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Vol. 50, No. 9 (2001)

2001-05-05
GENERAL
LINDEL?F'S EQUATIONS OF NONHOLONOMIC ROTATIONAL RELATIVISTIC SYSTEMS
QIAO YONG-FEN, LI REN-JIE, MENG JUN
2001, 50 (9): 1637-1642. doi: 10.7498/aps.50.1637
Abstract +
In this paper, the Lindel?f's equations of nonholonomic rotational relativistic systems are studied. First, the quasi-velocities of nonholonomic systems and the Hamilton's principle of rotational relativistic systems are introduced. Next, the Lindel?f's equations and their improvable expressions in terms of generalized coordinats and quasi-corrdinates are obtained by using Hamilton's principle. Finally, by means of inprovable Lindel?f's equations, the new form of Chaplygin's equations is derived and the transitional method from relativistic analytical mechanics of the rotational systems to general analytical mechanics is illustrated.
GLOBAL DEFORMATION GEOMETRY OFA SELF-GRAVITATIONAL ROTATIONAL BALL
QIANG WEN-CHAO
2001, 50 (9): 1643-1647. doi: 10.7498/aps.50.1643
Abstract +
In this paper deformation geometry of a self-gravitational rotational ball is studied globally. The formulas of Gaussian curvature, longitudinal and polar circumference are given. The effect of self-gravitational parameter and rotational parameter for global surface is analyzed. Finally, the upper limits of mass and angular velocity of a self-gravitational rotational ball are determined.
TRUNCATED EXPANSION METHOD AND NEW EXACT SOLITON-LIKE SOLUTION OF THE GENERAL VARIABLE COEFFICIENT KdV EQUATION
ZHANG JIE-FANG, CHEN FANG-YUE
2001, 50 (9): 1648-1650. doi: 10.7498/aps.50.1648
Abstract +
By using of the special truncated expansion, the soliton-like solution of the generalized KdV equation with variable coefficients is obtained. In this method, the form solution is assumed as the truncated expansion form which is based on the idea that the generalized KdV equation with variable coefficients is reduced to a set of algebraic equations of undetermined functions, so that we can obtain a set of ordinary differential equations of undetermined functions which are easily integrated. An example is given to illustrated that this method is very effective in solving soliton-like solution of a large class of variable coefficient nonlinear evolution equations.
BOUND STATES OF KLEIN-GORDON EQUATION AND DIRAC EQUATION FOR SCALAR AND VECTOR P?SCHL-TELLER-TYPE POTENTIALS
CHEN GANG
2001, 50 (9): 1651-1653. doi: 10.7498/aps.50.1651
Abstract +
The s-wave bound states of Klein-Gordon equation and Dirac equation with scalar and vector P?schl-Teller-type potentials are obtained.
RIGOROUS EVOLVING STATES OF EXP-SIN TYPE FOR THE GENERALIZED TIME-DEPENDENT QUANTUM OSCILLATOR WITH A MOVING BOUNDARY
LI BO-ZANG, LI LING
2001, 50 (9): 1654-1660. doi: 10.7498/aps.50.1654
Abstract +
In this paper the generalized time-dependent quantum oscillator with a moving boundary is studied. Its Hamiltonian is of the non-homogeneous quadratic form of space-coordinate and momentum with time-dependent coefficients. We obtain an orthonormalized and complete set of rigorous evolving states of Exp-Sin type, as well as the necessary and sufficient condition for the existence of states of this type. Our results are of considerable generality, including as particular cases almost all the results given in literature. In addition, a misunderstanding of a few authors on the differential with respect to time is clarified and we point out that the differentiation with respect to either time or space-coordinate can be performed in the ordinary sense.
LONG-RANGE CORRELATIONS IN QUANTUM SPECTRA
LI XI-GUO, SONG JIAN-JUN
2001, 50 (9): 1661-1665. doi: 10.7498/aps.50.1661
Abstract +
Starting From Berry-Tabor trace formula, Einstein-Brillouin-Keller (EBK) quantization condition is adopted to derive action quantization conditions of periodic orbits in two dimensional uncoupled oscillators. The correspondence relations between quantum levels and periodic orbits are found. They indicate that two levels' cotributions to recurrence function coherently interfere with each other if the two levels correspond to periodic orbits with identical topology. The peaks in recurrence spectra results from coherent interference among levels whose corresponding periodic orbits have identical topology. There are long-range correlations among these levels.
SPATIOTEMPORAL PERIODIC PATTERNS OF A TWO-DIMENSIONAL SYMMETRICALLY COUPLED MAP LATTICES
HU GANG, WANG ZHI-BIN
2001, 50 (9): 1666-1669. doi: 10.7498/aps.50.1666
Abstract +
Aim: The spatiotemporal periodic pattern of a two-dimensional symmetrically coupled map lattice is constructed. Method: Without solving the modeling equations, a series of spatiotemporal periodic orbits in coupled map lattices are deduced by known orbits of one-dimensional coupled map lattices with lower spatial period. The stability of the deduced orbits is analyzed. Results: The L2×L2 Jacobian matrices can be simplified as diagonal matrices of a few 2×2 matrices. Conclusion: The stability of constructed orbits can never be better than that of the original ones.
THE SYNCHRONIZATION OF CHAOTIC SYSTEMS BASED ON RBF NETWORK IN THE PRESENCE OF PERTURBATION
GUAN XIN-PING, FAN ZHENG-PING, PENG HAI-PENG, WANG YI-QUN
2001, 50 (9): 1670-1674. doi: 10.7498/aps.50.1670
Abstract +
Based on RBF neural network, the synchronization and different-structure synchronization of chaotic systems in the presence of perturbation are studied. The proposed method can overcome effectively the disruption of perturbation, and make the chaotic systems keep synchronous well. At last, Lorenz system is used to vertify the effectiveness of proposed method, and the simulation results confirm it.
ATOMIC AND MOLECULAR PHYSICS
GEOMETRY OF C42+ AND THE JAHN-TELLER EFFECT
WANG RONG, ZHU ZHENG-HE, YANG CHUAN-LU
2001, 50 (9): 1675-1680. doi: 10.7498/aps.50.1675
Abstract +
stable geometrical configurations of electronic states for C42+ are found with QCISD/6-311G method. These configurations are Cs,C∞v,C2v,D2h,D∞h,D4h,D2d and C3v, etc. The Jahn-Teller distortions from the configurations C42+(Td) and C42+(D4h) exist. The analysis of the relationships among these various geometrical configurations, based on the Jahn-Teller effect, vibronic interaction and the resolution of group representations, is in agreement with the calculated results. The most stable electronic state of C42+ is 3A″ of the planar Cs configuration.
RELATIVISTIC ENERGIES AND FINE STRUCTURES OF THE EXCITED STATES FOR BERYLLIUM-LIKE BⅡ
HAN LI-HONG, GOU BING-CONG, WANG FEI
2001, 50 (9): 1681-1684. doi: 10.7498/aps.50.1681
Abstract +
The Rayleigh-Ritz variational method is used with a multiconfiguration-interaction function and restricted variation method to obtain the energies of 1s22s2 1S, 1s22s2p1P0, 1s22s2p3P0 and 1s22p2 3P in beryllium-like boron, including the mass polarization and relativistic corrections. Fine structure, oscillator strengths, transition rates and wavelengths are also calculated. The results are compared with other theoretical and experiment data in the literature.
RADIATIVE TRANSITION OF CORE-EXCITED 2smd4De STATES TO THE 2pnd4Do STATES IN LITHIUM
WANG FEI, GOU BING-CONG, HAN LI-HONG
2001, 50 (9): 1685-1688. doi: 10.7498/aps.50.1685
Abstract +
The saddle-point variational method is used with restricted variation method to obtain the energies of the core-excited states 1s2smd4De(m=3—7) and 1s2pnd4Do(n=3—5) for lithium, including the mass polarization and relativistic corrections. Oscillator strengths, transition rates, lifetimes and wavelengths are also calculated. The results are compared with other theoretical and experiment data in the literature.
CLASSICAL AREA OF PHENOMENOLOGY
PREPARATION OF MULTI-ATIOM GHZ STATES VIA THE RAMAN INTERACTION OF V-TYPE THREE-LEVEL ATOMSAND ONE CAVITY-FIELD
LI HONG-CAI, LIN XIU
2001, 50 (9): 1689-1692. doi: 10.7498/aps.50.1689
Abstract +
A scheme is presented for preparation of multi-atom GHZ states via the Raman interaction of degenerate V-type three-level atoms and one cavity field.
INVALIDATION OF THE SLOWLY-VARYING ENVELOPE APPROXIMATION AND PRODUCING AND ELIMINATING OF THE SPATIAL SINGULARITY FOR ULTRASHORT PULSED-BEAM PROPAGATION IN FREE SPACE
FU XI-QUAN, GUO HONG, HU WEI, LIU CHENG-YI, WANG XIAO-PING
2001, 50 (9): 1693-1698. doi: 10.7498/aps.50.1693
Abstract +
In this paper we study the propagation of the single cycle or much shorter pulsed-beam in free space. We show the invalidation of the slowly-varying envelope approximation (SVEA) theory because it leads to the spatial singularity of the ultrashort pulsed-beam solution and is inconsistent with the physical significance of the beam propagation. We eliminate the spatial singularity by making use of the complex analytical signal theory (CAS), and then give the solution and simulation of the Gauss, hyperbolic secant and Lorentz pulse beam for SVEA and CAS. The SVEA and CAS solutions are consistent if the pulsed beam becomes long enough.
STUDY ON THE SECOND-ORDER NONLINEAR OPTICAL PROPERTIES OF 4-HYDROXY-3-METHOXY CINNAMYLIC ACID
QI TIE-LIU, ZHAO BO
2001, 50 (9): 1699-1702. doi: 10.7498/aps.50.1699
Abstract +
Analyzed the molecular structure of 4-Hydroxy-3-Methoxy Cinnamylic Acid (HMCA), and studied the second-order nonlinear optical properties. The results reveal that it has fairly strong SHG effect and good transparency. The cut-off wavelength λcut-off=420nm.Calculated its molecular second-order polarizability β, and a comparative study on its pertinent derivatives is carried out.
OPTICAL NONLINEARITIES IN TWO NOVEL NANOCOMPOSITES BASED ON FULLERENE C60 STRUCTURED SYSTEM WITH GOLD NANOPARTICLES
QU SHI-LIANG, SONG YING-LIN, WANG YU-XIAO, LIU SHU-TIAN, GAO YA-CHEN, DU CHI-MIN, LI YU-LIANG, ZHU DAO-BEN
2001, 50 (9): 1703-1708. doi: 10.7498/aps.50.1703
Abstract +
Two novel nanocomposites based on fullerene C60 structured systems with gold nanoparticles were investigated with 532nm, 8ns duration laser pulses. The comparison between Z-scan experimental results and theoretical analysis indicates that the nonlinear absorption primarily depends on the ligands, and the nonlinear refraction comes mainly from the contribution of gold nanoparticles in the materials. The comparison of the two nanocomposites with the well known C60 toluene solution in optical limiting properties was performed. The optical limiting mechanisms were discussed
INCOHERENTLY COUPLED BRIGHT-DARK SCREENING-PHOTOVOLTAIC SOLITON PAIRS IN BIASED PHOTOVOLTAIC PHOTOREFRACTIVE CRYSTALS
LI BIN, SUN XIU-DONG, HOU CHUN-FENG, LI SHI-QUN
2001, 50 (9): 1709-1712. doi: 10.7498/aps.50.1709
Abstract +
We investigate the incoherent coupling of two mutually incoherent optical beams with the same polarization and wavelength in biased photovoltaic photorefractive crystals, and predict that incoherently coupled bright-dark screening-photovoltaic soliton pairs can be established in biased photovoltaic photorefractive crystals.
RESEARCH ON THE NON-CRITICAL PHASE-MATCHING WAVELENGTH OF GdxY1-xCa4O(BO3)3 CRYSTAL
WANG ZHENG-PING, XU XIN-GUANG, SUN XUN, FU KUN, SONG REN-BO, WANG JI-YANG, LIU YAO-GANG, WEI JING-QIAN, SHAO ZONG-SHU
2001, 50 (9): 1713-1716. doi: 10.7498/aps.50.1713
Abstract +
Using the Sellmeier equations of GdCOB and YCOB, we determined the wavelength range in which non-critical phase matching in GdxY1-xCOB can be realized. Using a 704-5 type optical parametric amplifier, we measured the non-critical phase-matching wavelengths in several GdxY1-xCOB crystals with different compositional parameter x.
OPTIMIZED DESIGN OF A SYSTEM OF GENERATING TERAWATT LASER PULSES BY USE OF OPTICAL PARAMETRIC CHIRPED PULSE AMPLIFICATION
LIU HONG-JUN, CHEN GUO-FU, ZHAO WEI, WANG YI-SHAN, ZHAO SHANG-HONG
2001, 50 (9): 1717-1722. doi: 10.7498/aps.50.1717
Abstract +
Using the numerical method, an optimized design is presented for the generation of peak powers up to ~60 TW with pulse duration ~25 fs using an optical parametric chirped pulse amplifier (OPCPA) pumped by the high-power Nd:glass laser. The OPCPA system consists of an LBO preamplifier and an LBO power amplifier. The numerical simulation results demonstrate that this system can scale the pulse energy at nanojoule level to the joule level and generate terawatt pulses. So it provides great po-tential to efficiently produce and amplify very short femtosecond laser pulses, and can be regarded as a step toward generating petawatt laser pulses using optical parametric chirped pulse amplifiers pumped by powerful nanosecond systems.
QUANTITATIVE MEASUREMENT OF SOFT-X-RAY SPECTRUM USING TRANSMISSION GRATING SPECTROMETER
YANG JIA-MIN, DING YAO-NAN, YI RONG-QING, WANG YAO-MEI, ZHANG WEN-HAI, ZHENG ZHI-JIAN
2001, 50 (9): 1723-1728. doi: 10.7498/aps.50.1723
Abstract +
Transmission grating efficiencies for soft X-ray and quantum efficiencies of X-ray CCD in the energy range of 100-1500eV were carefully calibrated on Beijing Synchrotron Radiation Facility. A model is developed to simulate the calibrated grating efficiencies, another model is developed to calculate the CCD quantum efficiencies. The effect of CCD surface contamination on CCD quantum efficiency is also studied. Finally, a method for unfolding the soft X-ray spectrum measured with transmission grating spectrometer is introduced, in which the grating efficiencies, CCD quantum efficiencies and grating higher order overlapping have been taken into account. The developed quantitative measurement method has been applied to obtain X-ray spectrum from gold plasma.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
SELF-GENERATED MAGNETIC FIELD BY HIGH FREQUENCY MODULATIONAL FIELD IN PLASMA
MA SHAN-JUN
2001, 50 (9): 1729-1736. doi: 10.7498/aps.50.1729
Abstract +
Magnetic field generated in plasma with high frequency modulational field has been studied in detail.By solving the two time-scale and two fluid equations,a set of nonlinear equations has been obtained by which the behavior of self-generated magnetic field can be described. Numerical results show that magnetic field self-generated by high frequency modulational field can be produced and with increase of time this magnetic field may collapse,leading to great enhancement of the magnetic field.
NUMERICAL ANALYSIS OF SAWTOOTH OSCILLATION DURING ELECTRON CYCLOTRON HEATING PHASES
WANG SHI-QING, JIN YA-QIU
2001, 50 (9): 1737-1741. doi: 10.7498/aps.50.1737
Abstract +
By employing two models, namely the reconnection model and the turbulence model, we present a transport code simulation of sawtooth discharges in T-10 Tokamak in the electron cyclotron heating phases, and the trigger conditions are also coupled into the transport code. In one discharge, ECRH was located nearly on-axis, and in another ECRH was located well off-axis. The comparison of numerical results and experiment data show that good prediction was obtained with the turbulence model. In contrast, due to some fundamental shortcoming of the reconnection model, no satisfactory fit could be obtained using the latter.
DYNAMICS OF INTERACTION OF ULTRASHORT LASER PULSES WITH SOLID TARGETS
CANG YU, ZHANG JIE, WANG WEI
2001, 50 (9): 1742-1746. doi: 10.7498/aps.50.1742
Abstract +
Using Saha equation, a simple model is proposed for the dynamics of interaction between ultrashort laser pulses and solid targets. An adiabatic expansion model is adopted to study the expansion phase after the heating phase. Temporal evolvement of the dynamics of the interaction is obtained, from which the electron temperature, density, ionization balances can be determined.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
LOW TEMPERATURE SPECIFIC HEAT ON BULK AMORPHOUS Zr-Ti-Cu-Ni-Be ALLOY
LUO JIAN-LIN, BAI HAI-YANG, WANG WEI-HUA, CHEN ZHAO-JIA, MENG JI-BAO, WANG YU-PENG, JIN DUO, ZHANG JIE, TONG CUN-ZHU, LIN DE-HUA
2001, 50 (9): 1747-1750. doi: 10.7498/aps.50.1747
Abstract +
Specific heat of the bulk amorphous Zr-Ti-Cu-Ni-Be alloy and different heat-treated samples has been measured in temperature range from 4.5 to 30K. The specific heat result can be well fitted by electronic and phonon contributions. The value of electronic specific coefficient γ is much bigger than other samples and the Debye temperature ΘD increases regularly from amorphous to equilibrium crystallized phase. The different behaviors of different samples are interpreted primarily in terms of electronic density of states and Debye model.
NANO-Cu/Al2O3 ASSEMBLIES TEMPLATE SYNTHESIS AND OPTICAL ABSORPTION
MO JI-MEI, CAI WEI-LI, XU YAN-QI, WANG YIN-HAI
2001, 50 (9): 1751-1755. doi: 10.7498/aps.50.1751
Abstract +
Nano-Cu/Al2O3 assemblies were prepared by AC electrochemical deposition of Cu in the ordered pores of alumina membranes. TEM measurement show that the amount of Cu nanoparticls increase with the deposition time. Optical absorption characteristics in the wavelength range 200—800nm has been investigated for the assemblies, and only an absorption band-edge was observed. With the increasing deposition amount of Cu, the absorption band-edge red-shifts. The results are discussed in terms of Rayleigh scattering. Meanwhile the assemblies exhibit the optical features of a semiconductor with indirect band gap.
THE LOCAL ADSORPTION STRUCTURE OF SO2/Ni(111):THEMULTIPLE-SCATTERING CLUSTER STUDIES
CAO SONG, TANG JING-CHANG, WANG LEI, ZHU PING
2001, 50 (9): 1756-1762. doi: 10.7498/aps.50.1756
Abstract +
The multiple-scattering cluster (MSC) method has been used to calculate the sulphur 1s near edge X-ray absorption fine structure of SO2 adsorbed on the Ni(111). The local adsorption structure of SO2/Ni(111) was determined by a direct comparison between MSC calculation and the experimental NEXAFS spectra. This study confirms the flat-lying structure and shows that the fcc three-fold hollow site is the most preferable adsorption site.It has been shown that the O—S intramolecular bond length is elongated by (0.007±0.002)nm,∠OSO bond angle is reduced by 10° after adsorption,and the adsorption heihgt is (0.20±0.02)nm.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
GEOMETRIC PROPERTIES OF CHARGED -(PA)4-(PPP)m-(PA)4-TRIBLOCK COPOLYMERS
LIU DE-SHENG, WANG LU-XIA, CHEN YAN-XUE, HAN SHENG-HAO, MEI LIANG-MO, XIE SHI-JIE
2001, 50 (9): 1763-1768. doi: 10.7498/aps.50.1763
Abstract +
We present the results of the Austin-Model 1 (AM1) geometry optimizations aimed at determining the charged geometry properties of -(PA)4-(PPP)m-(PA)4- triblock copolymers that have the well-barrier-well structure. The distributions of the doped charges depend upon the density of doped charges and the length of the barrier.
STUDY ON STRESS INDEUCED LEAKAGE CURRENT TRANSIENT CHARACTERISTICS IN THIN GATE OXIDE
LIU HONG-XIA, HAO YUE
2001, 50 (9): 1769-1773. doi: 10.7498/aps.50.1769
Abstract +
FN tunneling and hot hole (HH) stress induced leakage current (SILC) transient characteristics in thin gate oxide are investigated. Under both stress conditions, the stress induced leakage current obeys a power-law time dependence with different power factor. For HH SILC, the power factor significantly departs from -1. HH SILC is found to have a more pronounced transient effect. The results show that HH SILC can be attributed to positive oxide detrapping and annihilation of positive charge-assisted tunneling current. The latter can be diminished by substrate hot electron injection.
EXTRACTION OF POLARIZATION-INDUCED CHARGE DENSITY INMODULATION-DOPED AlxGa1-xN/GaN HETEROSTRUCTURETHROUGH THE SIMULATION OF THE SCHOTTKY CAPACITANCE-VOLTAGE CHARACTERISTICS
ZHOU YU-GANG, SHEN BO, LIU JIE, ZHOU HUI-MEI, YU HUI-QIANG, ZHANG RONG, SHI YI, ZHENG YOU-DOU
2001, 50 (9): 1774-1778. doi: 10.7498/aps.50.1774
Abstract +
Polarization-induced charge density in modulation-doped AlxGa1-xN/GaN heterostructures is extracted through the simulation of the Schottky Capacitance-Voltage (C-V) characteristics. C-V measurements were made on Pt Schottky contacts on modulation-doped Al0.22Ga0.78N/GaN heterostructures. The C-V characteristics were simulated numerically using the three-dimensional Fermi model.Influence of sample parameters on C-V characteristics is analized by the simulation.Polarization-induced charge density,n-AlGaN doping level and Schottky barrier height have different influences on the C-V characteristics,and thus the polarization-induced charge density can be extracted accurately.The polarization-induced sheet charge density at the heterointerface is extracted to be 6.78×1012cm-2 in the Al0.22Ga0.78N/GaN heterostructure with the Al0.22Ga0.78 N thickness of 45nm.This work provides a method for quantitative analysis of the polarization-indeced charge in modulation-doped AlxGa1-xN/GaN heterostructures.
EFFECTS OF INTERFACE ROUGHNESS AND SPIN-FLIP ON TUNNELSPECTRUM IN FERROMAGNET-d-WAVE SUPERCONDUCTOR JUNCTIONS
DONG ZHENG-CHAO
2001, 50 (9): 1779-1782. doi: 10.7498/aps.50.1779
Abstract +
Taking into account the spin-polarized effect,rough interface scattering and spin-flip effects,we calculate,within Blonder-Tinkham-Klapwijk Scattering formalism,the spin-polarized tunnel spectrum in the ferromagnet-d-wave superconductor junctions.It is shown that,(1) the conductance exhibits a sharp peak at zero-bias with the increase in spin-flip scattering;(2) the interface roughness can induce a small central peak in the zero-bias conductance dip and decrease the height of the zero-bias conductance peak.The calculated results can account for the tunnel spectrum observed experimentally in La2/3Ba1/3 MnO3/DyBa2Cu3O7 and La2/3 Ba1/3 MnO3/YBa2Cu3O7-δ junctions.
HIGH PRESSURE SYNTHESIS OF Ca DOPED (RPr)-123 SUPERCONDUCTORS
XIONG HAN, CHE GUANG-CAN, YAO YU-SHU, NI YONG-MING, DONG CHENG, JIA SHUN-LIAN
2001, 50 (9): 1783-1786. doi: 10.7498/aps.50.1783
Abstract +
The nearly single phase (R0.4Pr0.6)0.5Ca0.5Ba2Cu3O7-δ superconductors (R=La, Pr, Nd, Sm, Eu, Gd, Y) were prepared under high temperature and high pressure using the cubic anvil apparatus. The measured result shows that we can get superconductivity in all these Ca doping compounds with Tc above 100K.
HYDROSTATIC PRESSURE AND TEMPERATURE INDUCEDPHASE TRANSITION AND DIELECTRIC PROPERTIES OF La-DOPED Pb(Zr,Sn,Ti)O3 ANTIFERROELECTRIC CERAMICS
XU ZHUO, FENG YU-JUN, ZHENG SHU-GUANG, JIN AN, WANG FANG-LIN, YAO XI
2001, 50 (9): 1787-1794. doi: 10.7498/aps.50.1787
Abstract +
Hydrostatic pressure and temperature induced phase transition and dielectric properties of La-doped Pb(Zr,Sn,Ti)O3 antiferroelectric ceramics were studied. The effects of temperature on the pressure-induced phase transition and the dielectric property dependence on pressure have been investigated.It was found that rise of temperature makes the ferroelectric-antiferroelectric phase transition pressure decrease.And it was observed that hydrostatic pressure makes the ferroelectric-antiferroelectric phase transition temperature decrease and the antiferroelectric-paraelectric phase transition temperature increase.The results are of help in understanding the behaviors of pressure-induced dielectric frequency dispersion and diffuse phase transition exising in the antiferroelectric ceramics with composition and polar nanodomain fluctuations.
THE EXPERIMENTAL STUDY OF IMPROVING RARE-EARTHDOPED MATERIALS'S ENERGY UP-CONVERSIONEFFICIENCY
LIU ZHEN-WEI, YANG XIAO-LIANG, XIAO SI-GUO
2001, 50 (9): 1795-1779. doi: 10.7498/aps.50.1795
Abstract +
Some conditions are put forward about improving the up-conversion efficiency through study of oxy-fluoride glasses based on TeO2,GeO2,ZnF2,SiO2 and PbF2. Hosts with low phonon energy benefit the energy up-conversion.It is also found that when the value of the quasi-field parameter of the oxy-fluoride host is adjusted near to that of the M parameter of the doped rare-earth, the materials show high up-conversion efficiency.Selecting suitable excitation photon energy to match the level of rare-earth ions and/or sensibilizer ions is a necessary condition for high up-conversion efficiency.The results provide some practical guidance to prepare rare-earth doped energy up-conversion materials.
THE UV PHOTOCONDUCTIVITY OF n-TYPE GaN FILMSDEPOSITED BY MOCVD
ZHANG DE-HENG, LIU YUN-YAN, ZHANG DE-JUN
2001, 50 (9): 1800-1804. doi: 10.7498/aps.50.1800
Abstract +
This paper studies the UV photoconductivity for non-doped and weakly Mg doped n-type GaN films deposited by MOCVD. It was observed that these n-type samples have notable UV photoresponse and the relaxation time of the photoresponse is relatively short.In the weak intensity range, the photoresponse decreases linearly with the light intensity and the relaxation time of the photoresponse becomes larger.
A STUDY OF FIELD EMISSION OF SINGLE-WALLED CARBONNANOTUBES USING FIELD EMISSION MICROSCOPY
SUN JIAN-PING, ZHANG ZHAO-XIANG, HOU SHI-MIN, ZHAO XING-YU, LIU WEI-MIN, XUE ZENG-QUAN, SHI ZU-JIN, GU ZHEN-NAN
2001, 50 (9): 1805-1809. doi: 10.7498/aps.50.1805
Abstract +
Using Field Emission Microscopy (FEM), the electron field emission from a bundle of single-walled carbon nanotubes (SWCNT's) was studied under vacuum better than 4.0×10-7Pa after being thermo-desorbed at different temperatures.Work function of the SWCNT's decreases as the temperature of desorption goes up.After heat treatment at 1000℃, the SWCNT's exhibits the lowest work function and their electron field emission pattern also shows a fine structure.As the temperature for thermo-desorption is raised further, the SWCNT's field emission power deteriorates and finally collapse of SWCNT's occurs.
SHORT-TIME DYNAMICS OF TWO-COMPONENTCOLLOIDAL SUSPENSIONS
ZHANG HAI-YAN, GERHARD M?GELE, MA HONG-RU
2001, 50 (9): 1810-1817. doi: 10.7498/aps.50.1810
Abstract +
We calculate the short-time translational and rotational self-diffusion coefficients for charge-stabilized binary colloidal suspensions where the density of one component is very dilute.The two-body and leading three-body contributions of hydrodynamic interaction (HI) to the diffusion tensor are taken into account.Due to both electrostatic interactions and HI, the self-diffusion coefficients depend on effective charge numbers,volumn fractions and sizes of two kinds of spheres, and the results can be explained by the effective hard sphere model.The influence of HI on charge-stabilized binary systems is less than that on hard-sphere binary systems.
STUDY OF CONCENTRATION RETRIEVING METHOD IN DIFFERENTIAL OPTICAL ABSORPTION SPECTROSCOPY FOR MEASURING AIR POLLUTANTS
ZHOU BIN, LIU WEN-QING, QI FENG, LI ZHEN-BI, CHUI YAN-JUN
2001, 50 (9): 1818-1823. doi: 10.7498/aps.50.1818
Abstract +
The principle of differential optical absorption spectroscopy (DOAS) for measuring the concentration of air pollutants is presented. The adjustment of measured spectra and the least-squares method are also described .We have been using this method in retrieving the concentration of air pollutants and measuring the air pollutants for a long time and the results were coincident with circumstances. This method was proved very suitable for retrieving the concentration of air pollutants in DOAS system and provides a good technique for environmental monitoring.
LETTERS
THE c-AXIS MAGNETORESISTANCE STUDY IN THE NORMAL-STATE Sr2RuO4
Y. MAENO, Z. Q. MAO, ZHENG PING, WANG NAN-LIN, CHEN ZHAO-JIA, GUO ZHONG-CHENG
2001, 50 (9): 1824-1828. doi: 10.7498/aps.50.1824
Abstract +
We studied the c-axis magnetoresistance (H∥ab,J⊥c) of a typical layered perovskite superconducting single crystals Sr2RuO4.It is shown that the magnetoresistance is anisotropic and strongly temperature dependent.When rotating the direction of magnetic field in the ab-plane, the magnetoresistance varies periodically, and the maximum appears as the applied magnetic field is in the (110) direction.We analyze this transport property with respect to the Fermi surface anisotropy,the quasiparticle scattering rate anisotropy and the band dispersion anisotropy, respectively.