Vol. 48, No. 1 (1999)
1999-01-05
GENERAL
1999, 48 (1): 1-5.
doi: 10.7498/aps.48.1
Abstract +
In this paper, with the help of Mathematica, three travelling wave solutions for a class of nonlinear evolution equations utt+auxx+bu+cu3=0 are obtained by trigonometric function method and Wu-eliminition method which include new trarelling wave solutions, bell soliton solutions and kink soliton solutions. Some equations such as Duffing equation, Klein-Gordon equation, Landau-Ginburg-Higgs equation and 4 equation are particular cases of the evolution equations. The method also can be applied to other nonlinear equations.
1999, 48 (1): 6-9.
doi: 10.7498/aps.48.6
Abstract +
By studying the Hawking radiation near the horizon of a static black-hole with a multipole moment, we find that its existence would violate thermodynamic laws of black-hole. Under a perturbation of dust, this kind of gravitational field is unstable. So we guess that this kind of black-hole does not likely exist in the universe.
1999, 48 (1): 10-15.
doi: 10.7498/aps.48.10
Abstract +
The model of driving Lorenz systems is examined in the case that there are some parameter differences between the drive system and the response system. It is found that the strict synchronization does not exist although the parameter difference is small. We also explore the dynamic behaviors of a stable laser system driven by the chaotic signal, and we show that there is no synchronization between the drive and the response. However, this leads to the concepts of driving two subsystems with the chaotic signal, and leads to the synchronization among the subsystems. We apply these ideas to the laser subsystems,and the synchronization of the two laser subsystems, which are of different parameters and driven by the x component of the Lorenz system, is presented.
1999, 48 (1): 16-22.
doi: 10.7498/aps.48.16
Abstract +
Estimate the degree of Conversion at self-ignition temperature, give a more precise temperature and the degree of conversion profiles on self-propagation combustion synthesis (SCS), propose an improved formula of energy conversion on SCS, and calculate the temperature profile function of ZrB2. This profile is in agreement with the experiment for the 95.4% reaction, only on approaching high temperatures deviation occurs.
1999, 48 (1): 23-30.
doi: 10.7498/aps.48.23
Abstract +
A novel stereo pseudo color real-time image-forming system of microscope is presented, and its cause is analyzed by the theory of partially coherent light. The analytic result shows that the distribution information about phase change of the input object function, under given conditions, is reflected in the output stereo pseudo color image while an incoherent light illuminates.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
1999, 48 (1): 31-35.
doi: 10.7498/aps.48.31
Abstract +
In the molecular field approximation, we study the effect of molecular biaxiality on the lowest supercooling temperature of nematic liquid crystals in isotropic phase. Theoretical results show that by taking into account the molecular biaxiality, the ratio of the lowest supercooling temperature in isotropic phase T* to the nematic-isotropic phase transition temperature Tc, approaches the experimental value. When the molecular biaxiality parameter δ reaches 0.3, the ratio T*/Tc reaches 0.9817, very close to the experimental value of 0.99.
ATOMIC AND MOLECULAR PHYSICS
1999, 48 (1): 36-43.
doi: 10.7498/aps.48.36
Abstract +
Based on relativistic HFS self-consistent field average atomic model, the effect of the fluctuation of free electrons on the threshold of photoionization in local thermal equilibrium plasmas is studied by employing the principle of entropy in grand-canonical ensemble. Some results are discussed.
1999, 48 (1): 44-48.
doi: 10.7498/aps.48.44
Abstract +
The dynamics of photon-dissociation of PCl3 in the range of 265—285nm was studied by using tunable dye laser. The measured emission spectra are similar in this excitation range, but their intensities are different. Three main peaks are observed in the range of 380—520nm in the emission spectrum. The strongest peak is at 43lnm, the other two weaker peaks are at 389 and 488nm, respectively. It is suggested that the peak at 488nm is from the transition of PCl(A) to PCl(X), and the peaks at 431 and 389nm are from the transitions of a new singlet state PCl(c?) to PCl(b) and PCl(a), respectively.
CLASSICAL AREA OF PHENOMENOLOGY
1999, 48 (1): 49-57.
doi: 10.7498/aps.48.49
Abstract +
In this paper, the disentanglement conditions in the intensity dependent coupling Jaynes-Cummings model are derived for large initial field (1). The atomic and the field disentangled-states are investigated in detail for varied initial atomic state, these disentangled-states and the periodicity of the dynamical evolution are examined by the distance between density operators.
1999, 48 (1): 58-64.
doi: 10.7498/aps.48.58
Abstract +
A detailed theoretical study on the mode correlation and coherent-mode representation of multi-mode laser beams has been performed.By using the theory of partially coherent light,the multi-mode laser beams behaving like Gaussian Schell-model(GSM) beams have been represented by the superposition of spatially coherent modes,which may be mutually correlated.The analytical expressions for the mode coherence cofficients have been given in the rectangular coordinate system.Furthermore,based on the M2-factor concept,the theory of the mode decomposition of multi-mode laser beams has been built up for the general case,where the mode correlation is considered.
1999, 48 (1): 65-68.
doi: 10.7498/aps.48.65
Abstract +
The absorption cross-section of Ce3+ ions in the Ce3+,Er3+∶YAG crystal has been measured.The laser threshold energy (or power) and laser slope efficiency are calculated using a formula deduced from rate equations on the transitions of energy levels.It is shown that the effect of Ce3+ ions in Ce3+,Er3+∶YAG on properties of the laser at ～1.6μm wavelength depends upon the active ion concentration and the length of the crystal rod.The effect of Ce3+ ion is to reduce the laser threshold energy and increase the slope efficiency,when the crystal rod is shorter or the concentration of Er3+ ion is lower.But when the crystal rod is longer or the concentration of Er3+ ion is higher,the effect of Ce3+ ions is on the contrary.
SECOND-ORDER OPTICAL NONLINEARITY INVESTIGA-TION ON THE GELLING PROCESS OF ORGANIC-DOPED SILICA FILM
1999, 48 (1): 69-73.
doi: 10.7498/aps.48.69
Abstract +
The gelling process of organic-doped silica film fabricated by sol-gel technique was investigated by using in situ second harmonic generation (SHG) measurement.SHG signal came from the doped hemicyanine molecules which automatically oriented in the film.We found that the SHG measurement can be used as a semi-quantitatively probe of the gelling process.The time of gelling was found to depend sensitively on the annealing temperatures.Film shrinkage during gelling resulted in disordering of the doped hemicyanine molecules,consequently,SHG intensity decreased during annealing.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
1999, 48 (1): 74-77.
doi: 10.7498/aps.48.74
Abstract +
In this paper,we have discussed the retarded effect,life time and coherent conditions of the superradiation pulses emitted by the prebunched electron beam in Super-Reltron.
1999, 48 (1): 78-85.
doi: 10.7498/aps.48.78
Abstract +
The motion of electrons in the laser pulse field arround a plasma interface is studied.The equations which present the general relationship between the longitudinal and the transverse momenta of the particle are derived.Results from the analysis show that the inhomogeneity leads to great changes in the characters of the motion of the particle.This inhomogeneity is helpful to the acceleration of injected electrons under some conditions.
1999, 48 (1): 86-93.
doi: 10.7498/aps.48.86
Abstract +
The dependence of the relativisic harmonic radiation on the parameters of laser and plasmas is investigated.Results show that the intensity of incident laser,the length,the shape of the pulse,and the plasma density play an important role in the relativisic harmonic radiation.The results can provide scientific basis for experiments.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1999, 48 (1): 94-101.
doi: 10.7498/aps.48.94
Abstract +
Low-energy electron diffraction(LEED) and scanning tunneling microscopy(STM) have been used to determine the adsorption structures of glycine on the Cu(001) surface at room temperature.Glycine can adsorb on Cu(001) to form three ordered structures:one c(2×4) and two of the type of (2×4) structures,i.e.,(2×4)1 and (2×4)2.According to the molecular resolution STM images and the rule about missing spots in LEED,it is deduced that the carboxylic groups of the two molecules in a unit cell of any of the two (2×4) structures have the same adsorption geometry with respect to the substrate,while the amino groups do not.The three adsorption structures are expected to have almost the same energy,as the narrow stripped domains of them may co-exist and the c(2×4) and (2×4)2 domains sometimes may even change from one to another.
1999, 48 (1): 102-106.
doi: 10.7498/aps.48.102
Abstract +
The amorphous (Ni,Cu)100-xPx+SiC composites were fabricated by self-catalyzing deposition, and the composition and crystallization characteristics were studied. The results showed that the composites kept at amorphous state when x was more than 14 or the fraction of SiC less than 12.8%; they would transform gradually into crystalline with the increase of aging temperature at 603—618K; and the crystallized phases were fcc Ni and NiyPz respectively; (Ni,Cu)P+Ni3P+SiC was formed as a stable microstructure. Compared with amorphous composites, crystalline materials exhibited higher machanical properties.
1999, 48 (1): 107-113.
doi: 10.7498/aps.48.107
Abstract +
A statistical theory of transgranular brittle fracture for metals is discussed. According to the continuum model of interface energy describing the interaction between transgranular brittle crack and grain boundaries and nonequilibrium statistical theory of fracture,the crack growth rate,fracture strength,fracture toughness,brittle-ductile transition temperature and their statistical distribution functions changing with grain size and interface energy are derived in a unified theory.
1999, 48 (1): 114-120.
doi: 10.7498/aps.48.114
Abstract +
The structures and the epitaxial growth behavior of the La0.5Sr0.5CoO3 thin films prepared by pulsed laser deposition on various substrates and at different deposition temperatures have been studied systematically.Epitaxial growth of the LSCO thin films with low resistivity and metallic conducting features has been demonstrated on the substrates of LaAlO3,SrTiO3 and MgO.Studies reveal that for the epitaxial growth of LSCO thin films,700—800℃ are the optimal deposition temperatures and LaAlO3 is the optimal substrate.Emphases are laid on the discussions of the influences and the mechanisms of substrates and deposition temperatures on the epitaxial growth of the LSCO thin films.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1999, 48 (1): 121-126.
doi: 10.7498/aps.48.121
Abstract +
The spin splitting in zero magnetic field between the up- and down-spin electrons in a two-dimensional electron gas is obtained for a pseudomorphic InGaAs/In0.52Al0.48As graded heterostructure.We have studied the spin splitting in the heterostructure by means of the Shubnikov-de Haas oscillations.By analyzing the characteristic beating pattern of the oscillations,a spin splitting of 8.76meV was determined as B→0.
1999, 48 (1): 127-133.
doi: 10.7498/aps.48.127
Abstract +
Taking into account the quantum size effects and considering three types of scattering from bulk impurities,rough surface and rough interfaces,we use the quantum-statistical Green's function approach to calculate the conductivity in multilayered cylindrical wire.It is found that in the lowest-order approximation of impurities,surface and interfaces scattering,the total conductivity is given by a sum of conductivities of all the subbands; and the scattering rates for the individual subbands due to the impurities,surface and interfaces are additive.
1999, 48 (1): 134-139.
doi: 10.7498/aps.48.134
Abstract +
Amorphous hydrogenated silicon, carbon nitride thin films (a-SiCxNy∶H) are deposited at room temperature by r.f. reactive-sputtering method. Thin film structure and optical, electrical properties are measured and analyzed using IR spectra, optical absorption spectra ［α(λ)］, electron spin resonance (ESR) and electrical conductivity (σ). The dark conductivity σd，optical gap Eopt, ESR spin density Ns as functions of N2 flow γN2 are studied with the H2 flow γH2=12% and N flow γN2 varying between 0—14%. The results show that the thin film structure and properties are obviously modified owing to the co-existence of carbon and nitrogen and suddenly changed when γN2 is about 5%.
1999, 48 (1): 140-147.
doi: 10.7498/aps.48.140
Abstract +
A theoretical explanation for L core-shell absorption edge of electron energy loss spectrum of Al, an analysis of the electronic populations and a comparison between different partial cross sections are given. The edge was first normalized to the same atomic ionization cross section (per atom per electronvolt). The contributions for the cross section come from three respects:the first one is the electronic transitions from the core-shell to valence-shell calculated by extended Hückel band model, the second one is the final ionization state obtained by electron gas model, the third comes from the elastic backscatting of outgoing waves by the atoms that neighbor the excited atom. The agreement between the calculation result and the experimental result is good.
1999, 48 (1): 148-153.
doi: 10.7498/aps.48.148
Abstract +
AC losses of Bi-2223/Ag tapes prepared by different processes and YBa2Cu3-xSnxOy bulk materials substituted partially by Sn for Cu have been investigated in a sinusoidal magnetic field H(t) with the frequency of 50 Hz at 77K. The experimental results showed that the appropriate decrease of temperature and time of the heat treatment can reduce AC losses in the monofilamentary tape.The reduction of thickness can also reduce AC losses.The subdivision of monofilamentary tape into multifilamentary tape will suppress the hysteresis loss.On the other hand, the coupling of interfilaments will increase the eddy current loss in Ag matrix.So the AC losses of the tape with 19 filaments are only about 20% less than the monofilamentary tape. The AC loss of Sn-added sample is lower than that of YBa2Cu3Oy.The content of Sn influences the dissipation characteristics of the YBa2Cu3-xSnxOy. The AC loss of YBa2Cu2.95Sn0.05Oy is lower than that of YBa2Cu2.94Sn0.06Oy.The addition of Sn has an important effect on the microstructure of the Y-system superconductor.The partial substitution of Sn for Cu can reduce the average size of Y2BaCuO5(211)particles and increase the boundaries between 211 and 123 phase. In addition,Sn can also lower the melting temperature of the Y-system superconductor.All of these lead to the increase of pinning-force and Jc hence the AC loss is decreased.
1999, 48 (1): 154-162.
doi: 10.7498/aps.48.154
Abstract +
We have measured in detail the resistive transition and the isothermal current-voltage curves in the case of applied magnetic field parallel and perpendicular to the surface of the film up to 10T for an epitaxial YBa2Cu3O7-δ thin film, respectively. The comparative study of the irreversibility line from the R-T curves with the vortex-glass line from the I-V curves was made. The results showed that the irreversibility line determined from the different reduced resistivity criterion and vortex-glass line follow the same power law, H∝(T(0)-T(H))n, and n=4/3 for the vortex-glass line, n=3/2 for the irreversibility line. The irreversibility line is dependent not only on the different reduced resistivity criterion but also on the measuring current density. The vortex-glass line lies below the irreversibility line. The possible origin of the difference between such two lines was discussed.
1999, 48 (1): 163-170.
doi: 10.7498/aps.48.163
Abstract +
The structural and magnetic properties of Sm2Fe15Si2C and Sm2Fe14CuSi2C were analyzed.The Curie temperature TC and saturation magnetization Ms were measured.The magnetocrystalline anisotropy field HA and anisotropy constant K1 and K2 at temperatures ranging from 1.5K to room temperature were obtained by analyzing the magnetic curve.We can conclude that Cu does not come into the Th2Zn17-type structure,while Cu doping modifies the micro-structure and enhances the coercivity of Sm2Fe14CuSi2C ribbons.The maximum intrinsic coercivity(μ0iHc)around 1.0 and 1.2 T at room temperature for Sm2Fe15Si2C and Sm2Fe14CuSi2C ribbons were achieved, respectively. The microstructural parameter αk and the averaged local effective demagnetization factor Neff were derived from the temperature dependence of coercivity.
1999, 48 (1): 171-179.
doi: 10.7498/aps.48.171
Abstract +
The structure and magnetic properties of a series of rf sputtered ［Co(1.5nm)/V(dV)］20(0.5nm≤dV≤4nm)multilayers have been studied.The multilayers structure is found by X-ray diffraction,cross-section transmission electron microscopy,and high-resolution transmission electron microscopy to be polycrystalline with small individual columnar grains and has fairly strong fcc Co(111)and bcc V(110) texture in the film growth direction.The structural characterizations also show composition-modulated structure and severely alloyed effect.Ferromagnetic resonance measurements show relatively small g factors and 4π Meff values,which also indicates that multilayers are severely alloyed.Complicated spin wave resonance spectra were observed and analyzed.The evaluated small interlayer coupling constant shows the effect of weak exchange coupling between Co layers across V spacers.
1999, 48 (1): 180-185.
doi: 10.7498/aps.48.180
Abstract +
Quantum wells of CdTe/CdZnTe were grown by molecular beam epitaxy. The highest order of satellite peak of the sample is 5 from XRD spectra and excition emission linewidth is about 4.8 nm at 77 K. It was shown that our samples are very good. The recombination dynamics of exciton in high-quality CdZnTe/CdTe multiquantum wells were investigated by means of time-resolved photoluminescence(PL) spectra with different excitation power at 77 K and photoluminescence spectra with different temperature. When weaker excitation was used, radiative recombination decay time of the exciton was reduced as the excitation intensity was decreased; the results indicate that the dominant mechanism may be the quenching of exciton emission by impurities and defects. The linewidth of the exciton emission becomes broader with increasing temperature, the linewidth at low temperature is only due to the well thickness, and the broadening linewidth at high temperature is contributed by the interactions among the exciton and LO and TO phonons and ionized donor impurities. The PL intensities are reduced with increasing temperature, which is mainly due to the thermal dissociation of excitons, i.e., the electrons or holes jump into the barriers from the wells by thermal excitations. The exciton emission from n=2 heavy hole exciton at 77 K has been observed, and the n=2 heavy hole exciton luminescence decay time is shorter than that from n=1. The investigation indicates that there is the exciton energy relaxation from the n=2 to n=1 heavy hole exciton state by phonons.
1999, 48 (1): 186-192.
doi: 10.7498/aps.48.186
Abstract +
Theoretical studies of oxygen 1s NEXAFS of c(22)(K+CO) adsorption on Co{1010} surface have been performed by the multiple-scatterring cluster method(MSC).The results show that the bond-length of adsorbed CO molecule is longer than that of the gas-phase one by about 0.01nm.The comparison between the calculated spectra and the experimental data demonstrates that a new weak -like structure appears on the right of the original resonance.This structure comes from the indirect interaction to CO molecule due to K atoms and the substrate.
