Vol. 39, No. 6 (1990)
1990-03-20
NUCLEAR PHYSICS
1990, 39 (6): 1-10.
doi: 10.7498/aps.39.1-3
Abstract +
The energy density of nuclear system is derived based on the Skyrme forces and semi-empirical surface correption and Coulomb contribution. For the case of finite temperature, the analytical energy density, entropy density and free energy density are acquired with help of Sommerfield expansion to the Fermi-Dirac integrals. The energy, entropy, free energy per nucleon and the equation of state for hot nuclear matter and hot finite nuclei are calculated, compared and analysed. The possibility of studying dynamical evolution of hot nuclei is predicted.
ATOMIC AND MOLECULAR PHYSICS
1990, 39 (6): 11-18.
doi: 10.7498/aps.39.11
Abstract +
In this paper we have analysed the spectrum of Gall by means of multichannel quantum-defect theory (MQDT). Here the MQDT parameters for even-parity J = 0,1,2,3 and odd-parity J=1,2 bound levels involving three limits are determined through a fit of the calculated results to experimental data. The unknown energy levels of eleven Rydberg series are predicted by using these optinum parameters. The interaction between these series are discussed. The predicted energy values are in good agreement with the experimental data from ref. [1] .
1990, 39 (6): 19-24.
doi: 10.7498/aps.39.19
Abstract +
The structral morphology of metal catalyst Ni in the synthetic diamond was measured by using the fluorecence EXAFS technique. The nickle impurities found exist as fee structure, which is similar to the pure metal Ni. The results obtained from the amount of C atoms coordinated surround Ni and the dilation of Ni-Ni distance show about 9 at-% carbon in the metal Ni matrix which is much more than the limit of earbon solubility 2.7 at-% in metal Ni at normal pressure. The coordination number of Ni in diamond found is less than that in pure metal. This shows that the nickle in the diamond distributes as small particles with dimension about 20?.
1990, 39 (6): 25-32.
doi: 10.7498/aps.39.25
Abstract +
A simple model of above-threshold ionization which takes into account the processes of autoionization has been studied and the analytic solution of photoelectron spectra is presented. The effects of autoionization on abovethreshold ionization are discussed. It is shown that autoionization will make processes of above-threshold ionization more complicated and a lot of new effects will appear.
1990, 39 (6): 33-39.
doi: 10.7498/aps.39.33
Abstract +
In view of the multivariate regression analysis, we proposed a stepwise regerssion analysis of the distibution of a hyperfine parameter with non-negative constraints in simulation of the overlapped M?ssbauer spectrum. In this method only those rational subspectra, which satisfy both importance and non-negative constraints according to the information in the studied M?ssbauer spectrum, could be comprised in the simulated result. The present method showed two advantages, i.e., fewer calculations and the optimum simulation result which is rational and has least mean square error.
1990, 39 (6): 40-46.
doi: 10.7498/aps.39.40-3
Abstract +
High-order ionization processes, which have been ignored previously in the studies of intense laser-field induced autoionization, are discussed. After obtaining the analytic solution for autoionization spectrum, we investigate in detail the effects of high-order processes. These processes, as shown in the present paper, will affect drastically the autoionization spectrum and the dreesed states of the autoionization state.
CLASSICAL AREA OF PHENOMENOLOGY
1990, 39 (6): 47-53.
doi: 10.7498/aps.39.47
Abstract +
The systematic method of Fokker-Planck equation (FPE) of the generalized Wigner distribution is used to study the multi-photon transition process of a driven optical system, which has the mixture of absorptive and dispersive feature. The multi-photon and mixture of absorptive and dispersive feature FPE and steady state equations are obtained. The properties of the steady state equation is discussed.
1990, 39 (6): 54-58.
doi: 10.7498/aps.39.54
Abstract +
The self-oscillations in a hybrid liquid crystal optical bistable device due to the competition between the DC electric field-induced drift of ionic charge carriers and molecular reori-entation in the liquid crystal are observed experimentally. The relaxation equations of the system are given. The numerical analysis are in qualitative agreement with the experimentalresults.
1990, 39 (6): 59-66.
doi: 10.7498/aps.39.59
Abstract +
IB this paper, two self-similar plane structures are designed, the corresponding diffraction screens arc made and its Fraunhofer pattern are obtained. Based on the view point of successive re-production, the spectral recurrence formulas are deduced, and aseries of spectral functioa curves are drawn. Finally we discuss some characters of the curves. This investigation provides an optical analogue method for researching practical self-similar problems.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
1990, 39 (6): 67-74.
doi: 10.7498/aps.39.67-2
Abstract +
The high β flute lower hybrid drift (LHD) instability is studied in detail. The dispersion relation governing LHD mode with density, electron temperature inhomo-geneities and magnetic drift resonance is derived via gyrokinetic equations. It is found that when ▽Te//▽n the magnetic drift resonance related to ▽Te, enhances the instability and when ▽Te//▽n the resonance reduces the instability. In both cases, the finite βprovides a stability effects and shifts the largest growth rate point to the longer wave length. The analytical and numerical results are in good agreement. Electron temperature anisotropy gives no contribution to LHD mode.
1990, 39 (6): 75-79.
doi: 10.7498/aps.39.75
Abstract +
A method bas been developed for measuring radiation temperatures using a set of absorption-foils coupled to a soft X-ray streak camera in laser plasme experiments. A result has been given for a planar gold target irrdiatcd by laser (λ = 1.053μm) pulses of about 360ps in duration with average intensities of about 1014W/cm2 from the LF-11# Nd: glass laser facility. In addition, applications to measuring time-resolved spectra and space-resolved temperature are discussed.
1990, 39 (6): 80-84.
doi: 10.7498/aps.39.80
Abstract +
This paper presents the studies of the dependence of soft X-ray emission on atomic-number and laser intensities by using a new diagnostic tool, pinhole transmission grating spectrograph (PTGS). Plasma X-ray spectra of various elements from Z = 6(C) to Z = 79(Au) produced by a laser beam with an average power density 5×l014W/cm2 reveal the strong dependence of X-ray emission on atomic number Z. Comparative experiments of Al or Au plasma X-ray emis-sion under both spot and line focused laser illumination show that changes of the laser intensity have more remarkable influence on low Z plasma X-ray emission than that on high Z.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1990, 39 (6): 85-89.
doi: 10.7498/aps.39.85
Abstract +
The effects of fast neutron irradiation on a Cu50Ti50 metallic glass are studied by X-ray diffraction and differential scanning calorimetry (DSC) measurements. It was found from DSC measurements that not only the position but also the profile of crystallization peaks were affected by irradiation. The irradiation was also seem in X-ray diffraction to produce changes opposite to those caused by low-temperature annealing. All these changes are finally discussed in conjunction with the relation between the fast neutron irradiation and the change of short range ordering of Cu50Ti50 metallic glass.
1990, 39 (6): 90-97.
doi: 10.7498/aps.39.90
Abstract +
Critical phenomena in optical bistability (OB) are studied in some detail. Theoretical an-alyeses, mainly based on the steady solution of the "thermodynamic" Fokker-Plank equation for absorptive OB, show that the critical phenomena in OB also can be brought into the framework of Landau's theory of scond-order phase transitions, and the relations between different kinds of critical index numbers obey the scaling laws.
1990, 39 (6): 98-104.
doi: 10.7498/aps.39.98
Abstract +
The ionic conductance of series of montmorillonite which have different submicroscopic structure have been studied after seperating from associated minerals. The absorption bands at 915cm-1 and 840cm-1 in the IR spectra and the resonance with g≈4.3 in the ESR spectra vary with the submicroscopic structure. The influence of the structure on the conductance of the montmorillonites have been discussed.
1990, 39 (6): 105-114.
doi: 10.7498/aps.39.105
Abstract +
The polycrystal material Li2Mo2O6 is prepared using solid phase firing method. By X-ray diffraction, IR and ESR spectra, we determined that the polycrystal material is composed of two phases: Li2Mo2O4 and MoO2. Molybdenum exists in MoO2 crystal phase in the form of Mo4+. The relationship between crystal interface and temperature is analyzed by AC complex impedance spectroscopy. The AC conductivity is measured and it is found that the ln(σT)-l/T curve consists of two straight and one curved segments. The conductivity is σ27℃=1.36×10-3(Ω·cm)-1,σ115℃=1.49×10-3(Ω·cm)-1,σ300℃=9.71×10-3(Ω·cm)-1,σ370℃=2.42×10-3(Ω·cm)-1. The activation energy is E1 = 0.043eV, E2 = 0.235eV, Eav = 0.76eV. The electronic conductivity σe is measured by Wagner method, σe27℃ = 2.24×10-5 (Ω·m)-1, σe300℃= 4.476×10-3(Ω·m)-1. It is proved that the material is a solid electrolyte at room temperature and a mixed conductor at 300℃.
1990, 39 (6): 115-120.
doi: 10.7498/aps.39.115
Abstract +
The layer doubling method of dynamic calculation of Low Energy Electron Diffraction is introduced. It was used to analyse the reconstruction of Cu(110)-(l×2) surface induced by adsorption of alkali metals. The result shows that missing row model with top layer spacing contracted to 1.13? is the most reliable structure.
1990, 39 (6): 121-127.
doi: 10.7498/aps.39.121-2
Abstract +
The cover-deposition chromium on diamond and graphite single crystal surfaces using X-ray and electron diffraction structure analysis technique have been studied. Under the condition of vacuum of 10-5 to 10-6 torr and the temperature higher than 900℃ while the small grain diamonds or highly oriented graphite platelets hid in electrolytic chromium powder, the Cr3C2 and Cr7C3 can be epitaxially grown on diamond or graphite surfaces. In this paper, we discuss the growth condition of chromium carbide and the physical mechanism of cover-deposition epitaxial growth.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1990, 39 (6): 128-134.
doi: 10.7498/aps.39.128
Abstract +
In this paper, using the extended potential model, the symmetrized wavefuntion of the unpaired electron of tetravacancy (V4-) in silicon is calculated. We obtain the localization parameters η2, s-character fractions α2, p-character fractions β2 and hyper-fine constants of the unpaired electron on atoms nearest to the defect. V4- is determined for A1(C3v) symmetric state of the energy 0.78eV. Theoretical values are compatible with the existing experiments. Our results point out that η2 on single dangling bond of V4- is smaller than that of other defects with single dangling bond, this is because the potential distribution for V4- deviates from the single dangling bond case.
1990, 39 (6): 135-141.
doi: 10.7498/aps.39.135
Abstract +
This paper presents a method for obtaining the dispersion relation of the refractive index near the direct band-gap of GaAs/GaAlAs multiple quantum wells (MQW) materials. Its characteristic is introducing room temperature excitonic oscillating factors into the dielectric coefficients on the basis of dealing MQW with optical transmit matrixes on the system of multi-layer media films, then to fit the curve of experimental reflection spectrum of the sample. This dispersion relation is very important to the design of optoelectronic elements and their theoretical expectations. By this way, we can obtain not only the dispersion relation of the real and imaginary part of the refractive index, but also the resonant excitonic absorption spectrum.
1990, 39 (6): 142-150.
doi: 10.7498/aps.39.142
Abstract +
The transferred electron effect between different valleys in AlGaAs/GaAs/AlGaAs heterost-ructure is studied using the one band two valleys model in this paper. Taking the contributions from various electric field and the band offset and current are derived. The tunnelling probabilities and currents for various hetorostructures, alloy components and electric fields have been calculated. The dependence of transferred electron effect on the heterojunction interface, the band structures of the well and barrier materials, and the electric field is discussed. The computed tunnelling current agrees with the experimental results, and so the effectiveness of this model in the research of many valleys system is demonstrated. Furthermore, the difference between this transferred electron effect and the well known Gunn effect is pointed out and its application in the developing 9f semiconductor devices is discussed.
1990, 39 (6): 151-156.
doi: 10.7498/aps.39.151
Abstract +
The electrical resistance and low-field magnetoresistance have been measured on three dimensional ZrCo alloys. The data of magnetoresistance can be accounted for by the contributions from the quenching of superconducting fluctuation and weak localization. The former described by the Maki-Thompson correction is predominant at lower temperatures. The interaction in the particleparticle channel gives rise to a negative magnetoresistance.The paraconductivity phenomenon has been observed and found to be in good agreement with the theory, the (M-T) term plays an important role, the depression by the pair breaking effects due to thermal phonons may only be 10% of the term.
1990, 39 (6): 157-162.
doi: 10.7498/aps.39.157
Abstract +
Based on the concept of effective flux pinning force proposed by the present authors, a method desoribing hysteresis of superconducting ceramic samples with great number of interfaces has been established. The dependences of residual magnetization on magnetizing field and temperature were measured and the effective flux pinning force was extracted from the magnetizations according to the method mentioned above. The force consisted of two types, one of which results from interface magnetic currents which conduct the force to crystal lattice directly, and governed by weak links if there are. The other arises from the flux pinning of intragrain pinning centres. The former is important in small fields whereas the later is dominant in high fields.
1990, 39 (6): 163-168.
doi: 10.7498/aps.39.163-3
Abstract +
The magnetization processes of the Ho and Fe sublattices in Ho2Fe14 compound along the [100] , [110] and [001] axes at 0 K are analysed in detail by the calculation based on the single-ion model. The high-field magnetization processes of Ho2Fe14 at 0 K along the principal crystal axes in a field up to 2000 kOe are predicted by the calculation.
1990, 39 (6): 169-174.
doi: 10.7498/aps.39.169-2
Abstract +
Crystallographic and magnetic properties of the Nd14Fe78B8-xCx compounds were investigated. The properly annealing treatment was found to be the condition that the compounds of light rare earth-iron-carbon belonging to the P42/mnm type structure could be formed. The magnetic ordering temperatures of the compounds decreased somewhat with increasing the carbon concentration, but the saturation magnetization σs had a gentle maximum, and the residual ma gnetization σr, intrinsic coercivity iHe as well as the anisotropy field Ha at room temperature showed a significant increase. The anisotropy behaviours of the C-containing samples were similar to Nd-Fe-B. The fact that the transition temperatures of spin reorientation gradually descended with increasing the carbon content while the canting angle at 1.5 K had a slight increase suggested that there was complicate coupling between the anisotropies of Nd and Fe sublattices. In addition, the suitably Nd-rich carbide exhibited relatively large anisotropy.
