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Volume 14 Issue 10
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Original Articles
The Most General Corrdinate Transformation Between the Hydrogen Atom and Harmonic Oscillator in Arbitrary Dimensions
SU Ka-lin
Chin. Phys. Lett. 1997, 14 (10): 721-723 .  
Abstract   PDF(pc) (107KB) ( 496 )
In this paper, we find out the most general coordinate transformation between a d-dimensional hydrogen atom and a D-dimensional harmonic oscillator by means of the SU(1,l) algebra. In other words, the generalized Kustaanheimo-Stiefel transformation is established.

A Study of the Off-Shell Calculation in the Quark-Gluon Vertex
YANG Jian-jun, LI Guang-lie, HUANG Tao,
Chin. Phys. Lett. 1997, 14 (10): 724-727 .  
Abstract   PDF(pc) (188KB) ( 341 )
The off-shell calculation is studied in the quark-gluon vertex with dimension-4 gluon condensate in the fixed-point gauge. It is noted that the evaluated result depends on whether the zero point is set on the fermionic or gluonic line for the off-shell calculation in the quark-gluon vertex. In order to obtain more reasonable results, it is suggested that a covariant gauge should be adopted.

Thermal Relaxation Time in Chemically Non-equilibrated Gluon Plasma
ZHANG Xiao-fei, ZHAO Wei-qin
Chin. Phys. Lett. 1997, 14 (10): 728-731 .  
Abstract   PDF(pc) (220KB) ( 485 )
The thermal relaxation time for a chemically non-equilibrated gluon plasma is calculated using the non-equilibrium Debye mass as the infrared regulator. The dependence of the thermal relaxation time on the fugacity is given. We find that there is a threshold fugacity λ g*. When λg < λ g*, τ NEQEQ decreases sharply with increasing fugacity, while λg > λg*, the ratio is almost unchanged.
Energy and Oscillator Strength for Lithium Atom
QU Lian-hua, WANG Zhi-wen, GUAN xiao-xu
Chin. Phys. Lett. 1997, 14 (10): 732-735 .  
Abstract   PDF(pc) (237KB) ( 557 )
The excitation energies of the excited states ls2nl (l = s,p, d, and f, and 6 ≤ n ≤ 9) and the dipole oscillator strengths of the 1s22s – ls2np, ls22p – ls2nd and ls23d - ls2nf transitions for lithium atom are calculated by using the full core plus correlation method.
Spectral and Temporal Emission Behaviors in Disordered Scattering of Rh640 Dye Solution
WANG He-zhou, ZHAO Fu-li, HUANG Xu-guang, ZHENG Xi-guang, WU Ming-mei, W. K. LEE
Chin. Phys. Lett. 1997, 14 (10): 736-739 .  
Abstract   PDF(pc) (243KB) ( 448 )
The fluorescent decays and spectra of pump power density dependent emission demonstrated that the excitation power density was enhanced in Rh640 dye solution containing scattering nanoparticles. Lasing in disordered scattering medium with low threshold, narrow bandwidth, and short duration was observed. The mechanism of this enhancement, together with the lasing properties of low threshold and narrow bandwidth, was discussed.
Optical Third Harmonic Generation in Methane
WANG Peng-qian, XIE Xiao-bo, SUN Tao-heng
Chin. Phys. Lett. 1997, 14 (10): 740-743 .  
Abstract   PDF(pc) (209KB) ( 512 )
Methane has been used as a nonlinear optical medium to produce tunable coherent vacuum ultraviolet and extreme ultraviolet radiation. A vibrational structure with a vibrational frequency of 820cm-1 was observed in a highly resolved third harmonic spectrum. This proved that third harmonic generation is an effective method to probe the higher excited states of molecular gases.
Generalized Boundary Conditions for Ultrasonic Scattering from a Cylindrical Layer Between Two Solids
ZHU Wei-yong, WANG Yao-jun
Chin. Phys. Lett. 1997, 14 (10): 744-747 .  
Abstract   PDF(pc) (234KB) ( 499 )
By asymptotically expanding the transfer matrix that relates stresses and displacements on both sides of a thin cylindrical interface between two solids, a new spring model is proposed to describe the scattering of an obliquely incident ultrasonic wave from an interface layer in composite structures. Generalized three-dimensional boundary conditions at the cylindrical interface are obtained. Two stiffness constants, besides three mass terms, for the interface layer are introduced. It is found that the accuracy of the new model satisfies the precision demand in ultrasonic nondestructive evaluation.
Vertical Vibration Isolation Using Displacement Feedback Control
LUO Jun, ZHOU Ze-bing
Chin. Phys. Lett. 1997, 14 (10): 748-751 .  
Abstract   PDF(pc) (257KB) ( 448 )
A vertical active vibration isolation system using the displacement feedback force, a method widely used in gravitational and other experiments, is reanalyzed in detail. We find that more effective vibration isolation could be obtained if the feedback variable is proportional to the relative displacement between the platform and the foundation other than the absolute displacement of the platform itself The physical meaning is first recognized by introducing the concept of quasi-fixed reference system, this is significant for improving the isolation ratio of an active isolation system.
Improved Confinement by Edge Multi-pulse Turbulent Heating on HT-6M Tokamak
MAO Jian-shan, LUO Jia-rong, LI Jian-gang, PAN Yuan, WANG Mao-quan, LIU Bao-hua, WAN Yuan-xi, LI Qiang, WU Xin-chao, LIANG Yun-feng, XU Yu-hong, YU Chang-xuan
Chin. Phys. Lett. 1997, 14 (10): 752-755 .  
Abstract   PDF(pc) (226KB) ( 442 )
In the recent experiment on HT-6M tokamak, an improved ohmic confinement phase has been observed after application of the edge multi-pulse turbulent heating, and variance of plasma current ΔIp/Ip is about 14-20%;. The improved edge plasma confinement phase is characterized by (a) increased average electron density Ne and electron temperature Te; (b) reduced Hα radiation from the edge; (c) steeper density and temperature profiles at the edge; (d) a more negative radial electric field over a region of ~ 5mm deep inside the limiter; (e) a deeper electrostatic potential well at the edge; ( f ) reduced magnetic fluctuations at the edge.
Crystallization and Fractal Formation in Annealed Al/a-Ge Bilayer Films
WU Feng, ZHANG Shu-yuan, CHEN Zhi-wen, TAN Shun
Chin. Phys. Lett. 1997, 14 (10): 756-759 .  
Abstract   PDF(pc) (553KB) ( 377 )
The crystallization and fractal formation in annealed Al/a-Ge bilayer films were studied. It was found that the effect of metal-mediated Crystallization increases with increasing annealing temperature and time. However, fractal patterns could be formed only in samples with proper thickness ratio. Some special phenomena at strain, broken, and step areas are also reported.
Topography of InP Surface Bombarded by O+2 Ion Beam
SUN Zhao-qi
Chin. Phys. Lett. 1997, 14 (10): 760-763 .  
Abstract   PDF(pc) (296KB) ( 487 )
The topography of InP surface bombarded by O+2 ion beam was investigated. Rippled topographies were observed for bombarded samples, and the data show that the ripple formation starts from a sputtering depth of about 0.4 μm. The wavelength and the disorder of the ripples both increase as the sputtering depth increases. The wavelength of the ripples appears to be sputtering depth dependent rather than sputtering rate dependent. It is confirmed that the ion- beam-induced surface rippling can be effectively suppressed by sample rotation during bombardment.
A New Molecular-Dynamics Approach for Fully Relaxed Crystals at Constant Pressure
LIU Gang, WANG En-ge, WANG Ding-sheng
Chin. Phys. Lett. 1997, 14 (10): 764-767 .  
Abstract   PDF(pc) (220KB) ( 390 )
A new molecular-dynamics method at constant pressure has been proposed. As the three edge vectors of a crystal cell as well as the position vectors of all particles are taken as independent variables, this method allows the crystal to relax fully. Furthermore, the effect of pressure on the crystal structure is explicitly given in this approach. As an example, the evolution process of cobalt from a structure far from the final one to the ideal hexagonal close packing structure was given.
Theoretical Study of Adatom Self-Diffusion on Metallic fcc {001} Surfaces
LI Jia-ming, ZHANG Pei-hong, YANG Jin-long, LIU Lei
Chin. Phys. Lett. 1997, 14 (10): 768-771 .  
Abstract   PDF(pc) (254KB) ( 494 )
Based on the discrete variational method with the local-density-functional approximation (DVLDA), we propose molecular cluster models to simulate the physical surface with and without an adsorbed atom respectively. Our DV-LDA calculations favor the atomic exchange process along the [100] direction for AI self-diffusion on AI fcc (001) surfaces and the atomic bridge hopping process along the [110] direction for Cu self-diffusion on Cu fcc (001) surfaces. Based on all available experimental and theoretical results, there is an interesting parameter which can correlate the favored self-diffusion mechanism on metallic fcc {001} surfaces.
Influence of Boron Dopant on Switching Behaviour of Polycrystalline Diamond Thin Films
WANG Xiao-ping, WANG Li-jun, XU Yue-e, SHEN Shu-po
Chin. Phys. Lett. 1997, 14 (10): 772-774 .  
Abstract   PDF(pc) (212KB) ( 471 )
Switching behaviour of polycrystalline diamond thin films is reported. Boron-doped diamond thin films were deposited by microwave plasma-assisted chemical vapor deposition on silicon substrate. Dependence of switching behaviour on boron impurity has been investigated. The threshold voltage obviously decreases with increasing content of boron dopant.
Valence Offsets of Three Series of Alloy Heterojunctions
ZHENG Jin-cheng, WANG Ren-zhi, ZHENG Yong-mei, CAI Shu-hui
Chin. Phys. Lett. 1997, 14 (10): 775-777 .  
Abstract   PDF(pc) (183KB) ( 448 )
Electron structure of three series of alloy heterojunctions (GaAs)x(Ge2)1-x/Ge,(AlAs)x (Ge2)1-x/Ge and AlxG1-xAs/Ge are calculated by linear muffin-tin orbital method with atomic-sphere approximation using the average-bond-energy theory in conjunction with a cluster expansion method. The results indicate the variations of ΔEv(x) at heterojunctions (GeAs)x(Ge2)1-x/Ge and (AlAs)x (Ge2)1-x/Ge are nonlinear, which are very different from that of AlxGa1-xAs/Ge.
Giant Magnetoresistance in Granular Type (Co- Ag) /Ag Multilayers
YOU Biao, ZHOU Shi-ming, CHEN Liang-yao, ZHAO Hong-wu, XIA Ke, DU Jun, TONG Liu-niu, LU Mu, ZHAI Hong-ru
Chin. Phys. Lett. 1997, 14 (10): 778-781 .  
Abstract   PDF(pc) (289KB) ( 433 )
The dependence of giant magnetoresistance of sputtered granular type (Co-Ag)/Ag multilayers on the thickness of Ag layers and magnetic layers with varying Co content in the magnetic layers was studied. The magnetoresistance ratio ΔR/R was found to be enhanced by 2-7 times comparing with the single layer granular films. The enhancement was explained by the antiferromagnetic coupling due to magnetostatic interaction between the Co clusters in neighboring magnetic layers.

Transfer Matrix for Multilayer Structure
WANG Shao-feng, WANG Zhong-cheng, ZOU Shi-chang
Chin. Phys. Lett. 1997, 14 (10): 782-785 .  
Abstract   PDF(pc) (194KB) ( 588 )
A transfer matrix which transfers the electron states from one side of the interface to the other is defined for crystalline multilayer with layers joined coherently. The total transfer matrix for several sequential interfaces can be simply obtained by multiplication of the matrices. The bound states as well as the extended states can be naturally described in terms of transfer matrix. As an illustration of using transfer matrix, the equation of quantum well states for sandwich structure have been given in this way.
Large Magnetic Entropy Change in Perovskite La0.67-xGdxCa0.33MnO3
HUANG He, GUO Zai-bing, ZHANG Jian-rong, DU You-wei
Chin. Phys. Lett. 1997, 14 (10): 786-788 .  
Abstract   PDF(pc) (153KB) ( 425 )
Magnetic entropy change larger than that of gadolinium has been observed in perovskite manganese oxides La0.67-xGdxCa0.33MnO3 (x =0, 0.1, 0.15) with fixed carrier concentration. The large magnetic entropy change produced by the abrupt reduction of magnetization is attributed to the anomalous thermal expansion just at the Curie temperature. This phenomenon indicates potential applications for magnetic refrigerants in an extended high temperature range.
Angular Dependence of the Interlayer Exchange Coupling on the Nonmagnetic Cap Layers
ZHANG Xiang-dong, LI Lie-ming, ZHAN Ye-hong, LI Bo-zang, PU Fu-ke,
Chin. Phys. Lett. 1997, 14 (10): 789-792 .  
Abstract   PDF(pc) (233KB) ( 442 )
Based on the one-band tight-binding model, the angular dependence of interlayer exchange coupling was investigated on the nonmagnetic cap layers in a magnetic sandwich covered on both sides by nonmagnetic films. The results show that (1) the appearance of noncollinear exchange coupling is very sensitive to the cap layers, (2) the nonoscillatory component of the coupling strength varies generally with the thickness of outer nonmagnetic films, and (3) the variation of exchange coupling exhibits distinct features in the cases where the thicknesses of both outer nonmagnetic films vary simultaneously and where the thickness of one of the two outer nonmagnetic films is fixed while the other is varied.

Photoemission of the Oxidation of Cerium Overlayers on GaSb(110) Surface
LIANG Qi, WU Jian-xin, JI Ming-rong, MA Mao-sheng, LIU Xian-ming, ZHANG Yu-heng
Chin. Phys. Lett. 1997, 14 (10): 793-797 .  
Abstract   PDF(pc) (258KB) ( 412 )
We have used x-ray photoelectron spectroscopy to study the oxidation of cerium overlayers on a semiconductor GaSb(110) surface. A GaSb (110) sample covered with 10 monolayers Ce was used to adsorb oxygen. When the exposure of O2 was up to 50L, the oxide of cerium, Ce2O3, began to change into unstable CeO2. The dissociation of CeO2 resulted in strong oxidation of the substrate. The main products are Ga2O3, Sb2O3, and then Sb2O5. After annealing, a part of the oxygen atoms transferred from cerium dioxide toward Ga and Sb.
Energy Dependence of Profile Width in Short Gamma-Ray Bursts
YANG Yu-xuan, CHE Hai-hong, WU Mei, CAO Sheng-lin
Chin. Phys. Lett. 1997, 14 (10): 797-800 .  
Abstract   PDF(pc) (209KB) ( 549 )
Using the high time-resolution and 64ms resolution data of the burst and transient source experiment, we performed an autocorrelation analysis of the energy dependence of burst pulse width in short gamma-ray bursts. A method free from potential cosmological effects has been proposed. This allows us to use a sample with a size comparable to that used for long and bright bursts. Our result shows that the profiles of short bursts exhibit a very good power-law between profile width and photon energy, with an index ~ -0.3. This result is consistent with a united origin of the bimodal distribution.

21 articles