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Volume 15 Issue 7
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Original Articles
Two-Parameter Correlated Negative Binomial State in Two-Mode Fock Space
FAN Hong-yi, PAN Xiao-yin, CHEN Bo-zhan
Chin. Phys. Lett. 1998, 15 (7): 469-471 .  
Abstract   PDF(pc) (177KB) ( 334 )
A kind of two-parameter correlated negative binomial state is constructed and analysed from the point of view of quantum optics theory in two-mode Fock space. By choosing a suitable two-mode correlated Holstein-Primakoff-analogue transformation, the state can be identified as a type of correlated SU (1,1) coherent state. The possible-physical uses of the state are also pointed out.
Bound States of the Perturbed Schrödinger Systems
HAI Wen-hua
Chin. Phys. Lett. 1998, 15 (7): 472-474 .  
Abstract   PDF(pc) (206KB) ( 540 )
A bound state of the Schrödinger system is disturbed by an additional potential. It is shown that the system is still in a bound state if and only if its energy correction is restricted to the corresponding value. This infers some previous series solutions in quantum mechanics to be unbound states for the order i > 1 of perturbation. The corrected bound states of the system are given and their physical meaning is discussed simply. Application of the method to Stark effect reveals its advantage for researches of quantum chaos.

Degenerate Solution Evolved from Non-degenerate Initial Data in Ashtekar’s Formalism
MA Yong-ge, LIANG Can-bin
Chin. Phys. Lett. 1998, 15 (7): 475-476 .  
Abstract   PDF(pc) (123KB) ( 313 )
The possibility of evolving a partial degenerate solution from non-degenerate initial data in Ashtekar formalism is considered in a constructed example. It is found that this possibility could be realized in the time evolution given by Ashtekar's equations on a 3-dimensional manifold with topology R1 × S2.

Adaptive Control of a Chaotic System with Delay
TIAN Yu-chu
Chin. Phys. Lett. 1998, 15 (7): 477-479 .  
Abstract   PDF(pc) (255KB) ( 382 )
A model-reference adaptive control strategy is proposed for a delay chaotic system with known or unknown parameters. Theoretical analysis and numerical simulations show that the controlled system state can track an arbitrarily given reference trajectory that may be an equilibrium point, a periodic orbit or a chaotic orbit.
Configuration and Spin Assignments of Yrast Band for Doubly Odd Nucleus 122Cs
PU Yun-wei, WEN Jia-yan, ZHU Shun-quan, ZHENG Ren-rong
Chin. Phys. Lett. 1998, 15 (7): 480-482 .  
Abstract   PDF(pc) (243KB) ( 478 )
Energy spectrum of yrast band for 122Cs is studied by using particle-rotor model (PRM) of odd-odd nuclei, in which special attention is paid to the model basis accounting for the effect of the instability γ vibration perturbation around axial symmetry. In order to check the assignments of this band, two calculation schemes are put into practice. The first one is for previous πh11/2 vg7/2 configuration with bandhead spin I0 = (6-) which was obtained from cranked shell model (CSM) calculation, and the other one is for πh11/2 vh11/2 configuration with I0 = (9+) supported by the systematic analyses of experimental data. A qualitative comparison between the present PRM calculation and that of CSM has also been made. The results indicate that, rather than πh11/2 vg7/2 I0 = (6-), πh11/2 vh11/2 with I0 = (9+) is a more reasonable assignment to the yrast band in 122Cs.

Influence of Relativistic Finite Volume Effect of Nucleons on the Dense Matter Properties
ZHANG Xiao-bing, ZHANG Qi-ren
Chin. Phys. Lett. 1998, 15 (7): 483-485 .  
Abstract   PDF(pc) (225KB) ( 407 )
The influence of the relativistic finite volume effect of nucleons on the properties of dense nuclear matter is examined at finite temperature and it is found that the abnormal nuclear state can appear at sufficiently high density. Then, by using this methed the phase transition between hadronic matter and quark-gluon plasma is studied. The numerical results show that the value of nucleon radius is important for reproducing this phase transition correctly.
In-Plane Angular Correlation of α Particle-Fragments in a 84Kr+27AI Reaction at 8.5 MeV/n
LIU Xin, JIANG Dong-xing, S . M. Lee
Chin. Phys. Lett. 1998, 15 (7): 486-488 .  
Abstract   PDF(pc) (234KB) ( 417 )
In-plane angular correlations between light charged particles and fragments with different charge number were measured in a 84Kr+27AI reaction at 8.5 MeV/n. An asymmetry in the angular correlation relative to the beam direction was found which cannot be explained in the fusion-fission reaction mechanism framework. This may imply the domination of deeply inelastic collisions over the complete fusion in the reaction.
Radial Electronic Density for the Ground State of the Lithium Isoelectronic Sequence
GUAN Xiao-xu, WANG Zhi-wen,
Chin. Phys. Lett. 1998, 15 (7): 489-491 .  
Abstract   PDF(pc) (248KB) ( 463 )
By using the full core plus correlation method recently developed, the accurately analytical charge densities for the lithium-like systems (Z=3-8) are obtained. The convergence pattern of the charge densities is analyzed. The electron-nuclear cusp condition is calculated for these systems. Also, at the region far from the nucleus, the behavior of the electron density is examined. The present calculations show that the wave functions used in this work can give the satisfactory and self-consistent results in full configuration space.
An Analysis of the Symmetry in ABA Coulomb Systems
SHI Ting-yun, BAO Cheng-guang
Chin. Phys. Lett. 1998, 15 (7): 492-494 .  
Abstract   PDF(pc) (221KB) ( 388 )
The nodal structures of quantum states of three-body ABA systems composed of two identical fermions and another one with an opposite charge are investigated. We expand the wavefunction in the body frame and show that the effect of symmetry such as rotation, space inversion, and permutation is to impose nodal surfaces on the components of the wavefunction. Based on the nodal surface, a classification of quantum states of ABA systems is presented. It is found that the quantum symmetry plays a crucial role in determing the energy levels and structures of the low-lying states.

Fabricating Master with Reactive Ion Beam Etching Method
ZOU Zhi-qiang, FANG Hong-li, FU Xin-ding, CHEN Guo-ming
Chin. Phys. Lett. 1998, 15 (7): 495-497 .  
Abstract   PDF(pc) (297KB) ( 504 )
The fabrication process of glass master or glass etching optical disk using reactive ion beam (RIB) etching method was studied. Photoresist was applied for image reversal. RIB etching using CF4 gas transferred the pregrooves into the glass substrate. The shape and depth of the pregrooves in the glass is a function of the RIB etcher settings. A glass substrate of Ф130mm with etched pregrooves (track pitch was 1.6 μm and groove depth 0.1 μm ) was obtained, showing that a glass master or glass etching disc can be fabricated by this technique.
Correlation Function and Time-Dependent Moments of the Intensity for Gain-Noise Model of a Single-Mode Laser with Exponential Function Correlation Noise
WANG Zhong-long, CAO L, QIU Jun-lin
Chin. Phys. Lett. 1998, 15 (7): 498-500 .  
Abstract   PDF(pc) (200KB) ( 468 )
The gain-noise model of a single-mode laser driven by correlated additive and multiplicative white noises is investigated theoretically. The analytical expressions of the time-dependent moments and correlation function of the laser intensity are derived by means of linear approximation method. Some novel phenomena are found. In certain cases, instead of monotonic evolution, the evolution curves of the intensity correlation function versus time exhibit the negative minimum value, whereas a peak for the evolution of the normalized variance of the laser intensity with time emerges.
Properties of Nonlinear Transverse-Electric Waves in a Two-Core Optical Waveguide with a Nonlinear Cladding
MA Chun-sheng
Chin. Phys. Lett. 1998, 15 (7): 501-503 .  
Abstract   PDF(pc) (215KB) ( 398 )
Expressions of dispersion relation and propagation power are presented for the nonlinear transverse-electric (TE) waves in a two-core optical waveguide with a nonlinear cladding. The properties of the nonlinear TE waves are analyzed. It is found that when the total core thickness and the distance between the two cores are sufficiently large, the power curves of the higher odd modes become very sharp in some narrow ranges of the effective refractive index, compared with those of the higher even modes.
Dark Optical Solitons on Influence of the Self-steepening Term
CHEN Xiang-jun, CHEN Zhi-de,
Chin. Phys. Lett. 1998, 15 (7): 504-506 .  
Abstract   PDF(pc) (201KB) ( 409 )
Essential difficulties caused by the nonvanishing boundary condition greatly hinder the development of the systematic perturbation theory for dark solitons. Recently a direct perturbation method for dark one-soliton is developed by the authors with rigorous proof of the completeness of squared Jost solutions. In this letter, influence of the self-steepening term is discussed analytically with the method.
Fractal Nature of Viscous Fingering in Random Sierpinski Carpet
TIAN Ju-ping, YAO Kai-lun,
Chin. Phys. Lett. 1998, 15 (7): 507-509 .  
Abstract   PDF(pc) (290KB) ( 384 )
The viscous fingering(VF) in a random Sierpinski carpet with bond radii of the truncated Rayleigh distribution has been investigated by means of successive over-relaxation techniques. A universal formulation of fractal dimension for VF in fractal space has been introduced. The topology and geometry of the porous media are found to have strong effects on displacement process. The fractal dimension D can be reasonably regarded as a useful parameter to evaluate the sweep efficiency and oil recovery.
On the Role of Neutral Particles on Edge Turbulence in the CT-6B Tokamak
WANG Gui-ding, YANG Xuan-zong, FENG Chun-hua, JIANG Di-ming, QI Xia-zhi
Chin. Phys. Lett. 1998, 15 (7): 510-512 .  
Abstract   PDF(pc) (239KB) ( 466 )
A positive limiter biasing on the CT-6B tokamak resulted in a slight increase of edge density and an obvious drop of electron temperature, which is in the temperature range where the rate coefficients for ionization processes are strongly temperature dependent. Concomitantly, edge fluctuations are enhanced, suggesting that the presence of neutral particles may play an important role in modifying edge turbulence.
Plasma Relaxation in a Reversed Field Pinch Experiment
LI Qiang, LUO Cui-wen, ZHANG Peng, LI Jie-ping, YI Ping, ZHAO Chang-lin, XUE Jun
Chin. Phys. Lett. 1998, 15 (7): 513-515 .  
Abstract   PDF(pc) (229KB) ( 355 )
The time evolutions for the magnetic energy Um, the magnetic helicity K, and the total helicity Ktotal with high pinch factor operation of reversed field pinch experiments on S WIP-RFP device are quantitatively calculated. It is shown that Um and K increase with increasing plasma current but Ktotal decreases. The results are analyzed and valuable information for the operation is obtained.
Nanocavities: an Effective Gettering Method for Silicon-on-Insulator Wafers
ZHANG Miao, ZENG Jian-min, HUANG Ji-po, LIN Zi-xin, ZHOU Zu-yao, LIN Cheng-lu
Chin. Phys. Lett. 1998, 15 (7): 516-518 .  
Abstract   PDF(pc) (295KB) ( 339 )
The 4×1016 /cm2 H+ and 9×1016/cm2 He+ have been implanted into the silicon substrate of separation-by-implantation-of oxygen (SIMOX) wafers, respectively, followed by a 700°C annealing to form nanocavities beneath the buried oxide (BOX) layer. The SIMOX wafers were intentionally contaminated with Cu impurities by implanting different doses of Cu in the top Si layer. Secondary ion mass spectroscopy and cross-sectional transmission electron microscopy technologies have been employed to investigate the gettering effect of nanocavities to the Cu impurities. The cavities induced either by H+ or He+ implantation are effective gettering centers for Cu in SIMOX wafers. After annealing at 1000°C for 90 min, up to 4 ×1015 /cm2 Cu has diffused through the BOX layer and been captured by the cavities. The gettering efficiency of cavities increases with the decrease of Cu implantation doses. The nanocavities provide an attractive method for gettering transition metal impurities in SIMOX materials.
Asymmetry in the Vertically Aligned Growth Induced InAs Islands in GaAs
GONG Qian, WU Ju, XU Bo, LIANG Ji-ben, FAN Ti-wen, WANG Zhan-guo, BAI Yuan-qiang
Chin. Phys. Lett. 1998, 15 (7): 519-521 .  
Abstract   PDF(pc) (384KB) ( 461 )
A 10-InAs-island-layer vertically coupled quantum dot structure on (001) GaAs was grown and investigated by molecular beam epitaxy and transmission electron microscopy. The result shows that the vertically aligned InAs islands are asymmetrical along the two < 110 > directions on the (001) growth plane. Such an asymmetry in the vertically coupled quantum dot structure can be explained with the chemical polarity in the III-V compound semiconductors.
Stability of Mo/Si Multilayer Structure Used in Bragg-Fresnel Optics
LE Zi-chun, CAO Jian-lin, LIANG Jing-qiu, PEI Shu, YAO Jin-song, CUI Cheng-jia, LI Xing-lin
Chin. Phys. Lett. 1998, 15 (7): 522-524 .  
Abstract   PDF(pc) (254KB) ( 576 )
The thermal and chemical stabilities of Mo/Si multilayer structure used in Bragg-Fresnel optics were studied to get optimal technological parameters of pattern generation. Mo/Si multilayers were annealed at temperature ranging from 360 to 770 K, treated with acetone and 5‰ NaOH solution, and characterized by small-angle x-ray diffraction technique as well as x-ray photoelectron spectroscopy and Olympus microscopy.

Investigation of Hole Distribution in Y1-xPrxBa2Cu3O7
YU Ya-bin, CAO Guang-han, JIAO Zheng-kuan
Chin. Phys. Lett. 1998, 15 (7): 525-527 .  
Abstract   PDF(pc) (272KB) ( 310 )
The electronic structure of Y1-xPrxBa2Cu3O7 is described by a tight-binding Hamiltonian in which the Pr-O hybridization and the 2pσ - 2pπ Coulomb repulsion are taken into account. The dependence of planar hole-density, localized hole-density and chemical potential of holes on Pr concentration is calculated by a coherent potential approximation. The result shows that the insensitivity of hole-density on the CuO3 chains with the Pr-doping is due to the 2pσ - 2pπ repulsion. Some other experimental facts can also be well interpreted.
Valences of Cu in Y1-xCaxBa2Cu3O6+y
WU Zhi-jian, MENG Qing-bo, ZHANG Si-yuan
Chin. Phys. Lett. 1998, 15 (7): 528-529 .  
Abstract   PDF(pc) (185KB) ( 303 )
The valences of Cu in Y1-xCaxBa2Cu3O6+y have been investigated by using complex chemical bond theory. The results for the valences of Cu(1) and Cu(2) in the calculation suggest that the holes introduced by calcium substitution only reside in CuO2 planes, and there is a competition mechanism for the hole density in CuO2 planes between Ca doping and oxygen depletion. These conclusions are satisfactorily in agreement with experiments.
Growth Mode of Superconducting La2-xSrxCul+yO4 Thin Films on LaAIO3 Substrate
QIN Yue-ling, LIU Wei, DONG Xiao-li, LI Lin, ZHAO Bai-ru,
Chin. Phys. Lett. 1998, 15 (7): 530-532 .  
Abstract   PDF(pc) (440KB) ( 373 )
La2-xSrxCul+yO4(LSCO) thin films sputtered from a Cu-rich target on a LaAIO3 substrate showed a columnar structure. The columnar grains penetrated the full thickness of the film, nucleating at the substrate surface defects. Transmission electron microscopy revealed two kinds of lattice images: one with a lattice spacing of 0.66 nm and the other with a spacing of 0.61 nm. The 0.66 nm spacing denotes a c-axis oriented LSCO film matrix. The 0.61 nm spacing has two categories: one with short white dashes, the phase of which is not yet identified, the other with no additional structure, which could correspond to the c-axis deviated LSCO.

Optical and Electric and Structural Properties of Til-xAIxN Thin Films
LI Zuo-yi, XIONG Rui, YANG Xiao-fei, HU Zuo-qi, XU Ying, LIN Geng-qi, LU Zhi-hong
Chin. Phys. Lett. 1998, 15 (7): 533-534 .  
Abstract   PDF(pc) (155KB) ( 326 )
A sequence of Til-xAIxN films has been prepared by rf reactive magnetron sputtering. The optical and electric properties versus aluminum content x have been studied. Values suitable for magneto-optic protective layers have been achieved in Til-xAIx N thin films with aluminum content x > 0.75. X-ray diffraction results show that Til-xAIx N thin films in this study are a bcc structure up to x = 0.75, further increase in the aluminum content gives a wurtzite structure. All of the results show that the optical and electric properties of Til-xAIx N films might be related to the crystal structure.

Optical Absorption Red Shift of Capped ZnFe2O4 Nanoparticle
YUAN Zhi-hao, YOU Wei, JIA Jun-hui, ZHANG Li-de
Chin. Phys. Lett. 1998, 15 (7): 535-536 .  
Abstract   PDF(pc) (208KB) ( 655 )
Nanometer-sized ZnFe2O4 particles capped with a layer of surfactant are synthesized and their optical absorption is investigated. Such capped ZnFe2O4 particles present a strong band edge absorption in visible region and their energy band gap is estimated to be about 1.53eV. It is also found that the capped nanoparticles have a significant red shift of optical absorption band edge in contrast with that of uncapped ZnFe2O4 nanoparticles, which is mainly related to the trapped and self-trapped excitons absorption resulting from an interfacial dipole layer formed on the surface of ZnFe2O4 nanoparticles.

Enhanced Hole Injection and Brightness of Organic Electroluminescent Devices with Indium Tin Oxide Surface Modification Using Oxygen Plasma Treatment
XIE Zhi-yuan, HUANG Jing-song, CHEN Bai-jun, HOU Jing-ying, NAN Jin, DAI Guo-rui, LIU Shi-yong
Chin. Phys. Lett. 1998, 15 (7): 537-538 .  
Abstract   PDF(pc) (169KB) ( 399 )
The improvement of indium tin oxide (ITO) anode contact to organic electroluminescent devices via oxygen plama-treatment is investigated. Enhanced hole-injection efficiency improved the performance of organic light-emitting devices. The injection current increased by 1-2 orders of magnitude and the turn-on voltages droped several volts. Much higher injection current could be applied to achieve much higher brightness. Maximum brightness and luminous efficiency can reach to about 4000 cd/m2 and 0.31m/W for the structure of ITO/TPD/Alq3/Al, respectively.
A Study of Field Electron Emission from Thin Amorphous-Carbon-Nitride Films
CHEN Jun, XU Ning-sheng, WANG En-ge, DENG Shao-zhi, CHEN Di-hu, WEI Ai-xiang
Chin. Phys. Lett. 1998, 15 (7): 539-541 .  
Abstract   PDF(pc) (213KB) ( 405 )
Significant field emission has been observed from thin (< 1000 Å) amorphous-carbon-nitride (a-CN) films. X-ray photoelectron spectroscopy, infrared spectrometry, and UV-visible optical absorption spectrometry have been used to characterize the films. The field emission properties of the thin film have been studied by using a transparent anode imaging system. It is proposed that this class of films should be studied as candidates of coating material for cold cathode emitter, in order for one to benefit from their very high thermal conductivity and super hardness.
Generalized Thermal Instability Criterion of Black Hole Accretion Disks
WU Xue-bing
Chin. Phys. Lett. 1998, 15 (7): 542-544 .  
Abstract   PDF(pc) (280KB) ( 393 )
The conventional thermal instability criterion cannot be applied to the advection-dominated accretion disks around black holes where the radiative cooling is insufficient to balance the viscous heating. The surface density change associated with the temperature perturbations, which was usually neglected in deriving the conventional criterion, was recently shown to be much significant in the advection-dominated disks. Considering both advection and surface density change, a generalized thermal instability criterion is suggested. By applying it to the optically thin and optically thick advection-dominated disks, it is found that the former one is thermally stable and the latter one is thermally unstable against short wavelength perturbations, which agrees well to those found recently by both analytic and quantitative stability analyses.
Superluminal Radio Source PKS 0420-014
HONG Xiao-yu, JIANG Dong-rong, SHEN Zhi-qiang, WAN Tong-shan
Chin. Phys. Lett. 1998, 15 (7): 545-546 .  
Abstract   PDF(pc) (177KB) ( 388 )
The very long baseline interferometry result of a superluminal radio source PKS 0420-014 at 5 GHz with Shanghai (China), Urumqi (China), Noto (Italy), and HartRAO (South Africa) telescopes is presented. Proper motions of the relativistic jet components in the source are calculated. Based on the Self-Compton emission in a uniform spherical model, the beaming parameters of the source are estimated. The results show that PKS 0420-014 has a high Doppler factor of 9.3, a Lorentz factor of 6.5, and a small angle of 5.5º to the line of sight.
28 articles