isotopic impurity is established. An increase in the mean-square displacements of p-H2 with the tensile load is discussed. Deformation-induced purification of a p-H2 crystal from the isotopic impurity is suggested to occur. 相似文献
9.
The photoluminescence properties of Eu2+, Ce3+ and Tb3+ doped α-Si3N4 have been studied and a possible structural model has been proposed on the basis of the Rietveld refinement of X-ray powder diffraction data. Nearly single phase rare earth doped α-Si3N4 was synthesized by a solid state reaction at 1600 °C in N2-H2 atmosphere starting from amorphous Si3N4 and rare earth oxides or nitrides. Because of small crystal field splitting of the 5d levels, the excitation and emission bands of Eu2+ and Ce3+ are positioned at higher energies as isolated ions in comparison with that in Ca-α-Sialon. Both Eu2+- and Ce3+-doped α-Si3N4 show blue band emission peaking at about 470 and 450 nm, respectively, under UV excitation. α-Si3N4:Tb3+ exhibits dominant green line emission mainly arising from 5D4→7FJ (J=6-3) with weak 5D3→7FJ (J=6-3) transitions of Tb3+ when excited by UV light. The thermal stability of α-Si3N4:Eu2+ is comparable with that of Ca-α-Sialon:Eu2+ and is much better than that of α-Si3N4:Ce3+. 相似文献
10.
The results of experimental investigations on thermal nonequilibrium ionization in CO2: N2: He mixtures are presented. Measurements of electron density, ne, in vibrationally excited nitrogen were made in a supersonic flow with different CO2 contents as well as in a CO2: N2: He = 1 : 5 : 4 mixture laser gas. The mixtures were heated in a shock tube and expanded through a supersonic nozzle. Furthermore, supersonic mixing of N2 and CO2 + He was used in some experiments. The measured values of ne in the plenum chamber and in the supersonic nozzle are reported, and the processes responsible for nonequilibrium ionization in a laser-active medium are discussed. 相似文献
11.
A. E. Gorodetsky R. Kh. Zalavutdinov V. L. Bukhovets L. P. Kazansky A. P. Zakharov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2013,7(6):1173-1182
The features of tungsten oxidation in a flowing O2 or O2/H2 mixture glow discharge with a hollow cathode are investigated in the cathode, plasma, and afterglow regions at T = 300–350 K. The structure and composition of the samples are analyzed via reflection high-energy electron diffraction, reflection X-ray diffraction, electron probe microanalysis, and X-ray photoelectron spectroscopy. The results of analysis show that the metal surface is covered by a thin film (5–10 nm thick) of amorphous porous hydrated tungsten oxide (WO3) after its exposure to the discharge and storage in air. The study of the film composition using a time-of-flight mass spectrometer indicates that the WO3 film contains (WO3) n (n = 1–6) clusters and water molecules adsorbed in the pores. After exposure of the polycrystals to the O2/H2 discharge, the selective intense oxidation of individual grains is detected in the cathode region; the surrounding areas are subjected to weaker oxidation. The thicknesses of the WO3 films on neighbouring grains differ by more than tenfold. Such grains can be the source of tungsten dust in plasma installations. 相似文献
12.
13.
Densities ρ, viscosities η, and refractive indices nD, of the binary and ternary mixtures formed by cyclohexanone + N,N-dimethylacetamide + N,N-diethylethanolamine were measured at (298.15, 308.15, and 318.15) K for the liquid region and at ambient pressure for the whole composition ranges. The excess molar volumes VmE, viscosity deviations Δη, and refractive index deviations ΔnD, were calculated from experimental densities and refractive indices. The excess molar volumes are positive over the mole fraction range for binary mixtures of cyclohexanone(1) + N,N-dimethylacetamide (2) and N,N-dimethylactamide (2) + N,N-diethylethanolamine (3) and increase with increasing temperatures from (298.15 to 318.15) K. The excess molar volumes of cyclohexanone (1) + N,N-diethylethanolamine (3) are S-shaped dependence on composition with negative values in the N,N-diethylethanolamine rich-region and positive values at the opposite extreme and increase with increasing temperatures from (298.15 to 318.15) K. The excess molar volumes are positive over the whole mole fraction ranges for the ternary mixtures at all temperatures. Viscosity deviations are negative over the mole fraction range for all binary and ternary mixtures and decrease with increasing temperatures from (298.15 to 318.15) K. Refractive index deviations are negative over the mole fraction range for all binary and ternary mixtures and increase with increasing temperatures from (298.15 to 318.15) K. The experimental data of constitute were correlated as a function of the mole fraction by using the Redlich–Kister equation for binary and , Cibulka, Jasinski and Malanowski , Singe et al., Pintos et al., Calvo et al., Kohler, and Jacob–Fitzner for ternary mixture, respectively. McAllister's three body, Hind, and Nissan–Grunberg models were used for correlating the kinematic and dynamic viscosity of binary mixtures. The experimental data of the constitute binaries are analyzed to discuss the nature and strength of intermolecular interactions in these mixtures. 相似文献
14.
Absolute cross sections of electron capture and dissociative excitation for the Na+-H2, N2 and K+-H2, N2 pairs are determined. The high intense hydrogen and nitrogen atomic lines HI (121.6 nm) NI (120.0 nm), have been observed.
For the Na+-H2 and K+-H2 pairs the qualitative interpretation of experimental results in the framework of quasidiatomic approximation are carried
out.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
Characterization of Zr-Si-N films deposited by cathodic vacuum arc with different N2/SiH4 flow rates
G.P. Zhang E.W. NiuX.Q. Wang G.H. LvL. Zhou H. PangJ. Huang W. ChenS.Z. Yang 《Applied Surface Science》2012,258(8):3674-3678
Zr-Si-N films were deposited on silicon and steel substrates by cathodic vacuum arc with different N2/SiH4 flow rates. The N2/SiH4 flow rates were adjusted at the range from 0 to 12 sccm. The films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), hardness and wear tests. The structure and the mechanical properties of Zr-Si-N films were compared to those of ZrN films. The results of XRD and XPS showed that Zr-Si-N films consisted of ZrN crystallites and SiNx amorphous phase. With increasing N2/SiH4 flow rates, the orientation of Zr-Si-N films became to a mixture of (1 1 1) and (2 0 0). The column width became smaller, and then appeared to vanish with the increase in N2/SiH4 flow rates. The hardness and Young's modulus of Zr-Si-N films increased with the N2/SiH4 flow rates, reached a maximum value of 36 GPa and 320 GPa at 9 sccm, and then decreased 32 GPa and 305 GPa at 12 sccm, respectively. A low and stable of friction coefficient was obtained for the Zr-Si-N films. Friction coefficient was about 0.1. 相似文献
16.
This paper reports on the first results obtained from the investigation of the effect of IR radiation on the low-temperature
(1.8 ≤ T ≤ 4.2 K) plasticity of solid hydrogen. It has been found that, when the samples are exposed to IR radiation, a drastic increment
ΔɛIR of the elongation per unit length ɛ (which was preliminarily achieved under a continuously applied mechanical stress σ =
const) occurs without an increase in the temperature of the samples. It has been revealed that the effect observed both in
the case of normal hydrogen (n-H2, 75% o-H2) and in the case of parahydrogen (p-H2, ∼0.2% o-H2) only for a sufficiently high power of the IR radiation source has a threshold character. The reverse deformation of solid
hydrogen is observed after the irradiation with a flux of IR photons is completed: the quantity ɛ rapidly decreases to values
provided only by the applied load. The appearance of jumps in the increment of deformation ΔɛIR
i
is interpreted as a consequence of the existence of the fundamental IR absorption band for solid hydrogens. It has been established
that, depending on the time t of exposure of the samples to IR radiation, the change in the quantity ΔɛIR
i
(t) obeys the logarithmic law, which is characteristic of the dislocation creep and observed in the case of unirradiated hydrogen.
It has also been found that, under multiple relatively long-term exposure to IR radiation, the constant α of the logarithmic
creep of n-H2 abruptly decreases, whereas the strength of both the n-H2 and p-H2 samples increases significantly, which indicates their explicit hardening (instead of the expected “superplastic” behavior
due to the exposure to IR irradiation). 相似文献
17.
A systematic analysis of the temperature dependences of the thermopower S(T) for different phases of the HgBa2Ca n?1Cu n O2n+2+δ family (n=1, 2, 3) at different doping levels is performed in the framework of a narrow-band phenomenological model. Quantitative estimates of the main parameters of the band responsible for conduction in the normal phase of HgBa2Ca n?1Cu n O2n+2+δ are given for optimally doped samples. The character of the variation in these parameters with an increasing number n of the copper-oxygen layers is discussed. A trend toward broadening of the conduction band with increasing n is revealed, which can be due to the increase of the density-of-states (DOS) peak near the Fermi level with an increasing number of the CuO2 layers responsible for the formation of the conduction band. It is found that an increase in the number n leads to an increase in the fraction of localized carriers in the band owing to a more defective structure observed in the more complex phases of HgBa2Ca n?1Cu n O2n+2+δ. The variations in the band-structure parameters in going from under-to overdoped compositions in the HgBa2Ca n?1Cu n O2n+2+δ family are also discussed. 相似文献
18.
Sh.B. Atakulov 《Solid State Communications》1984,51(6):415-419
The peculiarities of the potential shape in polycrystalline films were considered. It was shown that the barrier height (φB) in sites (the place where three or more crystallites are connected) with respect to the concentration of boundary states (BS) was higher or coincided with the barrier height (φA) at the crystallite boundaries (CB). That is why the sites for majority charge carriers in films were “blocked down” and current transport along CB was not realized. If inversion of the conductivity type at CB was absent, the Hall potential was generated in quasi-neutral regions of crystallites and in barrier regions perpendicular to the current lines. If the Hall potential coefficient (RH) of the film is determined by the carrier concentration n0 in quasi-neutral regions. In this case the activation energy of the Hall mobility was equal to the activation energy of the conductivity (σA). In the opposite case the inversion conductivity type takes place on CB. When the inversion regions are present near the barrier tops and conductivity is realized along CB, RHp ~ (NcNv/n0)-1 exp (Eg?φB/kT) and μHp ~ exp (?φB?φA/kT), where Eg is the band gap, Nc, Nv are the effective density of states in the conduction and valence bands. 相似文献
19.
I. Shirotani S. Yoshida Y. Wada T. Kajiwara M. Murakami S. Yoshimura 《Solid State Communications》1981,38(7):653-656
The electrical resistivity of N-n-propylpyridinium-TCNQ2 (NPPy-TCNQ2) and N-n-butylpyridinium-TCNQn (NBPy-TCNQn) has been measured as a function of temperature and pressure. Phase transitions in these salts have been studied at high pressures. The transition temperature (Tc) in NPPy-TCNQ2 at atmospheric pressure increased with increasing pressure at the rate of dTc/dP = + 12.0 degkbar?1. The value of volume change calculated from the Clapeylon-Clausius relation was + 4.4 cm3 mol?1. The electrical resistivity along the a- and c-axis increased with increasing pressure below 7 kbar. This anomalous electrical behaviour is closely related to the crystal structure of NPPy-TCNQ2. The resistivity dropped sharply at about 11 kbar. This abrupt change may be due to a new pressure induced phase transition.The Tc of the NBPy-TCNQn increased remarkably with increasing pressure up to 0.7 kbar, above which the phase transition disappeared. The phase transitions of N-n-alkyl-substituted pyridinium TCNQ salts depend strongly on the nature of cations. 相似文献
20.
Hall coefficient, resistivity and superconducting upper critical field Hn2 were measured on single-crystalline BaPb1?xBixO3 of compositions x = 0.20, 0.12 and 0, of which the normal-state properties differ significantly from those of polycrystals. The slope dHn2/dT at Tc was estimated from the normal-state parameters and was found to agree well with the observed value, suggesting that this material is a bulk BCS superconductor. 相似文献