Vol. 45, No. 4 (1996)
1996, 45 (4): 545-555. doi: 10.7498/aps.45.545
A clinical thermometer model is proposed, which can be described by discrete Langevin equation. The characteristic of the clinical thermometer is that its reading can only increase with the increasing of its temperature, but cannot fall even when its temperature decreases. "Pause" events are defined according to the non-decreasing character of the reading. Using the random walk thoery, we derive analitically the distribution of the duration of the pause events. Both numerical and analytical results show that the distribution function has the form of a power law D(s)∝s-ξ, indicting the critical behavior in this process.
ATOMIC AND MOLECULAR PHYSICS
1996, 45 (4): 556-562. doi: 10.7498/aps.45.556
Based on the calculated wavelengths and transition probabilities of n-3 to n-2 transitions for Ne-like, Na-like, Mg-like and Al-like ions of La, in the case of high temperature condition and local thermodynamic equilibrium approximation, we simulated the spectral structure of all the charged states by considering the broadening of individual line and overlapping of a large number of lines in plasma, presented the mean wavelengths and half width of the satellite peaks, interpreted the previous experimental spectral structures, and predicted some new satellite peaks in a larger wavelength region.
CLASSICAL AREA OF PHENOMENOLOGY
INFLUENCE OF CAVITY LOSS ON GENERATION OF STEADY STATE FOURTH-ORDER AND SQUARED AMPLITUDE SQUEEZING IN MICROMASER
1996, 45 (4): 563-572. doi: 10.7498/aps.45.563
The generation of the steady state fourth-order squeezing and squared amplitude squeezing in a micromaser by the coherent trapping approach is investigated. The results show that if two-level atoms injected into the cavity are initially in coherent state and the flight time of the atoms inside the cavity satisfies the trapping condition, the field can evolve into a coherent trapping state which exhibits steady state fourth-order squeezing and squared amplitude squeezing in the cavity as long as the flux of the atoms is moderately large.
1996, 45 (4): 573-579. doi: 10.7498/aps.45.573
The expression of uniform grow rate of laser is derived by using the high - signal gain formula of FEL, the effective time of interaction between electron and radiative wave in the FEL is analysed, and the effects of major physical parameters on the effective time of interaction are discussed.
MODIFACATION OF ULTRA-SHORT SOLITON-PAIR EVOLUTIONS IN FIBERS BY MEANS OF FREQUENCYSPECTRUM CONJUGATE INVERSION
1996, 45 (4): 580-586. doi: 10.7498/aps.45.580
In this paper we demonstrate theoretically and numerically that the conjugate inversion of the frequency spectra of solitons , periodically along the optical fiber lines, can restrain effectively both the interactions among the solitons and the influence of the self-frequency shift of the solitons on the ultra-short soliton-pair propagations.
1996, 45 (4): 587-594. doi: 10.7498/aps.45.587
In this paper , we have studied a perturbed Burgers-Korteweg-de Vries equation ut+uux+βuxxx=εuxx,|ε|?1, Under first order approximation and travelling wave case, the direct perturba-tion method to find the general solution is established. By means of the single soliton solution of the zeroth order equation we have obtained the general soliton solution of the first order equation. It con-tains many diferent soliton solutions and any one of them describes an array of solitons in semi-infinite space. The analyses show that the dissipation e makes the bright soliton the lower and narrower and the dark soliton the shallower and narrower than unperturbed KdV soliton.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
1996, 45 (4): 595-600. doi: 10.7498/aps.45.595
Considering the effects of both the finite ion-cyclotron frequency and the finite presure, We solved numerically the magnetohydrodynamics (MHD) equations describing a nonhomegeneous current-carrying cylindrical plasma. It is found that the resonant layer of the shear Alfven wave in an ideal plasma impelled by rf wave of antenna is not a singular layer and that Alfven wave can go across the resonant layer. The couple of an antenna with plasma is researched carefully and the results is given by some figures.
We obtain the wake field equation in thermal plasma by calculating the distribution function of the base plasma which temperature is not too high. This equation is helpful to study how to maximize the efficiency of wake field acceleration in thermal plasma. We also discuss the influence of temperature on plasma wake field acceleration.
1996, 45 (4): 608-618. doi: 10.7498/aps.45.608
The helical instability of an arc column with electrical conductivity of the distribution of the linear heat flux potential (a new "temperature") is discussed in axial magnetic field. The magnetohy-drodynamic equations serve as the starting point of the theory. In an electrostatic approximation and a linear time dependent perturbation theory, the perturbation equations for the arc column movement are deduced. Solutions of these equations are obtained analytically, from which the stability limit of the cylindrical arc and the growth rate of the helical instability are given. In comparison the results with those of uniform current distribution, it is found that the stable area is enlarged.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
SIZE DISTRIBUTION AND SPECIFIC INTERNAL SURFACE OF NANOCRYSTALS PRODUCED FROM ANNEALED AMORPHOUS ALLOY Al88Ce2Ni9Fe1
1996, 45 (4): 619-627. doi: 10.7498/aps.45.619
The small -angle X-ray scattering method was used to study the properties of nanocrystals produced from annealing the newly developed high-strength, high-toughness amorphous alloy Al88Ce2Ni9Fe1. The distribution of the nanocrystal size and the changes in specific internal surface were studied in a series of experiments. Information on the gyration radius , Porod radius, integration invariance, distribution of nanocrystal size, crystallity and the changes in specific internal surface are obtained.
1996, 45 (4): 628-634. doi: 10.7498/aps.45.628
The nucleation and undercooling of Al4Mn alloy have been investigated with 1.2 meter long drop tube. Melt droplets were solidified in vacuum and various sizes of droplets were collected at the bottom of the tube. Besides orthorhombic Al6Mn and β-Mn phases, there are two approximants of the decagonal quasicrystal, one approximant of the icosahedral quasicrystal, and decagonal domains, observed in the droplets. However, the amount of each phase is different in samples of various sizes due to the different cooling rates and undercooling. The relationship between the phase composition and the sample size was discussed on the basis of the classical nucleation and growth theories.
THE DIFFERENCE OF TWO KINDS OF F COLOR CENTERS IN PHOTOSIMULATION READOUT PROCESS OF BaFCl:Eu2+ PHOSPHORS
1996, 45 (4): 635-639. doi: 10.7498/aps.45.635
The photostimulated luminescence(PSL) of BaFCl:Eu2+ after ultraviolet irradiation is investigated. The photostimulation spectra after UV-irradiation are measured when we change irradiation temperature between 10 and 300 K. Meanwhile the dependence of PSL intensity of two kinds F-color centers on photostimulation temperature is studied, and the reasons which cause the difference of photostimulation spectra are analysed.
1996, 45 (4): 640-646. doi: 10.7498/aps.45.640
The effect of the direction of external electric field on the shear stress of an ER fluid has been studied by molecular-dynamics simulation. Due to the formation of inclined chains, the shear stress strongly depends on the direction of the field, and it may be very large under some special field direction. And theoretical model of ideal microstructure of ER fluids has proved this result. Thus the ER effect may be greatly enhanced just by choosing an optimum direction for the field without any additional requirement, suggesting a promising way to the practical application of ER fluids.
1996, 45 (4): 647-654. doi: 10.7498/aps.45.647
A study of Si, GexSi1-x growth mode on H-terminated vicinal Si substrate by RHEED is presented. About 10 nm Si epilayer is required to obtain a smooth Si substrate. Bi-atomic terrace dominate on the stable surface both of Si and GexSi1-x single atomic terrace is present in the mean time. Dimer row on bi-atomic Si terrace is perpendicular to terrace edge while dimer row on GexSi1-x bi-atomic terrace is paraller to it (90°rotation). GexSi1-x bi-atomic terrace edge is more straight than Si one.
1996, 45 (4): 655-660. doi: 10.7498/aps.45.655
The hydrogenated nano-crystalline silicon (nc-Si:H) films have attracted more attention for peoples, because of their novel structure and peculiar properties. The nc-Si: H films are prepared by the high purity hydrogen diluted methane as the reactive gases and actived at r. f. and d. c. double power sources, in a conventional plasma enhanced chemical vapor deposition (PECVD) system. The film samples have been studied by means of high-resolution electron microscopy, Raman scattering spectroscopy, scanning tunneling microscopy and other means. Based on the analysis of fabricated processes of the nc-Si: H films, a fractal growth model which called diffusion and reaction limited aggregation (DRLA) model was proposed. It is shown that results of computer simulation agree with the experimental results.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1996, 45 (4): 661-666. doi: 10.7498/aps.45.661
In this paper, we have studied the temperature dependence of the d. c. conductivity of DLC films. The results show that there are obviously different conductive mechanism in the three tempera ture regions (i.e., low, room and high). In the low temperature region , it agrees with the logσ-T-1/4 rule, while in the room and the high temperature regions, it agrees with the logσ-T-1 rule, but the thermoactive energies and the pre-exponential coefficients are different. The experi-ment results are discussed using the two-phase model.
1996, 45 (4): 667-674. doi: 10.7498/aps.45.667
Upon annealing Bi1.6Pb0.4Sr2Ca2Cu3Ox compound at 650℃ in flowing oxygen the modulated structure was changed from the Pb-type via the mixed type to the Bi-type. While the specimen was subjected to sequent annealing in flowing nitrogen at 650℃, the modualated structure was changed back from the pure Bi-type via the mixed type to the pure Pb-type. The process was almost reversible. The change in the modulated structure was closely related to the motion of Pb ions. And the inhomogenity of the Pb ion distribution led to the mixed modulated structure.
1996, 45 (4): 675-680. doi: 10.7498/aps.45.675
In the present paper, a theory of far-infrad antiferromagnetic resonance for Gd2CuO4 is presented. The result predicted by theory agrees well with that of Kaplan et al. experiment.
1996, 45 (4): 681-688. doi: 10.7498/aps.45.681
The response of an I=3/2 nuclear quadrupole resonance(NQR) system to a comb-pulse train is calculated by means of the density matrix theory and computer simulations. The influence of the off-resonance( including inhomogeneous line broadening) upon the comb-pulse NQR powder line shape is also discussed in detail. It was found that under the condition of small off-resonance, the comb-pulse NQR spectrum is analogous to that obtained with the two-dimensional nutation NQR technique, but the time required to perform the comb-pulse experiment is nearly two orders less than that required by the latter.
1996, 45 (4): 689-697. doi: 10.7498/aps.45.689
The Brillouin scattering tensers and the stiffening Christoffel equations in (100), (010), and (001) planes of C2v point group crystals are obtained at arbitery wave vector directions. Based on these results, all the independent elastic and piezoelectric constants of LBO crystals are determined by means of Brillouin scattering , and the sound velocity anisotropic curves in the three planes are also shown
1996, 45 (4): 698-708. doi: 10.7498/aps.45.698
The up-conversion luminescence phenomenon of TmP5O14 crystal at room temperature pumped by pulsed DCM dye laser is studied. It is found that there appear strong 450 and 360 nm and weak 347 nm fluorescences. Through careful experiment al investigation and theoritical analysis, we find that the 450 and 360 nm radiations are 1D2→3F4,3H6 two-photon upconversion fluorescence and 347 nm radiation is 1I6→3F4 three-photon fluorescence. The up-conversion process can be elucidated as follows: when a Tm3+ ion absorbs a first pumping photon and reaches the 3F2 state from the 3H6 bound state, the population of 3F2 state falls down rapidly to the 3H4, state due to the rather strong nonradiative relaxation. Then the excited state absorption from 3H4 to 1D2 takes place and the 360 nm two-photon up-conversion fluorescence from 1D2 state is appears. Meanwhile, there is a small possibility for energy transfer between 1D2 state and 3H4 state. It results in a converted population with respect to the 1I6 state and the 347 nm three-photon up-conversion fluorescence is appear, the up-con-version mechanism of which is a complicated process involving both the excited state absorption and the temperature of photons.
1996, 45 (4): 709-714. doi: 10.7498/aps.45.709
The influence of electronic barrier heights on the quantity of injection charge and electroluminescence (EL) in newly designed devices have been studied. By sandwithing Y2O3, ZnO thin films in between ITO and SiO or Al and ITO, we could change the electron barrier height and the quantities of the injection charges. It is found that Y2O3 film is a good electron barrier film, we sandwithed it in between Al and SiO layers and between ITO and SiO, respectively, and measured the injection charges data with different applied volotage. Using the Fowler-Nordeim tunneling current equation, the electron barrier height at SiO/Al 3.0 eV and at SiO/ITO 1.85 eV were obtained. The ZnO is a conducting film, the electron barrier height were reduced if sandwith it between Al and SiO layers or between ITO and SiO layers, by using the same method, we obtained the electron barrier height at ZnO/SiO, which is 0. 5 eV. The EL intensities of above devices have been measured and found that increasing the quantities of injection charges may increase the EL intensities in these new devices.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
1996, 45 (4): 715-720. doi: 10.7498/aps.45.715
We have developed a new method to treat GaAs (100) surface by CH3CSNH2/NH4OH solution Synchrotron Radiation Photoemission Spectroscopy (SRPES) and X-ray Photoemission Spectroscopy (XPS) have been used to investigate the chemical states and electronic states of the passivated GaAs (100) surface. The results show that the sulfides of Ga and As were formed on CH3CSNH2/NH4OH solution treated GaAs(100) surface . and the oxides of Ga and As were removed . The treatment has an apparently passivating role for the GaAs. After annealing for the passivated surface , band bending effect was observed and the offset of 0.22 eV toward the higher binding energy was obtained this meant that the densenty of the states of GaAs surface was decreased.