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Vol. 49, No. 8 (2000)

2000-04-20
GENERAL
CONNECTIONS AMONG HOMOGENEOUS BALANCE METHOD, WEISS-TABOR-CARNEVALE METHOD AND CLARKSON-KRUSKAL METHOD
FAN EN-GUI
2000, 49 (8): 1409-1412. doi: 10.7498/aps.49.1409
Abstract +
The homogeneous balance method is extended to search for the Bcklund transformations and similarity reductions of nonlinear mathematical and physical equations. The corresponding results coincide with those of Weiss-Tabor-Carnevale method and Clarkson-Kruskal method respectively. It is shown that there exist close relations among these three methods.
A NEW ENTROPY OF BLACK HOLE IN ACCORDANCE WITH THE THIRD LAW OF THERMODYNAMICS
LIN HAI
2000, 49 (8): 1413-1415. doi: 10.7498/aps.49.1413
Abstract +
I disagree to the former definition of black hole entropy which does not obey the third law of thermodynamics,and thus propose a new entropy formula which conforms to thermodynamics.
COMPLEXITY ANALYSIS OF ABNORMAL ECG RHYTHM:VENTRICULAR TACHYCARDIA AND VENTRICULAR FIBRILLATION
ZHANG HONG-XUAN, ZHU YI-SHENG, NIU JIN-HAI, TONG SHAN-BAO
2000, 49 (8): 1416-1422. doi: 10.7498/aps.49.1416
Abstract +
Based on surrogate data hypothesis testing, this paper presented an improved nonlinear test algorithm for deterministic chaotic signals, which is applied to the analysis of abnormal rhythm electrocardiosignals. It is pointed out that ventricular tachycardia(VT) and ventricular fibrillation(VF) are complex nonlinear chaotic signals, which was proved different from stochastic signal. On the basis of qualitative signal analysis and nonlinear dynamics, the authors forwarded a new definition of complexity rate and proposed relative detection methods for the quantitative analysis of VT and VF. The results indicated that the qualitative analysis and quantitative analysis of VT and VF can give objective and creditable results.
A NEW METHOD FOR CONTROL CHAOS BASED ON DELAY FEEBACK OF SYSTEM VARIABLES
LUO XIAO-SHU, KONG LING-JIANG, WENG JIA-QIANG, FANG JIN-QING
2000, 49 (8): 1423-1427. doi: 10.7498/aps.49.1423
Abstract +
A new method for control chaos based on delay feedback of system variables is proposed. The control results of three typical chaotic systems are given. The method of control chaos can be easily realized in physical systems, for the control price of this method is low. The mechanism of the method is also discussed based on varied of average value of Lyapunov function.
(e,2e) IONIZATION CROSS SECTION IN ONE-DIMENSIONAL COULOMB THREE-BODY SYSTEMS
DUAN BIN, BAI ZAI-QIAO, GU YAN
2000, 49 (8): 1428-1434. doi: 10.7498/aps.49.1428
Abstract +
We have studied the classical theory of (e,2e) collision between electron and atoms or ions based on three kinds of one-dimensional models, i.e., the s-wave model, the collinear e-Ze- and Ze-e- models. We find numerically the relation of ionization cross sections with increasing energy obey different threshold laws, i.e., the linear law, Wannier law and square root law. These results have been also discussed analytically.
HIGH RESOLUTION FOURIER-TRANSFORM INTRA-CAVITY LASER ABSORPTION SPECTROSCOPY: THEORY AND APPLICATION
HU SHUI-MING, HE SHENG-GUI, LIN HAI, CHENG JI-XIN, WANG XIANG-HUAI, ZHENG JING-JING, CHENG GUO-SHENG, ZHU QING-SHI
2000, 49 (8): 1435-1440. doi: 10.7498/aps.49.1435
Abstract +
The theory of detecting the Intra-cavity Laser Absorption Spectroscopy by utilizing a continuous-scan high-resolution Fourier-transform interferometer is introduced.The method to record the position and intensity of absorption lines with the Fourier-transform Intra-cavity Laser Absorption Spectrometer is discussed.By recording the atmospheric water absorption in the region of 12450—12700cm-1,the reliability of this method is investigated.And the technique is applied to record the νOD = 5 stretching overtone of the deuterated water(D2O and HDO).
ATOMIC AND MOLECULAR PHYSICS
APPLLICATIONS OF AVERAGE-BOND-ENERGY METHOD IN STRAINED-LAYER HETEROJUNCTION BAND OFFSET
LI SHU-PING, WANG REN-ZHI, ZHENG YONG-MEI, CAI SHU-HUI, HE GUO-MIN
2000, 49 (8): 1441-1446. doi: 10.7498/aps.49.1441
Abstract +
We have extended the average-bond-energy method to the study of strained-layer heterojunction band offset. Through a careful study of the effect of hydrostatic strain and uniaxial strain on band offset parameter Emv, we find that the average band offset parameter Emv,av(Emv,av=Em-Ev,av) is largely kept unchanged under different strain conditions. So, in the calculation of strained-layer band offset parameter Emv, it is only required the unstrained band offset parameter Emv,0, a deformation parameter b and the experimental value of spin-orbit splitting Δ0 to calculate the value of strained-layer Emv by simple algebraic operation. Obviously, it will be very convenient to calculate the valence band offset of heterojunction. The simplifed calculation scheme has the characteristic of small calculation amount and the calculation reliability can be improved by using the experimental value.
SCALED-ENERGY SPECTROSCOPY OF STRONTIUM |M|=1 RYDBERG ATOMS IN AN ELECTRIC FIELD
ZHAN MING-SHENG, LIU XIAO-JUN, CAO JUN-WEN, WANG JIN, ZHAO HONG-TAI
2000, 49 (8): 1447-1452. doi: 10.7498/aps.49.1447
Abstract +
The strontium atoms in ground states were excited to higher |M|=1 Rydberg states while the laser wavelength and the electric field strength are scanned simultaneously to keep the scaled-energy ε constant. Spectra were recorded for ε=-3.00, -2.50 and -1.88. The experimental Fourier transform recurrence spectra were compared with the hydrogenic closed-orbit calculation. The positions of the experimental recurrence peaks were well coincided with the theory, but the strengths of the peaks were strongly affected by the strontium core effect.
MONTE-CARLO SIMULATION OF TWO DIMENSIONAL ARRAYS
HE HONG-BO, ZHOU JI-CHENG, HU HUI-FANG, LI YI-BING, YAO KAI-LUN
2000, 49 (8): 1453-1456. doi: 10.7498/aps.49.1453
Abstract +
In this paper, a single-charge tunneling simulator, the Monte Carlo simulator of two-dimensional quantum dot array using standard single electron tunneling theory and Monte-Carlo method is introduced. The simulated results show that the two-dimensional quantum dot array has Coulomb charging effect at low temperatures. The quantum effect of the dot array exhibits great prospect in research and applications.
CLASSICAL AREA OF PHENOMENOLOGY
IMAGE DIPOLE METHOD FOR THE DIPOLE MOMENTS OF CONDUCTING PARTICLE CLUSTERS
JIANG ZE-HUI, XU SU-JUAN, CHEN WEI, MEN SHOU-QIANG, LU KUN-QUAN
2000, 49 (8): 1457-1463. doi: 10.7498/aps.49.1457
Abstract +
Often it is difficult to calculate the dipole moments of clusters of conducting particles imposed to uniform electric fields, because of the difficulty in handling the mutual coupling between the particles. Such mutual coupling generally causes the polarization of the particles to be dependent upon the structures and the sizes of the clusters. In this paper, an image dipole method is employed for the analysis of this effect. First, a pair of two identical conducting spheres with arbitrary separation immersed in a longitudinal or transverse field is considered, and the image dipoles and image charges, and their distribution induced in each sphere are determined. Then, the dipole moments for the clusters with 4 and 8 spheres arranged on the vertexes of a square or a cube are estimated, and closed-form expressions are given. Comparison with previous calculations is made, and good agreement has been obtained.
QUANTUM STATISTIC PROPERTIES OF NON-RESONANCE INTERACTION BETWEEN A THREE-LEVEL ATOM AND TWO MODE CAVITIES WITH KERR MEDIUM
TAO XIANG-YANG, LIU JIN-MING, LIU SAN-QIU, FU CHUAN-HONG
2000, 49 (8): 1464-1470. doi: 10.7498/aps.49.1464
Abstract +
We have studied the non-resonance interaction between a V-type three-level atom and two-mode cavity with Kerr medium. The results show that if the detunings of the two-mode cavities are equal (δ1=δ2), when initial strength ξ of the two cavities remains unchanged and photon difference q of the two mode cavities is decreased, the non-classical coherence degree between the two mode cavities is increased; when q remains unchanged and ξ is increased, the non-classical coherence degree between the two mode cavities is decreased. When Δδ=|δ2-δ1|=0 and q and ξ remain unchanged, the non-classical coherence degree is decreased with the increase of Kerr effect, and the value of Δδ has an importance influence on the non-classical coherence degree. The results also show that when δ1=δ2, the second-order coherence degree of the cavity 1 shows g211222222>1. On the other hand, the amplitude evolution of the second-order coherence degree of two-mode cavity is decreased due to the influence of Kerr effect.
INFLUENCE OF KERR EFFECT AND VIRTUAL PHOTON FIELD ON THE PHOTON ANTI-BUNCHING OF INTERACTION BETWEEN FIELD AND ATOM
TAO XIANG-YANG, LIU SAN-QIU, NIE YI-YOU, FU CHUAN-HONG
2000, 49 (8): 1471-1477. doi: 10.7498/aps.49.1471
Abstract +
We have studied the interaction between a cascacle three-level atom and the cavity field filled with Kerr medium by C-RWA. The influence of Kerr effect and virtual photon field on the photon anti-bunching is discussed. The results show that the quantum noise appears under C-RWA; the increase of x and ω or the decrease of g leads to the decrease of absorbance of atom and the reduction of photon antibunching;especially,the interaction is influenced obviouslly by g.
SPONTANEOUS EMISSION FROM A THREE-LEVEL ATOM EMBEDDED IN A THREE-DIMENSIONAL PHOTONIC CRYSTAL
XIE SHUANG-YUAN, YANG YA-PING, WU XIANG
2000, 49 (8): 1478-1483. doi: 10.7498/aps.49.1478
Abstract +
We have studied the properties of spontaneous emission from a three-level atom embedded in a photonic crystal. Due to the anisotropic dispersion relation, the density of states lacks singularity. The localized field can disappear and the diffusion field can become intense in some regions.This is different from that in the isotropic dispersion relation case. These properties are directly related to the relative positions of the two upper levels from the band edge.
QUANTUM NONDEMOLITION MEASUREMENTS IN DEGENERATE OPTICAL PARAMETRIC OSCILLATOR
WANG DAN-LING, GONG QI-HUANG, WANG KAI-GE, YANG GUO-JIAN
2000, 49 (8): 1484-1489. doi: 10.7498/aps.49.1484
Abstract +
The knowledge about nonlinear quantum optics is applied to the study of the degenerate optical parametric oscillator as a quantum non-demolition (QND) measurement device. We find that the model can perform a perfect QND measurement at the threshold in the resonant case, and the optimum QND measurement occurs at the nonlinear double resonances in the detuning case.
INFLUENCE OF THE VIRTUAL PHOTON FIELD ON THE ATOMIC QUANTUM CHARACTER IN TWO-MODE SQUEEZING VACUUM FIELD
HUANG CHUN-JIA, ZHOU MING, LI JIANG-FAN, FANG JIA-YUAN, HUANG ZU-HONG, HE HUI-YONG
2000, 49 (8): 1490-1494. doi: 10.7498/aps.49.1490
Abstract +
We have investigated in the time-evolution and the squeezing character of atomic operators in a system of two-mode squeezed vacuum field interacting with a two-level atom without the rotating-wave approximation by means of quantum theory.The results obtained using the numerical method indicate that the influence of the virtual-photon field on the atomic quantum character is mainly the cause for quantum chaos which is related to the quantum character of the system itself.
A SOLID STATE LASER RESONATOR CAPABLE OF COMPENSATING THERMAL LENS EFFECT ADAPTIVELY
ZHANG GUANG-YIN, SONG FENG, FENG YAN, XU JING-JUN
2000, 49 (8): 1495-1498. doi: 10.7498/aps.49.1495
Abstract +
A novel resonator structure for solid state laser is proposed. A lens with short focal length is introduced in the resonator, and the laser crystal (thermal lens) is put at its focusing point, so a special lens set is composed . By using the transform circle approach it is found that the lens set functions as an optical ‘ballast’. With adjusting one end mirror along optical axis adaptively such a resonator may guarantee TEM00 mode dynamic stable operation of high-power solid state laser while thermal focal length varies within a wide range. While the beam spots of TEM00 mode at the laser crystal and end mirrors keep unchangeable.
SELF FOCUSING-SELF DEFOCUSING TRANSFORMATION IN AN ORGANOMETALIC FULLERENE-C60 DERIVATIVE
FANG GUANG-YU, SONG YING-LIN, WANG YU-XIAO, ZHANG XUE-RU, QU SHI-LIANG, LI CHUN-FEI, SONG LI-CHENG, HU QING-MEI, LIU PENG-CHENG
2000, 49 (8): 1499-1502. doi: 10.7498/aps.49.1499
Abstract +
We studied the nonlinear refraction properties of an organometallic fullerene-C60 derivative fac- and mer- [bis(1,2-diphenylphosphino) ethane] (tricarbonyl)(η2-fullerene-C60) chromium by using Z-scan method.We also investigated the nonlinear refraction behavior of exited-state nonlinear optical materials and the switching between self-defocusing and self-focusing caused by the refrangibility of high excited state based on rate-equation theory.The transformation intensity was worked out,and the experiment was simulated numerically.The theoretical results agrees well with the experimental data.
INFLUENCE OF BOUND CHARGE ON THE SECOND-ORDER OPTICAL NONLINEARITY OF GLASS
XU ZHI-LING, YANG PENG, LIU LI-YING, HOU ZHAN-JIA, XU LEI, WANG WEN-CHENG
2000, 49 (8): 1503-1506. doi: 10.7498/aps.49.1503
Abstract +
By comparing the second-order optical nonlinearity of electrically poled glass film and bulk glass samples, it was shown that both of them have similar poling and decay behavior. After analyzing the formation of bound charge and its influence on the second-order nonlinearity of glass, a qualitative model was proposed, indicating that the electric field induced by the bound charge plays an important role on the poling and decay of both film and bulk glass.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
PRELIMINARY INVESTIGATION ON X-RAY RADIATION TRANSPORT IN CYLINDRIEAL TARGETS Ⅰ SIMULATIONS AND ANALYSES ON THE SIMPLE MODEL
JIANG SHAO-EN, ZHENG ZHI-JIAN, CHENG JIN-XIU, SUN KE-XU
2000, 49 (8): 1507-1512. doi: 10.7498/aps.49.1507
Abstract +
We use a simple X-ray radiation transport model to simulate and analyze X-ray radiation transport in cylindrical targets. The simple transport model is introduced, and the relative parameters are given, then the viewing factors are derived and calculated. The numeric methods for the X-ray transport equations based on the simple model are discussed. The scaling relations are obtained from the calculated results. Three kinds of free path relative to transport are advanced.
A COLLISION MODEL IN PLASMA PARTICLE SIMULATIONS
MA YAN-YUN, CHANG WEN-WEI, YIN YAN, YUE ZONG-WU, CAO LI-HUA, LIU DA-QING
2000, 49 (8): 1513-1519. doi: 10.7498/aps.49.1513
Abstract +
In order to offset the collisional effects reduced by using finite-size particles,β particle clouds are used in particle simulation codes (β is the ratio of charge or mass of modeling particles to real ones).The method of impulse approximation (strait line orbit approximation) is used to analyze the scattering cross section of β particle clouds plasmas.By this way,we can obtain the relation of the value of a and β and scattering cross section (a is the radius of β particle cloud).By using this relation we can determine the value of a and β so that the collisional effects of the modeling system is correspondent with the real one.We can also adjust the values of a and β so that we can enhance or reduce the collisional effects fictitiously.The results of simulation are in good agreement with our theoretical ones.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
ANALYSIS OF THE DECONVOLUTION OF X-RAY DIFFRACTION PROFILE AND SIMULTANEOUS CALCULATION OF BRAGG ANGLE
LIANG ZHI-DE, LIU GANG, LU KE
2000, 49 (8): 1520-1523. doi: 10.7498/aps.49.1520
Abstract +
To eliminate the influence of experimental error, analytical function is adopted to model the experimental profiles. Much attention has been paid to the analysis of the effects of such factors as Kα doublet, broadening and alignment of profiles etc. on the Fourier coefficients and deconvoluted profile obtained from the Stokes correction.The reliability of the separation of size-and strain-broadening from Fourier coefficients or deconvoluted profile is estimated. A method is proposed for the simultaneous refinement of accurate Bragg angle from the deconvolution procedure.
STUDIES OF HEXAGONAL DIAMOND OF NANO-GRAIN IN GRAPHITE SURFACE PRODUCED BY Ar+ ION BOMBARDMENT
RUAN MEI-LING, WANG ZHEN-XIA, YU GUO-QING, ZHU FU-YING, ZHU DE-ZHANG, PAN HAO-CHANG, XU HONG-JIE
2000, 49 (8): 1524-1527. doi: 10.7498/aps.49.1524
Abstract +
Hexagonal diamond nano-grains in irradiated surface of graphite produced by ion bombardment at high doses of 0.6keV Ar+ have been found,using high-resolution transmission electron microscopy (HRTEM).The average diameter (D) of the grains was varied between ~2 and ~50nm,and the grain population decreases almost monotonic ally as grain size increases.It is of interest to note that they exhibit a distinctly bimodal structure.For diameters less than 10nm,the microstructure of grains are single crystals,but the polycrystal structure of nano-grains with larger diameter (>10nm) can be also observed.The characteristics of this bimodal structure are on the basis of hexagonal diamond nano-grain nucleation and growth mechanisms,which are restricted by the characteristics of ion bombardment processes.
COULOMB EXPLOSIONS FOR SWIFT C60 ION-CLUSTERS PENETRATING IN SOLIDS Ⅰ—THE MODEL OF SPHERICAL SHELL
QIU HUA-TAN, WANG YOU-NIAN
2000, 49 (8): 1528-1533. doi: 10.7498/aps.49.1528
Abstract +
We study the Coulomb explosions for swift C60 ion-clusters penetrating through solids.Assuming that the directions of relative position vectors between ions in the cluster are random distributions and using the spherical-shell model to describe the structures of the C60 ion-cluster,some analytical expressions of the self-energy of the cluster are obtained based on the linear-response dielectric theory with the PLA dielectric function.It has been found that by solving the equations of motion for the cluster radius,the wake effects in the self-energy can reduce the Coulomb explosions,and even stabilize the cluster structure.
COULOMB EXPLOSIONS FOR SWIFT C60 ION-CLUSTERS PENETRATING IN SOLIDSⅡ—THE MOLECULAR DYNAMICS SIMULATIONS
QIU HUA-TAN, WANG YOU-NIAN
2000, 49 (8): 1534-1540. doi: 10.7498/aps.49.1534
Abstract +
We study the interaction of the swift C60 ion-clusters with solids. The dynamic interacting forces acting on the individual ions in the cluster are derived based on the linear-response dielectric theory with the PLA dielectric function, and a set of equations describing the motion of the individual ions is obtained. It has been shown that by solving the equations of the motion, the wake effects of the dynamic interactions result in the strong asymmetric structures of the high-velocity C60 clusters, i.e., the leading ions in the cluster explode very fast, while the trailing ions in the cluster almost remain in stable states.
MICROSTRUCTURES OF Zn,Ni,Mg DOPED La1.85Sr0.15CuO4 IN HIGH DOPING LEVEL
WANG FENG-ZHONG, WU XIAO-SHAN, JIANG SHU-SHENG
2000, 49 (8): 1541-1544. doi: 10.7498/aps.49.1541
Abstract +
We successfully synthesized La1.85Sr0.15Cu1-xMxOy (M=Zn,Ni,Mg) with y≤0.30 ceramic cuprates. X-ray diffraction studies show that there is no impurity phase in all Zn,Ni,Mg-doped LSCO. Rietveld refinement technique is used to obtain the lattice constant,atomic position coordinates and reflection profile parameters for all samples. There is a tetragonal-to-orthorhombic phase transition in the range of 0.10c of the samples in superconducting state.
ELECTRONIC STRUCTURES OF PbWO4 CRYSTAL CALCULATED IN TERMS OF DENSITY FUNCTIONAL THEORY
TONG HONG-YONG, GU MU, TANG XUE-FENG, LIANG LING, YAO MING-ZHEN
2000, 49 (8): 1545-1549. doi: 10.7498/aps.49.1545
Abstract +
The electronic structure of PbWO4 crystal is studied with the relativistic self-consistent discrete variational embedded cluster method in the framework of density functional theory. The results show that the valence band is mainly made up of O2p with a certain amount of W5d component, and the conduction band is mainly made up of the hybrid states of W5d and O2p. The bottom of the conduction band is first found to be occupied by a narrow Pb6p1/2 state. The band gap and the width of valence band are around 4.8 and 4.0eV, respectively. The results can successfully interpret the reflective spectrum of the crystal. The mechanism of the blue luminescence of the crystal is discussed.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
THEORETICAL STUDY OF LOW-ENERGY ELEMENTARY EXCITATIONS IN SPIN-PEIERLS SYSTEM
XU JING, CHEN HONG, ZHANG YU-MEI, FENG WEI-GUO
2000, 49 (8): 1550-1555. doi: 10.7498/aps.49.1550
Abstract +
By using bosonization technique and quantum self-consistent theory, we study the low-energy excitations of a spin-Peierls system. The ground state, one-particle excited state, two-particle bound state are calculated, and it is shown, as the frustration increases, the energy of the ground state decreases while the energy gap of the one- and two-particle states increases. By analysing the asymototic behavior of the longitudinal spin correlation function, we obtain that the two-particle bound state has similar spin structures as those of the singlet ground state. Thus, we regard the bound state as a singlet state, which exists between the ground state and the two-particle continuous excited state. Our results are qualitatively in agreement with the experimental phenomena observed by Ain et al. It is shown that the existence of bound state is one of the spin-Peierls system's characteristic features.
ELECTRONIC STRUCTURE OF DIBLOCK COPOLYMER
HAN SHENG-HAO, LIU DE-SHENG, XIE SHI-JIE
2000, 49 (8): 1556-1560. doi: 10.7498/aps.49.1556
Abstract +
We proposed a tight-binding model for diblock copolymers. Electronic structure calculations presented for poly(p-phenylene)/polyacetylene revealed that the band gap of copolymers can be tuned by changing the concentration ratio of the homopolymers. The effect of homopolymer interactions on the band structure of copolymers has been studied. The results were compared with the known experimental data.
CHARGE TRANSFER IN MIXED HALIDE MX COMPOUNDS
WEI JIAN-HUA, XIE SHI-JIE, MEI LIANG-MO
2000, 49 (8): 1561-1566. doi: 10.7498/aps.49.1561
Abstract +
Intrinsic charge transfer in mixed halide compounds PtXxX′1-x was studied in the framework of the two-band extended Pielerls-Hubbard model. It was found that the number of transferred charges can be a fraction times of the electronic charge. The maximum amount of transferred charges occurs at a certain x for a given mixed compound.
COLOSSAL MAGNETORESISTANCE BOLOMETER
GU MEI-MEI, ZHANG PENG-XIANG, LI GUO-ZHEN
2000, 49 (8): 1567-1573. doi: 10.7498/aps.49.1567
Abstract +
Based on the sharp resistance change near the metal-insulator transition (M-I) of the colossal magnetoresistance (CMR) materials, we design and test a new type CMR bolometer. La0.67Ca0.33MnO3 epitaxial thin films were used as the photosensitive element of the bolometer, and the optical response of this device to the He-Ne laser and the blackbody were measured. The measured signal and noise decrease with increasing modulation frequency; however, the signal-to-noise ratio shows no obvious change for the He-Ne laser. The temperature dependence of signal was measured in both ferromagnetic metallic and paramagnetic insulating states. It shows that the strongest signal appears in the ferromagnetic state very close to the M-I point. The film's Curie temperature can span from 70 to 350K, depending on the manufacture conditions. So, working near or at room temperature characterizes this CMR thin film bolometer. In this sense, it compensates the weakness of the high-temperature superconductor bolometer that can be used only around the liquid Nitrogen (LN) temperature.The measured detectivity is about 107 cmHz1/2/W and the thermal response constant is 20ms for this device. Compared with the high-temperature superconductor bolometer, the time constant of CMR bolometer is longer and the detectivity is lower. However, there is much room to improve yet.
QUANTUM BOUND STATES OF ONE KIND OF BENT QUANTUM WIRES
WANG CHUAN-KUI, JIANG ZHAO-TAN
2000, 49 (8): 1574-1579. doi: 10.7498/aps.49.1574
Abstract +
The ballistic transport properties of electrons in bent quantum wires are studied. The bent quantum wire composed of T-typed and single-bent quantum wires has finite length and connects to two semi-infinite quantum channels, which serve as emitter and collector when a potential difference is applied. The numerical results show that the conductance have two peaks at the energy of electrons less than the eigenvalue of the first transverse mode. Furthermore, these peaks are due to the resonant tunneling via bound states in the quantum structure. The detailed studies of these quantum bound states are shown in the paper.
MACROSCOPIC QUANTUM EFFECT IN SINGLE DOMAIN ANTIFERROMAGNETIC PARTICLES IN AN EXTERNAL MAGNETIC FIELD
ZHANG YUN-BO, LIANG JIU-QING, NIE YI-HANG, SHI YUN-LONG, PU FU-KE
2000, 49 (8): 1580-1585. doi: 10.7498/aps.49.1580
Abstract +
The effect of the external magnetic field on macroscopic quantum tunneling in biaxial single domain antiferromagnetic particles is studied with the help of the instanton method. It is shown that the decay rate increases with increasing external magnetic field applied along the easy axis of the magnetization, and that the tunneling splitting oscilates with respect to the external magnetic field in the direction of the medium axis. Our results may be helpful for experimental observation of the macroscopic quantum coherence and the tunneling decay in single domain antiferromagnetic particles.
EFFECT OF EXTERNAL MAGNETIC FIELD ON LOW-ENERGY BEHAVIOR OF ONE-DIMENSIONAL HEISENBERG CHAIN
GAO YANG, ZHANG YU-MEI, CHEN HONG
2000, 49 (8): 1586-1590. doi: 10.7498/aps.49.1586
Abstract +
Spin-1/2 anisotropic Heisenberg chain in longitudinal external magnetic field is studied by traditional Jordan-Wigner transformation and bosonization method. In the presence of an external field, both Fermi velocity and Fermi momentum are changed, thus the bosonization procedure is also changed. The antiferromagnetic phase and paramagnetic phase are discussed and the dependence of ground state energy and magnetization on the field are calculated and depicted for some typical cases.
ANALYSIS OF EDDY-CURRENT-LOSS IN Fe-BASED AMORPHOUS WIRES
LI YIN-FENG, CHEN DU-XING, M.VAZQUEZ, A.HERNANDO, GUO HUI-QUN
2000, 49 (8): 1591-1594. doi: 10.7498/aps.49.1591
Abstract +
On the basis of core-shell structure model of amorphous wires, for Fe-based amorphous wire we consider that there are an axial anisotropy Kc in the core and a radial anisotropy Ks in the shell, both of Kc and Ks are functions of λs and σ0,the constants of stress energy density. We deduce the ac circular permeability μφ(r) and calculate the anomaly factor of low-frequency eddy-current-loss for this model,η=2.2, from Maxwell equation and Ohm's law. Comparison of the theoretical value with the experimental results indicates that the magnetic structure of Fe-based amorphous wires can be well described by this improved core-shell structure model.
LA-Zn DOPED SrM FERRITE FOR HIGH-DENSITY MAGNETIC RECORDING
BAI JIAN-MIN, XU HAI, LIU XIAO-XI, WEI FU-LIN, YANG ZHENG
2000, 49 (8): 1595-1599. doi: 10.7498/aps.49.1595
Abstract +
La-Zn doped M type Sr-ferrite thin films with various doping concentration were prepared by conventional rf diode sputtering. La-Zn doping reduces the grain growth rate, so that fine grains with mean grain size about 12nm were prepared with superior magnetic properties. It is found that suitable amount of La-Zn substitution may increase the Ms of the films, and modify the tempareture coefficient of coercivity, while Hc increases with increasing concentration of La-Zn.
STRUCTURES AND MAGNETIC PROPERTIES OF ISOTROPIC NANOSTRUCTURED Fe-Pt THIN FILMS
ZHANG MAO-CAI, QIAO YI, HU BO-PING, WANG JIN, WANG YIN-JUN, SHEN BAO-GEN, WANG YI-ZHONG
2000, 49 (8): 1600-1605. doi: 10.7498/aps.49.1600
Abstract +
Two series of isotropic nanostructured Fe-Pt permenent magnetic thin films have been prepared by sputtering Fe/Pt multilayers and subsequent vacuum annealing. Their structures and magnetic properties have been inverstigated. Studies show that Fe-Pt permenent magnetic thin films with Fe-rich were composed of two phases: a hard FePt phase and a soft Fe3Pt phase. Saturation magnetic polarization and remaenence increase with increasing thickness of the Fe layer. Kelly-Henkel plot indicates that magnetic interactions in Fe-Pt thin films are mainly determined by ferromagnetic exchange interaction between neighboring grains.
PYROELECTRICITY OF TEMPERATURE-INDUCED PHASE TRANSITION IN TIN-MODIFIED LEAD ZIRCONATE TITANATE
FENG YU-JUN, YAO XI, XU ZHUO
2000, 49 (8): 1606-1610. doi: 10.7498/aps.49.1606
Abstract +
The pyroelectricity of Pb0.99Nb0.02[(Zr1-xSnx)1-yTiy]0.98O3 antiferroelectric and ferroelectric ceramics is investigated. Experimental results show that phase transitions are accompanied with drastic electric current changes and form positive or negative pyroelectric peaks. The transformations from ferroelectric into antiferro- or paraelectric phases make positive pyroelectric peaks, and the transformations from antiferroelectric into ferro- or paraelectric phases make negative pyroelectric peaks. Suppose electrostatic potentials of various phases are different, then the relation between the orientation of pyroelectric peak and the type of phase transition could be explained properly. With the above relation the phase transitions with temperature variations in Pb(Zr,Ti)O3 antiferroelectric-ferroelectric materials can be defined.
LONGITUDINAL ELECTRO-OPTIC MODULATION USING POLED POLYMER FILMS IN A FABRY-PEROT CAVITY
CHEN KAI-XIN, YI MAO-BIN, ZHANG DA-MING, HOU A-LIN
2000, 49 (8): 1611-1613. doi: 10.7498/aps.49.1611
Abstract +
Longitudinal Electro-optic modulation has been demonstrated using poled electro-optic polymer films placed in a Fabry-Perot(F-P) cavity, in which the directions of the poling electric field, the applied electric field and the light traveling are parallel with each other, and perpendicular to the surface of the polymer film. The F-P cavity used here had a fineness of about 18. The thickness of polymer films is about 1μm. The modulation depth about 0.012%, was achieved, in a low ac field of 1V/μm. The results demonstrate that it is possible to achieve electro-optic modulation of poled polymer films and to study the films using F-P cavity.
OPTICAL SPECTROSCOPY STUDY ON CARRIER CONCENTRATION AND MOBILITY IN GaN
G.Li, S.J.Chua, LI ZHI-FENG, LU WEI, YE HONG-JUAN, YUAN XIAN-ZHANG, SHEN XUE-CHU
2000, 49 (8): 1614-1619. doi: 10.7498/aps.49.1614
Abstract +
We have studied the carrier concentration and the mobility in GaN expitaxial thin films deposited on sapphire substrate using infrared reflection spectroscopy. By theoretical calculation and fitting with the experimental IR reflection spectra for a series of Si-doped GaN epilayers and the sapphire substrate, we obtain the phonon vibrating parameters and plasmon frequency and damping constant in GaN. The carrier concentration and mobility have been deduced. The results show that the data for carrier concentration coincide with Hall measurement while the mobility is lower than Hall data by a factor of about 0.5. The variation of the LO phonon-plasmon coupling mode with doping level has been clearly observed. Raman measurement has been performed on the same series of samples, showing that the behavior of the LO phonon-plasmon coupling mode is similar to that in IR measurement.
RARE EARTH DOPED AlF3-BASED FLOURIDE GLASS
ZHANG LONG, ZHANG JUN-JIE, QI CHANG-HONG, LIN FENG-YING, HU HE-FANG
2000, 49 (8): 1620-1626. doi: 10.7498/aps.49.1620
Abstract +
Energy transfers and upconversion fluorescence spectroscopy in both Er3+ singly doped and Tm3+-Yb3+ co-doped AlF3-based flouride glass,excited at 970nm,are investigated experimentally.In Er3+:AYF glass,the optium Er3+content for 550nm emission is about at 6mol%,which is 12mol% in AZF glass.With the increase of Er3+ content,the intensity ratio of the red emission to the green emission (Ired/Igreen) is increased in AYF and AZF glass,and the red emission intensity in these gass depends on (Pex)1.6.They are mainly due to a cross-relaxation process between two erbium ions,one in the 4S3/2 and the other in the 4I9/2.In Tm3+-Yb3+ co-doped AlF3-based flouride glass,the concentration quenching of Tm3+ in blue at 476nm is stronger than that in infrared light at 793nm,and the optimum content of Tm3+ for 476nm emission is about 0.1mol%,while it is (0.3—5)mol% for 793nm emission.The concentration quenching of Yb3+ to upconvertion fluorescence is also observed.It may be due to the back-energy transfer from the 3F4 level of Tm3+ to the 2F5/2 level of Yb3+.
INFLUENCE OF INTERFACE BARRIERS ON CARRIERS RECOMBINATION IN ORGANIC BILAYER DEVICES AT HIGH ELECTRIC FIELD
YANG SHENG-YI, WANG ZHEN-JIA, CHEN XIAO-HONG, HOU YAN-BING, DONG JIN-FENG, XU XU-RONG
2000, 49 (8): 1627-1631. doi: 10.7498/aps.49.1627
Abstract +
Based on the Fowler-Nordheim tunneling injection, a model for carriers transport and recombination in organic bilayer devices at high electric field is presented. The influences of applied bias and interface barriers on carriers recombination and its efficiency are calculated and discussed. The theory derived from this model reasonably elucidates the experimental phenomena, and it proves that the electric field can control the carriers recombination region.
MULTIPLE-SCATTING CLUSTER STUDIES OF SO2 ADSORBED ON Ag(110)
ZHU PING, TANG JING-CHANG, HE JIANG-PING
2000, 49 (8): 1632-1638. doi: 10.7498/aps.49.1632
Abstract +
The multiple-scattering cluster method (MSC) has been used to study theoretically the sulphur K-edge NEXAFS of SO2 adsorbed on the Ag (110) at 1/2 coverage.It is shown that SO2 is adsorbed on the Ag (110) with S atom sitting in the hollow site and two O atoms being in an asymmetric geometry,the molecular plane is rotated from the (110) by approximately 52° and tited slightly towards the substrate.Compared to the case of the gas phase SO2,the O—S intramolecular bond length is elngated by (0.014±0.006)nm and the OSO bond angle is reduced by 15°±5° after adsorption.The resonance located between π* and σ* is proved to be induced by the interaction between SO2 and substrate.
INFLUENCE OF NONELASTIC NUCLEAR INTERACTION ON THE PROTON BEAM ENERGY DEPOSITION
WANG YING-GUAN, LUO ZHENG-MING
2000, 49 (8): 1639-1643. doi: 10.7498/aps.49.1639
Abstract +
A precise and rapid analytical algorithm has been developed for calculating proton energy deposition in media. The results covering the radiotherapy energy range (50—250MeV) from this algorithm and data from Monte Carlo code are given. Comparison between them shows that 1) The Nonelastic nuclear interaction have severe influence on proton energy deposition, especially when the initial energy of proton beams is high. 2) The algorithm is 100 times faster than Monte Carlo methods. It satisfies the requirement of precision and speed. The algorithm shows its great potentiality in proton radiotherapy.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
STABILITY OF FRIEDMANN-ROBERTSON-WALKER UNIVERSE FILLED WITH MATTER
ZHAO REN, ZHANG LI-CHUN
2000, 49 (8): 1644-1647. doi: 10.7498/aps.49.1644
Abstract +
The stability of the universe filled with matter,which satisfies P=(γ-1)ρ,is investigated in Friedmann-Robertson-Walker the universe model containing a cosmological constant.The universe satisfying Einstein field equation is obtained for ε=-1 and Λ<0.When γ≥0,the universe is shown to be unstable by calculating the perturbation of gravitational wave and using the relation dP/dρ=γ-1.
THE EVENT HORIZON FORMULA OF BLACK HOLE
LI CHUAN-AN
2000, 49 (8): 1648-1651. doi: 10.7498/aps.49.1648
Abstract +
The general event horizon formula of black hole is given from null hypersurface equation.We prove that this formula is correct by Klein-Gordon equation,and we obtain yet the event horizon equation of arbitrarily accelerated black hole containing charges by using of this formula.
LETTERS
THE ALTERNATE OSCILLATION OF HIGH-REPETITIONRATE PULSE LASER BY TWO DIFFERENT PRINCIPLES IN ALKALINE-EARTH METAL VAPORS
FANG BEN-MIN, YAO ZHI-XIN, PAN BAI-LIANG, CHEN XING, CHEN GANG
2000, 49 (8): 1652-1655. doi: 10.7498/aps.49.1652
Abstract +
A new laser experimental phenomenon has been discovered by high-repetition-rate pulse discharge in the calcium-ion and strontium-ion vapor, that is, the alternate oscillation of self-terminating transition laser pulse and collisional radiative recombination laser pulse. On the basis of analyzing similarities and differences of their prompting mechanisms, some preparatory contrast experimental studies were undertaken.