Vol. 43, No. 6 (1994)
1994-03-20
GENERAL
1994, 43 (6): 864-871.
doi: 10.7498/aps.43.864
Abstract +
The energies of the ground state and the lowest-excited states of the one-dime-nsional NNN interaction quantum chain are calculated by using Lanczos method. The a no=nalous dimensions and normalizing constant are given from conformal field theory.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
1994, 43 (6): 872-878.
doi: 10.7498/aps.43.872
Abstract +
By using the kernels consisting of the projectors and function δ(t), both the co-nvergence to equilibrium and to get the propagators in covariant gauge are solved to-gether under the vanishing initial condition. Thus, the SQ prescriptions of gauge and non-gauge fields are united in using only these same kernels. The Maxwell, Chern-Si-mon and the linear gravitational theories are considered respectively. Again, it is shown that the use of this kernel does not yield the influence on the equilibrium distri-bution.
CLASSICAL AREA OF PHENOMENOLOGY
1994, 43 (6): 879-888.
doi: 10.7498/aps.43.879
Abstract +
Some main factors having influence on the resolution of X-ray holograms are analyzed theoretically. The smalles resolving distance of X-ray lensless Fourier transform holograms can not be less than the radius of the focus spot of the X-ray condenser or the filter aperture used in recording, and the resolution of X-ray in-line holograms can not be higher than the cutoff frequency of recording material, under the condition that X-ray is perfectly coherent. Relationships between the coherent length required by X-ray lensless Fourier transform holography and the resolution, and the radius of the object are quadric; and the coherent length requested by X-ray in-line holography is proportional to the square of the resolution and does not change with the size of object, under the condition that X-ray is partially coherent. With the resolution of X-ray holograms raised, the reguired coherent length will be increased by a large amount.
1994, 43 (6): 889-894.
doi: 10.7498/aps.43.889
Abstract +
Based on the forward four-wave mixing model, we abtain analytic expressions for the diffraction efficiency of the photorefractive gratings with weak reading beam and strong reading beam intensity respectively for various values of the spatial phase shift between index change and fringe pattern.
1994, 43 (6): 895-903.
doi: 10.7498/aps.43.895
Abstract +
In the present paper, considering the detuning and the initial atomic coherence, dipole squeezing in two-photon Jaynes-Cummings model is investigated by means of the time-evolution operator method. The influence of the frequency detuning on the dipole squeezing in interaction of field with atom and the relation between the mean photon number and the dipole squeezing are studied by numerical calculations.
1994, 43 (6): 904-912.
doi: 10.7498/aps.43.904
Abstract +
Influence of untrapped electrons on the sideband instability of electromagnetic Wiggler free electron laser (EM一FEL) is analyzed in detail with single-particle theory. The dispersion equation is derrived by applying the methode in Ref.[1]，and detailed discussions are carried out, some conclusions are drawn.
1994, 43 (6): 913-917.
doi: 10.7498/aps.43.913
Abstract +
We have obtained the characteristics of all-optical switching and modulation of C60 in toluene pumped by a pulsed Nd:YAG laser at λ=532.0nm and probed by a CW semiconductor laser at λ=747.0nm, based on nonlinear triplet-triplet absorption in C60. Dynamic processes of switching and modulation are simulated using rate equations, which coincide with the experimental results.
1994, 43 (6): 918-924.
doi: 10.7498/aps.43.918
Abstract +
OH-radical concentration in the (SAPS) doped with B2O3 for PANDA fibers is measured by infrared absorption method. B, Si, 0 and N in SAPS are analysed X-ray photoelectron spectroscopy (XPS). The Ge distribution in the core and the cathod luminescence at core-cladding interface of SAPS are measured by scanning electron microscopy, The ratio of absorption coefficient between the fundamental stretching vibration and its first overtone of OH bond is explained theoretically by using a vibrator model.
1994, 43 (6): 925-932.
doi: 10.7498/aps.43.925
Abstract +
The nonlinear equation governing the non-propagating solitary wave and its analytical solution in a channel with uniformly and slowly varying width has been derived using the perturbation theory of multiple scales. The result obtained predicts that the solitary wave always moves towards the narrow end of the channel with an approximately uniform acceleration which is proportional to the variation rate of the width. The method in the present paper can be extended in principle to the theoretical investigation of other linear and nonlinear waves in a uniformly and slowly varying wave guide.
1994, 43 (6): 933-941.
doi: 10.7498/aps.43.933
Abstract +
Based on equations of fluids nachanics, introducing new scale hypotheses, and by means of pertubative multiple-scale method, the governing equation and solution of non-propagating soliton wah counting of excition and damping are given. By damping analysis, the curves of the lower cut-off excited amplitude△ｃ versus the excited frenquency Ω and the soliton equalamplitude curves in △－Ω picture in a good agreemant with experiment to a certain extent are obtained.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
1994, 43 (6): 942-949.
doi: 10.7498/aps.43.942
Abstract +
Using the analytical solutions of the hydrodynamic equations of plasma, energy level populations of the plasma dominated by He-like Mg ions are obtained by solving the rate equations numerically for short pulsed pumping laser. Variations of gain coefficient for MgXI ls3d-ls4f(λ=154?)vs time and spatial position are given. Also, the influence of the pumping laser pulse duration is discussed.
1994, 43 (6): 950-957.
doi: 10.7498/aps.43.950
Abstract +
In this paper, the electron transport process in cathode sheath of helium dc hollow cathode glow discharge is studied by using Monte Carlo simulation. The electron is accelerated between collisions by the non-uniform electric field of the hollow cathode sheath. The electron free flying time between collisions is determined by collision frequency of electron with neutral particle. The experimental data of collision cross section are fitted to semi-experience expressions. The electron mean energy and spatial energy distribution, and other parameters distribution are studied. The results are in good agreement with experimental ones.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1994, 43 (6): 958-965.
doi: 10.7498/aps.43.958
Abstract +
The period thickness mean refraction corrected factor and the ratio between two difference materials in a period can be deduced from the Bragg equation with refraction correction. Based on this Bragg's law and theory of optical thin film, the formula introduced in this paper have been verified in theory and experiment with short-period Mo/Si multilayers.
1994, 43 (6): 966-972.
doi: 10.7498/aps.43.966
Abstract +
By lightly doping in a-Si: H films in the process of low-temperature annealing, the density of the nualeation centers was controlled, and the films of larger grain polysilicon with good quality were obtained. The results show that the crystallization was almost uniformly proceed in(， and direction (slightly faster in direction), the average grain size is about 1μm, the mobility is about 92 cm２/V·s, and the dark conductivity at room-temperature is between 10-２s/cm and 10-4s/cm. The optical gaps of the crystallized films were determined between 1.16-1.22eV from the absorption spectrum. The coefficient of optical absorption within the wave length range of 800-1000nm is on the order of 104cm-1, and the absorption efficiency is around 60%.The results of heavily doped annealing samples of a-Si:H, as a contrast, are also discussed.
1994, 43 (6): 973-978.
doi: 10.7498/aps.43.973
Abstract +
Millimeter-sized C60 single crystals were grown by the vacuum sublimation of the purified C60 powder in a sealed vacuum quartz tube. C60 single crystals, up to size of 0.5mm×0.6mm×l.0mm and free from solvent or C70, had excellent faces. X-ray diffraction, electron diffraction and Raman spectra measurement were carried out to determine the room-temperature structure of C60 single crystals. The experimental results show that the temperature T1 of the hot end of tube, the temperature T2 of the cold end of tube and the temperature gradient ΔT= T2- T1 are the primary factors for preparation of large C60 single crystals. The above growth conditions were discussed in detail.
1994, 43 (6): 979-984.
doi: 10.7498/aps.43.979
Abstract +
With the theory of electron-molecule scattering, we have investigated the scattering and energy loss for slow diatomic molecular ions in electron gases in solids and discussed the influence of the coherence effects between two ions to the energy loss. The scattering phase shifts are calculated using atomic IPM potential and the variable phase method. The stopping powers for atomic ions are compared with the results given by the nonlinear density-functional theory.
1994, 43 (6): 985-990.
doi: 10.7498/aps.43.985
Abstract +
We report in this paper the observation of visible photoluminescence (PL) at room temperature from nano-crystallites of silicon films, which are prepared in a PE CVD system by using strong hydrogen diluted silane as the reactant gas source, without any post-processings. We attribute the PL to the photons above the band gap of bulk crystal silicon created by the carriers in the nano-crystallites under the function of quantm size effect. The effective deposition parameters are concerned.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1994, 43 (6): 991-999.
doi: 10.7498/aps.43.991
Abstract +
The theoretical studies about site-diagonal disorder and off-diagonal disorder amorphous quantum. dots on diamond lattice are reported. We describe the electronic structures of the amorphous models by simple tight-binding Hamiltonian, solve the Ha-miltonian equation by recursion method, and study the localization behavior from the sensitivity of eigenvalues to a change in boundary conditions. It is found that if the band edges of amorphous quantum dots are consisted of extended states, the changing tendency of the band widths with size are similar to that of crystal quantum dots; if they are consisted of localized states, the band widths do not change with size when the size is greater than a critical one, but the densities of states at the band edges increase with size. The imaginary part of dielectric function ε2（?ω） of amorphous quantum dots is also studied. The ε2（?ω） corresponding to extended state is sensitive to the change of size. The ε2（?ω） corresponding to localized state has a small value and is insensitive to the change of size when the size is greater than localization length Lloc; when the size is close to or less than Lloc; there are no difierences between localized states and extended states, and ε2（?ω） increases quickly with the decrease of size.
1994, 43 (6): 1000-1007.
doi: 10.7498/aps.43.1000
Abstract +
Fluorescence spectra of nanostructured Ａｌ2Ｏ3 bulks, which were not doped by Cr, were investigated systematically. The results show that for nanostructured samples of boehmite, η－Ａｌ2Ｏ3 and γ－Ａｌ2Ｏ3, two broad fluorescence bands (ｐ1 and ｐ2) appear, and ｐ1 and ｐ2 bands are located in the wavenumber ranges of 20000 to ～14500cm－１ and ～14500 to l1500cm－１, respectively. The ｐ1 band can be attributed to the trace impurity (Cr3+ ions) fluorescence. This is consistent with the previous results for Cr doped Ａｌ2Ｏ3. The ｐ2 band is a new fluorescence band. Finally, the stress is put on the discussion of conditions and the mechanism of the appearance of the ｐ2 band.
1994, 43 (6): 1008-1016.
doi: 10.7498/aps.43.1008
Abstract +
Using the hydrogenic-effective-mass theory, the spectral structure is calculated employing a linear variational method and presented for a hydrogenic shallow donor in a spherical quantum dot of GaAs-Ga１－ｘＡｌｘAs with the donor ion located at arbitary position. It is an extension of the calculation in Ref.[10]. The quantum-level sequence and degeneracy for the single electron state in the dot are discussed. Results of calculations indicate that the quantum-level structures depend on the dot radius and the ion position apparently, and that it is important to choose a proper set of base functions in the calculation.
1994, 43 (6): 1017-1023.
doi: 10.7498/aps.43.1017
Abstract +
Metal Au was deposited onto oriented phosphorous doped n-type epitaxial silicon. wafers, with or without plasma hydrogen treatment, to form Au/n-Si Schottky barrier (SB). The experimental results indicate: hydrogen decreases the Schottky barrier height (SBH) of Au/n-Si by 0.13eV; the SBH of Schottcky barrier containing hydrogen (SB(H)) can be controlled by zero bias annealing (ZBA) and reverse bias annealing (RBA), i.e. ZBA decreases and RBA increases the SBH of SB(H); and the controlling of SBH is reversible in at least three ZBA/RBA cycles. The increased SBH value of SB(H) after RBA is related not only to the reverse bias used in annealiug but also to the annealing temperature.
1994, 43 (6): 1024-1028.
doi: 10.7498/aps.43.1024
Abstract +
The static Mahan-H?nsch quantum transport equation in applied magnetic fields is extended to spin glass systems through introducing physical self-energies of elastic and inelastic scattering. In the quasi-elastic scattering limit, the Hall conductivity for spin glass model with the s-d exchange interaction between electrons and localized moments is evaluated by using this equation. The relation between resistivity and the Edwards-Anderson (EA) spin glass parameter and local susceptibility is obtained. Finally, thermoelectric power of spin glass::s and some interesting characteristic temperatures are discussed.
1994, 43 (6): 1029-1034.
doi: 10.7498/aps.43.1029
Abstract +
Using the method of time domain and frequency domain dielectric spectrum, the response signals of applied field for grains, intergranuhr boundary layer, and barrier layer in a ceramics may be dissociated. So as to give the contribution of each mechanism in total resistance and total reactance of a sample. The effect of conductivity relaxation due to hopping conductance of polaron has been observed. This effect makes the impedance of the sample appear with inductance character. The properties of intergranular boundary in three kinds of typical ceramics of zinc oxide, strontium titanate, and barium titanate are compared.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
1994, 43 (6): 1035-1040.
doi: 10.7498/aps.43.1035
Abstract +
Barium additive, which can resutt in a varistor character. was doped in the usual ZnO-Bi2O3-Sb2O3 varistor ceramics. It was found that a new grain boundary phase which is barium meta antimonate (BaSbA) crystal phase dissolving other trace compositions was formed besides the known Bi2O3 and Ｚｎ2．３３Ｓｂ０．６７Ｏ4 grain boundary phases. It was also found that the ＢａＳｂ2Ｏ6 phase is thermally stable and it plays an important role in improving the degradation properties of the varistor ceramics. The anti-degradation abilities of the varistor ceramics under the long duration load voltage and the surge current are both enhanced obviously when the amount of the Bi2O3, Ｚｎ2．３３Ｓｂ０．６７Ｏ4 and ＢａＳｂ2Ｏ6 grain boundary phases are in an appropriate ratio by controlling the amount of various additives. It is particularly valuable that the degradation properties of the V-I characteristics in backward direction are improved significantly.
