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Volume 15 Issue 9
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Original Articles
Quantization and Squeezed State of Two L-C Circuits with Mutual-Inductance
FAN Hong-yi, PAN Xiao-yin
Chin. Phys. Lett. 1998, 15 (9): 625-627 .  
Abstract   PDF(pc) (173KB) ( 494 )
It is pointed out that the quantum mechanical Hamiltonian of two L-C circuits with mutual-inductance is equivalent to a pair of harmonic oscillators with a kinetic coupling term. We then diagonalize the Hamiltonian. It is shown that instantaneously switching on the external sources may result in a two-mode squeezed state of the system, which actually arises from the effect of mutual-inductance. The quantum fluctuation for the case of l1c1 = l2c2 is analysed and it is found that the current fluctuation in the circuits increases with the increment of the mutual-inductance.
Eigenvalues and Eigenfunctions of a Stadium-Shaped Quantum Dot Subjected to a Perpendicular Magnetic Field
LIU Bo, ZHANG Guang-cai, DAI Jian-hua, ZHANG Hong-jun
Chin. Phys. Lett. 1998, 15 (9): 628-630 .  
Abstract   PDF(pc) (284KB) ( 352 )
The eigenvalues and eigenfunctions of the stadium-shaped quantum dot subjected to a constant magnetic field in the perpendicular direction are computed by a simple and efficient method. With the magnetic field increasing, the nearest-neighour-energy-level-spacing distribution of the stadium-shaped quantum dot is found to transform gradually from the Wigner distribution to the Poisson distribution. The transition of the nearest-neighour-energy- level-spacing distribution indicates that system changes from quantum chaotic to regular. The variation of the spatial charge distribution indicates that the system varies from bulk Landau state to the edge state that mainly affects the transport properties of the stadium-shaped quantum dot. The change of the two dimensional charge distribution near the anticrossing point is also discussed.
Extended Technicolor Dynamics and Single Top Quark Production at the Fermilab Tevatron
YUE Chong-xing, LU Gong-ru
Chin. Phys. Lett. 1998, 15 (9): 631-633 .  
Abstract   PDF(pc) (232KB) ( 682 )
The large electron positron collider value of branching ratio Rb is larger than the standard model predicted value RSMb, this deviation δRb is treated as an allowed range for the correction to the single top quark production cross section σ(tb) arising from the extended technicolor dynamics. It is found that the relative correction δσ(tb)/ σ0(tb) is quite large for a certain range of the free parameters in the model, and may be detected in the future proton-antiproton collision experiments.
Contribution of Reggeon in Charge Exchange Processes of Deep Inelastic Scattering
ZHOU Yu-feng, PENG Hong-an, LIU Lian-shou
Chin. Phys. Lett. 1998, 15 (9): 634-635 .  
Abstract   PDF(pc) (171KB) ( 341 )
The experimental results on maximum pseudo-rapidity ηmax distribution in the charge exchange processes e +P →e + N + X ( X means anything) are discussed. The contributions of reggeon from Regge phenomenology and of π+-exchange from pion cloud model are calculated. The results show that neither the Rρ-exchange nor the pion cloud model alone can explain the experimental data well, but after considering these two processes together, by using Monte Carlo simulation, a good agreement between the theoretical results and experimental data is found.
Contribution of Fock Term to Properties of Exotic Nuclei
CHEN Bao-qiu, MA Zhong-yu, S. Krewald, F. Grümmer
Chin. Phys. Lett. 1998, 15 (9): 636-638 .  
Abstract   PDF(pc) (230KB) ( 395 )
Density dependent relativistic HartreeFock theory has been extended to describe properties of exotic nuclei. The contribution of Fock exchange terms is emphasized in this letter. It turns out that the influence of Fock terms on properties of neutron rich nuclei is very different from those for nuclei near stability line.
Medium Effects on Dynamical Properties of the Fermion and Mesons in the Gauged Nambu- Jona-Lasinio Model
JIANG Wei-zhou, QIU Xi-jun,
Chin. Phys. Lett. 1998, 15 (9): 639-641 .  
Abstract   PDF(pc) (257KB) ( 344 )
The gap equation for the fermion in the gauged Nambu-Jona-Lasinio (NJL) model is derived in nuclear medium with flavors Nf = 2. Based on the gap equation, the fermion mass in nuclear medium is obtained and used to determine the properties of the scalar and pseudoscalar mesons. In contrast to the NJL model, the gluonic part has the one-fourth contribution to the fermion mass. The critical density with the chiral symmetry restored is about 6ρ0.
Study of Giant Dipole Resonance of Super Heavy Compound System
CAI Yan-huang, WANG Jian-song, SHEN Wen-qing, MA Yu-gang, , FENG Jun, YE Wei, CAI Xiang-zhou, FANG De-qing
Chin. Phys. Lett. 1998, 15 (9): 642-644 .  
Abstract   PDF(pc) (252KB) ( 417 )
A microscopic semi-classical approach, i.e., the linearized Vlasov equation with a collision term treated by the relaxation time approximation, is simply described and is used to investigate the giant dipole resonance (GDR) from hot super heavy compound system. The possibility of such GDR γ rays emission is described also according to the fission delay. For Au+Au system (A =392) and Xe+U system (A = 374), the temperature dependence of strength distribution of GDR γ rays and the deformation effect on GDR γ rays are discussed in framework of this approach.
Suppression of Nuclear Drell-Yan Ratio due to Energy Loss
LI Guang-lie, YANG Jian-jun,
Chin. Phys. Lett. 1998, 15 (9): 645-647 .  
Abstract   PDF(pc) (204KB) ( 333 )
Nuclear effect in nuclear Drell-Yan (DY) process is not clear as that in the European muon collaboration (EMC) effect, and many EMC effect models overestimate it. In this letter, the energy loss effect in nuclear DY process is studied, and it is found that the nuclear DY ratio is suppressed due to the energy loss which balances the overestimate of the DY ratio in the EMC effect models.
Valence Shell Ionization Spectra of Propane by (e, 2e) Spectroscopy
PANG Wen-ning, ZHANG Wen-xin, GAO Nai-fei, SHANG Ren-cheng, DENG Jing-kang, CHEN Xue-jun
Chin. Phys. Lett. 1998, 15 (9): 648-650 .  
Abstract   PDF(pc) (253KB) ( 445 )
The measurements of the valence shell ionisation energy spectra (6-32eV) for propane (C3H8) by high resolution (ΔE = 0.9eV and Δp = 0.1 a.u.) (e, 2e) spectrometer at impact energy of 1200eV plus binding energy and symmetric noncoplanar kinematics are reported. The spectrum is consistent with a single particle picture of ionization from each of the seven outer-valence orbitals and the three inner-valence orbitals. The ionization energies are in agreement with published photoelectron spectroscopy data.
Statistical Properties of Lasers with Sub-Poissonian Pump
YANG Ming, CAO Li, WU Da-jin, LI Zai-guang
Chin. Phys. Lett. 1998, 15 (9): 651-653 .  
Abstract   PDF(pc) (188KB) ( 602 )
The effect of the pump-noise on the statistical properties of the output photon-number is discussed. The master equation for the radiation field valid for any pump fluctuation with steady atomic injection is presented. Far above threshold, the characteristic function for the photon-number distribution is derived without truncating the master equation, the mean value and fluctuation of the output photon-number are also calculated. Thereby the condition of generating sub-Poissonian light is derived and the effect of the pump-noise on the higher-order moment of the output photon-number distribution is analyzed.
An Alternative Form of Inverse Scattering Transform for the Korteweg-de Vries Equation
WU Ke-xue, CHEN Shi-rong
Chin. Phys. Lett. 1998, 15 (9): 654-656 .  
Abstract   PDF(pc) (185KB) ( 512 )
In the viewpoint of physics, for the Korteweg-de Vries (KdV) equation, we care the evolution effects of soliton with respect to space in perturbation theory, so the new boundary condition u → 0 as t → ∞ is under our consideration. We derive Zakharov-Shabat Equation of inverse scattering for the KdV equation under new condition starting from the second Lax equation. Finally the space dependences of scattering data are determined corresponding to time dependences of scattering data in traditional case, which are bases for developing perturbation theory under new condition.

Photosensitivity and Hydroxyl in Hydrogenated Silica Fibers
TAN Gu, LIN Xiang-zhi, LIU Hong-du, FU Li-bin(RS)E. Y . B. Pun, P. S. Chung
Chin. Phys. Lett. 1998, 15 (9): 657-658 .  
Abstract   PDF(pc) (166KB) ( 484 )
Optical loss spectra and refractive index changes have been measured in the hydrogenated standard telecommu-nication fiber and photosensitive fiber. The index changes due to ultraviolet exposure were found to be closely related with the OH formation in both types of fibers. A direct photolyticd model is proposed to explain the effect of hydrogen loading on the enhancement of the photosensitivity in silica fibers.
Characterization of Pattern Formation from Modulation Instability in the Cubic Schrodinger Equation
LONG Tao, HE Xian-tu,
Chin. Phys. Lett. 1998, 15 (9): 659-661 .  
Abstract   PDF(pc) (193KB) ( 360 )
The study of pattern dynamics in a Hamiltonian system(HS) having an infinite number of degree of freedom is very difficult due to the absence of attractors in such system. In this letter, we propose a useful method that only a few representative manifolds in phase space are investigated, and it can be used to reveal the pattern formation of HS. The conserved cubic Schrödinger equation is discussed. Although a special model is chosen, this method can be applied to more general case such as the near-integrable HS.
F+ Ion Implantation for Enhancing Surface Hydrophobicity of Medical Polymethylmethacrylate
LIU Bao-jun, LI De-jun, GU Han-qing
Chin. Phys. Lett. 1998, 15 (9): 662-664 .  
Abstract   PDF(pc) (235KB) ( 310 )
The surface of medical polymethylmethacrylate intraocular lens was treated by F+ ion implantation at 80 keV with various doses. Hydrophobicity test showed that contact angle was increased from 68.5º to 83.5º with increasing dose. No appreciable changes in optical transparency and tensile strength were observed. X-ray photoelectron spectroscopy and electron spin resonance analysis indicated that F+ ion implantation broke some original O-containing groups to form some new C-F bond and radicals on the surface.
Inner Modulation in Quasicrystals and Approximants
XU Lu, MAI Zhen-hong
Chin. Phys. Lett. 1998, 15 (9): 665-667 .  
Abstract   PDF(pc) (231KB) ( 452 )
Through a detailed analysis, it is found out that a quasilattice can be considered as one consisting of several mutually incommensurate interpenetrating sublattices, each sublattice being a modulated crystalline lattice. The modulation periods in one sublattice are given by the basic periodicities of the other sublattices. Also analyzed is the approximant quasilattice whose sublattices being mutually commensurate. In the density wave picture, the combination of crystal structures into one quasicrystal (or approximant) phase can be done in a natural procedure.
Enhancement of Atomic Rearrangement in Top Surface Layers by Low Energy Ions
MA Zhong-quan, LIU Bai-xin
Chin. Phys. Lett. 1998, 15 (9): 668-670 .  
Abstract   PDF(pc) (237KB) ( 323 )
Assuming rectilinear trajectories for the projectile into a solid surface, a specific expression for the “energy window” of the driving atoms in a monolayer has been derived for different ion-target systems, in which the atomic displacements occur primarily in the surface layer, while the subsurface layer is kept intact. The results obtained here are in good agreement with Brice et al.’s numerical estimations and close to experimental data for ion beam assisted depositions.
Zero-Point Motions in Trans-Polyacetylene
FU Rong-tang, RAO Xue-song, SUN Xin, Y .Kawazoe
Chin. Phys. Lett. 1998, 15 (9): 671-673 .  
Abstract   PDF(pc) (257KB) ( 416 )
In order to substantiate the applicability of the Takayama-Lin-Liu-Maki model to conducting polymer, the Su-Schrieffer-Heeger model is generalized to include the effects of lattice zero-point motions on electronic properties. Beyond the treatment of the white-noise approximation, some significant electronic properties of Peierls-Fröhlich states are documented. The finding shows that the correlation of lattice motions suppresses the effects of zero-point motions on the electronic properties more seriously.
Ge Related-Defect Energy and Microcavity Effect in GaN Epitaxial Layer
ZHAO Yi-guang, CHENG Lei, HUANG Xian-ling, ZHANG Guo-yi, LI Jing, YANG Zhi-jian
Chin. Phys. Lett. 1998, 15 (9): 674-676 .  
Abstract   PDF(pc) (204KB) ( 425 )
Using solid-phase regrowth technique, Pd/Ge contact has been made on the GaN layer, and very good ohmic behavior was observed for the contact. The Photoluminescence (PL) spectra for different structures formed by the Pd/Ge contact, GaN layer, sapphire substrate, and mirror were studied, and a defect-assisted transition was found at 450nm related to Ge impurity. The results show that the microcavity effect strongly influences the PL spectra of the band-gap and defect-assisted transitions.
Nonlinear Flux Diffusion and ac Susceptibility in High-Tc Superconductors
BAI Wei-ping, CHEN Han-dong, YIN Dao-le, LI Gang, LI Chuan-yi, CHEN Kai-xuan, LU Guo
Chin. Phys. Lett. 1998, 15 (9): 677-679 .  
Abstract   PDF(pc) (227KB) ( 395 )
It is shown that the flux motion in high-Tc superconductors can be well consistently analysed by a unified materials equation. The different models of U ( J ) so far suggested can be shown as specific forms or limits of this unified materials equation. The scaling law of flux pinning derived from this equation agrees with recent experimental observations on high-Jc NdBa2Gu3O7-δ single crystal. The amplitude dependence of ac susceptibility derived from this equation is compared with several experimental results of high-Tc superconductors and a general power law is found.
Pressure-Induced Charge Transfer and Pressure Dependence of the Superconducting Transition Temperature in HgBa2CuO4+δ
CHEN Xiao-jia, GONG Chang-de
Chin. Phys. Lett. 1998, 15 (9): 680-682 .  
Abstract   PDF(pc) (236KB) ( 429 )
The pressureinduced changes of hole concentration and pressure effects on Tc in HgBa2CuO4+δ(δ = 0.07 - 0.39) have been investigated on the basis of the pressureinduced charge transfer model. Detailed calculations show that large enhancements in Tc under high pressure can be obtained for materials which are underdoped, and not for compounds which have nearly optimal hole concentration. On the other hand, Tc enhancements in compounds which are heavily overdoped are found to be quite modest. The theoretical prediction is in agreement with experiments. The possible intrinsic factors which are responsible for the pressure dependence of the maximum Tc are discussed within the van Hove singularity scenario.

Periodic Instanton Calculations of Quantum-Classical Transitions in Spin Systems
ZHANG Yun-bo, NIE Yi-hang, KOU Su-peng, WANG Xiao-bing, LIANG Jiu-qing, PU Fu-ke,
Chin. Phys. Lett. 1998, 15 (9): 683-685 .  
Abstract   PDF(pc) (231KB) ( 355 )
The quantum-classical transitions of the escape rates in the molecular magnet Mnl2Ac and a biaxial anisotropic ferromagnetic spin model are investigated by applying the periodic instanton method. The effective free energies are expanded around the top of the potential barrier in analogy to the Landau theory of phase transitions. We show that the first-order transitions occur below the critical external magnetic field hx = 1/4 for Mnl2Ac and beyond the critical anisotropy constant ratio λ = 1/2 for the biaxial ferromagnetic grains, which is in good agreement with earlier studies.
Valence and Electronic Shell Configuration Characters of Damage-Resistant Dopants in LiNbO3 Crystals
ZHANG Guo-quan, ZHANG Guang-yin, LIU Si-min, XU Jing-jun, SUN Qian, LIU Jian-jun
Chin. Phys. Lett. 1998, 15 (9): 686-688 .  
Abstract   PDF(pc) (276KB) ( 474 )
We analyze the valence and electronic shell configuration characters of all damage-resistant dopants found in LiNbO3 crystals up to now. We show that all damage-resistant dopants have only one valence state. We also show that the electronic shell configurations of these damage-resistant ions are filled fully, as are the cases of the inert elements. from this point of view, we conclude that the anti-site NbLi should be involved in the charge transport process, while the Li vacancy VLi is not involved in the charge transport process. It also can give us some insights about how to select a damage-resistant dopant for LiNbO3 crystal.
Chemical Vapor Deposition of β-SiC Nanowires on Granular Active Carbon Cylinders Loaded with Iron Nanoparticles Inside the Pores
MENG Guo-wen, ZHANG Li-de, QIN Yong, F. Phillipp, QIAO Sheng-ru, GUO Hai-ming, ZHANG Shu-yuan
Chin. Phys. Lett. 1998, 15 (9): 689-691 .  
Abstract   PDF(pc) (385KB) ( 469 )
A new method for chemical vapor deposition of β-SiC nanowires on granular active carbon loaded with iron nanoparticles inside the pores is developed. In this process, mesoporous active carbon was used as both a carbon source material and a template to generate nanometer-diameter catalyst particles that define the size of wires produced by vapor-liquid-solid (VLS) growth. Transmission electron microscopy reveals that the products are nanowires with several microns in length and about 10nm in diameter. Selected area electron-diffraction and energy-dispersed x-ray spectra confirm that the productor is β-SiC. The observation of spherical nanoparticles containing iron at the end of the nanowires clearly indicates that the nanowires grow by the VLS mechanism.
SiGe Epitaxy with Graded Buffer by Ultrahigh Vacuum Chemical Vapor Deposition
HUANG Jing-yun, YE Zhi-zhen, LU Huan-ming, JIANG Xiao-bo, WU Hui-zhen, ZHAO Bing-hui, WANG Lei, QUE Duan-lin
Chin. Phys. Lett. 1998, 15 (9): 692-694 .  
Abstract   PDF(pc) (276KB) ( 368 )
A SiGe/Si epilayer with a linear-step-graded buffer was grown by ultrahigh vacuum chemical vapor deposition technique at a relatively high growth temperature (780°C) and a relatively high growth rate. Almost linear Ge content variation was realized in the buffer layer due to the Ge segregation to the growing surface during epitaxial growth. Double crystal x-ray diffraction and Raman spectroscopy show that the upper layer is fully relaxed. However, the measured results show that the density of dislocation in the composition graded structure is much lower than that in single-step epilayer structures.
Catalytic Oscillatory Oxidation of CO on Pt(ll0): on-off Control to Chaos
YANG Ling-fa, HOU Zhong-huai, XIN Hou-wen
Chin. Phys. Lett. 1998, 15 (9): 695-696 .  
Abstract   PDF(pc) (187KB) ( 325 )
An improved mean-field model, which specially takes into account pair correlation, was proposed to describe catalytic oscillatory oxidation of CO on Pt(110). By applying on-off control strategies under different frequency, the chemical oscillator shows an abundance of periodic doubling processes, even chaos response, and the route to the chaos and out of the chaos were both identified as period-doubling through analysis of its Lyapunov exponent spectrum. These response results reveal that structure delay effect plays an important role to the complexity of this system.

Dependence of Secondary Ion Mass Spectrometry Relative Sensitivity Factor on Matrix
YANG De-quan, FAN Chui-zhen
Chin. Phys. Lett. 1998, 15 (9): 697-699 .  
Abstract   PDF(pc) (239KB) ( 541 )
In secondary ion mass spectrometry, we define the slope of logarithm of relative sensitivity factor versus ionization potential as matrix effect factor. It was found that the matrix effect factor is dependent on the average atomic number and average electronegative values, as well as average oxide formation heat of matrix. The "combined local thermal equilibrium model and bond-breaking'' model proposed by us early was used to explain this dependence.
Electrorheological Properties of Rare Earth Oxide and Rare Earth Hydroxide
LI Jun-ran, ZHOU Li, SONG Yang
Chin. Phys. Lett. 1998, 15 (9): 700-702 .  
Abstract   PDF(pc) (254KB) ( 430 )
The electrorheological (ER) behaviors of 31 kinds of ER suspensions, 16 kinds of rare earth oxide and 15 kinds of rare earth hydroxide [RE(OH)3] are tested systematically under electric field. The microscopy shows that only Gd2O3, Pr6O11 from rare earth oxides and RE(OH)3. nH2O (RE = La, Y, Pr, Gd, Sm, Lu) from rare earth hydroxides dispersed in silicone oil produce fibrous chains in the direction of the ac field vector. The viscosities of ER suspensions with Gd2O3, Pr6O11, RE(OH)3. nH2O (RE = La, Y, Gd, Pr) dispersed in hydrocarbon oil are determined under different field strength (dc field). The results show that the ER activity of the materials is not influenced by the coordinated water with the rare earth ion, and it is related with the microstructure of the molecule.
27 articles