Vol. 40, No. 5 (1991)
1991-03-05
GENERAL
1991, 40 (5): 673-680.
doi: 10.7498/aps.40.673
Abstract +
The static general solution to Einstein's equations representing a plane-symmetric spaceti-me metric yielded by a massless scalar field is presented. The global properties of the space-time obtained, such as its symmetries and singularities are investigated. It is found that, unlike the spherical case, the singularity in the plane-symmetric case is not influenced essentially by the introduction of the scalar field.
1991, 40 (5): 681-685.
doi: 10.7498/aps.40.681
Abstract +
From the energy spectrum of Z2 symmetric quantum chain with periodic boundary condition, we calculated the central charge and the anomalous scale dimensions of the systems. The results are compatible with the predicfion of the conformal field theory.
ATOMIC AND MOLECULAR PHYSICS
1991, 40 (5): 686-692.
doi: 10.7498/aps.40.686
Abstract +
In this paper, the two-photon autoionization involving second-order ionization processes is investigated. The photoelectron spectra are calculated, and the effects of second-order process on the photoelectron spectra and the relation of spectra's variation with intensity of light are emphatically analyzed.
1991, 40 (5): 693-697.
doi: 10.7498/aps.40.693
Abstract +
Based on independent electron approximation, we have studied the delayed maxima of photoionization cross section of 4d→f transitions for Xe atomic ions. We illustrate the relations of delayed maxima with the enhancement of corresponding final channel electron collision with the residual atomic ions and relations of secondary delayed maxima with the difference of quantum defects of initial and final states. Our results show: (1) As the degree of ionization increases, the delayed maxima will move towards low energy and finally disappear. (2) for Xe atomic ions, the smaller the absolute value of difference of quantum defects of initial and final states is. the low energy the Cooper minima position is.
1991, 40 (5): 698-702.
doi: 10.7498/aps.40.698
Abstract +
Single photon ionization and fragmentation of benzonitrile is studied using synchrotron radiation. The ionization potential of benzonitrile, and the appearance potentials of spontaneous or prompt and metastable fragment ions for different flight time are measured precisely. Decay curves of metastable fragment ions is also obtained by means of ion energy loss scans spectroscopy.
1991, 40 (5): 703-708.
doi: 10.7498/aps.40.703
Abstract +
A Time-of-Flight Mass Spectrometer was developed by modification of a 200kV Ion Im-planter. The time resolution of the 20keV pulsed Ar beam was greatly improved using a part of rising edge of the scanning voltage.Mass distributions of positive and negative microclusters were measured for monocrysta-lline, polycrystalline and amorphous silicon sa microclusters were measured for monocrysta-mass spectra would be strongly related to the structure of the silicon targets.
CLASSICAL AREA OF PHENOMENOLOGY
1991, 40 (5): 709-717.
doi: 10.7498/aps.40.709
Abstract +
Using Rayleigh model, we study dc conductivity of the composite medium with layered inclusions. A generalized identity suitable to this kind of composite medium is proved and a definition of effective conductivity of the systems is given. For the systems with cubic symmetry, an analytic formula for effective conductivity is derived.
1991, 40 (5): 718-725.
doi: 10.7498/aps.40.718
Abstract +
The exact analytic expressions for the photon statistics distribution, the squeezing degree S and the second order degree of coherence g(2) of light field are obtained by using the master equation for the density operator of light field and applying the generation-function method. The evolution of these quantities with the scale-time τ are discussed. It is shown that the squeezing degree S, which is gradually reduced in two-photon absorption process, may still exhibit the squeezing feature. Moreover, the process is favorable to the existence and the enhancement of photon antibunching effect and photon sub-poissonian statistics feature, but the oscillatory characteristics of photon statistics distribution disappear rapidly after having been preserved in a short time.
1991, 40 (5): 726-730.
doi: 10.7498/aps.40.726
Abstract +
We studied the effects of the light intensity and temperature on the frequency of the Rb maser experimentally, and satisfactorily explained the changes of the light-independent frequency setting (LIFS) of the cavity and of maser frequency at LIFS under various cell temperatures. We presented a feasible method by which the effects of temperature and light intensity on maser frequency could concurrently be reduced.
1991, 40 (5): 731-738.
doi: 10.7498/aps.40.731
Abstract +
The method of obtaining self-consistent solutions of the field equation and the rate equations of photon density and carrier concentration has been used to study frequency locking, quasiperiodicity, subharmonic bifurcations and chaos in high frequency modulated stripe geometry DH semiconductor lasers. The results show that the chaotic behavior arises in self-pulsing stripe geometry semiconductor lasers. The route to chaos is not period-double, but quasiperiodicity to chaos. All of the results agree with the experiments. Some obscure points in previous theory about chaos have been cleared up.
1991, 40 (5): 739-747.
doi: 10.7498/aps.40.739
Abstract +
In this paper, the self-focusing processes and ability of helical wiggler, which is often used in Raman Free Electron Laser experiment,, are analyzed. And the conditions for steady beam transportation are given and compared with the Raman FEL experiment beam data. In addition, the theoretical analysis of EPA-74 FEL radiation is presented, which is in agreement with the experimental results.
1991, 40 (5): 748-755.
doi: 10.7498/aps.40.748
Abstract +
The 3-D motion of the relativistic electrons is analysed under the combination of a cylindrical waveguide TE mode (or TM mode) and an axial guide field. Both linear and nonlinear calculations are carried out. Generally speaking, the projection of the electron orbits onto the transverse plane is an annulus, the thickness of which is dependent on the amplitude of the electromagnetic wiggler. However, the electron orbits may diverge when ω+kzvzo+ ( m±1 )ωc≈0 Discussion is also given to the special case that the electromagnetic wiggler is a slow wave propagating parallel to the electron motion.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
1991, 40 (5): 756-766.
doi: 10.7498/aps.40.756
Abstract +
A fast mapping method used to the tokamaks is introduced. It relieves the structure of magnetic island and ergodic on plasma edge. The structure is produced by resonance between radial pertubation field, which is caused by additional coil, and the original tokamak field. The application to TEXT and some results are given.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1991, 40 (5): 767-770.
doi: 10.7498/aps.40.767
Abstract +
The positron lifetime and DSC measurements for EBBA have been made with heating and cooling clycles. The experimental results show that the shorter lifetime (τs) is essentially independent of temperature while the longer lifetime (τ1) and the intensity (I1) change abruptly twice with temperature. These two critical temperatures are in accordance with "he transition temperature measured by the DSC. In the heating and cooling clycles the transition temperature are different. The changes in microstructure during the phase transition have been explained by the ORE model of positron annihilation, which raised the idea that positron can be a probe in the study of EBBA phase tyansitioa
1991, 40 (5): 771-780.
doi: 10.7498/aps.40.771
Abstract +
We consider in this paper a straight dislocation moving uniformly parallel to the planar phase boundary in a two phase medium. We take a moving coordinate system, in which the dislocation is relatively at rest, and extend the general anisotropic elastic theory of dislocation to this coordinate system. We employ the Green function method in elastic theory to treat the phase boundary, thus obtain the total elastic field produced by this moving dislocation and the "image force" acting on it. Our theoretical method is applicable in general, it can be used to consider the interaction between this dislocation and other lattice defects, and mechanical properties of the two phase medium.
1991, 40 (5): 781-786.
doi: 10.7498/aps.40.781
Abstract +
This paper reports the results of crystallization of bulk metallic glassy sphere of Pd40Ni40P20 (with diameter range from 0.1 to 1.0 mm) under 4GPa pressure. Compared with the result obtained at ambient pressure, the crystallization temperature of the glass increased with pressure at the rate of 15K/GPa. As annealing temperature under pressure closed to the melting temperature of the sample, the single supersaturated solid solution phase with f.c.c. structure was obtained. The same phase was also obtained by annealing a cast Pd40Ni40P20 alloy under high pressure. This result indicates that the new phase is a high pressure phase.
1991, 40 (5): 787-795.
doi: 10.7498/aps.40.787
Abstract +
In this paper, a model of 3He liquid layer on an oscillating substrate with a thin super-fluid 4He film as a boundary layer is considered. The complex surface impedance is calculated using the transmission line theory. The slip boundary condition and the vortex motion are taken into account to compute the momentum exchange between 3He and the solid surface. The calculated values are compared with experiments.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1991, 40 (5): 796-806.
doi: 10.7498/aps.40.796
Abstract +
It is needed to improve the tight-binding SSH model which is used to describe the conducting polymers, since the conducting polymers are the systems with wide energy band. In order to study one-dimensional lattice instability of conducting polymers more precisely, it is necessary to go beyond the tight-binding approximation. In this paper the Wannier function method used in stable lattice is extended to calculate the electron energy band of insta-ble lattice. The numerical results show that our method has good convergence, the accuracy can be better than 1% when the third neighbor is included. Meanwhile the dimerization caused by the lattice instability can also be determined precisely.
1991, 40 (5): 807-814.
doi: 10.7498/aps.40.807
Abstract +
The crystal structure, oxygen content, resistance, Hall effect and superconducting crkical temperature of YBa2Cu1-xCox(Cu1-yZny)2Oz system (0≤x, y≤0.1) have been studied. It is found that with increase of Co and Zn contents, the transformation from superconducting metal with orthorhombic structure to non-superconducting semiconductor with tetragonal structure occurs. At the same time, the Tc and the carrier density nh decrease sharply. The effects with Co and Zn doping simultaneously are not simply additive. With increase of Co and Zn concentrations, there is a strong coorelation between Co doping on Cu(l) and Zn on Cu (2) sites. The experimental results show that the coupling between Cu-O planes and Cu-O chains gives much influence on the electronic transport properties in normal states and superconductivity. The characteristics of the hole carriers and its dependence on Tc in 123 phase compounds are also dicussed.
1991, 40 (5): 815-820.
doi: 10.7498/aps.40.815
Abstract +
The sample with the nominal composition Bi2Sr2Ca1-xBaxCu2Oy(A),Bi1.7Pb0.3Sr2Ca2-xBaxCu3Oy(B) were synthesized by solid state reaction. The analyses of phases and structure of the samples showed that a new kind of monoclinic phase exists in Bi-system with cell dimension a=24.84?, b=6.29?, c = 20.70?, β=114.2?. There exists special relation between the monoclinic phase and the superconducting property of Bi system. For 2212 phase, the diamagnetic transition at 95K was observed when the monolinic phase co-existed with 2212 phase, furthermore the addition of Ba ions facilitated the formation of the monoclinic phase. For Ba-doped 2223 phase, the study of electron diffraction indicated that Ba ions got into the 2223 phase and caused the change of crysral micro-structure of 2223 phase, a new additional superstructure appeared along b axis, and two kinds of modulation mode were observed simultaneously along this direction, the wavelength of which is 27?, 43? respectively. The measurement of physical property showed that the zero resistance temperature of the samples can reach as high as 113-114K by proper doping of Ba ions, and the diamagnetic transtion at 118K was also observed. This kind of increasing of the critical temperature of 2223 phase may be related to changes of its crystal microstructure.
1991, 40 (5): 821-825.
doi: 10.7498/aps.40.821
Abstract +
XPS measurements have been performed on the orthogonal single phase YBa2Cu3O7 superconductor. The higher valence-like state of Cu is observed clearly. The electronic states corresponding to the peaks in Cu2p and O1s XPS are discussed. It is suggested that the extra holes due to the excess oxygen are created on the O2p orbit. The higher valence-like state of Cu corresponds to the combination of Cu3d9L and Cu3d10L3 states.
1991, 40 (5): 826-832.
doi: 10.7498/aps.40.826
Abstract +
With the Green's function tequnique, we have exactly dealed with 3-dimesional lsing model, and obtained the linear equations of the ensemble average of the spin which are able TO be recurrent. Then by applying the decoupling approximation to the spin blocks, we can transform the solution of the transition temperature, magnetization and so on into the solution of algebraic equations. We have shown that for the smaller spin block we can obtain the results with higher precision.
1991, 40 (5): 833-843.
doi: 10.7498/aps.40.833
Abstract +
In this paper the structure, magnetic and magneto-optical properties of the Nd-doped MnBi thin films are discussed. The analyses by the Auger profile and X-ray diffraction of these films show that the crystal structure composed mainly of MnBi hop is formed after suitable annealing, and the structure of MnBiNd alloy which is much similar to the MnBi may be existed for the MnBi films doped with Nd. According to the crystal structure with NiAs type the lattice constants of MnBiNd alloy are calculated: a = 4.14?, c = 5.80?. The torque curve and the hysteresis loop show that the film possesses perpendicular anisotropy. When the ratio of raw materials Mn/Bi is two or so, we can obtain the suitable σs, the proper Hc(1-4 kOe), and a very large Kerr rotation angle θK (1.5-2°). The magneto-optical profile shows that the frequency corresponding to the maximum θK shifts to low frequency as Nd component increases .It was found that the grain size of all films which were deposited on the cooled glass substrates is limited in the range of 200 to 400?, moreover, the high temperature phase transition of MnBi alloy was avoided by Nd doping.
1991, 40 (5): 844-848.
doi: 10.7498/aps.40.844
Abstract +
X-ray diffraction, transmission electron microscopy and Mossbauer spectroscopy were used to verify nanocrystalline state of the SnO2 materials prepared by hydrothermal growth, The hyperfine parameters of Sn atom and relation between it and temperature have been measured by Mossbauer spectroscopy. It has been revealed that nanocrystalline SnO2 will cover to crystalline SnO2 at 600℃.
