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Vol. 39, No. 8 (1990)

1990-04-20
GENERAL
COMPUTER SIMULATION OF FRACTAL BEHAVIORS IN a-Ge/Au BILAYER THIN FILMS
BI LING-SONG, WU ZI-QIN, HOU JIAN-GUO
1990, 39 (8): 1-6. doi: 10.7498/aps.39.1
Abstract +
Based on the experimental observation, two models were proposed to described the fractal formation in a-Ge/Au films with different interfacial structures. Computer simulations were done according to the above models, the results are in agreement with experimental observations. The results also show that the local latent temperature fields play a dominant role in the fractal formation process, and the appearance of dense branching morphology is due to the local diffusion effect.
NUCLEAR PHYSICS
NONLINEAR DYNAMICS OF ONE-DIMENSIONAL CRYSTALLINE BEAM (Ⅰ)
SHAO MING-ZHU, I. HOFMANN, LUO SHI-YU
1990, 39 (8): 7-17. doi: 10.7498/aps.39.7
Abstract +
A coherent oscillation equation for one-dimensional Coulomb chain has been derived, which is the well-know Duffing equation, and some single modes have been discussed. An approximate solution has been found, and stability of system has been analysed. Besides, we have derived the error of magnetic field and some thermodynamic parameters, and also some critical parameters for ESR at GS1 of FRG.
NONLINEAR DYNAMICS OF ONE-DIMENSIONAL CRYSTALLINE BEAM (Ⅱ)
SHAO MING-ZHU, I. HOFMANN, LUO SHI-YU
1990, 39 (8): 18-24. doi: 10.7498/aps.39.18
Abstract +
An equation for coherent oscillation excited by parameters for one-dimensional Coulomb chain has been derived, which includes constant cooling force. An approximate solution of the system has been found using a multiple scale method, and its stability discussed by classical method. Besides, we have also discussed global bifurcation of the system by Melnikov method, and derived a critical error of gradient field for ESR at GSI.
NONLINEAR DYNAMICS OF ONE-DIMENSIONAL CRYSTALLINE BEAM (Ⅲ)
SHAO MING-ZHU, I. HOFMANN, LUO SHI-YU
1990, 39 (8): 25-31. doi: 10.7498/aps.39.25
Abstract +
In the linear approximation the effects of periodic cooling and electron screening have been discussed, the equation of motion for ions has been reduced to the well-know Mathieus equation. Stability of the system and dynamical behaviour of cross over resonances by ions have been discussed also. Taking ESR at GS1 in FRG as example, the characteristic time for cross over resonances and the cooling time for the beam have been derived.
ATOMIC AND MOLECULAR PHYSICS
LINEAR STARK EFFECT OF THE n′dnl AUTOIONIZATION STATES OF Ca AND Sr ATOMS IN THE LOW-FIELD REGION
ZHANG SEN, QIU JI-ZHEN, MEI SHI-MIN, CHEN XING
1990, 39 (8): 32-37. doi: 10.7498/aps.39.32
Abstract +
The electric field effect on the 3dnl and 4dnl doubly excited autoionization states of Ca and Sr atoms have been observed using a multisiep laser excitation technique. The Stark spectra show that splittings of the Stark levels are linearly dependent on the applied electric field in the lowfield region of F5. We have observed also that the autoionization resonance broadens with increasing electric field because of field-induced mixing of nearly degenerate 1 substates, which can play important role for increase of dielectronic recombination rate in plasmas.
WEAK COUPLING METHOD FOR TREATING THE SCATTE-RING OF ELECTRONS BY COULOMB POTENTIAL IN WEAK LASER FIELD
LI JIE-PING
1990, 39 (8): 38-46. doi: 10.7498/aps.39.38
Abstract +
In a cicularly polarized radiation field (dipole approximation), for electrons scattered by Coulomb potential, the Schr?dinger equation is handled by using a unitary transformation and a dressed potential. When the dressed potential is expanded into a proper form, the equations for the radial wave function are separated by Floquet partial expansion and they are integrable in weak coupling approximation. Therefore, the approximate wave function, S-matrix and the cross section can be expressed analytically. The comparison to the numerical iterated solution is discussed.
A STUDY OF EXCITED STATES IN COLLISIONS OF Ne+ IONS WITH LI ATOM
PAN GUANG-YAN, LEI ZI-MING, YANG FENG, LIU JIA-RUI, SUN XIANG, YU DE-HONG
1990, 39 (8): 47-51. doi: 10.7498/aps.39.47
Abstract +
We have studied the electron capture and the target excitation in collisions of Ne+ ions with Li atom by observing the emission spectrum. The emission cross sections of the observed lines and the excitation cross sections of the corresponding states are obtained in the visible region. The relations of the electron capture processes with the energy defect and the ionized potential of the target atom are discussed. The energy range of the Ne+ ions is 20-150 keV.
CLASSICAL AREA OF PHENOMENOLOGY
INVESTIGATIONS ON NONPROPAGATING GRAVITY-SURFACE TENSION SOLITON
HUANG GUO-XIANG, DAI XIAN-XI, YAN JIA-REN
1990, 39 (8): 52-60. doi: 10.7498/aps.39.52
Abstract +
In this paper, the method of multiple-scales is used to investigate the weak nonlinear self-modulation of the gravity-surface tension standing wave mode in a finite deep fluid which is filled in a rectangular resonator. The detailed analysis and calculations about the nonpropaga-ting soliton discovered by Wu et al. are made when external driving and damping of the surface wave are considered. The nonpropagating soliton theory established by Larraza, Put-terman and Miles is revised and developed. The correct second harmonic resonace condition about gravity-surface tension wave in the rectangular trough is obtained. The stabilities of propagating soliton are analyzed in detail according to σ-kd diagram. It is found, in addition to the static depth d, that the surface-tension of fluid is an important parameter which may control the formation of nonpropagating soliton. Finally, the nonlinear tuning curves of the surface wave resonator are discussed and compared with experimental results.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
NONLINEAR THEORY OF LOW FREQUENCY INSTABILITIES IN A HOT ELECTRON PLASMA
WU YING, HUANG CHAO-SONG
1990, 39 (8): 61-68. doi: 10.7498/aps.39.61
Abstract +
Nonlinear behaviors of low frequency drift instability and interchange instability in a hot electron plasma are analyzed. Nonlinear coupled equations describing evolution of perturbed densities are derived. Saturated amplitudes of plasma perturbations are found. Effects of the hot electron component on the saturated amplitudes are discussed. The amplitude of perturbed density of the drift wave is about 20%, and that of the interchange mode is about 5%. The amplitudes of plasma perturbations vanish if the hot electron component satisfies the linear stability criteria of the instabilities.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
ELASTIC FIELD OF A DISLOCATION UNIFORMLY MOVING ON THE PHASE BOUNDARY
YANG SHUN-HUA, WANG CHAO-YANG
1990, 39 (8): 69-77. doi: 10.7498/aps.39.69
Abstract +
We extended the method of Eshelby et al.for treating a static straight dislocation in infinite anisotropic medium, to compute the elastic field of a dislocation uniformly moving on the phase boundary of a two-phase medium. The simple theory proposed in this paper is applicable in general, and can be employed directly to investigate the behavior of a tranformation dislocation in high speed motion on phase boundary, and therefore be helpful in understanding the role played by the motion of transformation dislocation in diffusionless phase transformation. Finally, the method used in this work and the discontinuity appeared in the computed field are discussed in brief.
A STUDY OF FORMATION OF CHARACTERISTIC LAYERED INCLUSION IN THE CRYSTAL OF RUBIDIUM ACID PHTHALATE AND THEIR RELATIONSHIP WITH THE STRUCTURE
HUANG YI-SEN, ZHAO QING-LAN
1990, 39 (8): 78-83. doi: 10.7498/aps.39.78
Abstract +
The formation of characteristic layered inclusions in the single crystal of rubidium acid phthalate (RAP) is discussed in view of the effect of its microscopic structure. That the three types of micro structure channels trap the impurities or other different phase precipitates in solution, via a special pair of the conical planes with the highest growth rate and the fluctuation of the growth conditions in liquor, is the main mechanism of inclusion formation. The above argument is in fair agreement with the experimental results for real crystals.
INTERNAL FRICTION PEAK DUE TO MOVING FLUX IN Bi0.8 Pb0.2SrCaCuOy SUPERCONDUCTOR
ZHANG JIN-XIU, ZHENG WEN-GUANG, DU ZHONG-LIAN, LIN GUANG-MING, LIANG KAI-FENG, LIN ZHI-CHENG
1990, 39 (8): 84-89. doi: 10.7498/aps.39.84
Abstract +
The low-frequency internal friction in the magnetization process, where magnetic field increases linearly, is measured for (Bi0.8Pb0.2SrCaCuOy) in superconducting state by using a frequency variable inverted torsion pendulum system. Experimental conditions are as follows: measure temperature: 95 K, at which specimen is in resistance- free state; frequency: 0.5 Hz to 5 Hz. The characteristics of internal friction (IF) peak observed in curve of IF vs magnetic field strength H are as follows. 1. The peak height increases with an increasing of H (variance rate of magnetic field) but decreases as frequency increasing. 2. Magnetic field strength at which IF peak appears is 4-6 mT. 3. When H falis down to zero from a given value suddenly, IF peak disappears. 4. IF peak mentioned above disappears also when specimen turns to normal state.It is considered that, the eigen-IF of superconductor mentioned above during magnetization process stems from motion of quantum flux.
A STUDY ON THE SPECTRUM OF Agl(Cr2O3) COMPOSITE ION-CONDUCTOR
WANG YU-XIA, WANG LI
1990, 39 (8): 90-95. doi: 10.7498/aps.39.90
Abstract +
In this paper, we present the study on the infrared absorption spectrum, near ultraviolet region and visible region reflection spectrum of Agl(Cr2O3) composite ion-conductor. It is found that the two spectra observed are not the same as that of pure Agl and Cr2O3. There is a new absorption peak in the range of 882-889 cm-1 in infrared spectrum. The photodis-sociation characteristic at long wave direction from 430 nm of Agl disappears in electronic spectrum. The reflection spectrum hands of d-d absorption transition caused by ligand field effect of Cr2O3 are centered at 410 nm and 530 nm. For Agl(Cr2O3), the band at 410 nm disappears and the band at 530 nm shows red-shift and its intensity decreases with the increasing of Cr2O3. There is more strong absorption in the whole ultraviolet and visible region Based on the concept of the double-phonon coupling, the distortion polarization of medium and the ligand theory, combining with the TEM results, the phonon spectrum and electronic spectrum of Agl(Cr2O3) compsite ion-conductor are analyzed.
STUDY ON LOW ENERGY ION BEAM NITRIDATION OF Si BY HIGH RESOLUTION CHANNELING-BACKSCATTERING
CHEN GUO-MING, CHEN GUO-LIANG, YANG JIE, ZOU SHI-CHANG, ZHU DE-ZHANG, PAN HAO-CHANG, CAO JIAN-QING, ZHU FU-YING
1990, 39 (8): 96-99. doi: 10.7498/aps.39.96
Abstract +
Low energy ion beam nitridation of silicon has been investigated by high resolution channeling-backscattering technique. The profiles of nitrogen and displaced silicon atoms are obtained, During the bombardment, all the three processes of implanting, sputtering and releasing exist. A differential equation is deduced and the mechanism of formation of silicon nitride is discussed.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
THE ELECTRONIC PROPERTIES OF THE VERTEX MODEL FOR 2-DIMENSION QUASICRYSTALS
LIU YOU-YAN, MA PENG-HUI, ZOU NAN-ZHI, ZHOU YI-CHANG
1990, 39 (8): 100-107. doi: 10.7498/aps.39.100
Abstract +
This paper is devoted to the study on electronic properties of the vertex model of the Penrose lattice with five-fold rotational symmetric axis in the framework of tight-binding Hamiltonian. A similarity transformation is introduced to reduce the Hamiltonian, which helps to determine analytically the degeneracies of the eigenstates and to simplify the numerical calculation for the eigenenergies and the eigenvectors. It is found that two thirds of the states are doubly degenerate and the remains are non-degenerate. This conclusion is confirmed by group theory. The Hoursehold and improved Dean motheds are used to obtain the energy spectra and examine the localication of the electronic states. By several methods and criteria, three kinds of wavefunction behaviors are definitely found. The highly degenerate states are also investgated.
GaP BAND STRUCTURE STUDIED BY ARUPS
LU XUE-KUN, HOU XIAO-YUAN, CING XUN-MIN, CHEN PING
1990, 39 (8): 108-114. doi: 10.7498/aps.39.108
Abstract +
Hel ultraviolet light has been used to take angle resolved ultraviolet photoelectron spectra (ARUPS) of GaP(Ⅲ) surfaces. The observed photoelectron peaks have been explained based on detailed analysis of the data The measured characteristics of the bulk band structure agrees well with the theoretical prediction.
EXPERIMENTAL STUDY ON ECRH TRAPPED ELECTRON BEAM INJECTED INTO THE SIMPLE MIRROR
ZHANG JUN, WANG EN-YAO, GUAN WEI-SHU, CHENG SHI-QING, DUAN SHU-YUN, GU BIAO, SHANG ZHEN-KUI
1990, 39 (8): 115-120. doi: 10.7498/aps.39.115
Abstract +
The experiments on ECRH trapped electron beam injection in various ways have been carried out on a simple mirror-MM-2 device by use of a 15GHz high power gyrotron. The experimental results show that the preionization time of plasma will be greatly reduced for the electron beam injection ahead of the microwave. And because of ECRH trapped electron beam, the parameters of hot electron ring will be improved greatly, and the diamagnetic value increases about 62 percent. The trapping efficiency of electron beam for the increasing rate of diamagnetic is about 30-40 percent. The gas "pressure window" for building a hot electron ring is (4.67-21.3)×10-4 Pa, as the gyrotron output power is about 30kW.
INVESTIGATION OF THE LARGEST CURRENT IN A RANDOM RESISTOR NETWORK
BAD KE-DA, XIONG JIA-JIONG
1990, 39 (8): 121-127. doi: 10.7498/aps.39.121
Abstract +
In this paper it is shown that the expected largest current in a random resistor network can be scaled as (InL)α , where L is the size of the network and the exponent a not only depends on dimension and the ratio of two conductances in the network, but also depends on the value of vertex angle β of the defects remarkably. This result follows from an analysis of the funnel configuration with a channel in it. Here we have also suggested a qualitative explanation concerning the difference in the values of exponent α when σ2→0 of Machta et al. and DEL theory.
ROLE OF Sb5+ AND Sb3+ IN THE FORMATION OF NEW HIGH TcPHASE
XIA GUO-QIANG, WU XIAO-ZU, LI QING-YUN
1990, 39 (8): 128-131. doi: 10.7498/aps.39.128
Abstract +
By comparing the R-T curves and the X-ray diffraction patterns of samples containing Sb3+ and Sb5+ , we discuss the role of Sb5+ and Sb3+ in the formation of new high Tc phase. It is found that Sb3+ partly substitutes Bi3+ forming 2223 structure; but a new high Tc phase will be produced when Sb5+ is added to the system.
FINITE WAVENUMBER EFFECT ON AC JOSEPHSON CURRENT
WU YING, YAO KAI-LUN
1990, 39 (8): 132-137. doi: 10.7498/aps.39.132
Abstract +
A formula of the Josephson current in the presence of microwave and static magnetic field, taking finite wave-number effect into account, is derived. Finite wavenumber effect on ac Josephson current is discussed according to this formula. It can be used to explain such anomalous phenomena as missing of some rf-induced steps in the I-V curve, asymmetry of the I-V curves.
RESEARCH ON THE CONDUCTION BEHAVIOR OF YBa2Cu3O7-x AT HIGH TEMPERATURE
LIU FU-SUI, GAO ZHI-SHUANG, HOU ZHI-JIAN, DU BAO-SHI, WANG CHEN-XU, ZHU CHANG-YU, LI YUN-JUN
1990, 39 (8): 138-144. doi: 10.7498/aps.39.138
Abstract +
Based on the result of the YBCO's experiments at high temperatures, this paper analysed and discussed the Influences of oxygen on the YBCO's conduction behavior at high temperature and the conductive actions of one dimensional Cu-O chains. We also reported a new phenomenon of YBCO in N2, i.e., once the N2 atmosphere is replaced by the O2 atmosphere at high temperature, a rapid stractural phase transition from semconductor to metal will occur.
A SPIN-ONE DILUTED ISING MODEL ON A HONEYCOMB LATTICE
WANG ZHEN-LIN, LI ZHEN-YA
1990, 39 (8): 145-153. doi: 10.7498/aps.39.145
Abstract +
In this paper, the randomly site-diluted (quenched case) spinone Ising model on a honeycomb lattice is investigated under the constraint exp(K)cosh(J) = 1. The critical temperature and the magnetization as functions of concentration of spins and the percolation critical value are obtained.
DENSITY OPERATOR FORMALISM FOR SPIN SYSTEMS WITH PERMUTATION SYMMETRY IN MULTIPLE PULSE AND 2D NMR EXPERIMENTS (Ⅱ)——MULTIPLE QUANTUM PRODUCT OPERATOR FORMALISM
LIU AI-ZHUO, PEI FENG-KUI
1990, 39 (8): 154-161. doi: 10.7498/aps.39.154
Abstract +
Based on the Symmetry-Adapted Product Operator (SPO), the Moltiple Quantum Coherence Product Operator (MQCPO) formalism is introduced in this paper. The modified density operator theory is universal for the description of modern multiple pulse and two-dimensional NMR experiments performed on InS(I = 1/2, 5 = 1/2; n = an arbitray integer number) spin systems. In fact, MQCPO is a Hermitian combination of irredusible tensor operators for a compsite particle, and reveals symmetry properties of the spin system in a different aspect from SAPO. There exist simple linear relations between MQCPO and SAPO for In(I = 1/2, n = 2,3) spin systems, the SAPO forms of MQCPO are listed as a usual example. MQCPO shows a simple cyclic commutation relationship with the free procession Hamiltonian, but not with the Hamiltonian of a pulse effect. Therefore, MQCPO is convenient for description of evolution period. Using the linear relations between MQCPO and SAPO, as well as the permutation properties for the coordinate indices of Cartesian components in a SAPO, the description of a pulse action tarns out to be easy and direct under the "z"-representation. Analyses of the pulse sequences for heteronuclear spectra editing and spin topology filtration have shown the power of this formalism.
VARYING TEMPERATURE RAMAN SCATTERING STUDIES OF 12 mol% Ce TETRAGONAL ZIRCONIA POLYCRYSTAL
CHENG GUANG-XU, ZHANG XING-KUI
1990, 39 (8): 162-168. doi: 10.7498/aps.39.162
Abstract +
Raman scattering studies have been carried out on 12 mol% Ce-Tetragonal Zirconia Poly-crystal over 50-800cm-1, and a range of temperature 17-505K, a phase transition was observed from the tetragonal-like to monoclinic-like phase at approximately 165±1K when the temperature was lowering. The reverse transition occurred at approximately 450±2K when the temperature was raising.In order to study the reason of this transition, the condensation of the phonons in Brillouin zone and possible phase transition have been carefully discussed.
ANGLE-RESOLVED UPS INVESTIGATION OF COADSORPITON OF CO AND K ON Fe(110) SURFACE
BAO SHI-NING, ZHU LI, XU YA-BO, LI ZHUO-ZHI
1990, 39 (8): 169-174. doi: 10.7498/aps.39.169
Abstract +
A symmetry plane for K-CO coadsorbate at low coverage on Fe(1lO) surface was foundusing angle-resolved UPS with polarized light. This plane is parallel to the azimuth ofthe crystal surface. The dependence of the CO 4σ peak intensity on incidence angle was foundto be nearly the same as in the case without K, where the molecular axis of CO is perpendicular to the surface.