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Vol. 33, No. 3 (1984)

1984-02-05
CONTENT
SPECTROGRAPH WITH A HOLOGRAPHIC LENS AS DISPERSING/FOCUCING ELEMENT
TAO SHI-QUAN, LING DE-HONG
1984, 33 (3): 285-293. doi: 10.7498/aps.33.285
Abstract +
It is possible to construct a simple, compact spectrograph with a single off-axis hologra-fic lens which serves as dispersing and focucing element. In this paper, an optimum construction geometry is presented, the performance of this spectrograph is evaluated. Finally, the experimental results obtained from a prototype of such kind of spectrograph are given.
DUAL SYMMETRY OF CHIRAL MODEL AND GEOMETRICAL CORRESPONDENCE BETWEEN CHIRAL FIELD AND SINE-GORDON EQUATION
HOU BO-YUAN, WANG PEI, HOU BO-YU, GUO HAN-YING
1984, 33 (3): 294-301. doi: 10.7498/aps.33.294
Abstract +
In this paper, we show that the SO(3) chiral field can be regard as the normal Vector field over the pseudo-spherical surface, and thus obtain the correspondence between chiral field and sine-Gordon system, as well as the geometrical interpretation of chiral field. By means of the dual symmetry between chiral field and the pseudo-spherical surface, we are able to connect chiral field with s-G system, and express Backlund transformation, Riccati equation in the gauge invariant representations of the related properties of the same dynamical system in different frames.
THE STRUCTURES OF ELECTRODEPOSITED ALLOY OF NICKEL-PHOSPHORUS SYSTEM
LIN SHU-ZHI, HEI ZU-KUN
1984, 33 (3): 302-308. doi: 10.7498/aps.33.302
Abstract +
The structures of electrodeposited alloy of nickelphosphorus system were investigated by means of X-ray diffraction, method. It is shown that the structures of those alloy are a solid solution of phosphorus in nickel while the contents of phosphorus are less than 5.4 at%. When the contents of phosphorus increase up to more than 7.8 at%, the structures of alloys suffer a tremendous change, the diffraction patterns of these alloys may be interpreted by a model of random-layer (turbostratic) structures. The distances between neighbouring layers are 2.04? and the diameter of the layers are 6-8?. The thickness of stacking of layers is decreased as the contentes of phosphorus in alloy are increased. For examples, it changes from 124? for 7.8 at% P to 13? for 18 at% P. The diffraction pattern of the later is just the same as that of the typical amorphous alloys.Using the data of the ratio of intensities of {lll} or the data of the radial distribution function, the rootmean-square of static distortion can be calculated as (u2)1/2=0.17?. This value can be used to interpret why an arbitrary displacement between two neighbouring layers would be possible even though the distance between neighbouring layers is smaller than the diameter of an atom. Because of the small dimension of the layers and the large static distortion of the atom, it is easy to change the orientation of layer domain and no cr-ystallographic boundary region are necessary for the variation of orientation, so that the specimens are the continue distribution of atoms as a whole bat not an aggregation of micro-crystals.The β{lll} corresponding to the breadth of {lll} reflection at half-maximum intensity have been measured for some specimens. The results show that βlll/β222222/cosθlll, where θ is the Bragg angle, this means there would be some other factors (for example, the component fluctuation), to affect the breadth of the reflection line, besides the size factor.
NEOCLASSICAL TRANSPORT THEORY OF A MULTICOMPONENT PLASMA
ZHOU HAI-LIN
1984, 33 (3): 309-320. doi: 10.7498/aps.33.309
Abstract +
The neoclassical scaling relations satisfying kenetic requirements are derived for a mul-ticomponent plasma in an axisymmetric toroidal magnetic configuration, using a model collision-operator and the variational principle developed by Rosenbluth and Glasser. On the basis of these scaling relations, explicit expressions for the neoclassical fluxes of the multi-component system are obtained in terms of the component parameters nj,mj,Zj and Tj. Finally, the dependence of the neoclassical transport coefficients on the aspect ratio R/r is discussed in detail.
ON THE DISPLACEMENT STABILITIES OF A PLASMA COLUMN IN TOKAMAK
ZHENG SHAO-BAI, WANG LONG
1984, 33 (3): 321-330. doi: 10.7498/aps.33.321
Abstract +
A general stability condition against the horizontal and vertical displacements of a plasma column in tokamak and the change of its minor radius has been deduced, while the effect of the toroidal field and the interaction of the plasma column with the external circuits are taken into account, assuming circular minor crosssection of the plasma column and the ratio α/R<<1. In general, because of the effect of the strong field, the minor radius of the plasma column would change with the change of its major radius to maintain the conservation of the toroidal magnetic flux in the angular plasma current circuit. When the variations of the currents in external circuits are considered, the stability region for such displacement pertur-bance is wider than 0
COLD PLASMA WAVEBREAKING DUE TO RESONANCE ABSORPTION
GU BIAO
1984, 33 (3): 331-340. doi: 10.7498/aps.33.331
Abstract +
A nonlinear equation of the modified capacitor model has been solved by means of the Bogoliubov asymptotic method. Dawson only gave a wavebreaking condition which is not complete when it is applied to the inhomogeneous plasma. In this paper, the second wave-breaking condition has been added for completeness; thus the wavebreaking position and wavebreaking time can be uniquely determined simultaneously, and the formulas of the maximum energy of hot electrons and the localized electric field amplitude can also be obtained. The agreement between the theoretical predictions and the experimental results is very good, especially for the wavebreaking time and the maximum energy of the hot electrons.
METRIC PROPERTIES OF CHAOTIC REGION IN ONE-DIMENSIONAL MAPS
WANG YOU-QIN, CHEN SHI-GANG
1984, 33 (3): 341-351. doi: 10.7498/aps.33.341
Abstract +
In this paper, we use numerical and analytical methods to discuss the following problems. (1) The first is the relation between Hausdorff dimension d and Lyapunov exponent λ. We point out that in the relation N(ε) there is a multi-scaling-region phenomena which shows the structure of the point set at different scale. To analyse this phenomena seriously is significant for calculating d. (2) Acorrding to the relation between the one-dimensional map and the Poincare map of dynamic system, and the discontinuity and multivalue property of d( λ ) of one-dimensional map at λ=0, we conjecture that the relation d(λ) at λ= (0,0,-) of the dynamical system is also discontinuous and multivalued. (3) On the base of relation d(λ), we use λ>0 as a criterion to estimate the measure of chaotic solutions, of logistic model in chaotic region, on the axis of parameter. The result is mc= 0.893±0.022 (The total measure of chaotic region is normalized to unity).
ON THE ELECTRICAL CONDUCTION OF LUCS
XIONG SHI-JIE, CAI JIAN-HUA
1984, 33 (3): 352-361. doi: 10.7498/aps.33.352
Abstract +
Layered Ultrathin Coherent Structures (LUCS) made up of transition metals Nb and Ti exhibit peculiar electrical conduction properties, which reflect the energy band charateri-stics of these artificial superlattices such that there is a transition from metallic to semiconducting or semi-metallic properties with decreasing superlattice period. Owing to the supe-rlattice modulation, there are two catagories of electronic states in LUCS: extended states and strongly localized states in the direction of modulation. Electrons in these two kinds of states have very different effective masses along the modulation direction. We have considered separately the contributions of the two kinds of electronic states, and have obtained the resistivity and its temperature coefficient which show variations with the inverse superlattice period in accordance with measurements.
NORMAL ONE BEAM MODEL FOR FOURIER TRANSFORM ANALYSIS METHOD OF PHOTOELECTRON DIFFRACTION SPECTRUM
S. Y. TONG, TANG JING-CHANG
1984, 33 (3): 362-369. doi: 10.7498/aps.33.362
Abstract +
Using normal one beam model, an analytical formula of normal photoelectron diffraction (NPD) I-V curves is derived. For the system C(2×2) Se (3d)/Ni(001), NPD spectrum and phase shifts have been calculated. We find the "layer spacing modification" (LSM) from phase shifts. In the other hand, the LSM has been found by Fourier transformation of NPD spectrum. These two sets of LSM are shown to be very close to each other. Thus it is demonstrated that Fourier transformation of NPD spectrum could be used as an effective me-thod for surface structure determination.
EMPIRICALLY ADJUSTED ZONE-VARIATIONAL METHOD FOR BAND CALCULATIONS
XUE FANG-SHI
1984, 33 (3): 370-376. doi: 10.7498/aps.33.370
Abstract +
An empirically adjusted zone-variational method for energy band calculations is presented in this paper. The potential outside the sphere is adjusted empirically to make the resulted energy band closer to experimental results. This method has been used to compute the energy bands of Si and Ge. The results agree with the experimental ones very well. In accordance with the special feature of using differen methods to solve the Schrodinger equation in different potential regions, a new computational model for alloy band is also suggested. By using the same adjusting parameters, the energy band of Si-Ge alloy is computed, which is superior to the OPW result. Thus it can be seen that the zone-variational method is an effective and prospective computational method in band theory and has considerable wide application.
A STUDY OF TRANSIENT CAPACITANCE OF GOLD ACCEPTOR ENERGY LEVEL IN SILICON UNDER UNIAXIAL STRESS
YAO XIU-CHEN, QIN GUO-GANG, ZENG SHU-RONG, YUAN MIN-HUA
1984, 33 (3): 377-390. doi: 10.7498/aps.33.377
Abstract +
Using the method of transient capacitance at constant temperature, the shift of gold acceptor energy level in silicon under 〈100〉,〈110〉,〈111〉 uniaxial press has been studied. Considering the split of conduction band caused by uniaxial stress, a formula for electron emission rate from deep center to conduction band has been derived. With this formula and experimental data of emission rate and reported tangential deformation potential constant Ξu ,the active energy of gold acceptor under various uniaxial stress has been determined. In the range of experimental stress (0-9 kbar), a linear dependence of active energy on stress has been found. When uniaxial presses are parallel to 〈110〉,〈111〉 crystal orientations, the proportionality constants are α=-3.2±0.6 meV/kbar, α=-0.3±0.6 meV/kbar respectively. When uniaxial press is parallel to 〈100〉 crystal orientation and if we take Ξu = 9.2 eV, α= -5.8± 0.8 meV/kbar, or if Ξu =11.4 eV, α=-5.3± 0.8 meV/kbar. The changes of active energy are strongly anis-otropic. Further more, we have determined the shift coefficients of gold acceptor level in the presence of uniaxial stress relative to the bottom of conduction band in the absence of uniaxial stress. When Ξu=9.2 eV, the coefficients are S=-1.3±0.8 meV/kbar, S=0.7±0.6 meV/kbar, S=-0.7±0.6 meV/kbar respectively, when Ξu=11.4 eV, the values are S= - 3.5± 0.8 meV/kbar, S = 0.0±0.6 meV/kbar, S=- 1.0±0.6 meV/kbar. Deviations among three coefficients of each group are larger than uncertainty of experiments. Thus, the possibility that gold centers in silicon have cubic symmetry and at the same time both negatively charged and neutral gold centers have nondegenerate basic states is quite small.
RELATIONS BETWEEN CRYSTALLOGRAPHIC CHARACTERISTICS AND CRYSTAL STRUCTURE AND THE PROPERTIES FOR AMMONIUM BICARBONATE
ZHANG HAN-QING
1984, 33 (3): 391-398. doi: 10.7498/aps.33.391
Abstract +
The crystal of ammonium bicarbonate belongs to orthorhombic system with symmetry 3L2 3PC. They exist in three forms: prismatic, slaty or particle shape. The crystals appear colorless to white or light grey, transparent to semitransparent. The cleavage parallel to (110) is perfect. Hardness H=1.55. Density D= 1.573 g/cm3. They are biaxial negative crystals, with Ng=c= 1.5540, Nm = b = 1.5355, Np =α=1.4220; 2V=40°56′. γ=v is weak. On the curves of DTA, there is a big and wide endothermic peak (between 50-150℃ ). The curves of TGA showed a continuous weight-loss. On the infrared absorption spectra, there are two strong peaks (3330-3030, 1430-1380), corresponding to the stretching and bending of the ions NH4+. And there are two less strong peaks (2850, 2550), corresponding to the stretching and bending of the anions HCO3-. The unit cell dimensions are α = 7.220(1)?, b=10.672(l)?,c = 8.719(2)?, v = 671.927(3)?3. There are eight moloculs in the unit cell and the space group is Pccn. Dx =1.5215. In the structure, the HCO3- anion groups are connected by hydrogen bonds to form chains parallel to c axes. The NH4+ ione groups constitute tetrahedrons connected by four chains of the HCO3- anions. In the crystal, there are two form of hydrogen bonds, namely O-H…O and N-H…O.The framework exists as huge and complicated network of hydrogen bonds. It is obvious that the physical and chemical properties of the crystal are influenced greatly.
ENANTIOMORPHIC PHASE AMBIGUITIES AND THE MODIFIED COMPONENT RELATION——THE APPLICATION OF DIRECT METHODS TO PROTEIN STRUCTURES
FAN HAI-FU
1984, 33 (3): 399-407. doi: 10.7498/aps.33.399
Abstract +
Various kinds of enantiomorphic phase ambiguities and their generalized form in crystal structure determination are discussed. A modified component relation is given together with the associated probability formula. Using the modified component relation, it is possible to treat all kinds of the enantiomorphic phase ambiguities with a unified manner. Problems concerning the application to protein structures are also discussed.
BRIEF REPORT
A NEW METHOD FOR NORMALIZATION OF DIFFRACTION DATA FROM AMORPHUS MATERIALS
HEI ZU-KUN, LIN SHU-ZHI
1984, 33 (3): 408-412. doi: 10.7498/aps.33.408
Abstract +
It is shown that the intersection points of two RDF/r curves obtained from transformation of the interference functions with a little different attenuation should fall on the line -4πrρ0.This method has been used to determine the normalization factor and compared with other methods. It was shown that the accuracy of this method was about 1 %, higher than that of others.
SPECIFIC HEAT MEASUREMENT FOR Ti-Pd ALLOYS
JIN DUO, MA MING-RONG, LIU ZHI-YI, NI YONG-MING, JIN ZUO-WEN, LUO QI-GUANG
1984, 33 (3): 413-418. doi: 10.7498/aps.33.413
Abstract +
The specific heats of Ti-Pd alloys have been measured between 1-6 K, and the electronic specific heat coefficients γ of samples Ti0.92Pd0.08 and Ti0.8Pd0.2 are found to be 5.89 mJ/mol·K2 and 4.78mJ/mol·K2 respectively, which are obviously higher than 3.32mJ/mol·K2 of pure Ti. Therefore, the densities of states at Fermi surface for these alloys are higher than that of pure Ti, this is the reason why the alloys have much higher superconductive transition temperature Tc than pure Ti.
THE CALCULATION OF BACKSCATTERING FACTORS IN AUGER ELECTRON SPECTROSCOPY
WU ZI-QIN, DUAN JIAN-ZHONG
1984, 33 (3): 419-424. doi: 10.7498/aps.33.419
Abstract +
The backscattering factors in quantitative analysis in AES have been calculated using the "full diffusion" model which had been modified and simplified by us. Our results are quite close to the results obtained by Shimizu et al. using the complex Monte Carlo simulation, and better than the Reuter's empirical equation and Love's regression equation based on the simple Monte Carlo simulation. Our calculation are so simple that it can be applied easily in various experimental conditions without inter polation and extrapolation as used by Shimizu et al.
THE CRYSTAL STRUCTURE ANALYSIS OF KLiSO4 WITH NEUTRON DEFFRACTION AT ROOM TEMPERATURE
YAN QI-WEI
1984, 33 (3): 425-427. doi: 10.7498/aps.33.425
Abstract +
The crystal structure of KLiSO4 has been determined by neutron deffraction at room temperature. The position z/c of Li atom is in agreement (the difference is smaller than 1%) with previous X-ray study.
THE GENERATION AND THE CHARACTERISTICS OF INFRARED SURFACE SECOND HARMONIC AT THE GaAs-Al INTERFACE
CHEN ZHENG-HAO, CUI DA-FU, Lü HUI-BIN, ZHOU YUE-LIANG
1984, 33 (3): 428-433. doi: 10.7498/aps.33.428
Abstract +
Using a tunable TEA CO2 Laser and grating Coupling at the interface of GaAs-Al, we have obtained, for the first time, the output of the resonantly excited infrared surface pola-riton second harmonic. The charateristics of the surface second harmonic have been investigated, The agreement between theory and experiment is good.
EXPERIMENTAL OBSERVATION OF SUBHARMONIC IN LIQUID NITROGEN AND WATER
WANG BEN-REN, MIAO GUO-QING, WEI RONG-JUE
1984, 33 (3): 434-436. doi: 10.7498/aps.33.434
Abstract +
The phenomenon of subharmonic bifurcation is observed in experiments of sound wave of finite amplitude, which are performed in liquid nitrogen and water, respectively. The power spectrum is obtained.
LETTERS
ON THE NONCONVERGENCE PROBLEM IN COMPUTING THE CAPACITY OF STRANGE ATTRACTORS
WANG GUANG-RUI, CHEN SHI-GANG, HAO BAI-LIN
1984, 33 (3): 437-440. doi: 10.7498/aps.33.437
Abstract +
The convergence of box-counting algorithm for computing the capacity of strange attrac-tors is affected by the discretization procedure, because the period of the difference equations differs from that of the original ODE'S and, in addition, a damping factor appears. Simply decreasing the time-steps in the integration scheme not only costs more computer time, but also may deprive the convergence at all. The nonconvergence problem can be overcome by choosing at first a correct sampling interval. We give numerical evidence for what said above on the example of the periodically forced Brusselator.
IS 40Ca20 A STABLE ISOTOPE?
ZHAO WEI-QIN, QING CHENG-RUI, HE ZUO-XIU
1984, 33 (3): 441-443. doi: 10.7498/aps.33.441
Abstract +
It is shown that the 40Ca20 is unstable against the process 40Ca20+2e- → 40Ar18hh=2vc, its half lifetime is about 1.2×1033 yr.
SPIN WAVES IN MAGNETIC METALLIC SUPERLATTICES
MA HONG-RU, CAI JIAN-HUA
1984, 33 (3): 444-446. doi: 10.7498/aps.33.444
Abstract +
We study here, in terms of a simple model, the spin waves, magnetic phases, and respo-nces to alternating fields of magnetic metallic superlatticcs.
FURTHER REMARKS ON THE SUPERMODULUS EFFECT
XIONG SHI-JIE, CAI JIAN-HUA
1984, 33 (3): 447-448. doi: 10.7498/aps.33.447
Abstract +
On the basis of the explanation of the supermodulus effect given in a previous paper we discuss further the criterions for the appearance of this effect in compositionally modulated alloys. The results are in accord with all the existing experimental facts.