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Volume 15 Issue 10
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Original Articles
Collapses and Revivals of Interferencing Intensity in Two Bose-Einstein Condensates with Josephson-Like Coupling
KUANG Le-man, ZENG Zhao-yang
Chin. Phys. Lett. 1998, 15 (10): 703-705 .  
Abstract   PDF(pc) (258KB) ( 466 )
An approximate analytic solution is present for a system of two Bose-Einstein condensates (BECs) with a Josephson-like coupling. By the use of this approximate solution, it is shown that the existence of quantum collapses and revivals (QCRs) in the interferencing intensity of two BECs. It is found that QCRs are seriously affected not only by interatomic collisions and the atomic tunneling between two BECs but also by initial states of the two BECs, so that one can manipulate QCRs through changing scattering lengths of atoms, atomic tunneling and initial states of BECs.
Metric of Accelerating, Radiating, Rotating, and Charged Black Hole in de Sitter Space
XU Dian-yan
Chin. Phys. Lett. 1998, 15 (10): 706-707 .  
Abstract   PDF(pc) (177KB) ( 378 )
Metric of accelerating, radiating Kerr-Newman de Sitter black holes is derived in this letter.The metric involves (7+10) independent parameters. The volume density of space-time, and the electromagnetic potential in accelerating, radiating cases are the same as in nonaccelerating, nonradiating cases. The space-time related to acceleration is not asymptotic Minkowski flat. So the energy momentum tensor is not positive definite.




A Self-consistent Treatment of Disoriented Chiral Condensates
ZHUANG Peng-fei, Rolf Fauser
Chin. Phys. Lett. 1998, 15 (10): 708-710 .  
Abstract   PDF(pc) (238KB) ( 377 )
A system with disoriented chiral condensates (DCCs) is considered in the presence of residual thermal pion distributions. By self-consistently solving the coupled equations for the condensates, the thermal pion distributions, and the self-energies, it is observed that the neutral pion fraction f as a signal of DCCs is erased by the thermal pions.
Perturbative Quantum Chromodynamics αs4-Order Corrections to the Ratio R for τ Decay
B. P. Nigam
Chin. Phys. Lett. 1998, 15 (10): 711-712 .  
Abstract   PDF(pc) (131KB) ( 449 )
The perturbative quantum chromodynamics correction to the semihadronic decay rate R of the heavy lepton τ was expressed by Braaten as an expansion in powers of αs to order αs3. Braaten had found the αs3 order correction to be significant and conjectured that the αs4 order corrections might also be significant. Braaten et al. later corrected the αs3-order result. We have extended the analytic calculations to order αs4; it involves an unknown constant K3 which occurs in αs4 order. In order to estimate the effect of αs4 order correction, we have chosen K3 to range from -1000 to +1000 and we find that the value of R changes by about -11% to +10%, respectively, compared to the value of R = 3.5 obtained to αs3-order result.
Energy Properties of Single Helium Atom in Metals by Effective-Medium Theory
XU Hui-zhong, LONG De-shun, WANG Yan-sen, ZHAO Guo-qing, PENG Shu-ming, ZHAO Peng-ji, XU Zhi-lei
Chin. Phys. Lett. 1998, 15 (10): 713-714 .  
Abstract   PDF(pc) (180KB) ( 374 )
A simpler and refined version of effective-medium theory is adopted to calculate the fundamental energy properties of single helium atom in some metals, In this version, the relaxation effects of lattice have been taken into account. The calculated results of some typical energy values agree well with available experimental and other theoretical values.
Analytic Potential Energy Function for Doubly Charged Ions HBe2+, HB2+, and HF2+
WANG Fan-hou, ZHU Zheng-he, YANG Chuan-lu, JING Fu-qian
Chin. Phys. Lett. 1998, 15 (10): 715-717 .  
Abstract   PDF(pc) (244KB) ( 370 )
It is well known that the potential curve of ground state for almost all neutral diatomic molecules has only one minimum. However, the doubly charged diatomic ions may have both potential minimum and maximum or singly repulsive branch. In order to describe the potential of this kind of diatomic ions, two of the authors Zhu and Wang have proposed a new analytical potential function with four parameters ai (i=l,. . .,4), and ρ = R- Rmin for those with both minimum and maximum, and ρ= R for those with singly repulsive branch. The present work has derived this new potential function for HBe2+ with Rmin = 0.182 nm, Rmax = 0.335 nm and ΔE = Emax- Emin = 0.84 eV, and for HBe2+ with Rmin = 0.147 nm, Rmax = 0.185 nm and ΔE = Emax - Emin = 0.062 eV. It is found that the potential for HF2+ is one with singly repulsive branch. The dissociation limits, parameters ai(i = 1,. . . , 4 ) , force constants and spectroscopic data of these ions all are given out.
Operation of a Kerr-Lens Mode-Locked Cr:LiSGaF Laser with a Tight-Focusing Cavity Geometry
ZHANG Wei-li, WANG Qing-yue, ZHAO Jiang-shan, CHAI Lu, XING Qi-rong
Chin. Phys. Lett. 1998, 15 (10): 718-720 .  
Abstract   PDF(pc) (206KB) ( 402 )
A femtosecond Kerr-lens mode-locked Cr:LiSGaF laser based on a compact cavity geometry is demonstrated. With a combination of 488, 476, and 458nm lines as a pump source, 58fs pulses centered at 845nm were generated. The average output power is 30mW, and time-band product is 0.331, assuming a sech2 pulse shape. Neither acousto-modulator nor physical aperture or slit were used in this cavity.
Model for Heat Pinch in Reversed Magnetic Shear Tokamak Plasmas
QIU Xiao-ming, WANG Ai-ke
Chin. Phys. Lett. 1998, 15 (10): 721-723 .  
Abstract   PDF(pc) (239KB) ( 474 )
A simple model is proposed to explain the recent experiment in TFTR and the more recent one in JT-60U. In the model the significant reduction of effective thermal diffusivities of ions and electrons ( xieff and xeeff) is attributed to the inward flows of drift wave energy, induced by the synergistic effects of the reversed magnetic shear and E X B velocity shear, where E is due to ion pressure gradient. Numerical results demonstrate the predictions of the present model, in particular, the numerical results for xieff are in good agreement with experimental trents.
Atomic Force Microscopy on the Ga0.l6In0.84As0.80Sb0.20Epilayer Grown by Metalorganic Chemical Vapor Deposition
GAO Chun-xiao, LI Shu-wei, YANG Jie, LIU Bing-bing
Chin. Phys. Lett. 1998, 15 (10): 724-726 .  
Abstract   PDF(pc) (332KB) ( 430 )
The atomic force microscopy study was made on the quaternary Ga0.l6In0.84As0.80Sb0.20 epilayer prepared on GaSb substrate by metalorganic chemical vapor deposition. The island-like defects were found on the substrate surface pretreated chemically. With the growth process going, these island-like defects could be buried by the epilayer. In the initial stage, two-dimensional-growth-mode was followed. When the epilayer thickness reached 70nm, three-dimensional (3D)-growth-mode occurred and the perfect 3D islands were observed.

Diffusion in Fast-Ion Conductor Calcia-Stabilized Zirconia: a Molecular Dynamics Study
SUN Jing-ze, WANG Yu-ming
Chin. Phys. Lett. 1998, 15 (10): 727-729 .  
Abstract   PDF(pc) (233KB) ( 405 )
Molecular dynamics simulation technique is used to investigate the ionic conduction property of the fast-ion conductor calcia-stabilized zirconia (CSZ). The theoretical results coincide with experimental measurements well. It is suggested that the dopant cation distribution is a key factor controlling the ionic conduction property of the CSZ electrolytes, which can be used as a rule in the microstructure designing and controlling in material processing.
Growth and Interface Structure of Mn on InP (001)
DONG Guo-sheng, CHEN Yan, SHEN Xiao-liang, JIN Xiao-feng
Chin. Phys. Lett. 1998, 15 (10): 730-731 .  
Abstract   PDF(pc) (170KB) ( 379 )
An attempt to grow single crystalline thin films of body-centered-cubic (bcc) Mn on InP (001) has been carried out by molecular beam epitaxy. In situ reflection high energy electron diffraction and ex situ x-ray diffraction are used to characterize the film and interface structures. It is found that the metastable phase of bcc Mn fails to stabilize on the substrate despite of their perfect lattice-match. This result suggests again the importance of interface structure in the epitaxy of 3d metals on semiconductors.
C-axis Oriented AIN Thin Films on Silicon Prepared by Ultrahigh Vacuum Evaporation of AI Combined with Post-Nitridation
HUANG Ji-po, WANG Lian-wei, SHEN Qin-wo, GAO Jian-xia, NI Ru-shan, LIN Cheng-lu
Chin. Phys. Lett. 1998, 15 (10): 732-733 .  
Abstract   PDF(pc) (218KB) ( 365 )
A new technique for the preparation of AlN thin films by ultrahigh vacuum electron beam evaporation of AI followed by nitridation is reported and by using this method c-axis oriented AJN thin films have been success-fully grown on Si(111) substrates. X-ray diffraction, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy and cross-sectional transmission electron microscope were employed to characterize AIN films. Temperature of nitridation was found to play an important role in the formation of AIN film. By post-nitridation of as-deposited film at 1000°C for lh in N2, the crystalline AlN film with (002) orientation has been obtained.
Exciton Properties of Diluted CdTe/CdMnTe Quantum Wells
WU Hui-zhen, YANG Ai-ling, WU Jian-zhong, LI Zheng-zhi
Chin. Phys. Lett. 1998, 15 (10): 734-736 .  
Abstract   PDF(pc) (292KB) ( 669 )
Optical studies of the CdTe/CdMnTe multiple quantum well structures with diluted manganese in barriers are presented. The combined measurements of photoluminescence and photoluminescence excitation allowed direct observation of the binding energies of n=l heavy- and light-hole free excitons. The quantitative approach of variation of exciton binding energies with well width and barrier potential height is given. The calculated and measured exciton binding energies are in good agreement. Photoluminescence studies also show exciton-acoustic phonon scattering dominates the broadening of the exciton line width up to T = 50 K , while T > 50 K longitudinal- optical phonon scattering contributes to the line width broadening significantly.
Quantum Charge Transfer in Quasi-One-Dimensional Mixed Halide Compounds
WEI Jian-hua, LIU De-sheng, XIE Shi-jie, MEI Liang-mo
Chin. Phys. Lett. 1998, 15 (10): 737-738 .  
Abstract   PDF(pc) (192KB) ( 352 )
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 the transferred charges will occur at a certain proportion x for a given mixed compound.


Low-Lying of a Negatively Charged Exciton X in Two-Dimensional Quantum Dots
XIE Wen-fang, CHEN Chuan-yu
Chin. Phys. Lett. 1998, 15 (10): 739-741 .  
Abstract   PDF(pc) (225KB) ( 452 )
The Hamiltonian of a charged exciton X (trion) in a two-dimensional quantum dot with parabolic confinement has been diagonalized to obtain the low-lying eigenenergy values as a function of the dot size and the electron to hole effective mass ratio. The introduction of the transformation bracket for 2D harmonic oscillators facilitates the evaluations of Hamiltonian. By using this method, we have calculated the energies of the low-lying states of the charged exciton as a function of the mass σ and the radius of quantum dots. It is found that a charged exciton X in a quantum dot may have more than one bound states. Theoretical explanations derived from the first principles have been formulated.
Ginzburg-Landau Equations for (d+s)-Wave Superconductors in a Non-Fermi Liquid
HAN Qiang, ZHANG Li-yuan
Chin. Phys. Lett. 1998, 15 (10): 742-744 .  
Abstract   PDF(pc) (198KB) ( 465 )
The Ginzburg-Landau equations are microscopically derived for an anisotropic (d + s)-wave superconductor by assuming a non-Fermi-liquid normal state characterized by a nonvanishing exponent α. The transition temperature Tc as functions of α and the anisotropic parameter g which measures the ab anisotropy is studied. It is found that the anisotropic effect, which results in the enhancement of Tc and the nonzero bulk value of the s-wave order parameter, is strengthened due to the non-Fermi behavior.
Relationship Between Cohesive Energy and Superconductivity in Hg-System Superconductors
QIN Xiao-chuan, DU Xu, ZHANG Han
Chin. Phys. Lett. 1998, 15 (10): 745-747 .  
Abstract   PDF(pc) (263KB) ( 402 )
Calculation of cohesive energy on Hg-system superconductors HgBa2CuOy(1201), HgBa2CaCu2Oy(1212), HgBa2Ca2Cu3Oy(1223), HgBa2Ca3Cu4Oy(1234), and HgBa2Ca4Cu5Oy (1245) has been made. A program was developed to claculate the combinative energy between Cu-O planes and remaining parts, and between blocks in the superconductors. The result indicates that if the cell is considered as the two blocks combined together, a close relationship among the combinative energy of the two blocks, the value of Tc, and the number of the Cu-O planes in the Hg-system superconductors is established. The result gives a new way to understand the change of the value of Tc, as the number of the Cu-O planes. In contrast, the combinative energy between the Cu-O planes and the remains got from the method separating all the Cu-O planes from the cell and leaving some discrete remaining parts does not show any relationship with the value of Tc. This means that considering the cell as the two blocks in more reasonable, and the interaction between the two blocks plays an important role in superconductivity.
Magneto-Impedance in Amorphous FeCuNbSiB Films
XIAO Shu-qin, LIU Yi-hua, ZHANG Lin, HU Ji-fan, LOU Jian-xin, HUANG Bao-xin, DAI You-yong
Chin. Phys. Lett. 1998, 15 (10): 748-749 .  
Abstract   PDF(pc) (188KB) ( 425 )
Longitudinal and transverse magneto-impedance effects have been observed in amorphous FeCuNbSiB films made by radio frequency sputtering. Large magneto-impedance values have been obtained at lower frequencies. The field dependence and frequency dependence of the magneto-impedance are studied. The field dependence of effective permeability μe is also discussed.

Preparation and Magneto-Optical Effects of Co-Ag Granular Films
YANG Wei, JIANG Zheng-sheng, GUO Zai-bing, LA Ming-yuan, ZHANG Ning, ZHANG Jian-rong, DU You-wei
Chin. Phys. Lett. 1998, 15 (10): 750-752 .  
Abstract   PDF(pc) (336KB) ( 448 )
A series of Co-Ag granular films were deposited onto a glass substrate with a thickness on the order of 400nm using the ion-beam cosputtering technique. Granular films ranging in composition from about 0-100% fraction by volume of cobalt have been prepared. Polar Kerr rotation spectra of the films were measured at room temperature in the wavelength region between 400 and 850nm. A maximum Kerr rotation angle (θk) of 0.28º was obtained when a magnetic field of 10kOe was applied perpendicular to the film plane. Our results indicate that the Co particle density and the microstructure between the Co particles and Ag matrix may play an important role in the Kerr rotation.
A Classical Theory for the Raman Optical Activity
MA Shu-guo, WU Guo-zhen,
Chin. Phys. Lett. 1998, 15 (10): 753-755 .  
Abstract   PDF(pc) (233KB) ( 384 )
A classical theory for the Raman optical activity (ROA) is proposed based on a picture that for a normal mode, atoms of a molecule with partial residual charges act as oscillating dipoles around their equilibrium positions, which also induce magnetic moments on the other atoms (dipoles), reciprocally. Then the resulting coupling between electric dipoles and magnetic moments of the molecule contributes to the optical activity. Despite its crude approximation, this model offers a physical essence for ROA and produces results that are of quality comparable to the complicated quantum-chemical calculation, as far as the sign of the circular intensity difference for the ROA is concerned.
Photoluminescence Quenching of Porous Silicon by Molecule Adsorption
LI Xue-ping, YIN Feng, ZHANG Zhen-zong, XIAO Xu-rui
Chin. Phys. Lett. 1998, 15 (10): 756-757 .  
Abstract   PDF(pc) (129KB) ( 361 )
The photoluminescence of HNO3 chemically oxidized porous silicon can be easily quenched by organic adsorbates, and the ability of quenching was quantitatively estimated by two models- Langmuir adsorption isotherm and Stern-Volmer. A strong steric effect of organic adsorbates on the photoluminescence quenching of oxidized porous silicon was observed.
Blue-Light Emission from Nanocrystalline La0.5Na0.5TiO3
ZHANG Wei-feng, ZHANG Xing-tang, YIN Zhen, ZHANG Ming-sheng, MA Guo-hong, DU Zu-liang
Chin. Phys. Lett. 1998, 15 (10): 758-760 .  
Abstract   PDF(pc) (239KB) ( 535 )
Nanocrystalline La0.5Na0.5TiO3 powders were prepared by the stearic acid-gel method, and the grain sizes could be controlled by varying annealing temperatures. The sizes were determined to be from 14 to 50nm using Scherrer's formula. A very strong blue-light emission band around 480nm was clearly observed in the nano-sized La0.5Na0.5TiO3 with a grain size of 14nm at room temperature. Also, nano-size effects on the luminescence properties were investigated. These results could be explained with the aid of a self-trapped exciton model.

Application of Electron Cyclotron Resonance Assisted Plasma in GaN Deposition
CHEN Guang-chao, DU Xiao-long, JIANG De-yi, YAO Xin-zi
Chin. Phys. Lett. 1998, 15 (10): 761-763 .  
Abstract   PDF(pc) (200KB) ( 377 )
An electron cyclotron resonance assisted plasma with N2 being the plasma source gas was employed to deposit hexagonal GaN on (0001) surface of α-Al2O3 substrate. By special gas distributor, trimethgallium was introduced into reactant zone. A 10 ×10mm uniform GaN film was gained with relatively low deposition temperature, 560°C, and high growth rate of 1.4μm/h. A good crystal microstructure was confirmed by its spectrum with full width at half maximum of 15 arcmin.
Epitaxial Pb ( Zr0.52Ti0.48) O3/Y1Ba2Cu3O7-x Heterostructure Prepared by Pulsed Laser Deposition
HUANG Bi-ping, ZHENG Li-rong, GAO Jian-xia, WANG Lian-wei, HUANG Ji-po, LIN Cheng-lu
Chin. Phys. Lett. 1998, 15 (10): 764-766 .  
Abstract   PDF(pc) (201KB) ( 514 )
C-axis oriented Y1Ba2Cu3O7-x(YBCO) thin films and PbZr0.52Ti0.48O3(PZT)/(YBCO) heterostructures were deposited on single-crystal LaAIO3 by Nd:YAG pulsed laser deposition. The results showed that the YBCO films exhibited superconducting transition temperature above 86 K and ion beam channeling minimum yields xmin of 49%, indicating the relatively good quality of YBCO films deposited on the LaAIO3 substrate. The PZT films in situ grown on the YBCO films were epitaxially c-axis oriented with a saturation polarization and remanence as high as 57μC/cm2 and 39μC/cm2 (at 204 kV/cm), respectively. The coercive field of PZT films is about 55 kV/cm.
Thermal Stress Analysis of Floating-Gate Tunneling Oxide Electrically Erasable Programmable Read Only Memory During Manufacturing Process
ZONG Xiang-fu, WANG Xu, WENG Yu-min, YAN Ren-jin, TANG Guo-an, ZHANG Zhao-qiang
Chin. Phys. Lett. 1998, 15 (10): 767-769 .  
Abstract   PDF(pc) (301KB) ( 462 )
In this study, finite element modeling was used to evaluate the residual thermal stress in floating-gate tunneling oxide electrically erasable programmable read only memory (FLOTOX E2PROMs) manufacturing process. Special attention is paid to the tunnel oxide region, in which high field electron injection is the basis to E2PROMs operation. Calculated results show the presence of large stresses and stress gradients at the fringe: This may contribute to the invalidation of E2PROMs. A possible failure mechanism of E2PROM related to residual thermal stress-induced leakage is proposed.
Meshwork Supported Fluid Film Model of Cell Membranes
TANG Xiao-wei
Chin. Phys. Lett. 1998, 15 (10): 770-771 .  
Abstract   PDF(pc) (119KB) ( 480 )
A new model of cell membranes, a meshwork supported fluid film model, is proposed by unifying the features of the fluid mosaic and the skeleton meshwork. Several properties of cell membranes including cell shape, cell signaling, membrane protein diffusion and endocytosis are discussed from the point of view of this model.
Explosion of Comet Shoemaker-Levy 9 Impacting on Jupiter
MA Yue-hua, XU Pin-xin
Chin. Phys. Lett. 1998, 15 (10): 772-774 .  
Abstract   PDF(pc) (201KB) ( 393 )
The fragments of Comet Shoemaker-Levy 9 entering the Jovian atmosphere suffered ablation and dissociation as a result of interaction with the atmosphere, and then exploded in the twinkle of an eye. A typical comet fragment is modeled as 1013 kg with a density of 1.0g/cm3. Our results show that the fragment exploded below the ammonia cloud layer, near the 1-bar level, which can explain why there was ammonia but no water in the observations. Our simple explosion model shows that the explosion could uplift the atmosphere to 5000km above the Jovian atmosphere, as observed, with the area covered by the ejecta to Jupiter's center making an angle of about 10º.
Fireball/Blastwave Model and Soft γ-Ray Repeaters
HUANG Yong-feng, DAI Zi-gao, LU Tan
Chin. Phys. Lett. 1998, 15 (10): 775-777 .  
Abstract   PDF(pc) (261KB) ( 582 )
Soft γ-ray repeaters are at determined distances and their positions are known accurately. If observed, afterglows from their soft γ-ray bursts will provide important clues to the study of the so called “classical γ-ray bursts”. On applying the popular fireball/blastwave model of classical γ-ray bursts to soft γ-ray repeaters, it is found that their x-ray and optical afterglows are detectable. Monitoring of the three repeaters is solicited.
Density and Ionization Parameters of Line and Continuum Emission from the Outer Regions of Accretion Disk in Active Galactic Nuclei
LU Ye, YANG Lan-tian, DING Shi-xue, YANG Pi-bo
Chin. Phys. Lett. 1998, 15 (10): 778-780 .  
Abstract   PDF(pc) (180KB) ( 437 )
In this paper, the diffusion source model and the structure of magnetized accretion disk with self-gravity are used to study the density and the ionization parameter of the HII and H*1 zone, of which most likely the broad line emitting region consists. Two different densities and ionization parameters are determined: the first < n( HII) > and Ξ( HII) , corresponding to the mean density and ionization parameter in the completely ionized HII zone, and the second,< n (H*1) > and Ξ(H*1), to the mean density and ionization parameters in the H*1 zone.




29 articles