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Vol. 42, No. 4 (1993)

1993-02-20
GENERAL
DYNAMICS OF ROTATIONALLY SYMMETRIC SINE-GORDON SOL1TONS WITH APPLLCATIONS FOR A LARGE AREA JOSEPHSON JUNCTION
WANG QIANG-HUA, YAO XI-XIAN
1993, 42 (4): 513-521. doi: 10.7498/aps.42.513
Abstract +
The dynamics of rotationally symmetric sine Gordon solitons of large radius under poten-tial and dissipative perturbations is considered, with the help of a collective-coordinate desc-ription of the soliton and the Lagrangian variation method. The particle-like character of the soliton is emphasized The equation of motlon and in particular, the general momentum of the soliton are obtained in a canonical manner. It is possible to discuss the dynamics of the soliton even without applying the explicit form of the perturbating potential All dyna-mical regimes in the phase space are explored. Such phenomena as the soliron return effect, soliton escaping and saddle point are addressed In the presence of dissipation, the corrected equation of soliton motion is obtained from the generalized variational equation. Finally, the application of the theoretical treatment is considered for the fluxon dynamics in a circularly symmetric Josephson junction. The analytical results are examined by direct numerical simu-lations, fairly good agreements being achieved. it turns out that the presented ueaMnem provides a reliable description of the dynamics of the sol tons considered.
DOUBLE WAVE FUNCTION DESCRIPTION FOR SPACE ROTATOR SYSTEMS IN CARTESIAN COORDINATE
LIU QUAN-HUI
1993, 42 (4): 522-527. doi: 10.7498/aps.42.522
Abstract +
In this paper, a complete, so-called double wave function description for space rotator systems in Cartesian coordinate is given. The time evolution equation for every observable in the coordinate is presented. The classical mechanical time evolution equations are found as the classical limit case of the evolution equations. And the conventional quantum mechanical description is yielded in two equivalent statistical cases. Our studies show that the Cartesian coordinate offers more perfect description than the spherical polar one does.
ALGEBRAIC PROPERTIES OF THE SEMI-PLANE-SYMMETRIC STATIC SPACE-TIME YIELDED BY SEMI-PLANE-SYMMETRIC NON-NULL ELECTROMAGNETIC FIELDS
QIANG WEN-CHAO
1993, 42 (4): 528-535. doi: 10.7498/aps.42.528
Abstract +
The spin coefficients and the tetrad components of the Weyl tensor of the semi-plane-sym-metric static space-time yielded by semi-plane-symmetric non-null electromagnetic fields are found, It is shown that this space-time is of Petrov type I. The behavious of null-vectors and optic scaiars are also discussed.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
A GAUGE INVARIANT VERSION OF SELF-DUAL THEORIES AND ITS QUANTIZATION
MIAO YAN-GANG
1993, 42 (4): 536-543. doi: 10.7498/aps.42.536
Abstract +
For a newly proposed Lagrangian of self-dual fields interacting with gauge fields, we cal-culate its one-cocycle condition, i.e. Wess-Zum ino term, and construct its gauge invariant ver-sion. Through canonical quantization we show that the gauge invariant theory in a proper gauge-fixing is equivalent to its gauge noninvarianr version. Moreover, by using the Baralin-Fradkin-Vilkovisky formalism, we point out that the equivalence is gauge independent.
STRUCTURE OF THE ENERGY SPECTRUM FOR THE BOUND STATES OF A CHARGED FERM1ON AND A DIRAC DYON WITH ZZd?137
QI YONG-CHANG
1993, 42 (4): 544-550. doi: 10.7498/aps.42.544
Abstract +
It is found that the energy spectrum of the bound states of a charged fermion and a Dirac dyon is divided into many series of spectral lines according to the different K=n + [μ]integer as ZZd?137. The features of the structure are discu-ssed. The Zeeman effect for the system is also discussed.
STATISTICAL THEORY OF SC LIQUID CRYSTALS
YANG GUO-CHEN, QIAN XIANG-ZHONG
1993, 42 (4): 551-562. doi: 10.7498/aps.42.551
Abstract +
With cell model the integral equation of distribution function is obtained by minimiza-tion of the free energy function. The orienrational order parameter, the positional order pa-rameter and their coupling are defined. By a proper choice of the interaction potential, the approximate solution of the distribution function is obtained, and also for free energy. We find that SC-SA phase tdansition can be either the second order or the first. We have calcu-lated the temperature dependence of the tilt angle and of the order parameter, as well as the ent-ropy change and the heat capacity near the critical point for TBBA, TB8A and NOBA. The variation of the phase transition temperature with molecular chain length for homologous series of TBBA and 4-n-alkoxybenzylidene-4'-aminozobenzenes are also calculated. Our calculations agree satisfactorily with experimental results.
ATOMIC AND MOLECULAR PHYSICS
ELECTRONIC STRUCTURE AND SHAPE RESONANCE OF DIATOMIC MOLECULE C2 AND C2+ AND C2-
LIU LEI
1993, 42 (4): 563-567. doi: 10.7498/aps.42.563
Abstract +
We present a theoretical study of electronic structures and shape resonances of diatomic molecule C2 and C2+ and C2- Shape resonances are essentially quasi-bound states which are intimately connected with antibonding molecular orbitals. It is found that as the number of electrons decreases, the energy positions of the shape resonances shift downward, and as the corresponding antibonding molecular orbitals lie below the ionization threshold, the shape resonances disappear.
CLASSICAL AREA OF PHENOMENOLOGY
THE INFLUENCE ON THE LIGHT SQUEEZING DUE TO VIRTUAL PHOTON PRECESSES
LI GAO-XIANG, PENG JIN-SHENG
1993, 42 (4): 568-574. doi: 10.7498/aps.42.568
Abstract +
In this paper, we have examined the influence of the counter-rotating terms on the sque-ezing phenomenon of the field in the two-photon Jaynes-Cummings model by means of the non-relativestic quantum electrodynamics. We verified that the effect of the virtual photon field in-creases the squeezing. The relation between the degree of squeezing and the field frequency, the mean photon number and the atom-field coupling constant has also analyzed.
SOLITON CHARACTERISTICS OF GAUSSIAN OPTICAL PULSES PROPAGATION IN THE NONLINEAR GAIN MEDIUM
SUN JUN-QIANG, HUANG DE-XIU, LI ZAI-GUANG
1993, 42 (4): 575-581. doi: 10.7498/aps.42.575
Abstract +
In this paper, propagation of Gaussian optical pulses in the nonlinear gain medium is ana-lyzed theoretically. The mechanism of Gaussian optical pulses compression, broadening and optical soliton formation is also explained. Gaussian optical pulses with different parameters propagating in nonlinear gain medium are simulated with computer. The change of pulse width during the propagation is obtained. The results indicate that it is possible for the ini-tial Gaussian optical pulses with different peak power to form different order solitons in the medium, nevertheless, their propagation distance is limited due to the existence of gain.
THEORETICAL CALCULATION FOR MODULATION TRANSFER SPECTROSCOPY
DING LIANG-EN, MA LONG-SHENG, BI ZHI-YI
1993, 42 (4): 582-591. doi: 10.7498/aps.42.582
Abstract +
Based on density matrix equations, we studied the interaction process among phase-modula-ted beams, unmodulated beam and a cascade three-level system. Calculations of the line shape of optical heterodyne modulation transfer spectroscopy via nearly-degenerate four-wave mixing were made. The results show that the Doppler background due to the near resonance of the in-termediate level is eliminated and the signal of two-photon transition can be distinguished from saturation absorption.
A CALCULATION METHOD TO OBTAIN NONLINEAR INTER-NAL FRICTION MATERIAL PARAMETERS FOR THE MEASUREMENT WITH TORSIONAL PENDULUM
SUN ZONG-QI, YAN DE-QIN
1993, 42 (4): 592-596. doi: 10.7498/aps.42.592
Abstract +
Assuming the smallness of the internal friction which depends only on the amplitude of shear strain, based on analytical mechanics, we developed a calculation method to obtain non-linear material parameters of internal fiction and shear modulus from the sampled data of tor-sional displacements of the free-decay oscillation for the torsional pendulum.
NUMERICAL SIMULATION OF UNSTEADY THERMAL CONVE-CTIVE PROCESS IN CZOCHRALSK1 CRYSTAL GROWTH
TAO FENG, MA WEN-JU, ZHENG YUN, XUE MING-LUN
1993, 42 (4): 597-604. doi: 10.7498/aps.42.597
Abstract +
A numerical study for representing time-dependent natural convection of Czochralski melts, while the growing crystal and crucible do not rotate, is presented in this paper. Using a finite control volume algorithm with central-diference discretization of advective and diffusive fluxes, the Czochralski flow which is governed by the rwo-dimensional N-S equations based on Bous-sinesq approximation is computed. The calculations present some interesting streamlines and isotherms with typical time, total kinetic and thermal energy as function of time. The time-de-pendent transport phenomena in Czochralski melt extend into oscillatory for Gr = 1.6×106 in Pr=0.015. This results obviously influence the thermal fluxes at the crystal-liquid interface. The unsteady simulation in this paper is much helpful for the recognition of natural convection and actural crystal growth in Czochralski melts. The program are also available to other models of Czochralski crvstal growth.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
INVESTIGATION OF LaAlO3 CRYSTAL STRUCTURE
H. BOYSEN, YU YU-DE, XIE SI-SHEN
1993, 42 (4): 605-609. doi: 10.7498/aps.42.605
Abstract +
X-ray diffraction, neutron scattering and thermal analysis were used to determine the room temperature crystal structure of LaAlO3 and its phase transition. Two different models were calculated and compared. Tht space group of room temperature LaAlO3 is determined as R3C (a= 5.3648 ± 2?, c = 13.1113±3?). The influence of orientation of AlO6 octahedron or room temperature LaAlO3 crystal on the phase transition was studied.
EFFECT OF Pd2Si FORMATION ON X-RAY DIFFRACTION OF Pd/Si MULTILAYERS
YIN SHI-LONG, WANG BING, GAO CHEN, WU ZI-QIN, WANG XIAO-PING, ZHAO TE-XIU
1993, 42 (4): 610-616. doi: 10.7498/aps.42.610
Abstract +
The effect of Pd2Si formation on the X-ray diffraction of Pd/Si periodic multilayer films after annealing has been studied by X-ray diffraction in small and high angle regimes. The results show that the influence of Pd2Si in small period multilayers is more severe than that in large period multilayers. The periods of multilayers have been calculated with one peak posi-tion or with two peak positions after introducing the refractive correction, and the latter is more accurate than the former. The results of simulation show that an uniform Pd2Si layer formation in a period is not enough to explain the large variation of intensity after annealing. Roughness of the interface is another important factor to influencing the diffraction intensity.
ELECTRONIC STRUCTURES OF SOLID GALLIUM
GONG XIN-GAO
1993, 42 (4): 617-625. doi: 10.7498/aps.42.617
Abstract +
The electronic structures of solid gallium have been calculated by ab-initio moleculardyna-mics, the results are good in agreement with experiments. The results show that β-Ga, Ga-Ⅱ, fcc-Ga are metallic-like, but in α-Ga there is a covalent bond existing between the nearest neighbours. The phase stability of solid gallium has been also discussed.
BORRMANN IMAGE OF DISLOCATION IN THE CRYSTAL OF THALLIUM ACID PHTHALATE
GUAN TIE-TANG, ZHAO QING-LAN
1993, 42 (4): 626-630. doi: 10.7498/aps.42.626
Abstract +
The crystal of thallium acid phthalate (TAP) is a newly developed X-rays analyzing ele-ment with higher diffraction power. The Bormann image of the spiral dislocations has been observed and studied by means of X-ray topography. It is shown that the image contrast with fine structure nearly in the core of dislocation is decreasing not only with decreasing the crystal thickness, but also with decreasing the Borrmann coefficient s so greatly as to blur or even to make the fine contrast information loss completely when the images are inversed from "white" to "black" in the contrast.
ELECTRONIC STOPPING POWER AND EFFECTIVE CHARGE OF HEAVY ION-BEAM IN HOT TARGETS
WANG YOU-NIAN, MA TENG-CAI, GONG YE
1993, 42 (4): 631-639. doi: 10.7498/aps.42.631
Abstract +
Using linear-response dielectric theory, we have investigated the electronic stopping power and effective charge of heavy ionbeams in hot targets. For considering the charge distribution of the electrons bound to the projectile, the theoretical model of Brandt-Kitagawa is generali-zed to the situation of hot target. In the case of low and high velocities, the analytical expres-sions of the electronic stopping power and the effective charge are obtained, respectively. For low-velocity ion, it has been shown that the values of the effective charge are increased as the values of the electron gas temperature are increased. In certain temperarure range the values of the stopping power in the hot target are increased comparing with that in the cold target. For high-velocity ions in the hydrogen plasma, the theoretical values of the stopping power obtained in present work agree very well with experimental data.
STUDY OF OPTICAL-PHONON DEFORMATION POTENTIALS ON Λ-AXIS FOR III-V COMPOUND SEMICONDUCTORS
WANG REN-ZHI, ZHENG YONG-MEI, WU SUN-TAO, HUANG MEI-CHUN
1993, 42 (4): 640-646. doi: 10.7498/aps.42.640
Abstract +
The study of optical-phonon deformation potentials (ODP*s) versus wavevector on 1111A-axis in Brillioun zone for nine III-V compound semiconductors is carried out systematically, based on ab initio LMTO-ASA band calculation within the frozen-phonon approximation model. The ODP*s d30(∧),d10(∧,val) and d10(∧,con) obtained from the calculation are presented.
MULTIPLE-SCATTERING THEORETICAL STUDY ON NEAR-EDGE X-RAY ABSORPTION SPECTRA OF C2H4/Ni(100)
FENG XIAO-SONG, TANG JING-CHANG
1993, 42 (4): 647-655. doi: 10.7498/aps.42.647
Abstract +
In this paper the carbon K-edge near edge X-ray absorption fine strucure spectra (NE-XAFS) of adsorption system C2H4/Ni(100) are calculated by multiple-scattering cluster method. By a conparison between the theortical results and experimental spectra, the chemisorption geo-metries of this system are determined. The results show that the molecule is adsorbed on the perpendicular bridge site, and the distance between the C atom and the nearest Ni atom is 1.70? while the molecular plane tilting to the surface with 50°.It is found that the interaction between H atom and Ni substrate plays an important role in the formation of the adsorption structure. These results are verified by other ways.
INTERFACE DIPOLES FOR (111) SEMICONDUCTOR HETERO-JUNCTIONS AND THEIR INFLUENCES ON BAND OFFSETS
LU DONG, XIE JIAN-JUN, ZHANG TAO
1993, 42 (4): 656-664. doi: 10.7498/aps.42.656
Abstract +
The interface dipoles for (111) lattice-matched semiconductor hererojunctions are calcula-ted employing the tight binding interface-bond-polarity model. The calculated results are com-pared with that of (110) and (001) interfaces. The effects of the interface orientation and the interface composition on the interface dipoles are discussed. It is shown that the dependence of the interface dipoles on the interface orientation and the interface composition is very weak tor isovalent heterojunctions, therefore the corresponding band offsets are almost isotropic; the anion-mixed (111) interface has a negative dipole and the cation-mixed (111) interface has a po-sitive one for nonisovalent heterojunctions, their average equals to the dipole of the nonpolar (110) interface.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
BLOCKSPIN SCHEME AND THE CLUSTER-UPDATING ALGO-RITHMS FOR THE QUANTUM SPIN SYSTEMS
U. J. WIESB, YING HE-PING
1993, 42 (4): 665-673. doi: 10.7498/aps.42.665
Abstract +
In this paper, we proposed a blockspin scheme and developed the usual cluster-updating algorithms for the one-and two-dimensional quantum spin systems, saying s=1/2 isotropic Hei-senberg models. The results for he ferro-and antiferro-magnet chains showed that the criti-cal slowing down (CSD) was indeed eliminated, and so it offered a possibility to improve the estimations in the lower-temperature region. We expect that the algorithms could also be ap-plied to the anisotropic or/and the higher-spin cases, as will as some other interesting models, such as eight-vortex lattice model and low-dimensional Fermi-systems.
APPLICATION OF TIME DOMAIN METHOD IN STUDY OF FE PHASE TRANSITION
LI JING-DE, LI JIA-BAO, FU SHI-LIU
1993, 42 (4): 674-680. doi: 10.7498/aps.42.674
Abstract +
The concept of time domain parameter is defined. In a small temperature region of (49±1)℃, dielectric spectroscopy of the time and frequency domains of a TGS single crystal is measured was FE phase transition of the crystal occurs. The results are devided into three components contributed by polarization of lattice, motion of electric domains, and activation of screen charges respectively. The latler two components make the ratio between static die-lectric constant and dielectric constant of acoustic frequency increase from 1 to 2.5 in this tem-perature region. The loss peak is provided mainly by screen charges, and the corresponding anomaly of free relaxation time appears near 48.615℃
ANISOTROPIC DIFFRACTION IN DOPED KNSBN PHOTOREFRACTIVE CRYSTAL
BIAN SHAO-PING, ZHANG JING-WEN, XU KE-BIN, JIANG QUAN-ZHONG, CHEN HUAN-CHU, SUN DA-LIANG
1993, 42 (4): 681-689. doi: 10.7498/aps.42.681
Abstract +
Two wave coupling equations on anisotropic diffraction in photorefractive crystal is deri-ved according to coupling wave theory. Phase gratig diffraction results of a He-Ne laser beam (λ= 632.8 nm) passing through tungsten bronze crystals KNSBN doped respectively Ca, Ce and Co are given. The anisotropic diffraction patterns of these three kinds of photorefractive crystals is formally analyzed using these coupling formulae. It is concluded that the anisotro-pic diffraction ring pattern will present in one of the two kinds of diffraction (e→o or o→e diffraction) for different (positive or negtive) unixial crystal. Theory analysis and experi-mental results agree fair by well.