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Vol. 43, No. 1 (1994)

1994-01-05
Topics
GENERAL
POISSON-LIE STRUCTURE OF LAX-PAIR MATRIX OF INTEGRABLE CLASSICAL NON-LINEAR SIGMA MODEL UNDER THE MOVING FRAME
DING XIANG-MAO, WANG YAN-SHEN, HOU BO-YU
1994, 43 (1): 1-6. doi: 10.7498/aps.43.1
Abstract +
We give out the Poisson-Lie brackets of non-linear σ model in O(3)/O(2) sy-mmetric space. Covariant properties from fixed frame to moving frame are discussed, in the process the covariant decomposing methods are used. The r-s-matrix independent of field except the connection of the space is found.
MOTION ROUTE OF PARTICLES FROM PERIOD TO CHAOS IN LOCAL FIELD
OUYANG BI-YAO, HE XIAN-TU, CHEN SHI-GANG
1994, 43 (1): 7-13. doi: 10.7498/aps.43.7
Abstract +
We have studied the whole process from period to chaos in which the charged particle move in the periodic local solitary field, given out the character of orbit in phase space and the scale. We demonstrate that: in conservative system,the particle move from period to chaos by quasi-periodic way; but in dissipative system, it is achieyed by doubling periodic bifurcated way.
NUCLEAR PHYSICS
THREE-BODY DYNAMICS OF LIGHT NEUTRON RICH NUCLEI 11Li,14Be AND 17B
DUAN YI-WU, LI CHU-LIANG, HUANG DU-ZHI
1994, 43 (1): 14-19. doi: 10.7498/aps.43.14
Abstract +
Based on the three-body model proposed by Ren and Xu[1],an improvement on their variational wave function has been made. The structures and the interparticle correlations have been explored by inspecting the correlated densities. A direct veri-fication supporting the neutron halo structure has been found.
CLASSICAL AREA OF PHENOMENOLOGY
A NEW TYPE OF DYE LASER USED FOR A FEMTOSECOND SQUEEZED STATE──Stability analysis and experimental study
DAI JIAN-MING, ZHANG RUO-BING, WANG QING-YUE
1994, 43 (1): 20-29. doi: 10.7498/aps.43.20
Abstract +
A theoretical model for the laser which can produce femtosecond squeezed state has been developed. The stability of the cavity has been analyzed in detail by numerical computation. A stable mode-locked pulse train with pulse width of 160 fs and repetition rate of 67MHz has been obtained, which afforded a new important means for the realization of femtosecond squeezed state.
ELECTRON ENERGY DISTRIBUTIONS AND TRANSPORT COEFFICIENTS FOR MAGNETICALLY CONFINED GAS LASERS
LI JUN, XU QIANG-HUA, CHEN QING-MING
1994, 43 (1): 30-36. doi: 10.7498/aps.43.30
Abstract +
The effects of magneticfield on electrons have been introduced into the normal Boltzmann transport equation for a novel laser system-the magnetically confined gas lasers. As an example the equation has been solved numerically for CO2 lasers. Curves are presented of electron energy distributions and transport coefficients under the influence of transverse magnetic field. Finally, an idea of improving gas laser-efficiency is proposed.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
KINETIC EQUATION AND TRANSPORTS OF PLASMA IN A CIRCULARLY-POLARIZED INTENSE LASER FIELD
SHENG ZHENG-MING, XU ZHI-ZHAN, MA JIN-XIU, YU WEI
1994, 43 (1): 37-46. doi: 10.7498/aps.43.37
Abstract +
The kinetic equation for electron in an intense laser field is derived by transio-rming the Fokker-Planck equation into the local coordinate system of electron oscl-llation in the field. The electron-ion collision in circularly-polarized light is calcu-lated, and the electron-electron collision is discussed. The plasma thermo-electric transports are studied for different intensity regions of the circularly-polarized laser field. It is found that, when the electron quivervelocity in laser field is comparable with its thermal velocity, the thermo-electric transports can be largely decreased as compared to the case without laser field.
STOCHASTIC CHARACTRISTICS OF MAGNETIC FIELD LINE IN TOKAMAK
ZHU XIONG-WEI
1994, 43 (1): 47-51. doi: 10.7498/aps.43.47
Abstract +
Under the cylindrical approximation, we apply nonlinear Hamiltonian oscilation theory to investigate the process of transition of perturbed equilibrium magnetic field to randomness. The results show that perturbed magnetic hamiltonian is only rela-ted to the radial perturbation of magnetic field, the magnetic field line takes the form of regular magnetic island under a single mode perturbation. The overla-pping criterion for magnetic field to enter the random state is given for the case of existence of two mode action, and the relation of points on the poincare section is reduced to a kind of standard mapping under special multimode perturbation.
NUMERICAL SIMULATION STUDIES ON FILAMENTATION IN COHERENCE AND INCOHERENCE LASER
ZHANG JIA-TAI, NIE XIAO-BO, SU XIU-MIN
1994, 43 (1): 52-63. doi: 10.7498/aps.43.52
Abstract +
The filamentation instabilities in coherence and induced spatial incoherence laser beam have been investigated by computer simulation using a two-dimensional three temp-erature MHD laser target code. A numerical analysis is employed based on the random phase plate smoothing techniques and resolving of laser beam propagarion equations for the coupled simplified hydrodynamic model to derive the effects on the filamentation;nstability. These results show that the filarnentaion instabilities may be suppressed or eliminated under some conditions.
A NEW METHOD FOR DETECTION OF THE ELECTRON TEMPERATURE IN LASER-PLASMA SHORT WAVE CUT OFF OF STIMULATED RAMAN SCATTERING SPECTRUM
ZHANG JIA-TAI
1994, 43 (1): 64-68. doi: 10.7498/aps.43.64
Abstract +
From the theory of stimulated Raman scattering (SRS) three wave interaction, a new method of detecting the electron temperature in laser-plasma is obtained. SRS spectrum obtained from Shenguang 12# Nd-laser experiments are analysed. Using the wave length of short wave cut off of SRS, the electron temperature in corona plasma region is calculated consistently. These results agree reasonably with X-ray spectrum experiments.
THEORY OF FWM TRANSMISSION AMPLIFICATION IN PLASMAS
MHNG YUE-DONG, HUO YU-PING, LI JIAN-GANG, LUO JIA-RONG
1994, 43 (1): 69-77. doi: 10.7498/aps.43.69
Abstract +
The theory of FWM transmission amplification of ordinary wave mixing in magnetized plasma is investigated. The exact solutions are derived for the degenerate and nondegenerate cases and are adapted for EM wave mixing in unmagnetized plasma.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
CHARACTERIZATION OF MICRO-DEFECTS IN SILICON SINGLE CRYSTALS BY ANALYZING THE PENDELL?SUNG FRINGES
LI MING, MAI ZHEN-HONG, CUI SHU-PAN
1994, 43 (1): 78-83. doi: 10.7498/aps.43.78
Abstract +
Based on the statistical theory of X-ray dynamical diffraction, a method to obtain the static Debye-Waller facter from section topographs is described. By analyzing the intensity distribution of the Pendelldsung fringes in the X-ray diffraction topograghs for heat treated CZ and MCZ silicon single crystals, the number density and the size of the oxygen precipitates which are smaller than X-ray topographic resolution are estimated. This quantitative analysis method provides a new means of studying the micro-defects.
STATISTICAL DYNAMICAL DIFFRACTION IN NEARLY PERFECT CRYSTALS
LI MING, MAI ZHEN-HONG, CUI SHU-PAN
1994, 43 (1): 84-90. doi: 10.7498/aps.43.84
Abstract +
A new expression of Takagi-Taupin equations is applied to nearly perfect crystals with statistical lattice distortion, with which a formalism of the dynamical diffraction is proposed. A static Debye-Waller factor E is introduced to characterize the crystal. A solution of the equations is presented which describe the intensity distribution due to a narrow incident wave in the topography of a statistically homogeneous crystal. The application of this theory to the measuring of the micro-defects in crvstals is discussed.
GROUND-STATE ENERGY OF THE POLARON IN A QUANTUM WELL WITHIN CONS I ANT ELECTRIC AND MAGNETIC FIELDS
HUANG ZHUO-HE, CHEN ZHI-DE, ZHANG SHU-QUN, CHEN CHUAN-YU
1994, 43 (1): 91-98. doi: 10.7498/aps.43.91
Abstract +
In this paper, the system of the electron-bulk LO-phonon interaction in a quantum well within constant electric and magnetic fields along the growth axis, is analysed by the method of variational wave-function and harmonic oscillator operator algebra. The representation of the ground state energy which includes the correction of the second-order perturbation is obtained as a funtion of the electron-LO-phonon coupling constant, the width of the quantum well, the strength of the electric and magnetic field. The results have shown that, the polaronic correction to electron ground state energy reduces with increasing well width and electric field, but enhances with increasing magnetic field.
PHONON DENSITIES OF STATES IN Fe-BASED AMORPHOUS INVAR ALLOYS
XIAN YU-ZE, LU ZHI-CHAO, SHEN BAO-GEN, LI JI ZHOU, YE CHUN-TANG, LI ZHU-QI, KANG JIAN
1994, 43 (1): 99-102. doi: 10.7498/aps.43.99
Abstract +
Generalized phonon densities of states (PDOS) for amorphous Fe90-xCoxZr10(x=10,40) and Fe80-yCryP13C7(y=4,8) alloys have been deduced from inelastic neutron scattering experiments. And the softening phenomena of the PDOS in the energy region below 17 meV have been observed for the amorphous Invar alloys. The anomalies in the dynamics of Invar alloys were discussed, and preliminary results show that the phonon softening of the amorphous Invar alloys may closely connected with the enhanced electron—phonon interaction in lnvar alloys.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
THEORETICAL STUDIES ON THE VALENCE-BAND OFFSETS AT STRAINED SEMICONDUCTOR SUPERLATTICES
KE SAN-HUANG, WANG REN-ZHI, HUANG MEI-CHUN
1994, 43 (1): 103-109. doi: 10.7498/aps.43.103
Abstract +
Ab initio calculations of electronic structure for strained superlattices (SLS) (GaP)1(GaAs)1(001) and (InP)n(InAs)n(001)(n=1,3) are carried out, the valence-band maximum Ev and the average bond energy Em in each molecular layer of SLS's are investigated with the frozen shape approach. The average-bond-energy method for determining valence-band offsets at SLS's are suggestted and tested comprehensively. Based on this method, the valence-band offsets at five SLS's under three strain conditions are determined, their strain-induced effects are discussed. The results of present work show good consistency with available experimental data.
THEORETICAL CALCULATIONS OF THE RELATION BETWEEN THE GIANT MAGNETORESISTANCE IN Fe/Cr SUPERLATTICES
MEI LIANG-MO, WU JIAN-HUA, LI BO-ZANG, PU FU-CHO
1994, 43 (1): 110-117. doi: 10.7498/aps.43.110
Abstract +
Based on the phenomenological theory of Camley and Barnas and coworkers (C-B), the dependence of magnetoresistance in Fe/Cr multilayers on the applied magne-tic field is calculated. In these multilayers an antiferromagnetic coupling exists between any two adjacent Fe-layers. The applied magnetic field is either parallel or perpendicular to the layers. Good agreement of the calculated results with the experimental ones is found. The symmetry implicitly involved in the C-B theory is disclosed and is used to simplify the original C-B formalism, this leads to the closed expressions for the distribution function of conducting electrons and for magnetore-sistance.
SCALING FORMULAE OF REFLECTION COEFFICIENT FOR LIGHT IONS
LUO ZHENG-MING, LI TAI-HUA
1994, 43 (1): 118-123. doi: 10.7498/aps.43.118
Abstract +
Recently, it has been found that the transport behavior of light ions possesses obvious scaling property and can be scaled by using a parameter called scaled transport cross-section. According to this important property, we present the universal fitting formulae for the particle reflection coefficient and the energy reflection coefficient. The argument of these formulae is the scaled transport cross-section. Compared with the reflection formulae, in which the reduced energy a is taken as a scaled parameter, our formulae show excellent single value corresponding relation.
TRANSITION TEMPERATURE AND THERMODYNAMIC PROPERTIES OF SUPERCONDUCTORS AS ANISOTROPIC FERMI SYSTEMS
YI XUE-XI, WANG XI-FU, WANG ZHI-XING
1994, 43 (1): 124-133. doi: 10.7498/aps.43.124
Abstract +
In this paper, we regard the superconductor as an anisotropic Fermi system, taking into account topological transitions of the electronicenergy. We have worked out the relationship between the transition temperature Tc and chemical potential, and other thermodymanic quantities on the basis of the model of three overlapping energy bands. The results are in agreenment with experimental data.
FLUXON GENERATION BY A CURRENT PULSE IN JOSEPHSON JUNCTIONS──THEORY AND SIMULATIONS
WANG QIANG-HUA, YAO XI-XIAN
1994, 43 (1): 134-145. doi: 10.7498/aps.43.134
Abstract +
The problem of fluxon generation in Josephson junctions by a current pulse is addressed, with the help of the inverse scattering transform theory. The threshold conditions for soliton (breather or fluxon) generation are obtained analytically, with respect to relevant studies in the same direction. The reliability of the theory is examined by direct numerical experiments. Fairly good agreements exist between the theory and the numerical results, particularly in the case of semi-infinitely long junctions. Practically long (L~10λ) Josephson junctions are also explored, namely, overlap, in-line and circularly-symmetric annular junctions. Explained are those factors that complicate the generation processes suck as boundary effects, stability of soliton states against the driving current, soliton return effect and the applied magnetic field (in annular junctions only). The current pulse method is shown to be effective and practical for fluxon generation in Josephson junctions.
THEORETICAL AND EXPERIMENTAL STUDY ON COE-RCIVITY MECHANISM OF SINTERED Nd-Fe-B PERMANENT MAGNET ALLOYS
ZHOU SHOU-ZENG, LI FO-BIAO, ZHANG LI-DONG, GAO RU-WEI, LI HUA, JIANG SHOU-TING, ZHANG YA-MING
1994, 43 (1): 145-153. doi: 10.7498/aps.43.145
Abstract +
The coercivity dependence of sintered Nd-Fe-B permanent magnet alloys an orienting magnetic field was studied. The results indicate that demagnetization process of the magnet is basically the nucleation process of anti-magnetization in the soft magnetization regions located at the surface of magnetic grains,and the process in which the nuclei grow into domains and irreversible domain wall displacement takes place from the surface to the inside of grains. We compared the value and the variation dependence of nucleation field with that of depinning field on the orientation of magnetic field. we come to the conclusion that depinning field is the main mech-anism controlling the coercivity of sintered Nd-Fe-B permanent magnet alloys.
A MICROMECHANISM FOR B IMPROVING THE MECHANICAL PROPERTIES OF MONO- AND POLYCRYSTALLINE Ni3Al ALLOYS
DENG WEN, XIONG LIANG-YUE, LONG QI-WEI, WANG SHU-HE, GUO JIAN-TING
1994, 43 (1): 154-160. doi: 10.7498/aps.43.154
Abstract +
The microdefects and electronic structure have been studied by measuring the positron lifetime spectra of mono- and polycrystalline Ni3Al alloys with B content ranging from 0.00 to 2.22at%,The experimental results show that the opening space of the defect on grain boundary is larger than that of a monovacancy in polycry-stalline Ni3Al alloy. More valence electrons participate in Ni-Ni and Ni-Al bondings in bulk corresponding to stronger cohesion, while less valence electrons parti-cipate in those on grain boundaries corresponding to weaker cohesion. When B atoms segregate to defects, they form strong covalent bondings with Ni and A1 atoms and strengthen the bonding cohesion in those locations. The interaction of B atoms which occupy interstitial sites,with Ni and Al atoms in bulk leads to the increase of the density of valence electrons, thus increases the bonding cohesion in the bulk.
A PRINCIPLE FOR MICRO-REGION SUPERPOSITING OF ION SPUTTERING
WANG ZHEN-XIA
1994, 43 (1): 161-168. doi: 10.7498/aps.43.161
Abstract +
Solid surfaces subjected to energetic ion bombardment generally develop chara-cteristic structures, which may significantly change total and differential sputtering yields. The change is due to several competing effects, for instance, change of the effective projectile incidence angle, recapture of obliquely ejected particles (shadow effect), and element local-enrichment in different micro-region on the alloy surface. From these, we have now developed an efficient new theoretical method for covering all of the above effects exactly. This method and its application to the analysis of experimental results of element (Cd) and alloy system (AlxSn100-x)targets are de-scribed in detail.