Vol. 37, No. 4 (1988)
7Li NMR INVESTIGATIONS DURING PER-CRYSTALLIZATION PROCESS IN AMORPHOUS IONIC CONDUCTOR B2O3- 0.7Li2O-0.7LiCl-xAl2O3
1988, 37 (4): 529-537. doi: 10.7498/aps.37.529
To avoid absorbing moisture from the air, we have sealed all samples in high vacuum, and performed 7Li NMR investigations during pre-crystallization process of amorphous ionic conductor B2O3-0.7Li2O-0.7LiCl-xAl2O3(x = 0.15, 0.10 and 0.05) at 293 K and 77 K. We find that there is only spin-spin relaxation time of lithium ions in solid phase, T2= 87μs, which obeys Gaussian decay law at 77 K. At. room temperature all lithium ions devide into two phases. T2s of lithium ions in solid phase still obeys Gaussian law of decay, T2s =127 μs, but T2l of lithium ions in liquid phase obeys Lorentzian law. For three amorphous lithium-ionic conductor B2O3-0.7Li2O-0.7LiCl-xAl2O3 (x = 0.15, 0.10 and 0.05), T2l of lithium ions in liquid phase increases rapidly, i.e. their width of 7Li NMR absorption line becomes much narrower at about 401°,388°and 381℃ respectively. Hence the physical picture of interfacial effect between amorphous matrix and the crystallites is again confirmed.
1988, 37 (4): 538-545. doi: 10.7498/aps.37.538
The impedance spectroscopy of non-crystalline ionic Conductors in systems of P2O5-Li2O-LiCl-Al2O3, P2O5-Cul-CuCl, GeO2-Ta2O5-Li2O are studied. The models of equivalent circuit for impedance spectroscopy measurement box of non-crystalline specimen is presented, and the dispersion relations for boundery impedance are obtained under certain conditions, the boundary impedance presented here will transit to the constant phase angle impedance.
1988, 37 (4): 546-556. doi: 10.7498/aps.37.546
The Grad-Shafranov equilibrium equation for an anisotropic Tokamak plasma is rederived using the method of Greene, Johnson and Weimer. The stabilizing effect of the anisotropic energetic particle component on the internal kink mode in the Tokamak plasma has been analyzed with the generalized energy principle. Detailed calculation on this effect is performed for two kinds of energetic particle distribution function of slowing down in energy and square top poloidal pressure profile. The stability window of internal kink mode due to the energetic trapped particles with magnetic turning point at high field side is obtained. It's relation with various physical parameters is discussed in some depth.
INDIRECT EVIDENCE OF FORWARD SCATTERING——PERIODIC STRUCTURE OF THE STIMULATED BRILLOUIN SCATTERING SPECTRA OBTAINED IN LASER.PLASMA INTERACTION EXPERIMENTS
1988, 37 (4): 557-565. doi: 10.7498/aps.37.557
Periodic structure of stimulated Brillouin backscattering spectra have been observed in ex-periments of intense Nd glass laser irradiating planar targets. Analysis and calculation indicate that this period structure results from the interaction between the ion-acoustic wave and the scattering light wave, the former is produced by the stimulated forward scatting and the latter by the stimulated backward scatting or scattering in other directions. From the wavelength shifts and period of the spectra, the temperature or drift velocity of the coronal plasma and the direction of forward scattering can be estimated.
1988, 37 (4): 566-572. doi: 10.7498/aps.37.566
In this article, the second order perturbation theory is used to obtain the expression of T-matrix for the Simultaneous photon-electron excitations of hydrogen. The convergence and resonance of the T-matrix are discussed in brief.
THE MULTI-PHOTON QUANTUM STATISTICAL THEORY OF DRIVEN OPTICAL SYSTEMS (Ⅰ)——FOKKER-PLANCK EQUATION AND GOOD CAVITY CASE
1988, 37 (4): 573-581. doi: 10.7498/aps.37.573
The systematic method of Fokker-Planck equation (FPE) for the generalized Wigner distribution is used to study the multi-photon transition process of a driven optical system. The general multi-photon FPE, the state equation and the spectrum of transmitted light in good cavity limit are obtained- The two-photon optical bistability spectrum of transmitted light is calculated and compared with single-photon case. It is shown that for multi-photon case, the atom -atom correlation is also negligible in the good cavity limit.
A METHOD FOR CALCULATING D. C. CONDUCTIVITIES OF THE POROUS MEDIUM AND COMPOSITE (Ⅱ)——AN APPROACH TO THE ISOTROPIC AND ANISOTROPIC COMPOSITE
1988, 37 (4): 582-588. doi: 10.7498/aps.37.582
The first-principle approach for calculating the D. C. conductivities of the composites is discussed systematically. The integral equation for determining the effective conductivities of the composites with local anisotropic componentes is derived, and a convenient method for calculating effective conductivity tensor is proposed. We have dealt with effective conductivity tensor of the composites with local anisotropic components. A theoretical method which can treat the more common composites with no periodicity is developed. A new approximate method for solving integral equation by means of expansion with two bases is also proposed, by which we can calculate composites with large porosity and complicate structure with high precision, and it could have the advantage of saving lot of computing time.
1988, 37 (4): 589-597. doi: 10.7498/aps.37.589
Electromagnetic modes are studied in the long wavelength limit, with a nonlocal dielectric tensor valid in this limit and at low temperatures and adaptable to type-l semiconductor superlauices, such as GaAs/GaAlAs alternative multilayers. The TM and TE modes are considered and dispersion relations are obtained respectively.
1988, 37 (4): 598-607. doi: 10.7498/aps.37.598
A two-conduction band lattice Anderson hamiltonian is studied by the Slave-Boson technique and the functional integral method. The electronic density of states (DOS) of the system as well as low temperature thermodynamic quantities are obtained under the saddle point approximation. The results show that a pseudo-gap structure in DOS appears near the Fermi level due to the f-c hybridization and the coherence effect, and the low temperature thermodynamic quantities of the system possess the heavy-fermion properties.
1988, 37 (4): 608-617. doi: 10.7498/aps.37.608
General expressions for elastic constants and analytic formulas for calculating force constants from the elastic constants were derived by means of group theory. On the basis of an approxomation of four nearest neighbour force constants, several ultrasonic wave velocities were calculated for LaNbO4 crystal.
SPONTANEOUS EMISSION OF AN ATOM NEAR THE SURFACE OF A SUPERLATTICE FILM WITH PERIODIC OR QUASI-PERIODIC STRUCTURE
1988, 37 (4): 618-628. doi: 10.7498/aps.37.618
The surface-dressed optical Bloch equations and the Maxwell equations are combined consistently to obtain spontaneous decay rates and frequency shifts for an atom near the surface of a superlattice film with periodic or quasi-periodic structure. The effects of the number, thickness and dielectric properties of the layers constructing this film on the spontaneous emission properties are discussed. The results for the two different cases of periodic structure and quasi periodic structure are comparable.
In this paper, the atomic vibration modes of Si(lll) planar strcture with different layers have been calculated using the dynamic matrix method. The Raman frenquency shift, which moves to lower wave number greatly for microcrystals compared with single crystals, can be explained by the activation of surface modes. By hybridized orbical theroy, the change of surface force constants was obtained. The calculated frequency of surface modes, 469cm-1, is close to the experimental result 430 cm-1 first reported by Okada.
1988, 37 (4): 638-644. doi: 10.7498/aps.37.638
A cell theory of nematic liquid crystals is presented, which provides a calculable theoretical model for investigation of molecular short-range correlations. Numerical calculations are made for PAA The theoretical values are improved in compared with the other theories'. The effects of molecular correlations on calculated results and relations between the cell theory and the other theories are discussed.
1988, 37 (4): 645-649. doi: 10.7498/aps.37.645
The magnetic properties of the pseudobinary compounds Dy (Fe0.9M0.1)2 (M = B, Al, Ga) have been studied. Substitution of M atoms for Fe atoms decreases the Curie temperature and varies the magnetic moment of the Fe atom. The coercivity of the samples increases very rapidly with decreasing temperature. This increase is considerably enhanced by the substitution elements. Anomalous phenomena and pronounced thermomagnetic history effects are observed in the temperature dependence of the magnetization. These effects may be explained by a local environment of iron atom and by an exponential increase in magnetic hardness on lowering the temperature.
1988, 37 (4): 650-654. doi: 10.7498/aps.37.650
Under the mean-field approximation, the Josephson tunnelling of superconductor-grain-superconductor junction is analyzed in this paper by using the path-integral formulation. For the cases with coupling and without coupling between the grains, the temperature deperdence of Josephson critical current Ic and the phase dependence of Josephson current I are obtained.
1988, 37 (4): 655-659. doi: 10.7498/aps.37.655
Disaccommodation (DA) of initial permeability of metallic glass (Fe0.8Ni0.15Cr0.05)78Si8B14 was measured at various temperatures in the range of 77-553 K. The measurements have shown that DA exhibits an asymmetric spectrum with a single relaxation peak. Kinetic behaviour of DA was examined at 273 K. An asymmetric activation energy spectrum with a single peak and the most probable activation energy of 1.40 eV was obtained by fitting a kinetic curve of DA by means of Hesse-Rubartsch's method. Effect of annealing on DA and kinetic behaviour of the annealing were examined. It was shown that the annealing essentially affects on DA and the kinetice behaviour of the annealing is approximateiy governed by Int kinetics.
A MONTE-CARLO SIMULATION STUDY ON THE INFLUENCE OF THE STRESS FIELD ASSOCIATED WITH A DISLOCATION ON CRYSTAL GROWTH
1988, 37 (4): 660-665. doi: 10.7498/aps.37.660
We use the stress energy function suggested by van der Hoek et al. to simulate the formation of dislocation hollow cores. Both average formation energy of the solid-fluid bond ω and driving force △μ affect the formation of hollow cores greatly. The relation between radius of hollow core and diffussion is expressed by the back-force effect. The results of our Monte-Carlo simulation show that a straight step passing a dislocation will be retarded by the stress field.
1988, 37 (4): 666-669. doi: 10.7498/aps.37.666
The unperturbed separatrix crossings driven by a single wave are discussed. The separa-trix crossings are followed by a mixing process, and a small-scale structure occurs in the distribution function in h-ψ plane. The separatrix crossings form a convective process in h-ψ plane, and the convective flux and the net flux are calculated. The separatrix crossings are accompanied by a radial flux, which is composed of a directional flux and a diffusional flux, both of them are calculated.
1988, 37 (4): 670-673. doi: 10.7498/aps.37.670
The optothermal spectrum of infrared MPA of CF3CDC12 obtained by using optothermal cell with a platinum filament as a detector is reported here. It is found that the absorption peak at 944 cm-1 in infrared linear absorption spectrum splits into two peaks at 947 cm-1 and 927cm-1 in MPA spectrum. This phenomenon could be related to-the coupling of normal vibrations produced by Coriolis forces and anharmonisity. So one could select a more suitable excited wavelength according to this new result in laser separation of deuterium isotop. The absoption peak at 986 cm-1 in infrared linear absorption spectrum shows a red shift of 6cm-1 in MPA spectrum. This is due to the anhamonicity of vibrational levels of the molecule.
1988, 37 (4): 674-679. doi: 10.7498/aps.37.674
First, on the base of the correlation function of atoms, we investigate the state function of resonance fluorescence field with one-photon transition and calculate its power spectrum which is totally identical to the Mollow's result. Then, we extend the method to the calculation of resonance fluorescence spectrum with two-photon transition. The results exhibit characteristics different from the one-photon transition.
1988, 37 (4): 680-682. doi: 10.7498/aps.37.680
The crystal structure of tetragonal barium titanate (space group P 4 mm) was determined at 13.6℃, using the data collected by neutron four-circle diffractoraeter, R(F) = 0.0186. The O atoms near b sites distribute disorberly.
We generalize our former work to superlattices with finite number of layers, and obtain the corresponding dispersion relations for the bulk as well as the surface modes. Numerical computations show a superlattice with 20 supercells behaves already very near to an infinite su-perlattice with regard to the propagation characteristics of electromagnetic waves. However, important differences appear when the number of supercells is small.
1988, 37 (4): 688-690. doi: 10.7498/aps.37.688
By the analogy between electron and phonon behaviors,results of renormalization study of the electron localization problem are used to obtain informations of phonon localization in inhomogeneous disordered systems. It is found that three mobility edges may appear in the phonon spectrum of such systems.
1988, 37 (4): 691-693. doi: 10.7498/aps.37.691
The wave functions of electrons in superlattices with random layer thicknesses are studied. They are localized in the direction perpendicular to the layers characteristic of one-dimensional systems and extended in the plane of the leyers. Numerical results of computation of localization lengths are given.
1988, 37 (4): 694-697. doi: 10.7498/aps.37.694
The production kinetics of thermal defects is discussed. The formula for thermal defect concentration has been derived.
STUDY OF SCATTERING OF PLANE WAVE THROUGH DISCRETE RANDOM MEDIUM BY DIRECT ANALOGUE AND STATISTICAL ESTIMATION
1988, 37 (4): 698-704. doi: 10.7498/aps.37.698
In this paper, starting from transport theory, estimated functions of Monte carlo direct analogue and statistical estimation have been obtained by means of term wise integration. We deal with variations of transmissivity and reflectivity in optical thickness τ, albedo of a single partical a, and anisotropy g when plane wave passes through a layer discrete random media. The results of statistical estimation method are in good agreement with those given in reference . As a result of considerable statistical fluctuation of scattering point samples in direct analogue method, the deviation of calculation would be larger as the optical thickness increases or anisotropic scattering or absorption becomes stronger.