Vol. 46, No. 3 (1997)
1997-02-05
GENERAL
1997, 46 (3): 417-422.
doi: 10.7498/aps.46.417
Abstract +
Using the factorization method,four kinds of raising and lowering operators of a three-dimensional isotropic harmonic oscillator were derived and the corresponding selection rules and conserved quantum numbers were discussed.
1997, 46 (3): 423-427.
doi: 10.7498/aps.46.423
Abstract +
Using the factorization method,four kinds of raising and lowering operators of a two dimensional isotropic harmonic oscillator were derived, and the corresponding selection rules and conserved quantum numbers were discussed.
1997, 46 (3): 428-434.
doi: 10.7498/aps.46.428
Abstract +
Using the factorization method,the angular momentum raising and lowering operators of two-and three-dimensional hydrogen atoms were derived.The other three kinds of raising and lowering operators were also obtained by using the recurrence relations of hypergeometric function.The corresponding selection rules and conserved quantum numbers were discussed.The similarity between two-and three-dimensional hydrogen atoms was found.
1997, 46 (3): 435-441.
doi: 10.7498/aps.46.435
Abstract +
A group of evolution equations and a expression of the flow speed, in traffic describing a 2D cellular automaton traffic-flow model are presented.A turning probability is introduced into the model to simulate the traffic jam.The effects caused by the turning probability are abserved in computer simulation.
1997, 46 (3): 442-447.
doi: 10.7498/aps.46.442
Abstract +
By using the embedding techniques for reconstructing chaotic attractors,this paper proposes a macroscopic information entropy approach for identifying the delay in a chaotic time series sampled from a continuous-time system.The effectiveness of the proposed approach is illustrated through numerical experiments.
1997, 46 (3): 448-457.
doi: 10.7498/aps.46.448
Abstract +
The collision strength of excitation among configuration-average levels by electron impact in Auq+(q=47,55)ions are computed systematically by using the quasirelativistic distorted wave(QRDW)methods.We discuss the behavior of the collision strengths in high energy range and applicable condition of the plane wave approximation.It is shown that the QRDW method can reproduce major relativistic effects as compared with the fully relativistic distorted wave results of Zhang and Sampson et al.In this paper the collision strength are scaled and fitted with a least-square spline method.As a result thermal average rate coefficients in the entire range can be determined by five parameters for one transition process.We also offers some typical curves which demonstrate the variation of the collision strengths with electron energy and the variation of effective collision strengths and rate coefficients with electron temperature.The result shows that the discrepancy of single electron excited data of eight kinds of ions around Ni-like gold is lower than 10%.This is very favorable for the average atom(AA) model which simulates dynamics process in thermal plasma.
ATOMIC AND MOLECULAR PHYSICS
1997, 46 (3): 458-466.
doi: 10.7498/aps.46.458
Abstract +
The absolute optical oscillator strength density spectrum of oxygen has been measured at an impact energy of 1.5 keV and a mean scattering angle of 0° in an energy region of 5.7—28.5 eV with typical FWHM 60 meV.The absolute optical oscillator strengths corresponding to vibrational levels of E3Σ-ｕ,ν′=0,1,2 and 23Πｕ,ν′=0,1 are reported and compared with previous experimental and theoretical results.The validity and accuracy of the Bethe-Born conversion factor is confirmed down to 6 eV by comparison.
CLASSICAL AREA OF PHENOMENOLOGY
1997, 46 (3): 467-473.
doi: 10.7498/aps.46.467
Abstract +
By making use of thermo-field dynamics(TFD),we construct the thermal Kerr states with finite temperature.We investigate the quantum statistical properties of these states and their dependence on temperature.We discuss the fluctuations of amplitude in these states and squeezing.We also introduce the definition of thermosqueezing for thermalized states and discuss the effect of temperature on thermosqueezing for thermal Kerr states.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
1997, 46 (3): 474-480.
doi: 10.7498/aps.46.474
Abstract +
The turbulence driven by ion temperature gradient,mass flow shear,parallel to the magnetic field,and the impurity ion density gradient in plasmas with multiple ion species is studied in a sheared slab magnetic configuration.The particle diffusion induced by the turbulence is obtained with quasi-linear fluid theory.The possible inward ‘pinch' of the majority ions and the inward flow of the impurity ions,depending on plasma parameters,are both calculated,and the corresponding diffusion coefficients are given.It is shown that the increase of parallel velocity shear may have benificial effects on plasma confinement.The correlations with Tokamak experimental observations are discussed.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1997, 46 (3): 481-485.
doi: 10.7498/aps.46.481
Abstract +
Entirely (111) oriented C60 single films are grown successfully on GaAs (100) substrate by a physical vapor deposition technique with double temperature zone.The structure and morphology of films are studied by X-ray diffraction and SEM.The results show that the highly oriented growth of C60 films occurs only at narrow range of substrate temperature,higher or lower substrate temperature leads to random orientation of grains.A reasonable explanation for experimental results is given and the growth mechanism of C60 epitaxial films is discussed.
1997, 46 (3): 486-489.
doi: 10.7498/aps.46.486
Abstract +
The concept of restricted-branched random fractal is suggested and the fractal dimension has been calculated with the statistical theory of branched random growth.The result shows that the fractal dimension of ideal random-fractal would be between 2 and 4.Finally,a discussion about the linear degree of random fractal shows how it is related to the anisotropy of the interactions in physical systems.
1997, 46 (3): 490-499.
doi: 10.7498/aps.46.490
Abstract +
The amorphous Ni88P12 alloy films were prepared on the p-Si(100) substrate by chemical deposition in solution at 363K. The structure, composition and morphology of the films were studied by STM, AFM, XRD and XPS before and after the treatment of oxidation, reduction and crystallization. The results showed that the amorphous Ni88P12 alloy film was in the form of the micrometre-scale grains and each of which consisted of nanoparticles. The surface crystallization started as the films were oxidized and reduced at the temperature lower than that at which crystallization occurred. The morphological feature of the crystallites developed from the nanophase of the amorphous film was also observed after crystallization.
1997, 46 (3): 500-504.
doi: 10.7498/aps.46.500
Abstract +
Formation and shape of the gold islands formed by vacuum deposition on the highly oriented pyrolytic graphite (HOPG) surface has been studied by means of scanning tunneling microscopy (STM). In the early stage of formation, gold atoms tend to aggregate into large clusters, which may be disturbed easily by the STM tip in the course of imaging. With the increasing coverage, the gold clusters can move and coalesce into large oblong islands, and the islands can further aggregate into clusters with variable shapes. When the coverage reaches about 20 monolayers, the islands or island clusters can be imaged without being disturbed by the tip, provided that the tunneling resistance is high enough. It has been noticed that the islands have a very similar ratio of width to height. The value of this ratio indicates that the islands essentially have a thermodynamically equilibrium shape. Such islands formed by self assembly may have potential in investigations of mesoscopic physics as well as applications.
1997, 46 (3): 505-510.
doi: 10.7498/aps.46.505
Abstract +
It is demonstrated that nanometer-sized gold single crystal islands or even clusters of the islands,which were formed by deposition of gold onto an air-cleaved highly oriented pyrolytic graphite (HOPG) surface,can be manipulated on the surface in a controllable manner with the tip of a scanning tunneling microscope when the tunneling conductance is set to a large value. Since the tip does not disturb the islands if the tunneling conductance is small enough,even the islands are repeatedly scanned over by the tip, the results of the manipulation can thus be imaged with the same tip. The mechanism of the manipulation is suggested to be that at large tunneling conductance a metallic cohesive force may form between the tip and islands and may exceed the frictional force between the islands and the HOPG surface.
1997, 46 (3): 511-523.
doi: 10.7498/aps.46.511
Abstract +
The structures in β-BaB2O4(BBO) growth solutions, which are BaB2O4-Na2O binary melts with different molar concentrations of Na2O(12.5%,20%,25%,30%), have been studied by molecular dynamics simulations. The simulated B-O radial distribution functions with different Na2O concentrations show that the first peaks become high and sharp with the increasing of Na2O concentration. Based on the instantaneous configurations given by the simulations, the local structures of the binary melts were analyzed by means of the bond order parameter method combined with the statistics of rings and chains. The results indicate that the adding of Na2O as a flux into the melt systems will make more planar BO3 structure units and more isolated BO3, B2O5 and B3O7 clusters while the network in the melts will be greatly weaken, which are all beneficial to the forming boroxol groups B3O6 and the growing of BBO crystal. The statistics also shows that the percentages of B atoms in isolated BO3 and the percentages of B atoms in long chains are in good agreement with the experimental values of volatility and viscosity of hte solution systems, respectively.
1997, 46 (3): 524-529.
doi: 10.7498/aps.46.524
Abstract +
It is very difficult to obtain SiC polytypes distribution by normal X-ray powder diffraction quantitative phase analysis methods. The whole pattern fitting Rietveld method is introduced to address this problem. The principle and advantages of Rietveld method in determining SiC polytypes distribution are described. The final results show that the distribution of the most common four SiC polytypes, 6H, 4H, 3C and 15R, can be given accurately. The detection limits of each polytypes are also estimated based on their standard deviations
1997, 46 (3): 530-535.
doi: 10.7498/aps.46.530
Abstract +
Nitride carbon thin films have been deposited by plasma-enhanced chemical vapor phase deposition. The results of transmission-electron diffraction indicated that films have polycrystal structures. Carbon and nitrogen atoms binding energies and the nitrogen content of the-films are measured out by X-ray photoelectron spectroscopy.The Fourier transform infrared spectrum show that there is no graphite phase in the films,and the Vickers hardness of the films vary from 29.2 to 50.0GPa.
1997, 46 (3): 536-543.
doi: 10.7498/aps.46.536
Abstract +
The longitudinal diffusion equation of the solute atom along dislocation core for P′1 peak is numerically solved and the P′1 peak is derived on the base of dislocation kink atmosphere model. The variation of internal friction and modulus defects with temperature and strain amplitude is calculated. The theoretical and experimental results are compared and found to be in consistence with each other. Therefore, the P′1 peak can be quantitatively explained.
1997, 46 (3): 544-549.
doi: 10.7498/aps.46.544
Abstract +
CO+Cs/Ru(101-0) system has been investigated using HREELS. Two molecular adsorption states of CO were found. One with higher C—O frequency was similar to that on clean Ru(101-0) surface, while the other with lower C—O frequency appears on a Cs-precovered Ru(101-0) surface. Two states of CO were occupied sequentially during the exposure to CO. The frequencies of both two loss peaks shift to higher values with exposure to CO and to lower values with higher Cs precoverage.
1997, 46 (3): 550-555.
doi: 10.7498/aps.46.550
Abstract +
BaTiO3/YBa2Cu3O7-δ bilayer structures have been synthesized on SrTiO3 substrates using the pulsed laser deposition technique. The X-ray analyses show that the BaTiO3 films are highly c-axis oriented. In the studies of dielectric and ferroelectric properties of the BaTiO3 films, typical hysteresis loops and butterfly C-V plots are observed. The results indicate that the BaTiO3 films are promising in FRAM and related application fields.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1997, 46 (3): 556-562.
doi: 10.7498/aps.46.556
Abstract +
Photoconductivity (PC) spectra of impurities in n type GaAs under magnetic field are presented. The resonant interaction between high excited states of bound electrons and LO phonons under relatively low magnetic field was observed. The magnetic field dependency of PC response of resonant polaron and the physical origin of the PC peak stuck on the energy position of LO phonon are discussed.
1997, 46 (3): 563-567.
doi: 10.7498/aps.46.563
Abstract +
The structures of three-electron systems of three-dimensional quantum dots are investigated via an analysis of quantum mechanical symmetry and the possibility of magic numbers exitence is pointed out. We compared it with the magic numbers of three-electron systems of two-dimensional quantum dots. Within the effective-mass approximation, the energy spectra of three-electron systems in a parabolic potential (?ω0=2meV) are calculated. The results show that there is the trace of the magic numbers exitence. The ground state of three-electron systems of three-dimensional quantum dots is 1- state.
1997, 46 (3): 568-578.
doi: 10.7498/aps.46.568
Abstract +
Using Green's function approach and the Kubo formula,have studied the electronic transport in metallic films.Taking into account the quantum size effects and the scattering of impurities and two rough surfaces,we calculate the one-particle Green's functions and the in-plane conductivity.It is found that (1) the density of electrons,the impurity mean free path,and the conductivity in a metallic film show oscillations as a function of its thickness with a period of half the Fermi wavelength;(2) under the approximation of the lowest order in the surface scattering,the conductivity formula obtained can reduce to the quasiclassical result suitable for thick films as well as the previous quantum formula for thin films.
1997, 46 (3): 579-586.
doi: 10.7498/aps.46.579
Abstract +
The nonlinear optical properties of Fe2O3 nanoparticles coated with a layer of organic molecules(DBS) in toluene and bare nanoparticles in hydrosol have been studied in the transparency region by Z scan technique.The key parameters such as nonlinear refractive index γ,two-photon absorption coefficient β and the variation of refractive index per unit photoexcited carrier density σr as well as free-carrier absorption cross section σab were determined.The influences of free-carrier effects on optical nonlinearities of Fe2O3 nanoparticles were discussed.
1997, 46 (3): 587-595.
doi: 10.7498/aps.46.587
Abstract +
The band lineup of a Ge/ZnSe(100) polar interface has been studied by synchrotron radiation photoemission spectroscopy.Surface sensitive core level spectra indicate that Ge atoms in the overlayer can react with Se atoms at the interface.The valence band offset of this heterojunction has been obtained using core level techniques,and found to be 1.76±0.1eV.The effect of polar surface ZnSe(100) on the valence band offset has been discussed in light of the interface bond polarity model.The experimental results agree well with the theory.
1997, 46 (3): 596-603.
doi: 10.7498/aps.46.596
Abstract +
Using the two-component model with the mixing of itinerant carriers and nearly localized carriers with negative -U correlation we study the Josephson effect along c-axis on YBCO/Pb junction.In this model the itinerant carriers have s-wave symmetry and smaller energy gap.The nearly localized carriers have d-wave symmetry and its critical temperature establishes the superconducting transition temperature of the system.the Josephson current is contributed completely by the s-wave.Using the calculated s-wave energy gap and the corresponding critical temperature we have quantitatively explained the product of Josephson current at 0K and junction resistance, Ic(0)RN ,and the variation of Ic with temperature.In addition,we can explain the observed variation of Ic with bias voltage and the Fraunhofer pattern,and the model is consistent with other SQUID experiments probing the symmetry of order parameter of YBCO.Therefore,the two-component model gives a consistent explanation for the two kinds of experimental results which seem to contradict with each other.We also briefly discuss the experimental method which can distinguish different models.
1997, 46 (3): 604-611.
doi: 10.7498/aps.46.604
Abstract +
There is evidently a difference between the dynamic and static Faraday effects in magnetooptical medium.The real part θ′t of the alternating Faraday rotation θt all is less than the real part θ′s of the static Faraday rotation θs,and the imaginary part θ″t all is bigger than the imaginary part θ″s.It is shown by the experimental result of Faraday effect in (BiTm)3(FeGa)5O12 films that the frequency dependence of θt has a direct bearing on the mechanism of magnetic lag in the high-frequency region of ω>104Hz,and is mainly depend on the magnetic hysteresis in the low-frequency region of ω≤103Hz.Even if ω→0,θt does not equal θs as a result of the magnetic hysteresis loss in the medium.It is also indicated by the theoretical analysis that it is impossible to realize completely the on off state of the switch for a modulator utilizing the magnetooptical medium with magnetic losses.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
1997, 46 (3): 612-617.
doi: 10.7498/aps.46.612
Abstract +
A novel passivation film on GaAs surface has been grown by microwave sulfur glow discharge technique.Electronic properties of GaS/GaAs interface have been studied by C-V,I-V, and DLTS measurements.C-V measurement shows that the properties of GaS/GaAs interface are nearly ideal and interface state density is about 1012／（cm2·eV),which agrees with result from DLTS measurement.From leak current of MIS′s structure in I-V spectra,the resistivity of GaS is estimated about 1011Ω·cm.
1997, 46 (3): 618-624.
doi: 10.7498/aps.46.618
Abstract +
Diamond films were alternatively deposited on alumina ceramic wafers by microwave plasma chemical vapor deposition (MPCVD) and hot-filament chemical vapor deposition (MPCVD).The qualities of the deposited diamond films deposited on different wafers with different deposited techniques were appraised by the method of fitting the spectra, and the domain size and strain of the films were calculated.The results of calculation were consistence with that derived from the X-ray diffraction analyses.
