Vol. 49, No. 6 (2000)
2000-03-20
GENERAL
2000, 49 (6): 1023-1027.
doi: 10.7498/aps.49.1023
Abstract +
The Pfaff-Birkhoff principle and the Birkhoff equations for relativistic Birkhoff systems are given. The definition of an infinitesimal generator for the relativistic Birkhoff systems is given; by using the invariance of the ordinary differential equations under the infinitesimal transformations, the determining equations of Lie symmetries for the systems are established; the structure equation and the conserved quantities are obtained. And the inverse problem of Lie symmetries of the systems is also studied. Two examples are given to illustrate the application of the result.
2000, 49 (6): 1028-1030.
doi: 10.7498/aps.49.1028
Abstract +
In this paper, Simultaneously considering the problem of classical variable mass and the relativistic effect of mass variation with velocity, the fundamental relativistic equation of dynamics, Dalembert principle and Lagrange equation for fixed-axis rotational variable mass system are built.
2000, 49 (6): 1031-1034.
doi: 10.7498/aps.49.1031
Abstract +
Using Regge-Wheeler's method,axial perturbation equation of generalized Schwarzschild geometry is derived.The numerical results of quasi-normal modes for given angular momentum L and parameter λ indicate the instability of the geometry,which is in agreement with our analytic results.
2000, 49 (6): 1035-1038.
doi: 10.7498/aps.49.1035
Abstract +
The Hawking radiation for a charged axially symmetric nonstationary black hole is studied. We obtain the event horizon equation and the Hawking thermal spectrum formula. Both the shape and the temperature of the black hole depend on the time and the angle. They can reduce to the well-known results when there is no electric charge.
2000, 49 (6): 1039-1042.
doi: 10.7498/aps.49.1039
Abstract +
We present a theory for control of Chen's chaotic system using sampled-data feedback control technology. First, the output of Chen's chaotic system is sampled at a given sampling rate. Then the sampled data are used to construct a discrete-time feedback control algorithm for controlling Chen's chaotic system to the origin. The theory of the asymptotic stability of the controlled system is presented. Numerical experimental results are given.
2000, 49 (6): 1043-1046.
doi: 10.7498/aps.49.1043
Abstract +
With three kinds of condenser zone plates (CZPs) and pinholes, the linear monochromator transmits soft X-rays of 1.97—5.44nm wavelength range. The soft X-ray diffraction images (i.e. the optical field distribution of the monochromator) were recorded from the combination of CZP32 and a pinhole of 30μm by using positive photoresist under the conditions of an appropriate focusing and a large focusing error. The properties of optical field, such as the radius of Airy pattern and the good spatial coherence region, were also obtained. The experimental results agreed well with the theoretical calculation.
ATOMIC AND MOLECULAR PHYSICS
2000, 49 (6): 1047-1051.
doi: 10.7498/aps.49.1047
Abstract +
In this paper, a model program has been established to investigate the amplified spontaneous emission (ASE) in the Nd:glass disk amplifier with the Monte Carlo method and rays tracing. The distribution of ASE loading on the edge of a disk is firstly calculated. The effect of disk aspect radio on ASE gain reduction is also investigated. Allowance is made for the effect of different reflectivity under the condition of different incidence on two faces.
2000, 49 (6): 1052-1057.
doi: 10.7498/aps.49.1052
Abstract +
We have improved the prior-form eikonal approximation to the corrected effective-potential eikonal approximation, using the valence electron effective-potential of Li atom, and calculated the total electron capture cross sections for H+， He2+ ions collided with Li atom. The present results are in agreement with experments.
2000, 49 (6): 1058-1063.
doi: 10.7498/aps.49.1058
Abstract +
Through the Coulormb-Explosion of MeV ion microcluster in self-supported superthin carbon foil, the determined value of 4HeH+ internuclear separation, generated by rf ion source,is obtained to be 0.094±0.003nm. It is found that 4HeH+ is different from H+2 and H+3, and their internuclear separations are closely related to the species and parameters of ion source. By means of the mechanism and condition of 4HeH+ formation, the difference of internuclear sepapation for 4HeH+ produced in the rf and deuplasmatron ion source was discussed.
CLASSICAL AREA OF PHENOMENOLOGY
FRACTAL CHARACTERISTICS INVESTIGATION ON ELECTROMAGNETIC SCATTERING FROM 2D CONDUCTING ROUGH SURFACE
2000, 49 (6): 1064-1069.
doi: 10.7498/aps.49.1064
Abstract +
A normalized two-dimensional band-limited Brown fractal function is presented for modelling the rough surface. An analytic solution of electromagnetic scattering field from this conducting band-limited Brown fractal surface is given based on Kirchhoff approximation. The average scattering field, the average scattering coefficient and the average intensity of scattering field are derived with emphasis on examining the relation of fractal dimension with the scattering pattern. The important conclusion is obtained that the diffracted envelope slopes of scattering pattern can be approximated to a slope of linear equation.
2000, 49 (6): 1070-1075.
doi: 10.7498/aps.49.1070
Abstract +
Based on the Bergman's representation,a semi-analytical method for the calculation of electrostatic field in electrorheological fluids was presented.The electric field for BCT structure was calculated as an example.The multipole contribution as a function of the separation of particles was discussed quantitatively and the range of validity of dipole approximation was given.
2000, 49 (6): 1076-1080.
doi: 10.7498/aps.49.1076
Abstract +
The Imaging theory of two-photon and multi-photon confocal scanning microscopy is presented. The three-dimensional point spread function and three-dimensional optical transfer function of two-photon confocal scanning microscopy is derived. By using the three-dimensional point spread function and three-dimensional optical transfer function theory, we have proved that the horizontal and vertical resolutions of two-photon confocal scanning microscopy are higher than those of the single photon confocal scanning microscopy, and the space resolution of multi-photon confocal scanning microscopy is higher than that of two-photon confocal scanning microscopy.
2000, 49 (6): 1081-1085.
doi: 10.7498/aps.49.1081
Abstract +
The effect of the phase of driving field on spontaneous emission in V-Model has been discussed.We find that the spectrum is not only related with the phase of the driving field,but also with the initial status of the atoms.We present an analytical explanation in dressed state representation.
2000, 49 (6): 1086-1090.
doi: 10.7498/aps.49.1086
Abstract +
The cubic nonlinear refraction index n2 and the nonlinear absorption coefficient β of several new ruthenium complexes at 460nm are measured by Z-scan technique and the third-order nonlinear susceptibility χ(3) of the samples are calculated.The effects of molecular structures on the third-order nonlinear optical properties are discussed.
2000, 49 (6): 1091-1093.
doi: 10.7498/aps.49.1091
Abstract +
Pattern formation and transverse effect are reported for azobenzene polymer film.We show,through scanning electron microscopy and polarizing optical microscopy investigation of azobenzene polymer film after being irradiated by degenerate four-wave mixing,that many peak-like islands of azobenzene polymer molecules array in some patterns.Experimental evidence that it is possible to control the photoinduced micro-patterns of the nonlinear organic film via adequately polarized write beams and appropriate power of the write beams,thus making easy growth of nanostructures crystals in azobenzene polymer film.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
2000, 49 (6): 1094-1100.
doi: 10.7498/aps.49.1094
Abstract +
We have investigated the dynamics of dust particles in electrode sheaths of dc glow discharges.The charge of dust particles,the various forces and the suspension position are also calculated.The dynamics and the suspension position of dust particles are determined by their size and the forces acting on them. We find that the suspension position in the collisional sheath is closer to the electrode than that in the collisionless sheath.It is also shown that in the lower sheath (above the lower electrode) only those particles of the same size can be suspended in the same position.In the upper sheath (under the upper electrode) grains with different sizes can be suspended in the same position.All the dust particles suspended in the sheath are charged negatively and satisfy Fnet=0 and dＦnet/dx<0.However,whether the dust particles that satisfy these conditions can be suspended in the sheath is also determined by their initial position and velocity.
2000, 49 (6): 1101-1105.
doi: 10.7498/aps.49.1101
Abstract +
The experimental investigation on the X-ray radiation transport is made.The method for studying X-ray transport is analyzed.Two kinds of targets which are source and cylinder targets are investigated separately.From the source target,the initial condition for transport is obtained.From transport target,the transport result is obtained.The experimental results for the two kinds of targets measured by a soft X-ray spectrometer,flat response X-ray diffraction and transmission gratings are given and analyzed using the simple X-ray radiation transport model.Plasma expansion in cylinder targets are investigated.
2000, 49 (6): 1106-1108.
doi: 10.7498/aps.49.1106
Abstract +
Making use of graphite as electrode,we have prepared carbon nanotubes by the direct current arc-discharge method.The experimental results indicate that the carbon nanotubes are generated on the front-end surface and within the carbon accretion on the cathode.Using SEM adn TEM,we find no significant difference for the shapes and the structures of the generated carbon nanotubes when the pressure and the direct arc-current change.Under the pressure of hydrogen gas 11999Pa and direct arc-current 60A,we obtain a large number of straight and long carbon nanotubes with uniform calibers.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
2000, 49 (6): 1109-1113.
doi: 10.7498/aps.49.1109
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The deposition of Fe on the Ru(1010) surface has been studied by low-energy electron diffraction angle-resolved UPS and Auger Electron-Spectroscopy.Upon annealing,Fe overlayers on Ru(1010) formed (1×1) and P(2×1) structures.For Fe coverages more than 10ML,incommensurate layer of Fe with a fcc(111) face epitaxial structure is formed.For Fe overlayer at low coverages,the valence bands near Fermi level are similar to the clear surface,while for Fe overlayer at high coverages with the fcc(111) epitaxial structure,different energy band structures related to this epitaxial layer were observed.
2000, 49 (6): 1114-1119.
doi: 10.7498/aps.49.1114
Abstract +
We have investigated the alignment of liquid crystal LC-6710A molecules with Cinnamate material 2-(cinnamoyloxy) ethyl methacrylate (CEMC).The change of alignment of substrate surface was observed before and after photochemical reaction.The pretilt angle of LC molecules in photo-alignment cell was measured.The electro-optical property and time response curves of twisted nematic liquid crystal display (TNLCD) with single side photo-alignment substrate were obtained.The process of photochemical reaction of the material CEMC using linear polarized photopolymerization method by UV-light was studied in this paper.The mechanism of liquid crystal molecules alignment on substrate surface was discussed.
2000, 49 (6): 1120-1123.
doi: 10.7498/aps.49.1120
Abstract +
Skutterudite compounds FexCo4-xSb12 were synthesizedby solid state reaction using high-purity powders of Co,Fe,and Sb as starting materials.FexCo4-xSb12(x＝0—10) compounds were obtained at 900—1000K.The lattice constant of FexCo4-xSb12 increased with increasing substitution of Fe for Co sites.Carrier concentration and electrical conductivity increased with increasing Fe content.Seebeck coefficient decreased and Topt of Seebeck coefficient shifted to higher temperature with increasing Fe content.Lattice conductivity was reduced significantly by substitution of Fe for Co sites.The maximum ZT value of 05 was obtained for Fe0.92Co3.08Sb12 at 750K.
2000, 49 (6): 1124-1131.
doi: 10.7498/aps.49.1124
Abstract +
The Au/Au(100) epitaxial growth with energetic deposition was simulated by using kinetic Monte Carlo method.The influences of energetic atoms on morphology and atomistic processes in the early stage of film growth were investigated.The reentrant layer-by-layer growth was observed in the temperature range of 450K to 100K.We found the energetic atoms can promote the nucleation and island growth in the early stages of film growth and enhance the smoothness of film surface at temperatures of film growth in 3-dimensional mode and in quasi-two-dimensional mode.The atomistic mechanism that promotes the nucleation and island growth and enhances the smoothness of film surface is discussed.
2000, 49 (6): 1132-1135.
doi: 10.7498/aps.49.1132
Abstract +
GaN films of about 300nm were grown on GaAs(001) substrates by molecular beam epitaxy (MBE).X-ray double-crystal diffraction and room-temperature photoluminescence measurements show that the films grown on nitridized GaAs nucleation layer are pure cubic GaN while the films grown on nitridized AlAs nucleation layer are pure hexagonal GaN.The present study shows that the phase of GaN samples grown on GaAs substrates can be controlled using different nucleation layers
2000, 49 (6): 1136-1139.
doi: 10.7498/aps.49.1136
Abstract +
The activated energy of single quantum well structures obtained by the admittance measurements is varied with different thickness of capping layer and with one sample under different applied bias voltages.The electric potential distribution is the key effect on the energy variation.The correctness of the measured results can be judged by using the admittance measurements under different applied bias voltages
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
2000, 49 (6): 1140-1143.
doi: 10.7498/aps.49.1140
Abstract +
Based on the results of total-energy calculations using full-potential linearized augmented plane wave method within the generalized gradient approximation (GGA),we determined the tetragonal fine structure of K(Ta0.56Nb0.44)O3，i.e.,the equilibrium configuration of B-site cations (Ta and Nb)in the ferroelectric phase. Ta is found to have an off-center displacement,relative to the oxygen octahedron,of about 0.005nm along [001]. The off-center displacement of Nb is as large as 0.016nm,thus makes a major contribution to the occurrence of the ferroelectric instability.
2000, 49 (6): 1144-1147.
doi: 10.7498/aps.49.1144
Abstract +
Angle-resolved photoemisson spectra were measured at normal emission on the cleaved (111) surface of C60 single crystal.Valence band dispersions have been studied with varying photon energy of synchrotron radiation rays from 13.0eV to 34.0eV. The largest dispersions are 0.27eV and 0.42eV along the Γ—L direction for the HOMO and HOMO-1 derived bands respectively. The dispersion curves coincide with the theoretical electronic structure fairly well.
2000, 49 (6): 1148-1152.
doi: 10.7498/aps.49.1148
Abstract +
In the paper, according to the energy-band structure of C-BN and specific characteristics of polar semiconductor, the main scattering mechanism of C-BN is built, and the physical model applicable to Monte Carlo(MC) simulation is set up. It is the first time that the stable-state electronics transport characteristics of bulk C-BN is simulated by single electronics MC method. The variation laws of mean drift velocity, mobility as well as electronic energy with electrical field are obtained respectively. Also, the variation laws of electronic energy relaxation time and momentum relaxation time with electrical field are obtained respectively.
2000, 49 (6): 1153-1158.
doi: 10.7498/aps.49.1153
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By solving the single particle Shrdinger equation in different regions,we have discussed the spin effect on the energy levels of electron and the magnetoconductance in the magnetic quantum antidot. It is shown that the interaction of spin and the magnetic field results in the split of the energy levels. The splitting features are different from those in homogeneous magnetic field,i.e.the extent of the splitting is closely related to the angular momentum quantum number. Electron resonant tunneling to the magnetic edge states gives rise to the oscillations of the magnetoconductance. And spin-assisting magnetoconductance is quite different from that in the case where electron spin is ignored.There are more and shallower dips in the magnetoconductance spectrum for the former case.
2000, 49 (6): 1159-1162.
doi: 10.7498/aps.49.1159
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The Au-SiO2-Si thin film MIS(Metal-Insulator-Semiconductor)tunnel junction was fabricated.The light emission property and I-V characteristic of this junction were measured and analyzed.Result indicated that the light emission was due to the excitation of Surface Plasmon Polariton(SPP)and the couple of SPP with the surface roughness subsequently in the MIS system.We observed the negative resistance phenomenon(NRP) in the I-V curve of this MIS junction,which was explained by the electrons bonding model. We also got the AFM(atomic force microscopy)photo of the surface of MIS junction, by which the relation among the electrons tunneling, the excitation of SPP,and the light emission of the MIS junction was discussed.
2000, 49 (6): 1163-1167.
doi: 10.7498/aps.49.1163
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Breakdown characteristics of the thin gate oxide are measured under constant voltage stresses. Breakdown mechanism of time-dependent dielectric breakdown are studied and effects of the areas of the gate oxide on breakdown characteristics are discussed. Breakdown charge QBD is measured and analyzed, the results show that breakdown charge QBD is not constant, it depends on the areas of the gate oxide and the voltage of the gate. Relative coefficients are fitted and analytical expression of QBD is presented in the paper.
2000, 49 (6): 1168-1170.
doi: 10.7498/aps.49.1168
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Monte Carlo simulations of critical dynamics has been used to study the short-time process and scaling behavior of two-layer Ising model. The result shows that there are critical points even when the coupling between the two layers is not equal to zero; the short-time dynamic critical exponent θ was determined; the traditional critical exponent 1/νz was estimated also.Our result encouraged the supposition of the existence of the critical line and evidenced that this model was likely a weak universal model.
2000, 49 (6): 1171-1175.
doi: 10.7498/aps.49.1171
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The heavy-hole—heavy-hole scattering in GaAs has been investigated by taking into account the static screening of the excited carrier Gaussian distribution. It has been shown that the scattering rate decreases strongly with the decrease of the initial energy of heavy holes. This can be attributed to the effects of static screening and the overlap of the |p〉 like wave functions of excited carriers. The overlap of the |p〉 like wave functions reduces the scattering rate by a factor of 3 for the low heavy-hole energy. The theoretical predictions are in good agreement with the experimental results.
2000, 49 (6): 1176-1179.
doi: 10.7498/aps.49.1176
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This article analyze the physics of up-conversion process excited by CW laser. The key metastable state is very important because it initiates the up-conversion process.By analyzing the dynamic process of the key metastable state, a qualitative “population branching ratio β” model is proposed. The physical significance of this method is that it helps to understand the general characteristics of up-conversion.Further analysis indicates, spontaneous emission Ａ and non-radiative relaxation Wn do act simultaneously.And the reason why the up-conversion fluorescence of quartz,pentaphosphate non-crystalline is about ten thousand times smaller than that of fluoride glass is that their multi-phonon nonradiative relaxation rate Ｗn is much larger than the spontaneous emission rate Ａ. We also report the benefit value and the condition Wn＜A of phonon for up-conversion.
2000, 49 (6): 1180-1184.
doi: 10.7498/aps.49.1180
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Blue-emitting porous silicon(PS) prepared by hydrothermal etching was treated by rapid thermal oxidation (RTO) process.Accompanying with the blue shift of the whole photoluminescence(PL) spectrum, the previous single PL peak split into two separate PL peaks. Simultaneously, the size-reduction and size-separation of the silicon nanocrystallites were observed. This result indicates that the short-wavelength emissions in PS are also strongly size-dependent.
2000, 49 (6): 1185-1190.
doi: 10.7498/aps.49.1185
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On the basis of a brief presentation of the characteristic for the Fibonacci-class quasilattices (FC(n)),the properties of the spectra were studied for the second harmonic light (SHL) through the N layers ferroelectric superlattices constructed following FC(n) by means of the small-signal approximation.It was found that in the real space there existed perfect self-similarity for the most intense spectral peaks of SHL.On the other hand,the self-similarity for the spectra will be broken if the refractive dispersion is taken into account.The effect of vacancies which was valid only for the SHL's dim spectra lines but invalid for the bright ones is also discussed.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
2000, 49 (6): 1191-1195.
doi: 10.7498/aps.49.1191
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The resistance-temperature properties of the complex conductive silicone rubber were studied.The change of the resistance of the conductive silicone rubber during the process of rising temperature was analyzed,and the influences of the content of conductive fillers on the resistance-temperature properties of the complex conductive silicone were studied in detail.The specific resistivity changes at different annealing temperatures and the resistance relaxation time with pulling force were measured,and the influence of thermal treatment and content of conductive fillers on the mechanism of the resistance properties was also analyzed.
2000, 49 (6): 1196-1201.
doi: 10.7498/aps.49.1196
Abstract +
Good adherent indium-tin oxide (ITO) (10wt% SnO2 impurity) films with a transmittance of about 80% in visible range and resistivity as low as 6.3×10-4Ωcm,were deposited on water-cooled PPA (Polypropylene adipate) substrate by bias r.f. magnetron sputtering.The transmittance in wavelength range of 300—550nm of these films was found to increase with the negative bias applied to the substrate.All these films have a preferred orientation of [222].The X-ray diffraction peaks of [200] decrease with increasing negative bias of the substrate.This means the number of crystal grains growing along [400] decreases.The grain sizes,as well as the conductivities of the films have a maximum value indicated by both AFM microscopy and XRD pattern in the range of -20—-40V of the bias applied to the substrate.The proper working pressure of argon is about 0.5—1Pa,and the proper impurity density of SnO2 is 7.5%—10%(w.t.).
LETTERS
2000, 49 (6): 1202-1205.
doi: 10.7498/aps.49.1202
Abstract +
Numeric simulation of compensating gain-narrowing in femtosecond Ti:sapphire amplifier by shaping seed pulse is made in this paper,the gain spectral narrowing process are compared for multipass amplifiers with general and shaping seeding pulses injection respectively.On this base,we define the band width narrowing ratio,the simulation results show the gain-narrowing effect can be well overcome by shaping laser pulses from oscillator.
