Vol. 29, No. 5 (1980)
1980-03-05
CONTENT
1980, 29 (5): 533-556.
doi: 10.7498/aps.29.533
Abstract +
In solving the crystal structures containing heavy atoms by patterson method, if the heavy atoms have a pseudo-symmetry which is higher than that of the whole structure, this will result in multi-solution positions of light atoms (two, four or eight possible positions). Expressed in reciprocal space, this problem is equivalent tc that some of the component signs of the diffraction structure amplitudes are undetermined. Seventy four space groups of low symmetry systems (trielinic, mono-clinic and orthorhombic systems) have been analysed. For an asymmetric unit involving only one heavy atom, with the possible positions of the heavy atom and the pseudo-symmetry given, the multi-solution types of light atoms and the distribution rule for components of diffraction struture amplitudes are obtained. In addition, a possible way for resolving these problems by direct method is proposed.
1980, 29 (5): 557-565.
doi: 10.7498/aps.29.557
Abstract +
The Co-Ga binary system has been investigated by X-rays in conjunction with differential thermal analysis.It has been established that besides Ga and γ-Co which is the room temperature modification of pure cobalt, there are three phases in the entire system, α′,β and ψ. α′ is a superstructure phase based on a face-centred cubic fundamental lattice, and may be considered as a solid solution of α-Co which is the high temperature form of pure cobalt, stabilized at room temperature due to the addition of gallium. The homogeneous range of this phase at room temperature is 2.4-10.7 at % Ga. The β phase is formed by a peritectic reactio α+L ←→β at 1177℃, with a homogeneous range 36.3-59.8 at % Ga at room temperature. The structure of this phase is of the CsCl (B2) type. The lattice spacing changes with composition in such a way that it rises at first, reaches a maximum, and then falls off with the gallium content. This is similar to the β phase in the Al-Ni system. In the Co-rich side of the maximum, it appears as a substitutional type solid solution, while in the Ga-rich side, it belongs to the defect type, the addition of Ga atoms being equivalent to the dropping off of some Co atoms from the normal lattice. The homogeneous range of the ψ phase is extremely narrow, existing only at the near neighbourhood of the stoichiometric composition 75 at % Ga. This phase belongs to the tetragonal system with space group D4h14-P42/mnm. Bach unit cell contains four formula weights CoGa3, and the lattice spacings at 75.4 at % Ga and 20℃ are α=6.2365?, c=6.4347?, c/a = 1.0318. It is formed peritectically (α + L←→ψ)at 833℃.Neither Ga in γ-Co nor Co in Ga shows any detectable solid solubility. There exists an eutectic horizontal from CoGa3 to Ga at 27℃, with the eutectic point very close to pure gallium.
1980, 29 (5): 566-576.
doi: 10.7498/aps.29.566
Abstract +
A model of impurity precipitate-dislocation generation, impurity atom-dislocation interaction and impurities rapid diffusion along grain boundaries has been used to explain the out-diffusion behaviour of implanted impurities and defect movement in the amorphous layers due to high dose ion implantation during reerystallization annealing. Taking the resultant stress effect of the dislocations in to account, the diffusion equation of impurities has been established. By using Pb+ ions with energy of 80 keV implanted in (111) silicon to the dose of 1016cm-2 as an example, a mathematical and physical treatment of the diffusion equation has been carried out. Thereby a method of deducing the apparent diffusion coefficient varying with time and the longitudinal profile of the force exerted by the resultant stress of dislocations on the impurities according to the experimental measurements has been proposed. The measured constant of interaction between dislocations and impurities, α, is α≈8.4×10-28dyn·cm3, and the time variation of the apparent diffusion coefficient D in a time interval can be expressed as a exponential function.
1980, 29 (5): 577-587.
doi: 10.7498/aps.29.577
Abstract +
Tokamak is an experimental fusion device in which hightemperature toroidal plasma is produced, it belongs to the category of complicated modern electro-physical facilities. CT-6 is the first small tokamak device in operation in our country, its main parameters are as follows: major radius R: 45cm; minor radius a: 9.2cm; toroidal magnetic field: 2TL; plasma current Ip: 30 kA. After careful test operation and adjustment design goal had been achieved and stable hot toroidal plasma with electron temperature about 250 eV was produced. CT-6 device consists of electro magnetic system (toroidal, Ohmic heating and equilibrium field systems), ultra-high vacuum system (toroidal vessel and pumping system), power supply and control system, diagnostic system. It is designed, developed and operated jointly by Institute of Physics and Institute of Electrical Engineering of Academia Sinica, in collaboration with many other institutions.In the present article the design, structure, engineering development, and also relevant results given by the test operation of CT-6 device are described.
1980, 29 (5): 588-593.
doi: 10.7498/aps.29.588
Abstract +
This paper reports the experiment in which by using broadspeetrum 5314? laser beam as the pumping radiation, an intense 6296? stimulated Raman scattering stokes emission was achieved in the organic solution (CH3)2SO. With a intermediate power density, the efficiency of energy conversion to forward stimulated Raman scattering approached 38%. The backward Stokes stimulated emission was observed, and the backward wave intensity was about 80% of the forward scattering intensity. The gain of the forward scattering wave was measured and was about 2.5×10-3cm/ MW, the spatial distribution and the beam divergence of the forward and backward waves were measured. The improvement of the beam direction of the backward wave was demonstrated.
1980, 29 (5): 594-601.
doi: 10.7498/aps.29.594
Abstract +
Thermally induced birefringence and transmission coefficient for several commonly used YAG: Nd crystal rods were calculated theoretically and relations between the transmission coefficient and the polarizer angle and the output power were measured experimentally. The theoretical results are in good agreement with that of experiments. Our results show that when the above mentioned rods are used, if we follow the orientation relations and use the transmission coefficients given in this paper, with a polarizer properly placed in the Laser cavity, then excellent polarized output can be achieved.
1980, 29 (5): 602-608.
doi: 10.7498/aps.29.602
Abstract +
The absorption spectra of Nd3+ in pure anhydrous neodymium chloride crystals and in anhydrous praseodymium chloride crystals (containing 0.1% NdCl3) have been examined systematically examined. The structures of the groups of their absorption lines are found to be similar to those of Nd3+ in NdCl3 crystals diluted by LaCl3 (containing 2% NaCl3 in LaCl3), except for a shift of the spectrum towards the long wave side. The shifts (relative to the ground state) of these corresponding sub-levels are proportional to the length of unit cell of the single crystals.
1980, 29 (5): 609-617.
doi: 10.7498/aps.29.609
Abstract +
The properties of an electron in the polar crystal is discussed by means of a model which takes account of the atomic property of the lattice. The lattice vibration and the interactions of the electron with the lattice displacement are treated by second quantization method. The self energy, effective mass of the polaron and the temperature dependence of the polaron effective, mass are derived.
1980, 29 (5): 618-634.
doi: 10.7498/aps.29.618
Abstract +
In consequence of the spontaneous symmetry breaking, non-zero energy Goldstone, modes with dissipation are excited in a non-equilibrium stationary state with space-time structure. In this paper, as a specific example, the Ward-Takahashi identities formulated in the close time path Green's function method is applied to the saturation state of a single mode laser. A generalized Goldstone theorem in a weak inho-mogeneous dissipative system is established and the physical interpretation of the Goldstone mode is discussed. As a result of the Goldstone theorem, the pole in the Green's function of the laser light splits into two with equal weights, each corresponding to a quanta with the same frequency but different dissipation. Together with the order parameter (the average value of the vector potential), these two kinds of quanta (one of which is the Goldstone mode) give a complete description of the order-disorder transition of the phase symmetry in the saturation state of the laser. A detailed discussion on the restoration of the spontaneously broken symmtry of the phase is given.
1980, 29 (5): 635-643.
doi: 10.7498/aps.29.635
Abstract +
We presented here a theory of the Heisenberg ferromagnetic system with biquadratic exchange interaction at, low temperatures. In our theory, the kinematic and dynamic interactions are correctly included. The expansion for Sz in terms of temperature and the temperature dependence of spin wave spectrum are obtained ri-grously.
1980, 29 (5): 644-650.
doi: 10.7498/aps.29.644
Abstract +
This paper suggests a method of measuring the microwave tensor susceptibility and the effective linewidth using the same sample in both the non-resonanee and re-sononce regions. In this method the applied steady magnetic field can be rotated to form a certain specified angle with the microwave magnetic field, so that the effect of the measured sample on the quality factor of the resonant cavity can be adjusted. The iterative method used by C. E. Patton in the calculation of effective linewidth is extended to the calculation of the components of microwave tensor susceptibility. A brief description of the experimental set and the results of the measurements are presented.
BRIEF REPORT
1980, 29 (5): 651-657.
doi: 10.7498/aps.29.651
Abstract +
Using 50% HCI as etchant, we studied the morphology of dislocation etch pits on cleavaged (0001) basal faces of PbFe12O19 single crystals grown by the fluxed method. Three kinds of etch pits are found and two of them correspond to {1010} and {1011} types of dislocations, respectively. The third kind of etch pits is related to the presence of screw dislocations which are responsible for growth mechanism. Dislocation etch pits arrays observed on (0001) faces are interpreted by applying the mechanism proposed by Matthews et al.
1980, 29 (5): 658-660.
doi: 10.7498/aps.29.658
Abstract +
It is proved rigrously that the long range order for isotropic multi-quadratic Heisenberg model is absent in the 1 and 2-dimensional systems.
1980, 29 (5): 661-666.
doi: 10.7498/aps.29.661
Abstract +
Lithium ionic conductivity of LISICON single crystals grown by Czochralski method has been investigated. It was found that the conductivities in different orientations do not show strong anisotropy and the relations between them are: σb≤σa≤σc≤σ[110]. The lithium content in the crystals have obvious influence on conductivity. When Li/Zn ratio changes from 6.7 to 9.2, the conductivity in a-direction at 300℃ increases from 4.3 × 10-2Ω-1·cm-1 to 1.25×10-1Ω-1·cm-1. Three transition points at ～80℃, ～140℃ and ～300℃ have been shown in logσT vs. 1/T curves. The activation energy for conduction are 0.5-0.58 eV (25-80℃), 0.92 eV (80-140℃), 0.64 eV (140-300℃) and 0.36 eV (> 300℃) respectively. The polarization experiments indicated that LISICON is a lithium ionic conductor with negligible electronic conductivity.
1980, 29 (5): 667-672.
doi: 10.7498/aps.29.667
Abstract +
In this paper gravitational mass defect in charged static and spherically symmetric metric discussed by [1,3] is extended to the case in which charge is kept constant in the course of gravitational mass defect. Some curves showing defected mass M variation as a function of the primary mass M0, the specific charge a and the radius r are presented, (ref 4)
1980, 29 (5): 673-676.
doi: 10.7498/aps.29.673
Abstract +
An apparatus for measuring the ellipsometric spectra has been set up in our laboratory. From the experimental values of Imax,Imin and θmin, it is easy to determine the ellipsometric parameters ψ, △ as functions of wavelengths. The ellipsometric spectra of SiO2 films of several thicknesses on silicon have been determined. When comparing the experimental data with the theoretical curves calculated by computer, we find that they are generally in agreement. The ellipsometric spectrum method for measuring the film thickness has also been compared with the extinction method.
