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Vol. 28, No. 1 (1979)

1979-01-05
CONTENT
THE KINETICS OF LASER ISOTOPE SEPARATION
MA XING-XIAO
1979, 164 (1): 1-14. doi: 10.7498/aps.28.1
Abstract +
In this paper, the isotope enrichment processes were described generally. A kinetic model involving its mechanism and equations was set up in attempt to represent a great number of processes corresponding to various ways and methods in laser isotope separation. The simplified results for typical cases were given, upon which the high selectivity conditions were derived. Finally, the effects of reversible reaction to the isotope enrichment was investigated.
MODE-VOLUME MATCHING OF OSCILLATING MODES OF LASER CONTAINING SEVERAL ACTIVE ELEMENTS
YE BI-QING, MA ZHONG-LIN, LING JUN-DA
1979, 164 (1): 15-20. doi: 10.7498/aps.28.15
Abstract +
Using matrix method, we analyzed the high power c.w. laser of several YAG:Nd rods in series. The thermo-focal lengths and dimensions of these laser rods may be different. By using the electronic computer, the parameters describing operating characters of laser (especially mode-volume match parameter) have been obtained as a function of the geometric construction of resonator and the thermo-focal lengths of laser rods. In addition, experiments of laser oscillating were carried out on a laser with two rods of different dimension. The experimental results are quite agree with the theoretical analysis.
PROFILES OF JUNCTION CURRENT AND CARRIER-CONCEN-TRATION IN GaAs INJECTION LASERS WITH FILAMENT
GU SHI-JIE, HUO CHONG-RU
1979, 164 (1): 21-32. doi: 10.7498/aps.28.21
Abstract +
The profiles of junction current and voltage and carrier-concentration in an injection laser with filament were calculated on the basis of a simple model. Numerical results indicate how the various parameters such as bulk resistivity and carrier diffusion length in the active region affect the profiles. Particularly, the filament width is strongly dependent on the bulk resistivity. The model connects the stimulated radiation characteristics of the device with the measurable quantities of the external circuit. It shows that there is obvious difference between average density of operating current and current density in the filament rigion. It shows also that nonuniformity of material will play an important role in locating the filament.
CELLULAR INTERFACE AND CELLULAR STRUCTURE DUE TO CONSTITUTIONAL SUPERCOOLING IN CZOCHRALSKI-GROWN LiNbO3 SINGLE CRYSTALS
MING NAI-BEN
1979, 164 (1): 33-39. doi: 10.7498/aps.28.33
Abstract +
In this paper, we studied the morphology of the cellular interface and cellular structure due to constitutional supercooling in Czochralski-Caxis grown LiNbO3 single crystals which were unintentionally doped with Al impurities.The cellular interface consists of a crowd of trigonal-shaped pyramids and the indices of three pyramidal planes are {0112}, between these pyramids there are solute (Al)-rich grooves. The cellular structure in the grown crystal appears as a bundle of prism-shaped cells parallel to the growth direction [0001] divided by {0112} cell walls relatively rich in solute (Al), or as many forks of three solute-rich {0112} walls. These experimental results establish that the white-stripes, veils and solute trails are the manifestations of cellular structure and that the intermittent cellular structure has originated from the temperature fluctuation. The morphology of cellular interface and cellular structure of oxide materials has been compared with metals and their morphological differences are correlated with their entropy of fusion.
ON THE CORRELATION BETWEEN GROWTH FORMS AND INTERFACE MOLECULAR GROUP WAVINESS OF SYNTHETIC QUARTZ
ZHANG YUAN-LONG
1979, 164 (1): 40-53. doi: 10.7498/aps.28.40
Abstract +
By using the seed crystals of designed profiles so that inward as well as outward growth may take place with respect to the z axis, various growth forms of synthetic quartz are displayed. The formations of three different types of trigonal tripezohedron, i.e. the vicinal of 5161, 6155 and the closed pair of triangular facets deformed from 2112 and 10559 are described. Direct evidences are given, demonstrating that during the lateral progression across z (0001) plane, the-x direction will overtake that of + x.The general sequence of growth rate of different faces including + x≥ - x is explained in terms of the duly proposed concept of interface molecular group waviness. In addition to the acuity of the molecular reentrant angles upon z(0001), the more widely opened and therefore more readily fitted lateral reentrant angles formed during the lateral movement of the growth front along the negative polar directions enhances the rate of progression.The reentrant angles of the growing molecules, projected on certain chosen reference axial plane, will act as a measure of the interface molecular group waviness. A hybrid series of interface types are classified, in which the degree of flatness of the molecular group waviness will determine the degree of "flatness" of the interface, while the share of "stepness" and "kinkness" is estimated by resolving the normal of the oriented interface into the directions of the diad and triad axes of the crystal respectively.The assumed statistically dominant form of the molecules in the supersaturated hydrothermal solution is ring shaped Si6O6(OH)12 with the least specific surface free energy, being a relatively more stable metastable stage, appear to be the more appropriate growth units. In accordance with the structure of the crystal and the orientation of the growing interface, the growing molecules will be oriented to adopt the maximum possible molecular reentrant angles so as to minimise the interfacial free energy. This basic assumption explains why growth on the prism faces is likely to be very slow.The polarization of molecules and adsorption of foreign ions on the growing polar faces and also the possible grouping of the ring shaped molecules before crystallization are finally discussed.
THE CRYSTAL STRUCTURE OF MnGa AND THE DEGREE OF ORDER
LU XUE-SHAN, LIANG JING-KUI, YANG ZHONG-RUO
1979, 164 (1): 54-54. doi: 10.7498/aps.28.54
Abstract +
The crystal structure of the γ3 phase in the Mn-Ga system has been determined by the Debye-Scherrer method, and thence the degree of order in the atomic arrangement in this phase region has been estimated as a function of the gallium content.The structure of the γ3 phase belongs to the tetragonal system, the space group being D4h1-P4/mmm. The ideal stoichiometric composition is MnGa, and each unit cell contains one formula weight, the manganese and gallium atom occupying (000) and 1/2 1/2 1/2) positions respectively. It is a distorted form of the B structure, and if it is rotated π/4 about the c-axis, the transformed unit cell can be shown to be of the type LI0, isomorphous with CuAu-I. At room temperature, the lattice spaeings of the original cell at 42.9 at.% Ga are α=2.7475? and c=3.6756?.This phase may be considered as a substitutional solid solution of γ-Mn, stabilized at room temperature due to the partial substitution of manganese atoms by gallium atoms as a tetragonal face-centred ordered structure. In this entire phase region, the degree of order increases with the gallium content.
INVESTIGATION OF THE PSEUDO-TERNARY SYSTEM SrNb2O6-NaNbO3-LiNbO3
TANG DI-SHENG, LIANG JING-KUI, SHI TING-JUN, ZHANG YU-LING, TIAN JING-HUA, LI WEN-XIU
1979, 164 (1): 62-77. doi: 10.7498/aps.28.62
Abstract +
The pseudo-ternary system SrNb2O6-NaNbO3-LiNbO2 has been investigated by means of DTA, heat treatment and X-ray diffraction techniques. It has been found that at room temperature Sr2Na(NbO3)5(S2N) is a metastable intermediate compound which has a tetragonal tungsten-bronze structure with a=12.36?, c=3.906?. LiNbO3 can be dissolved in S2N up to a limit about 10 mol% ; and in the range of 5-10mol% of LiNbO3, the S2N phase is distorted into S2N′, which belongs to the orthorhombic system and is also a metastable phase. After long time annealing at 900-1100℃, the metastable phases S2N, S2N′ will decompose into a mixture of SrNb2O6 and a phase of solid solution based on NaNbO3. The phase diagram of the corresponding binary systems and the isothermal section of the pseudo-ternary system have been established.
ON OVERLAPPING OF ELECTRON DIFFRACTION PATTERNS FROM TWO CRYSTALS WITH A SIMPLE ORIENTATION RELATIONSHIP
YE HENG-QIANG
1979, 164 (1): 78-87. doi: 10.7498/aps.28.78
Abstract +
For two phases having a simple orientation relationship, some of the reciprocal points coincide in the reciprocal space. The electron diffraction pattern corresponding to the reciprocal planes consisting of common reciprocal points only will superpose on the matrix spots. In this paper, a simple method is established to identify the indices of zone axis which give the second phase electron diffraction pattern superimposed on the matrix spots. The method is applied to examine the cases of the overlapping of cubic matrix pattern with that of the twin crystal, the hexagonal close packed structure, the hexagonal ω-phase, etc.
A UNITARY GROUP TREATMENT FOR STRONG CRYSTAL FIELD IN OCTAHEDRAL SYMMETRY
WEN ZHEN-YI
1979, 164 (1): 88-103. doi: 10.7498/aps.28.88
Abstract +
By utilizing the commutation properties of second quantized operators, a chain of groups has been obtained. This chain can serve the purpose of classifying state of d-electrons in octahedral symmetry. The symmetry wave functions, which are adapted to the chain of groups and expressed in the form of linear combinations of Gelfand state, are constructed. Moreover, The methods of calculating matrix elements are discussed systematically in this paper.
INFLUENCE OF EFFECTIVE PHONON SPECTRUM α2F(ω) ON Tc OF SUPERCONDUCTORS
LI HONG-CHENG
1979, 164 (1): 104-116. doi: 10.7498/aps.28.104
Abstract +
Results of some 3500 numerical solutions of Tc for 64 different effective phonon spectrum a2F(ω) are presented. It can be seen from these results that the Tc has the conditional maximum (Tc/A)max, if the area of spectrum is unchanged. Tc depends chiefly on the position and area of the peak of spectrum. Its dependence on the peak width is comparatively unimportant. If the double δ spectrum is replaced by the double ω spectrum with same and 2>, the rms error is 3.2%. In this paper I analysis and settle the dispute regarding the "λ=2 limit" in the literature.
BRIEF REPORT