Current Issue

Volume 16 Issue 11
Online Date:
Previous Issue    Next Issue
Original Articles
Modification of Bertrand’s Theorem and Extended Runge-Lenz Vector
WU Zuo-bing, ZENG Jin-yan
Chin. Phys. Lett. 1999, 16 (11): 781-783 .  
Abstract   PDF(pc) (210KB) ( 544 )
It is shown that for a particle with suitable angular momenta in the screened Coulomb potential or isotropic harmonic potential, there still exist closed orbits rather than ellipse, characterized by the conserved aphelion and perihelion vectors, i.e. extended Runge-Lenz vector, which implies a higher dynamical symmetry than the geometrical symmetry O3. The closeness of a planar orbit implies the radial and angular motional frequencies are commensurable.
Entropy of the Nonminimally Coupled Quantum Scalar Fields in a Stationary Axisymmetric Einstein-Maxwell Dilaton- Axion Black Hole
JING Ji-liang, WANG Yong-jiu
Chin. Phys. Lett. 1999, 16 (11): 784-786 .  
Abstract   PDF(pc) (242KB) ( 346 )
The statistical-mechanical entropy of the stationary axisymmetric Einstein-Maxwell dilaton-axion black hole is investigated by using the “brick wall” model in which the original Dirichlet condition is replaced by a scattering ansatz for the field functions at the event horizon and regularized with the Pauli-Villars scheme. It is also shown, for the Kerr black hole, that the statistical-mechanical entropy obtained from our derivation coincides with the one-loop correction to its thermodynamical entropy obtained by the conical singularity method.
An Integrable Bose Fermion Model
YANG Fan, WANG Yu-peng, CHEN Shu, PU Fu-ke,
Chin. Phys. Lett. 1999, 16 (11): 787-789 .  
Abstract   PDF(pc) (193KB) ( 293 )
In this paper, we derive the higher order Hamiltonian of the three-wave interaction fermion model II by the Neumann expansion and find it physically interesting as related to the pairing process of the high Tc super-conductivity. The eigenvalues and Bethe-ansatz equation are also obtained by the quantum inverse scattering method.
Effects of Condensates of Higher Dimensional Operators on Quarkonium System
LIANG Wei-hong, LIU Ji-feng, SHEN Peng-nian, , Li Xue-qian
Chin. Phys. Lett. 1999, 16 (11): 790-792 .  
Abstract   PDF(pc) (244KB) ( 342 )
The effect of higher dimensional quark-gluon condensates on the effective quark-antiquark potential is investigated. In this scenario, cc and bb spectra are studied. It is shown that the vacuum condensates of the d = 5 and d = 6 operators, where d denotes the dimension of the operator, still cause notable effects. The perturbative loop contributions from the s-channel scattering and t-channel annihilation processes to the potential are almost the same. These contributions are opposite in sign to the non-perturbative contributions of the d = 4 operator condensates.
Effective Mass of ρ-Meson in Medium
WANG Ping, SU Ru-keng
Chin. Phys. Lett. 1999, 16 (11): 793-795 .  
Abstract   PDF(pc) (219KB) ( 326 )
The effective mass of ρ-meson in medium has been calculated for the Welecka, Bonn potential, Zimanyi-Moszkowski, quark-meson coupling and vector-tensor coupling models, respectively. The vacuum fluctuation effects are taken into account. It is shown that the formula of nucleon effective mass suggested by Brown-Rho scaling can get a best fit with experiments provided the adjusted parameter y equals to 0.10 and 0.19 for strong and weak tensor coupling, respectively.
Correction of the Directional Correlation of Oriented Nuclei for Detector Efficiency
LI Guang-sheng
Chin. Phys. Lett. 1999, 16 (11): 796-797 .  
Abstract   PDF(pc) (161KB) ( 367 )
Correction of the directional correlation of oriented nuclei for detector efficiency has been investigated by using in-beam γ-ray spectroscopic method. The result indicates that this correction is quite necessary for the low-energy γ-rays. On the basis of the corrected directional correlation of oriented nuclei ratios the spin assignment of the new rotational band for 170Hf was yielded.
J/ψ and γ Photoproduction at Relativistic Heavy-Ion Collider
LI Yun-de, XU Xiao-mei, LIU Lian-shou
Chin. Phys. Lett. 1999, 16 (11): 798-799 .  
Abstract   PDF(pc) (173KB) ( 372 )
Hard photoproduction of J /ψ and γ at the Relativistic Heavy-Ion Collider Au-Au, I-I, Cu-Cu, Si-Si, and 0-0 collisions is discussed in the process A+A → A+ J/ψ ( γ ) + X . It shows that in the rang of transverse momentum Pt < 4GeV the hard photoproduction process can be used to test the gluon distribution in the nucleus. So the process also provides a new way of testing the EMC effects. The large Pt heavy quark Qc and gluon fragmantizing into J /ψ are also studied in the range of 4 < Pt < 10 GeV.

J /ψ Suppression and the Effect of Quark Flavor Kinetics
LI Pan-lin, DENG Cheng-feng, WANG Li-lian, XU Meng-jie
Chin. Phys. Lett. 1999, 16 (11): 800-802 .  
Abstract   PDF(pc) (213KB) ( 345 )
The dilepton spectrum emitted in the phase transition process of an expanding quark gluon plasma formed in the collisions of 238U - 238U and l84W -l84W at 200 GeV/(cu) is calculated by using the theoretical framework of relativistic hydrodynamics, including the effect of quark flavor kinetics, and phenomenological SU (3) string model is used in the calculation of the quark flavor kinetics. The calculated results are compared with the experimental data from the Center of European Research of Nucleon SPS and analysis is carried out. The results show that the effects of quark fragmentation and flavor kinetics cause a peak suppression of J /ψ →μ+μ-, while the dilepton spectrum increases for small invariant mass. The calculated results show that the phenomena of suppression under the rich-baryon condition is greater than those under the poor-baryon conditions. Under the same conditions of collision, the J / ψ peak suppression produced in 238U - 238U collisions is greater than that in l84W -l84W collisions.

Molecular Dynamics Simulation on Interface Characteristics of Micro Droplets
YANG Chun, CHEN Min, GUO Zeng-yuan
Chin. Phys. Lett. 1999, 16 (11): 803-804 .  
Abstract   PDF(pc) (188KB) ( 382 )
Liquid droplets of argon surrounded by the vapor for various temperatures have been simulated by the molecular dynamics method. Macroscopic characteristics of droplets such as density, pressure and temperature profiles are evaluated with emphasis on the temperature characteristics, which was usually regarded uniform in the surface region for an equilibrium liquid-vapor system. The 12-6 Lennard-Jones potential and periodic boundary conditions are employed in the 1000-particles three-dimensional simulation. What differs from the literatures is that the temperature in the surface region is not uniform, but exhibits a curve with two extrema. The peak and valley values are higher and lower than the bulk saturation temperature respectively. The magnitude of the peak and valley values becomes smaller when the saturation temperature is closer to the critical temperature.
Magneto-Optical Trap for Cesium Atoms Without a Separate Repumping Laser
FU Jun-xian, CHEN Xu-zong, LI Yi-min, YANG Dong-hai, WANG Yi-qiu
Chin. Phys. Lett. 1999, 16 (11): 805-807 .  
Abstract   PDF(pc) (266KB) ( 498 )
A magneto-optical trap (MOT) for cesium atoms that operates without a separate repumping laser is reported. The differences between a normal MOT and this kind of MOT have been experimentally studied. The influences of a repumping laser on cooling and trapping cesium atoms in the MOT have been carefully investigated. The results reveal that it is the critical injection-locked state of the diode laser that makes magneto-optical trapping of cesium atoms possible without a separate repumping laser.
Structure of the Ground Rotation Band of the Na+3 Molecular Ion
HE Yan-zhang, BAO Cheng-guang
Chin. Phys. Lett. 1999, 16 (11): 808-810 .  
Abstract   PDF(pc) (233KB) ( 337 )
A complete set of quantum numbers for the eigenstates of the Na+3 system has been introduced. The structure of the ground rotation band has been deduced based on symmetry considerations. This band is found to be different from that of H+3, though they are similar in dynamics.
Boundary Diffraction Method for Aperture Near-Field Diffraction
XIE Jian-ping, WU Wei-min, FANG Hui, SUN Xiao-hong, WU Yun-xia, MING Hai
Chin. Phys. Lett. 1999, 16 (11): 811-813 .  
Abstract   PDF(pc) (211KB) ( 813 )
The boundary diffraction method is introduced to analyze the near-field diffraction of a subwavelength aperture. A self-consistent formula of boundary diffraction suitable to near field is derived. The near-field diffraction patterns of slits and circular apertures are obtained. The influence of incident light polarization on these diffraction patterns is also shown. These results are in good agreement with other theoretical and experimental results.
Thermal Lensing Measurement and Laser Performance of End-Pumped Lightly Doped Nd:GdVO4 Crystal
LIU Jun-hai, SHAO Zong-shu, MENG Xian-lin, ZHANG Huai-jin, ZHU Li, JIANG Min-hua
Chin. Phys. Lett. 1999, 16 (11): 814-815 .  
Abstract   PDF(pc) (200KB) ( 335 )
The thermal lensing effect generated in an end-pumped lightly doped Nd:GdVO4 crystal was found to be considerably weaker than that in Nd:YVO4 having the same Nd3+ concentration. Consequently, the laser performance of Nd:GdVO4 at high pump powers over 20 W was found to be superior to that of Nd:YVO4. TEM00 mode cw radiation of 14.3 W at 1.06μm was achieved with an optical conversion efficiency of 55%, and average slope efficiency of 62%.
Three-Photon Resonant Third Harmonic Generation of H2 in Vacuum Ultraviolet and Extreme Ultraviolet Regions
XIE Xiao-bo, WANG Peng-qian, CAO Chuan-shun, SUN Tao-heng
Chin. Phys. Lett. 1999, 16 (11): 816-818 .  
Abstract   PDF(pc) (249KB) ( 304 )
Tunable coherent vacuum ultraviolet and extreme ultraviolet radiation have been produced in H2 by three-photon resonant third harmonic generation via B1 Σ+u(v’) ← X1 Σ+g (v = 0 ) and C1 IIu(v’) ← X1 Σ+g ( v = 0 ) transitions. Highly resolved third harmonic spectrum exhibits some distinct characteristics. Phase-matching effect of the nonlinear optical process is also discussed.

Reflected Beam Displacements of a Slightly Divergent Ultrasonic Gaussian Beam on a Water-Glass Interface Near Rayleigh Angle Incidence
ZHU Guo-zhen, LIU Liang, FU De-yong
Chin. Phys. Lett. 1999, 16 (11): 819-821 .  
Abstract   PDF(pc) (322KB) ( 325 )
Two reflected beams of a slightly divergent ultrasonic Gaussian beam on a water-glass interface are observed and recorded by a Schlieren system. The lateral displacements of the two reflected beams are measured for incident angle θi in a wide range of 10° around the Rayleigh angle θc. The displacements decrease as the incident angle increases, which is different from the previous predictions for bounded plane-wave beams, where the displacements have extremum at the Rayleigh angle θc.The explanation is based on the fact that the Gaussian beam generated by an ultrasonic transducer with a button (or strip) back electrode is actually slightly divergent. We extend Bertoni and Tamir's theory (Appl. Phys. 2 (1973) 157) to this case, and our calculated curves of the displacements against the incident angle are in agreement with the experimental results for |θi - θc| < 2°.

Instability from Steady and Axisymmetric to Steady and Asymmetric Floating Half Zone Convection in a Fat Liquid Bridge of Larger Prandtl Number
CHEN Qi-sheng, HU Wen-rui
Chin. Phys. Lett. 1999, 16 (11): 822-823 .  
Abstract   PDF(pc) (177KB) ( 388 )
The linear instability analysis of the present paper shows that the thermocapillary convection in a half floating zone of larger Prandtl number has a steady instability mode ωi = 0 and m = 1 for a fat liquid bridge V = 1.2 with small geometrical aspect ratio A = 0.6. This conclusion is different from the usual idea of hydrothermal instability, and implies that the instability of the system may excite a steady and axial asymmetric state before the onset of oscillation in the case of large Prandtl number.
Micro Perpendicular Pickup Process of Newborn Ions
CAO Jin-bin, WANG Xue-yi, ZHOU Guo-cheng
Chin. Phys. Lett. 1999, 16 (11): 824-826 .  
Abstract   PDF(pc) (246KB) ( 396 )
The micro perpendicular pickup process of newborn ions is considered by means of one-dimensional electromagnetic hybrid computer simulations of homogeneous plasmas. It is found that there exists the micro perpendicular pickup process for newborn ions. The phase angle diffusion time is Jess than (not larger than) the time for pitch-angle scattering to a relatively thin shell and much faster than the energy scattering time for broadening of the shell toward a thermal distribution.
Anomalous Wave Energy Deposition in the Beginning Phases of Wave Injection in JT-60U Lower Hybrid Current Drive Experiments
FANG Yu-de, Kenkichi USHIGUSA, Takashi KONDOH
Chin. Phys. Lett. 1999, 16 (11): 827-829 .  
Abstract   PDF(pc) (284KB) ( 389 )
An anomalous phenomenon of wave energy deposition and its evolution were noticed in the beginning phases of lower hybrid wave injection in JT-60U experiments. It was found that the driven currents are always formed in the central region of the plasma column in the first several hundred milliseconds of the wave pulses, no matter what N|| spectrum of the waves is. Then the driven current profile will change to their normal situation gradually, which depends on N|| spectrum closely.
Plasma Current Profile During Current Reversal in a Tokamak
HUANG Jian-guo, YANG Xuan-zong, ZHENG Shao-bai, FENG Chun-hua, ZHANG Hou-xian, WANG Long
Chin. Phys. Lett. 1999, 16 (11): 830-832 .  
Abstract   PDF(pc) (298KB) ( 417 )
Alternating current operation with one full cycle and a current level of 2.5kA have been achieved in the CT-6B tokamak. The poloidal magnetic field in the plasma is measured with two internal magnetic probes in repeated discharges. The current distribution is reconstructed with an inversion algorithm. The inversed current first appears on the weak field side. The existence of magnetic surfaces and rotational transform provide particle confinement in the current reversal phase.
Investigation of Absorption of Nanocrystalline Silicon
MA Zhi-xun, LIAO Xian-bo, KONG Guang-lin, CHU Jun-hao
Chin. Phys. Lett. 1999, 16 (11): 833-835 .  
Abstract   PDF(pc) (281KB) ( 389 )
Nanocrystalline silicon embedded SiO2 matrix is formed by annealing the SiOx films fabricated by plasma enhanced chemical vapor deposition technique. In conjunction with the micro-Raman spectra, the absorption spectra of the films have been investigated. The blue-shift of absorption edge with decreasing size of silicon crystallites is due to quantum confinement effect. It is found that nanocrystalline silicon is of an indirect band structure, and that the absorption presents an exponential dependence of absorption coefficient on photon energy in the range of 2.0-3.0eV, and a sub-band appears in the range of 1.0-1.5eV. We believe that the exponential absorption is due to the indirect band-to-band transition of electrons in silicon nanocrystallites, while the sub-band absorption is ascribed to transitions between the amorphous silicon states existing in the films.
Localized Vibrational Modes of Excitation in Electroluminescent Polymers
JIANG Hao, XU Xiao-hua, SUN Xin, K. Yonemitsu
Chin. Phys. Lett. 1999, 16 (11): 836-837 .  
Abstract   PDF(pc) (136KB) ( 256 )
The localized vibrational modes of exciton and polaron are investigated, and the results show that the frequencies of the three even parity modes of exciton are very different from those of polaron. For the exciton, three modes are distinctly separated; but, for the polaron, two modes with higher frequencies are close to each other, Then, it is possible to distinguish exciton from polaron by watching their Roman spectra. Therefore, the localized mode may be used to specify the exciton and polaron in the electroluminesent polymers.
Effects of Chamber Pressure on Current-Voltage Characteristic of Metal-Insulator-Metal Element in Heat-Treating Anodized Ta2O5 Film
LIU Hong-wu, GAO Chun-xiao, WANG Hui, CUI Qi-liang, ZOU Guang-tian, HUANG Xi-min
Chin. Phys. Lett. 1999, 16 (11): 838-840 .  
Abstract   PDF(pc) (207KB) ( 558 )
Ta/anodized Ta2O5/Al is used as metal-insulator-metal (MIM) element in experiments, The current- voltage (I- V) characteristic of the MIM element depends on the chamber pressure in heat-treating anodized Ta2O5 film. Good nonlinear I- V characteristic has been obtained in the pressure range from 10-2 to 10-4 to Torr. Meanwhile, the conductivity coefficient α of the Poole-frenkel (PF) equation which describes the I- V characteristic can be regulated by about two orders of magnitude in this pressure range, while the non-linearity coefficient β of the PF equation is not affected by the chamber pressure.
AIN:TbF3 Electroluminescence Thin Film Prepared by Radio-Frequency Magnetron Sputtering
ZHAO Yan-li, ZHONG Guo-zhu, FAN Xi-wu, LI Chang-hua
Chin. Phys. Lett. 1999, 16 (11): 841-843 .  
Abstract   PDF(pc) (233KB) ( 347 )
High quality AlN thin films doped with TbF3 were prepared by rf magnetron reaction sputtering. High purity AI metal and TbF3 were used as target materials with N2 and Ar as sputtering gases. The influence of preparation conditions on the photoluminescence brightness was studied, and the electroluminescence was found to have a similar dependence on the concentration of TbF3 and substrate temperature. The characteristic emission of Tb3+ ions was obtained in an AIN:TbF3 alternating current thin film electroluminescence device prepared with 600°C substrate temperature and 4.0mol% concentration of TbF3.

Reduced Sputtering Yields Induced by Fast Neutrons
YE Bang-jiao, FAN Yang-mei, Yoshimi KASUGA, Yujiro IKEDA, ZHOU Xian-yi, HAN Rong-dian
Chin. Phys. Lett. 1999, 16 (11): 844-846 .  
Abstract   PDF(pc) (211KB) ( 517 )
The reduced sputtering yield (yRn) of materials induced by fast neutron is presented. Based on the experimental yRn results for (n, 2n), (n, p), (n, α) and (n, np) reactions, the value of yRn for (n, non-elastic) reaction is deduced by using data of cross sections in JENDL-3.2 and ENDF/B-VI. The value of yRn for (n, n) reaction is predicted by relation between yRn and the mean projected ranges of recoil nuclides. Combining both yRn for (n, n) and (n, non-elastic) reactions, the total yRn is obtained. Systematics of yRn for (n, non-elastic), (n, n) and (n, total) reactions have been demonstrated.
Effect of Substrate Temperature on Carbon Nitride Thin Films Prepared by Radio Frequency Sputtering
YANG Bing-chu, N. Tajima, T. Sogoh, O. Takai, CHEN Zhen-hua
Chin. Phys. Lett. 1999, 16 (11): 847-849 .  
Abstract   PDF(pc) (270KB) ( 449 )
Carbon nitride thin films have been deposited by radio frequency sputtering at different substrate temperatures. The electronic structure and optical properties of the films have been systematically studied for the different substrate temperatures. The maximum N concentration in the films arrived at 41 at.%. The binding energy of core levels C 1s and N 1s produces a large shift in the range of 3.5-0.3eV depending on substrate temperature Ts. The band gap is at about 0.61-1.22eV. N atom concentration and shift of core level as well as electron band gap decrease with increasing Ts, which illustrates that raising Ts is not a good way to form carbon nitride films. Ultraviolet-visible near infrared spectra show that the films have a good transparency in near infrared region, but there is a sharp absorption peak around 2720 nm. The peak disappears when Ts is higher than 400°C.

Final Structures of Crystallization of Liquid Copper Studied by Molecular Dynamics Simulation
XIA Jun-chao, ZHU Zhen-gang, LIU Chang-song
Chin. Phys. Lett. 1999, 16 (11): 850-852 .  
Abstract   PDF(pc) (274KB) ( 317 )
Molecular dynamics simulation is performed to study the cooling rate effects on the resulting crystallization microstructure of bulk liquid copper (homogeneous nucleation). Our studies reveal that mixtures of the metastable hcp phase and most-stable fcc phase, in all sorts of proportion and in various forms such as layering and phase separation, can be obtained by controlling the cooling rate. We have also found that, below the glass forming critical cooling rate, the ratio of the number of fcc-type polyhedra to the number of hcp-type polyhedra at 0K decreases with increase of the cooling rate.
Atomic Force Microscopy of Surface Reconstructed SrTiO3 Vicinal Substrates for Epitaxial Growth of YBa2Cu3O7-δ Thin Films
HU Wen-fei, LI Lin, WANG Tian-sheng, LIU Wei, TAO Hong-jie, TIAN Yong-jun, CHEN Ying-fei,
Chin. Phys. Lett. 1999, 16 (11): 853-855 .  
Abstract   PDF(pc) (545KB) ( 360 )
SrTiO3(001) vicinal substrates of miscut 1°, 3°, and 6° toward the (001) plane were annealed at 800-1000°C in pure flowing O2 for 6h and examined by atomic force microscopy. The high temperature annealed vicinal SiTiO3(001) displayed arrays of straight steps and smooth terraces. The step heights vary from about 2 to 6 unit cell depending on the annealing temperatures. At 1000°C, step bunching becomes obvious. The height steps of 1 unit cell are difficult to be observed by our atomic force microscopy. The YBa2Cu3O7-δ thin film grows epitaxially on the step-terrace surface with c-axis orientation by magnetron sputtering in the two-dimensional island mode. Prospect of step-flow growth is being discussed.
Difference Between the Ion Gyroviscous Effect and Hall Magnetohydrodynamic Effect in the Magnetic Reconnection
CAI Chun-lin, ZHOU Guo-cheng, CAO Jin-bin, WANG De-ju
Chin. Phys. Lett. 1999, 16 (11): 856-858 .  
Abstract   PDF(pc) (212KB) ( 462 )
We study the ion gyroviscous effect and Hall magnetohydrodynamic (MHD) effect separately using the modified MHD simulation of the magnetopause. Simulations show that the ion gyroviscous effect is on the order of a characteristic scale of ion Larmor radius and is mainly limited near the magnetosheath boundary. The Hall MHD effect is on the order of a characteristic scale of ion inertial length and occurs mainly in the central region of the current layer. The magnetic field component out of the simulation plane has a bipolar structure near the magnetosheath boundary from the ion gyroviscous effect and a quadrupole structure in the central region of the current layer from the Hall MHD effect. These results are of fundamental importance in understanding the reconnection processes in space and astrophysical plasma.
28 articles