Vol. 37, No. 5 (1988)
1988-03-05
CONTENT
1988, 37 (5): 705-713.
doi: 10.7498/aps.37.705
Abstract +
The static Josephson effects in the circular symmetric annular junctions are discussed in this paper. When the annular widths are smaller than λJ, analytic solutions of magnetic field dependence of the maximum Josephson current Im, are obtained. Because the external magnetic field is nonuniform distributed in the junctions, the minima of lm are not equal to zero. These results exhibit a quasi-diffraction characteristic. When the annular widths are larger than λJ, the numerical solutions of the self-field equations are obtained, which show the magnetic field dependence of the maximun Josephson current Im and the current distribution. Due to the 2-dimensional character, the points of maximum of Im are not on the axis where the external field is equal to zero in the plot of Im vs. IH.
1988, 37 (5): 714-719.
doi: 10.7498/aps.37.714
Abstract +
The stability of the solutions of the self-field equations for the circular symmetric annular Josephson junctions is analyzed in this paper. The stability of the solutions is determined by the signs of the second-order variation of the free energy with respect to the variation of the phase difference in the junctions. This criterion can then be tranformed to a eigenvalue problem. The solutions may be stable, nonstable, or metastable for a given bias current.
1988, 37 (5): 720-726.
doi: 10.7498/aps.37.720
Abstract +
In this paper, using the local approach, we calculated the correlation energy, the local moments and the polarisation around the local moments in paramagnetic phase up to second order in the extended Hubbard model. It is shown that the polarisation is always antiferro-magnetic for different values of W. The correlation energy increases with W increasing for n = 1 and large U. The local moments and the antiferromagnetic polarisation decrease with W increasing for fixed n and U. While the effect of W on both the local moments and the antiferromagnetic polarisation is not obvious for small n or for large U and n = 1.
1988, 37 (5): 727-734.
doi: 10.7498/aps.37.727
Abstract +
In discussion of the many body effect of homogenenus Fermion system with hypernetted chain method, RPA is always applied and original wave function is taken as a Fermi sphere distribution function. In this paper, the validity of this method is investigated and the relation between the valid range of this method and the properties of potential and density is obtained.
1988, 37 (5): 735-742.
doi: 10.7498/aps.37.735
Abstract +
This paper presents and analyzes the focusing of pump beams and the excited EPW (electron plasma wave) in a PBWA (plasma-beat-wave accelerator) by beating two self-trapped laser beams. The equations governing the saturated amplitudes of EPW in nonuniform pump beams have been derived analytically. With these, the condition for self-trapping of pump beams has been studied self-consistently. The optimum frequency mismatch parameter and the corresponding optimum initial plasma density as well as the maximum amplitde of the EPW have been obtained analytically. The transverse distribution of the EPW for Gaussian pump profiles has been calculated numerically and shows peculiar characteristics for certain frequency mismatch parameters. In addition, the component of the EPW electric field due to the nonuninformity of pump beams has been obtained and its influence on particle acceleration in PBWA has been briefly discussed.
1988, 37 (5): 743-750.
doi: 10.7498/aps.37.743
Abstract +
The population on 6p2 3P2 metastable state and 6p2 3P0 ground state of Pb atoms are de-monstrated, which are originated from dissociating PbCl2 by the fourth harmonic of YAG lasers. The population ratio of 3P2 to 3P0 is measured in terms of laser-induced fluorescence. The results indicate that the dissociation of PbCl2 is a two photon process and the population inversion between 3P2 and 3P0 exists. The stimulated Raman radiation based on the population of 3P2 metastable state is observed. The possible way of dissociation is studied.
1988, 37 (5): 751-759.
doi: 10.7498/aps.37.751
Abstract +
The quatum statistical properties of two-photon radiation from two-level atomic system are investigated by using complete set in the nth subspace of generalized Jaynes-Cummings hamiltonian, and the general expression for field variance is obtained. The conditions for optimum squeezing as well as the optimum squeezed quantity are found out for an arbitrary initial state, and the time evolution of the optimum squeezed state is then analysed. As an example, the squeezing in an initial state with bare atomic system in thermal equilibrium is discussed, which demonstrates the dependence of squeezing on several parameters, such as, temperature, detuning, coupling strength. The conditions for squeezing are given analytically and numerically. Finally, the physical picture of the squeezing is pointed out.
1988, 37 (5): 760-768.
doi: 10.7498/aps.37.760
Abstract +
The propagation characteristics of TE0 modes is studied in an asymmetric leaky waveguide of Kerr-type dielectric film under certain boundary condition. Our result shows that steady guided wave cannor exist if the film thickness is greater than a critical value, and two TE0 modes with different wave numbers may exist if the film thickness is less than that critical value. The propagating powers and the positions of the field amplitude peaks of these two modes in the film vary quite differently when the film thickness or the wave frequency changes. The dispersion relations of these two modes are also different. In the limit of symmetric structure, the dispersion of the weaker TE0 mode is zero.
1988, 37 (5): 769-775.
doi: 10.7498/aps.37.769
Abstract +
When a chopped light impinges on a solid sample in an photoacoustic cell, an acoustic signal is produced not only with the fundamental but also with the second harmonic component because of the nonlinear photoacoustic effect. An equation of nonlinear thermal wave beam is presented with nonlinear boundary conditions and solved by using the perturbation approach method under the case that the light source has a Gaussian profile. The Hankel transformation is utilized to attain the first and second order approximation solutions of the equation.The analytic results show that the thermal wave beam of second harmonic still maintains the Gaussian profile with a smaller Gaussian radius than that of the fundamental component and also the amplitude of the second harmonic relates with not only the linear but also the nonlinear thermal parameters which might be expected to provide more information from the sample than the linear one.Basing on these vesults, a new nonlinear paotoacoustic technique would be expected to develop.
1988, 37 (5): 776-781.
doi: 10.7498/aps.37.776
Abstract +
The binary collision Monte-Carlo method is used to calculate the blocking angular distri-bution of α-particles of about 2 MeV around〈110〉axis in Al single crystal, in which a surface Al2O3 amorphous layer of different thickness is considered. The thermal vibrations of lattice atoms and electronic multiple scattering are taken into account. The resulting angular distribution is closer to the experimental measurements than that with perfect crystal.
1988, 37 (5): 782-788.
doi: 10.7498/aps.37.782
Abstract +
In the paper, the electrical properties of crystalline LiCl-noncrystalline Li2O·3B2O3 composite Li ionic conductor are studied. Some new phenomena of changes in electrical properties of this composite ionic conductor have been found, i.e. a "two-peak" effect of conductivity enhancement appears on macroscopic conductivity σm versus composition curve. Correspondingly, "two-valley" appears on apparent activation energy Em versus composition and dielectric constant εm versus composition curve. These experimental phenomena have been discussed in detail, and the results are consistent with conduction theory.
1988, 37 (5): 789-795.
doi: 10.7498/aps.37.789
Abstract +
The atomic configurations of sub-steps created on (111) growth surface of fee crystal by stacking faults with fault vectors 1/6〈112〉and 1/3〈111〉show that they can act as growth step sources. Growth kinetics of stacking fault growth mechanism has been analysed. It has been shown that the nucleation barrier at the sub-steps is always smaller than that of the 2-di-mensional nucleation.
1988, 37 (5): 796-803.
doi: 10.7498/aps.37.796
Abstract +
The crystallization kinetics of quasicrystalline decagonal phase in a rapidly quenched Al80Mn20 alloy has been investigated. The results of DSC experiments show that the activation energy for crystallization is a constant during the whole process. The experimental curve showing kinetic mechanism of crystallization has been obtained. The activation energy and frequency factor are determined to be 224 kJ/nol and 1.2×1012/s, respectively, The analysts of the kinetics indecates that the crystallization of decagonal phase is controlled by long range atomic diffusion, and the nucleation rate should be zero during the process.
BRIEF REPORT
1988, 37 (5): 804-808.
doi: 10.7498/aps.37.804
Abstract +
The magnetic properties of amorphous Fe90-xMnxZr10 (X = 0, 4, 6, 10, 15) alloys prepared by the drum spinning technique are reported. The dependence of the average magnetic moment per atom μ and Curie temperature Tc on Mn content and the behaviour of the quasi-spin glass in these amorphous alloys are discussed. The magnetic phase diagram of amorphous FeMnZr alloys has been obtained. It is observed that the thermomagnetic curves show a irreversible variance in crystallized Fe84Mn6Zr10 alloy. This phenomenon may be originated from the α→γ phase and γ→α phase transformations at high and low temperatures, respectively.
1988, 37 (5): 809-813.
doi: 10.7498/aps.37.809
Abstract +
The electrical resistivity of amorphous (Fe1-xZrx)84.5B15.5 (X=0, 0.02, 0.04, 0.06, 0.08, 0.1 and 0.15) and Fe90-xBxZr10 (X = 0, 4, 10, 16 and 20) alloys has been studied as a functiom of temperature in the range of 300 to ≈950 K. We find that, for the samples with X = 0.02 to X = 0.08, the curves of ρ(T)/ρ(300 K) vs T have two linear slopes and the turning point appears above curie temperature Tc. The temperature coefficients α1 of the electrical resistivity at Tc decrease with the increase of Zr content. Above 8 at% Zr, ρ(T)/ρ(300 K)-T curves of the all samples show negative temperature coefficients and a minimum near Tc. Finally, the composition dependence of the minimum temperature Tmin and the temperature coefficients α of resistivity are discussed in brief.
1988, 37 (5): 814-816.
doi: 10.7498/aps.37.814
Abstract +
The characteristics of electron wave functions in one-dimensional incommensurate systems with or without disorder are studied. In disordered systems, the wave functions are always exponentially localized in contrast to systems without disorder.
1988, 37 (5): 817-822.
doi: 10.7498/aps.37.817
Abstract +
We study systematically the coupled electromagnetic modes in magnetic superlattices. Dispersion relations are obtained for most general directions of the magnetic field and the wa-vevector, in the magnetostatic limit. A general discussion is also given for magnetic polari-tons including retarded effects.
1988, 37 (5): 823-829.
doi: 10.7498/aps.37.823
Abstract +
The effect of interfacial roughness on the plasmon mode in superlattices is discussed. The corresponding frequency shift, mean free path and life time of the plasmon mode have heen derived.
1988, 37 (5): 830-835.
doi: 10.7498/aps.37.830
Abstract +
An impurity-plasmon model is presented to describe the superconducting process of some doped semiconductors. The linear decreasing Tc-△P relation is obtained which is verified qualitatively by the hydrostatic pressure experiments. A criterion for superconductivity is given and a new method of measuring the Fermi energy level is proposed for semiconductors exhibiting superconductivity.
1988, 37 (5): 836-841.
doi: 10.7498/aps.37.836
Abstract +
This paper reports the process for fabricating Nb/Al-AlOx/Nb tunnel junction using rf-magnetron sputtering. The S-I-S sandwich structure is prepared without breaking vacuum. A detailed AES and XTEM analysis of the Nb/Al-AlOx/Nb sandwich structure shows the good quality of Al barrier. Typical l-V characteristic curves of tunnel junction are also given.
1988, 37 (5): 842-846.
doi: 10.7498/aps.37.842
Abstract +
Several surface properties of implanted GaAs after Nd:YAG and ruby laser annealing have been investigated by the techniques of RBS combined with channeling, Auger and X-ray photoelectron spectroscopy. The results indicate that recovery of the implanted amorphous layer exhibits a threshold and no appreciable surface decomposition occurs in narrow energy density window just above the threshold. High energy densities cause significant surface decomposition and damage. We calculate the redistribution by heat flow theory. High ratio of Te substitution in GaAs is obtained.
1988, 37 (5): 847-850.
doi: 10.7498/aps.37.847
Abstract +
An investigation of spin dependent recombination processes in p+in+ a-Si:H solar cell by photovoltaic detection of magnetic resonance (PDMR) is reported. The study indicates that the PDMR signals for various solar cells made by different technology have different g-values and line shapes, so the dominant recombination processes are different. The influence of the speed of growth, substrate temperature and intrinsic thickness of a-Si:H film on solar cell properties is discussed in terms of the PDMR results.
1988, 37 (5): 851-856.
doi: 10.7498/aps.37.851
Abstract +
The phase contribution of asymmetry of pulse shape in a synchronously pumped dye laser is discussed. We also give the phase contribution of cavity components. The analytic expressions of the pulsewidth, peak position and amplitude are obtained in the presence of asym-metry of pulse shape and chirp.
1988, 37 (5): 857-862.
doi: 10.7498/aps.37.857
Abstract +
The photoluminescence spectra of conducting polymer P3MT with different doping densities at different excitation intensities and temperatures are reported. It is demonstrated experimentally that there are three kinds of radiative transitions, i.e., direct interband transition, recombination of exciton and radiative transition between polaron level and edge of band for the conducting polymer P3MT with nondegenerate ground state.
1988, 37 (5): 863-870.
doi: 10.7498/aps.37.863
Abstract +
Exact analytic method is used to derive a threeparameter family of solutions for the steady-state selfconsistent density profile in a laser plasma. Several special cases are discussed, and the density profile of plateau structure given by Lee ei al. is shown to be just one of thesecases.
1988, 37 (5): 871-873.
doi: 10.7498/aps.37.871
Abstract +
The strong anisotropy of the neutron diffraction intensity enhancement effect observed in α-LiIO3 single crystal under dc voltage was investigated systematically with a 4-circle neutron diffractometer. Analysis of the result shows that both the enhancement and its anisotropy can be explained in the framework of the classical neutron diffraction extinction theorey only if the applied dc voltage is low enough.
1988, 37 (5): 874-880.
doi: 10.7498/aps.37.874
Abstract +
We stutied the nonlinear modulation of the gravitation surface-tension waves on the interface between two layers of imcompressible inviscid fluids which are contained in a rectangular waveguide with horizontal solid walls, by the meth rd of multiple scales technique, and generalized the theory of Larraza and Putterman. Including the surface-tension effects, we found that the first order modulated wave satisfies the cubic Schrodinger equation. Then me derived the non-propagating solitary solution, and made some discussion on the results obtained.
