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Vol. 38, No. 7 (1989)

1989-04-05
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THE CONFORMALLY SPHERICALLY (PLANE-) SYMMETRIC ELECTRO-VACUUM SOLUTION TO EINSTEIN EQUATIONS
LIANG CAN-BIN, FAN LI
1989, 38 (7): 170-176. doi: 10.7498/aps.38.170
Abstract +
In this paper, we generalize two theorems in General Relativity. The symmetry in the conditions for the theorems is relaxed to conformal symmetry. The generalized theorems read as follows:1. Any conformally spherically symmetric electro-vacuum solution to Einstein equations must be the Reissner-Nordstr?m solution.2. Any conformally plane-symmetric electro-vacuum solution to Einstein equations must be the Kar solution.
RESONANT RADIATION OF ATOM IN SGUEEZED LIGHT FIELD
ZHANG WEI-PING, TAN WEI-HAN
1989, 38 (7): 1041-1047. doi: 10.7498/aps.38.1041
Abstract +
In the paper, applying the stochastic statistical methods, we obtain the resonant radiation spectrum of a two-level atom ensemble driven by multimode squeezed light. Co-responding to different squeezing degrees of the quantum fluctuations of the driving field, the central peak of radiation spectrum exhibits subnatural-and supernatural-linewidth phenomenon, and in all cases the side peaks are broadened. The positions of the side peaks and the character of symmetry of radiation spectrum depend upon the coherent excitation direction and the squeezing direction of the driving field.
EXPERIMENTAL STUDY OF RYDBERG STATES OF AU ATOM
DING GANG-JIAN, SHANG REN-CHENG, ZHANG LIAN-FANG, WEN KE-LING, HUI QIN, CHEN DIE-YAN
1989, 38 (7): 1048-1055. doi: 10.7498/aps.38.1048
Abstract +
A beam of gold atoms was produced by heating the gold containing material by electrothermal method. Two UV laser beams then orthogonally irradiated the atomic beam, exciting the Au atoms to very high Rydberg states from their ground states (6S1/2). A high voltage pulsed electric field was applied to the interaction region approximately 200 ns after the laser pulse, it ionized the Au atoms into Rydberg states. By scanning the wavelength of laser in a certain range, the positions of 38 energy levels of Au atoms in n2D3/2 (n = 18-38) and n2S1/2 (n = 21-34; 36-38) series have been determined. the ionization limits of the n2D3/2 and n2S1/2 series were found to be ED = 74409.8 (3)cm-1 and Es = 74410.0(2) cm-1, respectively, by parametric fitting. The quantum defects of all these levels were also calculated.
CORRELATION INTERACTION IN ATOMIC INNER SHELL PHOTOELECTRIC EFFECT
WU YING-JIAN, LI JIA-MING
1989, 38 (7): 1056-1061. doi: 10.7498/aps.38.1056
Abstract +
Based on the Hartree-Slater self-consistent field theory, we considere the residual interaction which is omitted in obtaining the Hartree-Slater self-consistent field in previous calculation. We calculate the near threshold photoionization cross sections of K-shell of atomic Ne-and Ne+ ion and the cross section ratios as examples. We discuss the effects of residual interaction and compare our results with experiments.
STUDY OF SURFACE MAGNETISM IN A SEMI-INFINITE ISING FERROMAGNETIC SYSTEM
JIANG QIN, LI ZHEN-YA
1989, 38 (7): 1062-1068. doi: 10.7498/aps.38.1062
Abstract +
We use the mean field renormalization group method to treat the semi-infinite Ising ferromagnetic system with the amorphization of the surface. The critical behavior of the surface with a surface random field, including critical temperature, the possibility of tricritical and reentrant phenomena, are investigated in detail.
A NEW ATOMIC STRUCTURE MODEL OF Si {001} 2×1 SURFACE
LAN TIAN, XU FEI-YUE
1989, 38 (7): 1069-1076. doi: 10.7498/aps.38.1069
Abstract +
In this papar,a new atomic structure model of the Si{001}2×1 surface determined from band theory calcution of low-energy-electron diffraction are prensented.The new structure model involves a dimer band length ld = 2.387? and thee atomic layer distances d1 = 0.50±0.01?, d2= 0.96±0.01?, d3 = 1.17±0.01? and two asymmetric displacements of dimer atoms.
SURFACE ATOMIC STRUCTURE OF THE Si (111) 7×7 SURFACE STUDIED BY LOW-ENERGY ELECTRON DIFFRACTION
LAN TIAN, XU FEI-YUE
1989, 38 (7): 1077-1085. doi: 10.7498/aps.38.1077
Abstract +
In this paper, a scalene triangle-dimer-adatom model of the Si(lll)7×7 surface determined from band theory calculation of Low-Energ electron diffraction is prensented. We found the first-layer spacing distance d1 = 0.95±0.02?(expanded 21.3%±0.02?), the second-layer spacing distance d2=0.83±0.02?(expanded 5.9%±0.02?), the third-layer spacing distance d3 = 0.69±0.05?(contracted 10.9%±0.05?) and the fourth-layer spacing distance d4 = 2.38±0.08? (expanded 3.8%±0.08?).
PHOTOLUMINESCENCE STUDIES ON InxGa1-xAs-GaAs STRAINED QUANTUM WELLS STRUCTURE UNDER HYDROSTATIC PRESSURE
WANG LI-JUN, HOU HONG-QI, ZHOU JUN-MING, TANG RU-MING, LU ZHI-DONG, WANG YAN-YUN, HUANG YI
1989, 38 (7): 1086-1092. doi: 10.7498/aps.38.1086
Abstract +
In this article we report the results of photoluminescence studies on In0.25Ga0.75 As-GaAs straiaed quantum wells grown by molecular beam epitaxy under pressure at 77 K. The applied hydrostatic pressure ranges from 0 to 50 kbar. The pressure coefficients of T valley of (InGa)As-GaAs strained quantum wells are presented. We have observed the crossover between the energy level in the well and X valley in the barrier GaAs. With the analysis of its behavior under pressure, the ratio of conduction band offset to valence band offset in In0.25 Ga0.75 As-GaAs heterojunction is determined as Qc =△Ec:△Ev = 0.68:0.32. The theoretical studies on (InGa) AsGaAs strained quantum wells under normal pressure fit the experimental results very well. Some discussions about (AlGa)As-GaAs quantum wells are also included in this paper.
COUPLING EFFECT BETWEEN A SHALLOW-IMPURITY POTENTIAL AND A NARROW QUANTUM-WELL
ZHU JIA-LIN
1989, 38 (7): 1093-1102. doi: 10.7498/aps.38.1093
Abstract +
Using a novel variational wave function for the ground state of the shallow donor in a narrow GaAs/Ga1-xAlxAs quantum-well, we have calculated the wave function and the binding energy for impurity ground state. The numerical results shown that it is important to describe the coupling between the narrow quantum-well and the impurity potential correctly.
A SINGLE BAND-DOUBLE VALLEY THEORY FOR SUPERLA-TTICE AND QUANTUM WELL
XUE FANG-SHI
1989, 38 (7): 1103-1110. doi: 10.7498/aps.38.1103
Abstract +
In this paper, an analytical energy band easy to calculate for GaAs, AlAs and AlGaAs is proposed. The transfer eigenvalue and energy effective mass are obtained by asing the LCAO transfer matrix model. By studing the transfer eigenrunction for two energy valleys, the transformation between different energy valleys is derived, from which new concepts about symmetry transformer and symmetry filter are suggested. Using the energy effective masses and the transformation coefficients between energy valleys at the interface, we derive the equations of envelope function and their boundary conditions for this single band-double valley model. Applying this theory to GaAs/AlGaAs/AlAs system, the confined energy level and wavefunc-tion are calculated. Finally, the significance of this generalized effective mass theory is discussed.
ION RANGE DISTRIBUTION IN MULTILAYER MATERIALS
YANG HONG, SUN XIU-FANG, XIA YUE-YUAN, XU XIAN-GANG, ZHANG ZHAO-LIN, TAN CHUN-YU
1989, 38 (7): 1111-1121. doi: 10.7498/aps.38.1111
Abstract +
In this paper, we present a new method for calculation of depth profiles of implanted ions in multilayer materials. It combines the Monte Carlo simulation method with the method of numerical solution of the LSS transport equation. Taking into account the reflection of the ions at the interfaces of the layers the analytical expression of the range distribution in the multilayer materials is obtained. The comparison between the theoretical and the experimental results is made and good agreement is shown.
A STUDY OF He TRAPPING AND RELEASE IN THE HR-1 STAINLESS STEEL
LI YU-PU, WANG PEI-XUAN, ZHANG GUO-GUANG, MA RU-ZHANG, LIU JIA-RUI, ZHU PEI-RAN, QIU CHANG-QING
1989, 38 (7): 1122-1126. doi: 10.7498/aps.38.1122
Abstract +
The HR-1 austenic steel have been irradiated with 70 keV 4He ions to the dose of 5×1016—1018cm2 at room temperature. Isochronal post-annealing has been carried out at temperatures up to 1273 K. 2.5 MeV proton elastic scattering,TEM and SEM are used to investigate the trap-ping, migration and release of He.
THE APPLICATION OF DISLOCATION GAUGE FIELD FOR THE DISLOCATION CORE
GAO FEI, ZHANG HONG-TU
1989, 38 (7): 1127-1133. doi: 10.7498/aps.38.1127
Abstract +
In this paper, the strain and stress fields produced by the dislocation are analysed by means of continuous dislocation distribution. The dislocation distribution inside the core is expressed by the dislocation gauge fields which are calculated under certain gauge condition. The stresses inside and outside the core of a screw dislocation are obtained. Outside the core, the stresses are the same as that of Volterra dislocation, but inside the core, the stresses of the screw dislocation approach zero when ρ goes to zero. Finally, the energy of the screw dislocation is calculated.
X-RAY TOPOGRAPHIC CONTRAST OF INCLUSIONS IN CRYSTAL OF POTASSIUM ACID PHTHALATE
ZHAO QING-LAN, HUANG YI-SEN
1989, 38 (7): 1134-1139. doi: 10.7498/aps.38.1134
Abstract +
X-ray topographic contrast of inclusions in the crystal of potassium acid phthalate (KAP) has been studied experimentally and theoretically. The nature of inclusion formation was determined in view of their black and white contrast. An "Inclusion Decoration Method" for use in determining the nature of the strained regions in the crystal with very large areas has been proposed. The results together with such an analysis technique are presented in this paper. It has provided a practical way to identify the structural weakness in single crystals.
SELF-AVOIDING TRAILS ON FINITELY RAMIFIED FRACTALS
ZHENG DA-FANG, LIN ZHI-FANG, TAO RUI-BAO
1989, 38 (7): 1140-1045. doi: 10.7498/aps.38.1140
Abstract +
Using an exact real-space renormalization-group technique, we show that self-avoiding trails (SAT) and self-avoiding walks (SAW) on the Sierpinski gasket enjoy the same critical exponent ν for the ‘correlation length' and therefore belong to the same universcllily class. On the other hand, it is shown that SAT on branching Koch curves with maximum ramification number Rmax>3 belongs to another universality class different from that of SAW.
THEORY OF VELOCITY OF ULTRASOUND WITH I NFRARED DIVERGENCE IN GIASSES AT LOW TEMPERATURES
WANG GUO-LIANG, DAI PEI-YING
1989, 38 (7): 1146-1153. doi: 10.7498/aps.38.1146
Abstract +
The behavior of velocity of ultrasound in glasses below 3 K is analysed by combining the tunneling model and the infrared divergence theory. The variation of sound velocity is regarded as consisting of two parts, i.e., non-relaxation process and relaxation process. The former is analysed by the Bose elementary excitation theory and the latter by the theory of tun neling relaxation with infrared divergence. The theoretical curve of sound velocity vs temperature is consistent with the experimental data. The observed In T rule of sound velocity for normal frequency (107Hz) at 0.3-1K, and the phenomenon of appearance of sound velocity minimum for ultrahigh frequency (2GHz) belowe 0.1 K are also explained.
AN ARUPS STUDY OF CO ON Fe(110) SURFACE
BAO SHI-NING, HUANG QIN-LONG, XU YA-BO
1989, 38 (7): 1154-1161. doi: 10.7498/aps.38.1154
Abstract +
The chemisorption of CO on Fe(ll0) surface has been investigated using angle resolved ultraviolet photoemission spectroscopy (ARUPS)The experimental results, compared with the calculation, show that the molecular axis of Co is nearly perpendicular to the iron surface at 150K and low coverage of CO. The angle between CO axis and the surface normal is less than 10 degrees.
A METHOD FOR MEASURING THE MICRO-VIBRATION AMPLITUDE BY USING INTENSITY-COMPARISON LOCK-IN TECHNIQUE OF LASER
JI YU-LING, LI YONG-GUI, ZHUANG JIE-JIA
1989, 38 (7): 1162-1166. doi: 10.7498/aps.38.1162
Abstract +
A method of measuring micro-vibration amplitude with laser is presented. By using the optical resonant characteristic of Fabry-Perot etalon and intensity-comparison lock-in technique of laser, we have completed a measurement with the minimum amplitude of vibration at the order of 10-12 cm under the condition of an ordinary laboratory.
FREQUENCY MATCHING IN BEAT WAVE LASER ACCELERATOR
ZHU SHI-TONG
1989, 38 (7): 1167-1171. doi: 10.7498/aps.38.1167
Abstract +
Arccording the general covariant equation of motion and Maxwell equations, we derive the analytical expressions for various quantities of electron plasma wave. It is pointed out that the plasma wave with △ω = 2ωp is completely harmonic. The condition of complete resonance is given by △ω= 2ω(p0) [1+(e2(A2((1)2)+(A2((2)2))/(2m2c4)+(3e2A2(1)A2(2))/(m2c4)]-1/2.
RESONANCES OF PHOTOIONIZATION OF Ca AND Sr ATOMS IN AN ELECTRIC FIELD
QIU JI-ZHEN, ZHANG SEN, WANG GANG
1989, 38 (7): 1172-1176. doi: 10.7498/aps.38.1172
Abstract +
Photoionization spectra of Ca and Sr atoms above the classical field-ionization threshold are observed by using two-photon excitation method. The relation between the resonances and the applied electric field as well as polarization, of laser beam are discussed.
MAGNETO-EXCHANGE MODES IN ANISOTROPIC MEDIA
LI YI-BING, LI SHAO-PING
1989, 38 (7): 1177-1181. doi: 10.7498/aps.38.1177
Abstract +
This paper presents an investigation of dipole spin modes in an anisotropic medium with uniaxial anisotropy and a weak exchange effect. The critical angle between surface wave and volume wave is given according to the new circumstance and the real ω vs k figure in space is analysed. The experimental results of single crystal YIG FMR spectra agree well with our calculation.
A NEW MODEL FOR INDUCED ANISOTROPY IN AMORPHOUS ALLOYS
GUAN PENG, LIU YI-HUA
1989, 38 (7): 1182-1186. doi: 10.7498/aps.38.1182
Abstract +
Some previous experimental results about the concentration dependence of magnetic ani-sotropy for metalmetal amorphous alloys were analyzed. By introducing a new parameter, a model of tetrahedral directional order was proposed. The comparison with some experimental data shows good agreement.
AN APPROXIMATE SOLUTION FOR SQUARE-LATTICE SPIN-1 MODEL
YE QING
1989, 38 (7): 1187-1190. doi: 10.7498/aps.38.1187
Abstract +
In this paper, we apply the decoration and decimation transformation to the square-lattice spin-1 model and show that it is equivalent toa checkerboard Ising model with cross and four-spin interactions. Then, the approximate critical condition is obtained for the model and it reduces to Onsager's exact solution in the Ising-model limit.
THE FREE-FERMION APPROXIMATE SOLUTION FOR KAGOME-LATTICE MIXED-SPIN MODEL
TANG KUN-FA
1989, 38 (7): 1191-1195. doi: 10.7498/aps.38.1191
Abstract +
In this paper, we consider a Kagome-lattise mixed-spin model and show that it is equivalent to an eight-vertex model via decimation and duality transformation. According to the free-fermion approximate solution of the eight-vertex model, the approximate expressions are given for the free energy and critical condition of the model.
CRITICAL BEHAVIOUR OF ISING MODEL WITH THREE-SPIN INTERACTIONS ON THREE-NODE HIERARCHICAL LATTICES
WANG FU-GAO, TANG KUN-FA, HU JIA-ZHEN
1989, 38 (7): 1196-1198. doi: 10.7498/aps.38.1196
Abstract +
The critical behavior of Ising model with three-spin interactions on three-node hierarchical lattices is investigated by using an exact renormalization group transformation. As in the case of Bravais lattices, the model with two-spin interactions and the one with three-spin interactions belong to different universality classes.
QUASI-TWO DIMENSIONAL BOSE CONDENSATION AND HIGH-Tc SUPERCONDUCTIVITY
CHENG KAI-JIA, LI WEN-ZU, WU JIAN-BIN, CHEN FENG
1989, 38 (7): 1199-1204. doi: 10.7498/aps.38.1199
Abstract +
Starting from the quasi-two dimensional Bose condensation, we studied the influence of layer-thickness and ox gen-vacancy on the critical temperature Tc in real high-Tc, superconductors. The results are consistent with known experiments qualitatively.
THE DIFFRACTION INTENSITIES OF INCOMPLETELY POLED FERROELECTRIC CRYSTALS
ZHONG WEI-LIE
1989, 38 (7): 1205-1209. doi: 10.7498/aps.38.1205
Abstract +
Incomplete poling of ferroelectric crystals has significant effect on their diffraction intensities. In the crystal structure determination, this effect must be taken into account. For lead hydrogen phosphate, appropriate equations are derived to correct this effect. Incorporating this correction in the structure determination of this crystal, a better fit is obtained.
INVESTIGATION OF THE ANOMALOUS HALL EFFECT IN n-Ge AT ROOM TEMPERATURE BY THE INVERSION LAYERS MODEL
XING XU, WANG XI-FU, JIANG WEI
1989, 38 (7): 1210-1214. doi: 10.7498/aps.38.1210
Abstract +
In this paper, we make quantitative rheor ncal calculation for the anomalous Hall effect in n-Ge semiconductor at room teperature by use of the inversion layers model. The results are in agreement with the experiments.
FREE ELECTRON CYCLOTRON RESONANCE LASER
WANG CHANG-BIAO
1989, 38 (7): 1215-1224. doi: 10.7498/aps.38.1215
Abstract +
A new kind of oscillator configuration of free electron laser, the free electron cyclotron resonance laser, is proposed and analyzed. The expressions for electron efficiency and startup current are given.
THEORETICAL CALCULATION OF POLARIZATION SIGNALS FOR THREE-PHOTON TRANSITIONS
BAO ZHEN-CHUAN, XIA HUI-RONG, PAN ZUO-DI, ZHENG YI-SHEN
1989, 38 (7): 1225-1234. doi: 10.7498/aps.38.1225
Abstract +
Starting from population density matrix equations, five kinds of nearresonant enhanced three-photon electronic transitions in the interaction between differently polarized laser fields and molecules with casecade four-level structure and folding four-level structure are discussed respectively. And, taking the third transition as the probe signal, the relative intensities and the characteristic of the signals are derived analytically. The line-shape factors and intensity factors of the relative intensities are greater by different degrees when compared with those of three-level molecules. Therefore the relative intensities of the probe signal may be greater by several orders. The potential applications of these results in molecular spectroscopic analysis are also discussed.
LATERAL PHOTOVOLTAIC EFFECT IN a-Si:H JUNCTIONS
PENG SHAO-QI, SU ZI-MIN, LIU JING-XI
1989, 38 (7): 1234-1252. doi: 10.7498/aps.38.1234
Abstract +
The steady and transient characteristic of lateral photovoltaic effect in a-Si:H juncitions have been explored by theoretical analysis. The results show that the theoretical predictions are in good agreement with the experiments. It is worthy to note that two important parameters of the sample (i.e. the sheet resistance 1/σs of a-Si: H and the transit time Tm) evaluated according the theoretical relations with the conventional accepted mobility and conductivity of undoped a-Si: H are much larger than that deduced from the experimental data. Based on this with a reasonable analysis, we suggest that electrons in a-Si: H layer may transport parallel to the junction with a surprisingly high mobility.
MEASUREMENT OF ANISOTROPIC OPTICAL CONSTANTS BY ELLIPSOMETRY——APPL ICATION ON KNSBM FERROELECTRIC CRYSIALS
CHEN SHU-GUANG, MO DANG, HU QI-HONG
1989, 38 (7): 1253-1258. doi: 10.7498/aps.38.1253
Abstract +
The effects of the incidence angle and the azimuth of polarizer on the sensitivity, in the ellipsometric measurement of anisotropic crystal have been analyzed. We discuss how to choose the proper experimental condition to measure the optical contants of crystal with small anisotropic character (|n0 - nc| 0-nc|< 0.1.
A STUDY OF GROWTH SECTOR BOUNDARIES IN NATURAL BERYLS BY X-RAY DIFFRACTION TOPOGRAPHY AND OPTICAL BIREFRINGENCE TOPOGRAPHY
JIANG SHU-SHENG, LI QI, XU XIU-YING
1989, 38 (7): 1259-1264. doi: 10.7498/aps.38.1259
Abstract +
The growth sector boundaries in natural beryls have been investigated by means of X-ray topography and optical birefringence topography. The boundaries of the same families usually show no contrast by the two different topography techniques. The t-s boundaries show the dynamical interference fringes in the X-ray topographs, which is characteristic for translation-type boundaries. Their displacement vectors, determined from extinction behaviour of the fringes, are probably perpendicular to the corresponding boundaries respectively. In the birefringence topographs, the contrast of the boundaries of different families is attributed to the long range strain fields on the two sides of the boundaries. From the experimental results, we may recognize that the two different topographies are complementary in the study of growth sector boundaries.
THE AGGREGATION EFFECT OF METAL IONS ON SILVER SOL AND THEIR RAMAN SPECTRA
YU FENG-QI, LAN GUO-XIANG, ZHANG CHUN-PING, LI BING, ZHANG GUANG-YIN
1989, 38 (7): 1265-1270. doi: 10.7498/aps.38.1265
Abstract +
Comparing the transmission spectra with the electon micrographs and Raman spectra of metal ions-silver sol systems, we summarized the general relations between the aggregation state of silver sol with surface enhancement factor.
INTERFACIAL PROPERTIES OF Si/GaP(111) HETEROJUNC-TION GROWN BY MOLECULAR BEAM EPITAXY
JIANG WEI-DONG, SUN HENG-HUI, DENG RONG-PING
1989, 38 (7): 1271-1279. doi: 10.7498/aps.38.1271
Abstract +
In this paper, the interfacial properties of n-N type Si/GaP(lll) heterojunction prepared by MBE growth have been studied. The conduction band offset and the interface charge density are derived from the apparent carrier concentration distribution obtained by the C-V profiling techniqe. The experimental result shows that the n-N type Si/GaP(111) forms a weak rectifying contact. The conduction band offset is △Ec = 0.l0eV and the interface charge density is σi = 8.8×1010cm-2. A theoretical simulation of the apparent carrier concentration distribution coincides well with the experimental curve, this confirms the reliability of our results.
ELECTRON CORRELATION AND MANY-BODY WAVE FUNC-TION OF THE SEMICONDUCTOR INVERSION LAYER
SUN XIN, FENG WEI-GUO, SHAO JIN-SHAN, WANG HONG-WEI
1989, 38 (7): 1280-1289. doi: 10.7498/aps.38.1280
Abstract +
The correlation factor u(R) m the quasi two dimensional system——the inversion layer isobtained with the effective interaction potential Veff (R) and the collective oscillation behavior of the electron gas. The pair correlation function the correlation energy and the many-body wave function have been calculated on the basis of the CBF theory.
PHASE TRANSITION IN SOME FERROELECTRIC NIOBATE CRYSTALS WITH TUNGSTEN BRONZE STRUCTURE AT LOW TEMPERATURES
LI WU, XU YU-HUAN, LI ZHONG-RONG, WANG HONG
1989, 38 (7): 1290-1298. doi: 10.7498/aps.38.1290
Abstract +
Dielectric and pyroelectric properties have been measured in six ferroelectric niabate single crystals with tungsten bronze structure from 15K to room temperature. The dielectric and pyroelectric results showed that, in all the three kinds of ferroelectric niobate single crystals SBN, PBN, KNSBN with TTB structure, a new phase transition occured between 50K and 70K, which were further supported by the X-ray experiment. The crystal symmetry changes from point group 4mm to point group mm2, and the direction of ferroelectric polar-axis changes from the c-axis of tetragonal lattice cell to the b-axis of orthogonal lattice cell as the temperature drops. The difference between high frequency dielectric constants and low frequency dielectric constants indicates that the phase transition possesses diffuse character. According to the specific heat measurement, it is confirmed that this phase transition is a higher order transition. A model of structural change has been proposed to explain this phase transition.
INTERNAL FRICTION OF MONO-AND POLY-CRYSTAL PURE ALUMINUM DURING CREEP TESTS
SHAN BING, XU WEN, KONG QING-PING
1989, 38 (7): 1299-1305. doi: 10.7498/aps.38.1299
Abstract +
Internal friction of mono- and poly-crystal pure aluminum during creep at about IHz was studied. It was observed in monocrystal specimens that the internal friction decreased monotonously in the early stage of creep. A significant creep time-internal friction (Q-1-t) peak was observed during the latter half of the primary creep under suitable experimental conditions. And the internal friction kept constant during the secondary creep. But no Q-1-t peak was observed with polycrystal sample under similar experimental conditions. We suggest that the appearence of Q-1-t peak is due to the increase of the damping coefficient of moving dislocations during primary creep. A specific dislocation mechanism is proposed, and the expression thereby deduced for the internal friction during creep is satisfactorily consistent with the experiments.
FOUR-PARAMETER MODEL FOR DESCRIBING THE BEHAVIOUR OF INTERNAL FRICTION MEASU-RED DURING CREEP TESTS
KONG QING-PING, SHAN BING
1989, 38 (7): 1306-1312. doi: 10.7498/aps.38.1306
Abstract +
Experiments show that the internal friction measured at low frequency during creep tests exhibits both the behaviours of Maxwell two-parameter model and standard anelastic three-parameter model.In this paper, a four-parameter model is proposed for describing the behaviour of such internal friction. Based on this model, the expression of internal friction is derived to be Q-1=1/(ωτ1)+△(ωτ2)/(1+ω2τ22) where ω is the circular frequency of vibration, τ1 and τ2 are respectively the relaxation times for viscoelastic and anelastic relaxation, and △ the relaxation strength. This expression can satisfactorily explain the change of internal friction with creep time, and the dependence of internal friction on the creep rate, test temperature and the measuring frequency. The physical origin of each element in the four-parameter model is analyzed in the light of the micro-structure.
DOUBLE-ELECTRON CAPTURE INTO EXCITED STATES IN COLLISION BETWEEN He2+ AND H2, O2
PAN GUANG-YAN, LEI ZI-MING, YANG FENG, LIU JIA-RUI, YU DE-HONG, SUN XIANG
1989, 38 (7): 1313-1321. doi: 10.7498/aps.38.1313
Abstract +
Double-electron capture into excited states have been observed in collision between He2+ and H2, O2. One electron capture into excited states have also been observed in this collision system. In the channel of direct excitation of target H2, O2, the emission spectra of Balmer series Hα,Hβ,Hγ, and OI have been measured. This article also give emission cross sections of Hel, Hell, and Hα,Hβ,Hγ, OI dependence of that on the velovity of projectile.
BALMERα,β, γ EMISSION IN COLLISIONS OF H1+,H2+, H3+ WITH He,Ne,Ar
LIU JIA-RUI, LEI ZI-MING, YANG FENG, PAN GUANG-YAN, YU DE-HONG, SUN XIANG
1989, 38 (7): 1322-1328. doi: 10.7498/aps.38.1322
Abstract +
Balmer α, β, γ emission have been measured in collisions between H1+, H2+, H3+ and He, Ne, Ar respectively, by using TN-1710 Optical Multichannel Analysis System (OMA), in laboratray energy range of 50-150 keV. The emission cross sections of Hα, Hβ, Hγ lines are given in this paper. The experimental results demonstrate that the emission cross sections of Hα,Hβ,Hγ in H3+ + He, Ne, Ar collision systems are greater than that in H1+ , H2+ + He, Ne, Ar respectively, it means the probabilities of one electron capture into excited states are larger in the former than that in the latters from the targets.
THE INFLUENCE OF VISCOUS ELASTIC DAMPING ON THE LONGITUDINAL SOLITARY WAVES IN AN ELASTIC ROD
ZOU FENG-WU, YAN JIA-REN
1989, 38 (7): 1329-1333. doi: 10.7498/aps.38.1329
Abstract +
We obtained the time dependence of the transverse profile, velocity and energy of longitudinal solitary waves in an elastic rod, in the case for which the viscoelastical damping is small but cannot be neglected, by using the method of perturbation. The results showed that owing to the presence of viscoelastical damping, the height and velocity of solitary wave diminish, while the width increases with time and the energy dissipates gradually until it disappears.
CACULATION OF CONCENTRATION-DEPENDENT DIFFUSION COEFFICIENT——THE APPROXIMATION METHOD
WANG JING-CHANG, WANG KE-YI
1989, 38 (7): 1334-1338. doi: 10.7498/aps.38.1334
Abstract +
A new metbod to obtain concentration-dependent diffusion coefficient the method of approximation is developed. By applying the approximation method, we overcome some difficulties encountered in using Boltzmann-Matano method, and are able to caculate concentration-dependent diffusion coefficient as accurately as we want. The approximation method is proved to be valid both theoretically and practically.
A STUDY OF FRACTAL GROWTH RULES USING THE METHOD OF TRANSMISSION SPECTRUM
ZHANG CHUN-PING, YU FENG-QI, ZHANG GUANG-YIN
1989, 38 (7): 1339-1343. doi: 10.7498/aps.38.1339
Abstract +
Fractal growth in different systems is discussed primarily in this paper. By analyzing the transmission spectra of many kinds of fractal in different systems, we found that the position of the new absorption band in the transmission spectrum was proportional to logarithmic time. Furthermore we found that the whole curve of position of new absorption band as function of logarithmic time could be divided into two straight parts. This shows that while the fractal growth proceeds, there are mainly two different processes according to the fractal growth speed.
NEW LOCALIZED ELECTRONIC STATES OF Bi-POLARON IN cis-(CH)x
SUN XIN, XIE SHI-JIE, MEI LIANG-MO
1989, 38 (7): 1344-1347. doi: 10.7498/aps.38.1344
Abstract +
We have studied the energy spectra and the electronic states of Bi-polaron in cis-(CH)x with SSH-Hubbard model by using a selfconsistent approach. Four new localized electronic states are discovered. They form four discrete levels outside the conduction and valence bands: two locates near the bottom and the top of the conduction band, the other two near the valence band. The e-h symmetry is destroyed by the e-e interaction. And these localized electronic states vary with the coupling constant λ and the Hubbard e-e interaction parameter U.
STUDY OF SLIP DISLOCATIONS IN GaAs CRYSTAL BY X-RAY TOPOGRAPHY
MA BI-CHUN, CHEN JIAN-BANG, WANG YONG-HONG, MAI ZHEN-HONG, GE PEI-WEN, HE JIB, CUI SHU-FAN, HE CHU-GUANG
1989, 38 (7): 1348-1353. doi: 10.7498/aps.38.1348
Abstract +
Slip dislocation in In-doped and undoped GaAs single crystal were investigated by meant of X-ray topography. Different configurations of the slip dislocations were observed, which resulted from the different densities of dislocations. The mechanism of die slip dislocation and cellular network structure formation is also discussed preliminarily.
X-RAY STUDY ON THE CRYSTALLOGRAPHIC CHARACTER-IZATION OF FERROELECTRIC CERAMICS: (Na0.5Bi0.5)TiO3 AND ITS SOLID SOLUTION SYSTEM
ZHOU FANG, XU YUE-YING, LI DE-YU, HE CHONG-FAN, GAO MIN, WANG TIAN-BAO
1989, 38 (7): 1354-1359. doi: 10.7498/aps.38.1354
Abstract +
The (Na0.5Bi0.5)TiO3-BaTiO3 system, at certain composition range, is a new kind of ultrasonic transducer ceramics material which has good and unique properties. By means of Xray powder diffraction method, we precisely determined the cell parameters of (Na0.5Bi0.5)TiO3, and propose a new type of lattice structure for it different from that in previous reports. For this system, the lattice parameters at different compositions were determined. And the preliminary discussions on the relations between the properties, cell dimensions and compositions as well as the phase relation were also given.
DIFFUSION OF ELEMENTS AND FORMATION OF INTERME-TALLIC PHASE AT THE INTERFACE OF THE BINARY DIFFUSION COUPLES
YANG CHUAN-ZHENG, ZHONG FU-MIN
1989, 38 (7): 1360-1363. doi: 10.7498/aps.38.1360
Abstract +
Based on the data of element diffusion, formation heat of phases and their stabilities, we-analysed the element diffusion at the interface of a binary diffusion couple and the formation of intermetallic phases. The results of experimental investigation for Ti-Ni, Nb-Sn and Ta-Pt systems are presented.
PHONON-MEDIATED SPECIFIC TRAPPING RATE OF POSIT-RONS TO THE SHALLOW ENERGY LEVEL OF A SMALL VACANCY CLUSTER
WANG KE-LIN, SHEN JI-QIANG, LONG QI-WEI
1989, 38 (7): 1364-1368. doi: 10.7498/aps.38.1364
Abstract +
If there is a trapped state of a positron with binding energy lower than Debye energy at a small vacancy cluster, the capture of positrons from free state to this level will be strong temperature dependent. There are two kinds of the dependences and the specific trapping rate may be quite high, which shows great differences between small vacancy clusters and dislocations.
MEASUREMENTS OF THE CROSS SECTION OF ELECTRON PAIR PRODUCTION NEAR THRESHOLD USING A LOW INTENSITY 60Co γ RAY SOURCE
LIN XIANG-HONG, BIAN ZU-HE, TANG XIAO-WEI
1989, 38 (7): 1369-1374. doi: 10.7498/aps.38.1369
Abstract +
The absolute cross sections of electron pair production in Al, Zn, Sn and Pb have been measured using a 2.7 μCi 60Co γ-ray source and two detectors (Ge(Li) and Nal(Tl)) in coincidence. The results are in good agreement with published works using high intensity γ-ray source. The measurements prove that the Z-dependence of the cross section near threshold satisfies the equation σpair= (Z2 +αZ4)σ0 of Jaeger. We also obtained α=(1.51±0.23)×10-4,σ0=(1.95±0.11)×10-2mb for 60Co γ-rays.
TRANSPORT PROPERTIES FOR IMPERFECT LnBa2Cu3O7-y SINGLE CRYSTALS
FANG MING-HU, XIA JIAN-SHENG, ZHANG QI-RUI, SUN DUN-MING, CHEN JIAN, CHEN ZU-YAO
1989, 38 (7): 1375-1378. doi: 10.7498/aps.38.1375
Abstract +
A series of experimental facts for Ln Ba2Cu3O7-y single crystals indicate that imperfect structure and non-uniformity composition in samples have an important effect on their normal state resistivity, normal-superconductive transition behavior, Tc and critical current and so forth. We think that in imperfect single crystals, there also exist superconductive glass state effects, similar to single phase polycrystal LnBa2Cu3O7-y samples.
THE SUPER-BELTRAMI ALGEBRA OF SUPER-QUASICONFORMAL TRANSFORMATION
XU KAI-WEN, GUO HAN-YING, SHEN JIAN-MIN
1989, 38 (7): 1379-1383. doi: 10.7498/aps.38.1379
Abstract +
In this paper, we construct a super-Beltrami algebra. It is related to the super-quasicon-formal transformation on super-Riemann surfaces and contains two super-conformal (NSR) slgebras as subalgebras.
X-RAY DIFFRACTION INVESTIGATION FOR ANNEALING OF Co-SPUTTERED W-Si FILMS ON SiO2
CHEN CUN-LI, ZHOU HENG-NAN, CAO MING-ZHU, JIANG HONG-WEI, XU WEI-WEN, GUO LING, HUANG MIN
1989, 38 (7): 1384-1390. doi: 10.7498/aps.38.1384
Abstract +
Tungsten-silicon films were deposited on oxidized silicon wafers by direct current magnetron Co-sputtering from a W-Si mixture target. Films were then rapid thermal annealed in vacuum at temperature between 500 and 1000℃ for 15 s. The sheet resistance of W-Si films as a function of the annealing temperature shows an anomalous maximum. This phenomenon has been studied by using XRD. We observed that there were W5Si3 appeared in the annealed films at temperature up to 1100℃, which contributed partly to the sheet resistance.