Vol. 31, No. 2 (1982)
1982, 31 (2): 143-149. doi: 10.7498/aps.31.143
In this paper, we studied the instabilities excited by head-on collision of two rela-tivistic electron beams in transporting, taking account of the magnetic field B0 and the thermal pressure ▽p of the beams. The conditions under which the instabilities occur and the growth rate of instabilities are obtained. The results show that these instabilities can be excited or inhibited by controlling the velocity of the beams.
1982, 31 (2): 150-158. doi: 10.7498/aps.31.150
The mechanism of rf-driven currents by high frequency electromagnetic waves is discussed. It is shown that the current will be driven both by the electric force and Lorentz force, and either the resonant effects or the nonresonant effects may be domi-nant,and there exist some differences between the l0 resonances. It is also shown that under some conditions the collisional power dissipation may be stronger than the resonant power dissipation.
1982, 31 (2): 159-169. doi: 10.7498/aps.31.159
The influence of the abrupt density change near the limiter radius in Tokamak on the coupling of lower hybrid wave with grill is considered. It is discovered that the serious wave reflection, which exists in the region of the abrupt density change, would reduce the coupling efficiency of the grill. A standing wave is formed between the region of the abrupt density change and vacuum chamber wall by the reflected wave. The power and the energy flux spectra would be changed and more sensitive to the plasma boundary condition. In addition, the accessibility criterion of LH wave would be loosened.
1982, 31 (2): 170-179. doi: 10.7498/aps.31.170
We discussed the nonlinear effects of ponderomotive force, which is exerted by powerful LH waves with large electrical fields (|E|～1.5 kV/cm). An obvious nonlinear nonhomogeneity of density in the direction parallel to B0 has been found. It might be serious enough to influence the propagation of the long waves (such as waves with N‖～1). As for the direction perpendicular to B0,if there is reflection inside the plasma (for example, from the region close to the limiter of Tokamak), a series of density cavities might appear along the path of LH wave transmission, and the picture of plasma displacement is no longer suitable.
1982, 31 (2): 180-184. doi: 10.7498/aps.31.180
Using electron microscopy and electron diffration methods, we have investigated the microstructures, shortrange order and their changes with increasing temperature in amorphous Tb31Fe69 and Tb27Fe73 films prepared by vapour deposition in a vacuum of 10-5 torr. The process of crystallization have also been observed and analysed. The microstructures of samples with different oxygen contamination and different annealing temperatures were found to be different. However, the phase separation of both samples seemed to occure by a mechanism similar to spinodal decomposition, by which an initial amorphous phase first decomposed into two or more compsitionally discrete amorphous phase, each of which then crystallized independently with rising temperature. Thus, the whole process of crystallization consisted of several stages. Finally a poly-crystalline mixture would be formed.
1982, 31 (2): 185-190. doi: 10.7498/aps.31.185
We have studied magnetic and electrical properties of TbFe2 amorphous film prepared by R. F. sputtering. Saturation magnetization Ms(T) (77-800K), electrical resistivity ρ(T) (4.2-400K) and M?ssbauer spectra (18K, 400K) measurements were made. We obtained the Curie temperature (Tc～400K), temperature of the resistivity minimum (Tmin～360K) and the negative temperature coefficient of resistivity. M?ssbauer spectra at room temperature were resolved using both of the method of Hesse and that of Window. The hyperfine field distributions obtained by both methods are in good agreement. There are two distributions at H=210 kOe and H=25 kOe respectively. The first is consistent with ferromagnetism and the second is probably associated with Kondo-type resistance minimum. The M?ssbauer effect results indicate that the spin of the iron ion is also subjected to a local anisotropy field of random orientation. This result is consistent with the Harris model.
GENERAL RULE ON THE APPEARANCE OF MULTIPLE SOLUTION IN THE DETERMINATION OF CRYSTAL STRUCTURES CONTAINING HEAVY ATOMS
1982, 31 (2): 191-198. doi: 10.7498/aps.31.191
In the determination of crystal structures containing heavy atoms, special arrangement of the heavy atoms leads often to the failure of determining uniquely the positions of the light atoms. This is the case not only occured frequently in Patterson analysis but also in heavy-atom method ar direct methods. Hence it is a common difficult problem in crystal structure analysis. The authors have proposed systematically a series of procedures to tackle this problem. The present paper deals with the general rule on the appearance of multiple solution in the determination of crystal structures containing heavy atoms. It is concluded that whenever the distribution of heavy atoms possesses higher symmetry than that of the light atoms by an additional inversim centre and lor sulperiodicity of translation, multiple solution would be obtained for the light atoms that two or more structure images of the light atom portion related by the additional symmetry would result simultaneously.
1982, 31 (2): 199-206. doi: 10.7498/aps.31.199
The transformation characteristics of the probability amplitude corresponding to an arbitrary sublevel system of a nucleus is studied. The nucleus, with arbitrary spin, is placed in a magnetic and an electrostatic field and irradiated selectively. The possible physical implication of the above mentioned transformation characteristics is discussed. The differences between the two characteristics, i.e., the 2π or 4π symmetry of the wave functions under space rotation and the 2π or 4π periodicity of the probability amplitude corresponding to a sublevel system under selective irradiation are explained.
1982, 31 (2): 207-212. doi: 10.7498/aps.31.207
In this paper, we have extended the Hawking evaporation of Dirac particles in extreme Kerr and Kerr-Newman black hole background to the case of general Kerr-Newman black hole. The physical solutions of the Dirac equation with non-zero rest mass are found outside the event horizon of a general Kerr-Newman black hole by a proper transformation. The Hawking thermal spectra formula is also derived. The problem of the Hawking evaporation of Dirac particles in general Kerr-Newman black hole background have been solved, (ref. ).
1982, 31 (2): 213-219. doi: 10.7498/aps.31.213
The asymmetry of ultrashort light pulse may be detected by third order intensity correlation. As compared with the results of SHG method, more information may be obtained about the shape of the pulse. According to our measurement, the shape of the pulse of passively mode-locked Nd: YAG Laser can be considered approximately as Gaussian-exponential. The correlation width obtained by third order intensity correlation was 22.3 ps+15.7 ps, its corresponding pulse width was about 27ps. The leading edge of the pulse was steeper than the trailing edge.
1982, 31 (2): 220-225. doi: 10.7498/aps.31.220
The cluster model and the self-consistent extended Huckel method are used to calculate the stable configuration for the chemisorption of Al on both the Si(lll) and GaAs(110) surfaces. The calculated results show that the threefold ionic chemisorption for Al/Si (111) is more stable than that for the covalent top site, and the LDOS for the threefold site agrees quite well with the experimental data. In the case of Al/GaAs(110), the Al adatom substitutes the surface Ga atom to form an AlAs layer, and the Al chemisorption leads the relaxed GaAs (110) back to the unrelaxed ideal position.
1982, 31 (2): 226-233. doi: 10.7498/aps.31.226
In this paper, starting from ray optics, the chromatic aberration equations of selfoc-rod lenses are obtained. Chromatic aberration of Tl-1, Cs-1, DAP-MMA and CE39-8FMA selfoc-rod lenses are calculated. The solutions of chromatic aberration equations in specific cases are given.
1982, 31 (2): 234-236. doi: 10.7498/aps.31.234
The effects of Coulomb interaction on the stimulated scattering by relativistic electron beams are investigated. The analytical expression for reflected laser field is obtained in the case of monoenergetic electron beam. It is shown that the contributing factor characteristic of Coulomb interaction is proportional to the square of electron density. If the electron density is relatively high and the incident radiation intensity is relatively low, the contribution of Coulomb force will be significant and its effects cannot be neglected.
1982, 31 (2): 237-242. doi: 10.7498/aps.31.237
A theory is proposed about the third order optical nonlinearity which is induced by the saturation effect of interband transitions in semiconductors near the absorption edge. The value of the exceptionally large nonlinear refractive index of InSb is given.
1982, 31 (2): 243-246. doi: 10.7498/aps.31.243
In this paper, we report on the measurement of the absorption and the relaxation time of the Chinese fast saturable absorbers D1 and D2 used for mode-locking Nd-doped laser material.
1982, 31 (2): 247-251. doi: 10.7498/aps.31.247
This article presents results of our studies on PZT-8 polycrystalline ferroelectric ceramics of lead zirconate titanate. We have measured the dielectric constant and dielectric loss over a low frequency range (from . 100kHz-20MHz) and temperature range from room temperature to 500℃. The mechanism of dielectric loss, the relaxation process and the impurity effects are discussed. The main loss above Tc is attributed to conducting loss.We also propose some suggestions for improving electrical properties of PZT-8 ferroelectric ceramics.
1982, 31 (2): 252-257. doi: 10.7498/aps.31.252
In an anisotropic plasma, the electrostatic shielding of a static test particle is always complete for an arbitrary distribution function. In this paper the analytical formula and the numerical values of the electrostatic shielding potential in a bi-Max-wellian plasma are given. When the distance R is large, the potential is proportional to R-3. Under certain conditions, there might appear some supershielding regions about the test particle.
AN EMPIRICAL CORRELATION BETWEEN SUPERCONDUCTING ENERGY GAPS 2△0 AND THE HALL COEFFICIENTS IN AMORPHOUS SUPERCONDUCTORS
1982, 31 (2): 258-261. doi: 10.7498/aps.31.258
An empirical correlation between superconducting energy gaps 2△0 and the Hall coefficients RH of amorphous state and between superconducting energy gaps 2△0 of amorphous state and the Hall coefficients RHL of corresponding liquid metals is found respectively, that is: in numerous non-transition metals and alloys, 2△0 takes a maximum value as RH (or RHL)=-3.5--4.0×10-11m3/AS.
1982, 31 (2): 262-267. doi: 10.7498/aps.31.262
In this paper, an explanation for the increase in temperature coefficient of electrical resistivity of Cu3Au with increasing degree of long-range order is given on the basis of a recent theory of resistivity for crystalline alloys proposed by the author. The ρT and dρ/dT of Cu3Au calculated by using a simple model pseudopotential appear to be in relatively good agreement with experimental data.
1982, 31 (2): 268-270. doi: 10.7498/aps.31.268
The microstructure and superconducting-normal transitions of fast quenched Al-8.3 at%Si-8.5at%Ge have been studied. Structural analysis of the samples indicated that Al-Si-Ge alloy consists of two phases: an amorphous phase and a supersaturated α-Al (Si, Ge) solid solution. After heat treatment at 100℃ for 50 hr, a double superconducting transition can be observed in both their resistance-temperature and resistance-intensity of magnetic field characteristics.