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Volume 16 Issue 3
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Original Articles
Evolution of the Topological Linear Defects
DUAN Yi-shi, JIANG Ying, YANG Guo-hong
Chin. Phys. Lett. 1999, 16 (3): 157-159 .  
Abstract   PDF(pc) (196KB) ( 388 )
In the light of ø-mapping method and topological current theory, the topological structure and the topological quantization of topological linear defects are obtained under the condition that Jacobian J (ø / v ) ≠ 0. When J ( ø / v ) = 0, it is shown that there exists the crucial case of branch process. Based on the implicit function theorem and the Taylor expansion, the generation, annihilation and bifurcation of the linear defects are detailed in the neighborhoods of the limit points and bifurcation points of ø-mapping, respectively.
Preparation of Entangled Atomic States via Atoms Interacting with the Cavity-Field in SU(1,1) Coherent State
SONG Ke-hui, GUO Guang-can
Chin. Phys. Lett. 1999, 16 (3): 160-161 .  
Abstract   PDF(pc) (152KB) ( 338 )
A new scheme is presented for generating atomic entangled states based on atoms-cavity-field interaction. After suitably prepared Ξ-type atoms interact with the cavity-field in the SU(1,1) coherent state initially, a subsequent measurement on this field projects the atoms onto the entangled states.

A New Solution of Einstein-Maxwell Equations
WANG Yong-jiu, LU Mao-wang
Chin. Phys. Lett. 1999, 16 (3): 162-163 .  
Abstract   PDF(pc) (129KB) ( 391 )
A new generation theorem of Einstein-Maxwell field is attained. According to it, a new solution of Einstein-Maxwell equations can be generated from a static vacuum solution. Starting with Schwarzschild solution, a new solution of the Einstein- Maxwell equation is obtained by means of this theorem.
Non-Abelian Black Holes in Higher Derivative Gravity
DENG Chang-xue, HUANG Chao-guang,
Chin. Phys. Lett. 1999, 16 (3): 164-166 .  
Abstract   PDF(pc) (204KB) ( 366 )
The static spherically symmetric black hole solutions in R+αR2 gravity coupled to a massive Yang-Mills field, namely, a Proca field are studied. Through the numerical integrations, it is shown that for positive α, there exist two distinct classes of solutions which have the horizon. One class approaches the Schwarzschild solution and the other may be interpreted as black holes with the new hair due to the αR2 term.
A Crisis with a Special Scaling Behavior
DING Xiao-ling, WU Shun-guang, YIN Yue-cai, HE Da-ren,
Chin. Phys. Lett. 1999, 16 (3): 167-168 .  
Abstract   PDF(pc) (173KB) ( 275 )
A kind of crisis with special scaling properties has been observed in a discontinuous map. The crisis happens via a collision between a discontinuity of the mapping function and an unstable periodic orbit locating on the basin boundary of the chaotic attractor. The scaling property of the crisis is <τ>∝ ∈-1.8, where <τ> and ∈ stand for the average characteristic time and the control parameter value crossing the critical point, respectively.

Octupole Deformation Bands of πh ll/2 in Neutron-Rich 145,147La Nuclei
ZHU Sheng-jiang, WANG Mu-ge, J. H. Hamilton, A. V. Ramayya, B. R. S. Babu, W. C. Ma, LONG Gui-lu, ZHU Ling-yan, LI Ming, A. Sakhaee, GAN Cui-yun
Chin. Phys. Lett. 1999, 16 (3): 169-171 .  
Abstract   PDF(pc) (210KB) ( 497 )
Octupole deformation bands built on πh ll/2 orbital in neutron-rich odd-Z 145,147La nuclei have been investigated by measuring the prompt γ-rays emitted from the 252Cf source. The alternating parity band structures and strong E1 transitions observed between negative- and positive-parity bands in both nuclei indicate the octupole deformation enhanced by the h ll/2 single proton coupling. According to observed energy displacements the octupole deformation becomes stable at the intermediate spin states.

A Criterion of Superdeformed Triaxial Shape
XING Zheng, , WANG Zi-Xing, CHEN Xing-qu, XU Jin-zhang
Chin. Phys. Lett. 1999, 16 (3): 172-174 .  
Abstract   PDF(pc) (219KB) ( 329 )
Using axially-symmetric and triaxial superdeformed models π[600 1/2] band in 165Lu is investigated. The observed γ-transition energies can be reproduced quite well in both models. However, the triaxiality factor F(I) and the ratio of dynamical quadrupole moment Q(l) to Q(2) in axially-symmetric superdeformed model are essentially different from those in triaxial superdeformed model, which may be used to determine the nuclear shape. Precise measurement of the electromagnetic transition probabilities, combined with the information from the energy levels is necessary. Experimental information which may differentiate triaxial superdeformation from axially-symmetric superdeformation is discussed.
A Note on Gluon Condensate with Translational Invariance
LI Guang-lie, YANG Jian-jun, , SHEN Hong-qing, HUANG Tao,
Chin. Phys. Lett. 1999, 16 (3): 175-177 .  
Abstract   PDF(pc) (187KB) ( 291 )
A non-local two-gluon vacuum expectation value is expanded as a power series of space-time interval x - y and possesses the translational invariance in Lorentz gauge. The coefficients of the first two terms in the power series are related to <0|B2|0> in Lorentz gauge. The value -(127MeV)2 of <0|B2|0> is estimated with the phenomenological values for the vacuum condensate <0|G2|0> and <0|ψψ|0> through the quantum chromodynamics equation of motion.

Inherent Nodal Structures in Doubly-Excited Intrashell States of Atoms
BAO Cheng-guang
Chin. Phys. Lett. 1999, 16 (3): 178-180 .  
Abstract   PDF(pc) (247KB) ( 364 )
Quantum mechanical systems are strongly constrained by symmetry. Consequently, inherent nodal surfaces are imposed on the wave functions. In this paper, the inherent nodal surfaces existing in the doubly-excited intrashell states of atoms have been investigated. The decisive effect of these surfaces on low-lying states has been demonstrated. The feature of the spectra has been explained.
Thermal Lens Determination of End-Pumped Solid-state Lasers by a Simple Direct Approach
LIU Jun-hai, LU Jian-ren, LÜ, Jun-hua, SHAO Zong-shu, JIANG Min-hua
Chin. Phys. Lett. 1999, 16 (3): 181-183 .  
Abstract   PDF(pc) (245KB) ( 509 )
The stability of linear planar resonators involved in solid-state lasers is entirely decided by the thermal lens of the laser crystal. There exists a critical point between stable state and unstable state at which the thermal focal length equals the distance from the center of the crystal to one end mirror. Based on this fact, a new method for measuring the thermal focal length of the laser crystal has been presented and applied to a Nd3+:YVO4 crystal at various absorbed pump power levels up to 10 W. The results have shown to be in good agreement with theoretical calculation.
A New Nonlinear Optical Crystal GdCa4O(BO3)3
ZHANG Shu-jun, CHENG Zhen-xiang, ZHANG Shao-jun, ZHANG Ji-guo, HAN Jian-ru, CHEN Huan-chu
Chin. Phys. Lett. 1999, 16 (3): 184-186 .  
Abstract   PDF(pc) (319KB) ( 405 )
Large size and high quality single crystals GdCa4O(BO3)3 have been grown from platinum crucible under air atmosphere by the conventional rf-heating Czochralski method. The crystal growth conditions, growth habits, and transmission spectra were investigated. The crystal is transparent in the visible and near-infrared region (320-2600nm). It has a good second harmonic generation phase-matching condition. The phase-matching experiment result is well consistent with the theoretical one. The frequency-doubling efficiency is 26.7% in the phase-matching angles θ = 45o and ø = 45.1o direction.

Thermoelastic Excitation of Transient Lamb Wave in an Orthotropic Thin Plate
CHENG Jian-chun, FU Tao, ZHANG Shu-yi
Chin. Phys. Lett. 1999, 16 (3): 187-189 .  
Abstract   PDF(pc) (239KB) ( 390 )
A numerical method to simulate thermoelastic excitation of transient Lamb wave propagating along arbitrary directions in orthotropic plates is presented by employing the expansion method of the Lamb wave modes. The displacement is expressed by a summation of the symmetric and antisymmetric modes in the surface stress-free orthotropic plate, and it is particularly suitable for waveform analyses of Lamb wave in orthotropic thin plates because one needs only to calculate the lowest few modes. The characteristics of dispersion and transient wave-forms are analyzed for a transversely isotropic plate. The results show that this method provides a quantitative analysis to Characterize anisotropic properties and elastic stiffness properties of the orthotropic plates by the laser-generated Lamb wave detection.

Wavelet Analysis of Fluctuation of Plasma Density in Hypersonic Flow
YANG Hong-bo, CAO Jin-xiang
Chin. Phys. Lett. 1999, 16 (3): 190-192 .  
Abstract   PDF(pc) (241KB) ( 451 )
By use of wavelet transform, a high frequency fluctuation is identified in the presence of low frequency disturbance through the zoned wavelet energy spectrum. The high frequency fluctuation of the plasma density may be stimulated by an ion-acoustic instability. These results can help to study the mechanism of the perturbation of plasma density in hypersonic wake.
On the Correct Form of the Saha Equation for Two-Temperature Plasmas
HAN Peng, CHEN Xi, LI He-ping
Chin. Phys. Lett. 1999, 16 (3): 193-195 .  
Abstract   PDF(pc) (245KB) ( 766 )
Two quite different Saha equations modified to a two-temperature plasma were proposed and employed in many literatures. In order to clear up this confusion phenomenon lasted for a few decades in the community of thermal plasma science and technology, this paper re-examines the thermodynamic derivation of the two-temperature Saha equations. It is pointed out that the modified Saha equation deduced by using the minimum Gibbs or Helmholtz free energy is incorrect for the two-temperature plasma. Instead, a more rigorous derivation is presented here from the basic thermodynamic principle that the entropy in an isolated system always assumes its maximum value at chemical equilibrium.
Modification of TiN Coatings by N+ and C+ Implantation with High Ion Flux
ZHANG Tong-he, WU Yu-guang, ZHAO Zhi-yong, DENG Zhi-wei
Chin. Phys. Lett. 1999, 16 (3): 196-198 .  
Abstract   PDF(pc) (313KB) ( 289 )
The TiN coating changed from columnar structure to compact texture after N+ and C+ implantation. X-ray analysis showed that combining with N atoms, Ti and Ti2N would be transformed into TiN Phases during N implantation. The ternary solid solution mixtures TiCN have been formed, while Ti, Ti2N would be transformed into TiC and TiCN phases combining with C atoms after C implantation. The hardness of the TiN coating increased by 2.3-2.4 times after N+ or C+ implantation. The wear resistance of implanted TiN coatings is 2-3 times higher than that of unimplanted TiN coatings. When the drills were treated with the method, their lifetime would increase by 7 times comparing with unimplanted ones. As an attractive procedure, the ion implantation of the TiN coatings would find new applications in many fields.

Ab Initio Electronic Structure of CrO2
TAN Ming-qiu, TAO Xiang-ming,
Chin. Phys. Lett. 1999, 16 (3): 199-201 .  
Abstract   PDF(pc) (239KB) ( 390 )
We report the spin-polarized as well as non-spin-polarized band structure calculations of CrO2 based on the local spin-density approximation of the density functional theory. Our result shows that the Fermi level of magnetic CrO2 is located in an insulating gap in the minority-spin bands between oxygen p and chromium d states with “half-metallic” behavoir. The spin moment is 2μB per Cr atom, in good agreement with experiment. The densities of states at Fermi level N(EF) are 1.85 and 6.0 states/eV per CrO2 formula unit for spin-polarized and non-spin-polarized cases, respectively. These calculated parameters have remarkable improvements Compared with previous calculations. We also conclude from our calculation that the specific-heat parameter γ is about 4.49mJ/(K2.mole) for CrO2, which is quite close to experimental data.
Exchange Splitting and Insulating Gap in La2CuO4
WU Hua, ZHENG Qing-qi,
Chin. Phys. Lett. 1999, 16 (3): 202-204 .  
Abstract   PDF(pc) (230KB) ( 360 )
A full-potential band calculation for La2CuO4is performed within the local-spin-density approximation. It is shown that the strongly orbital-dependent exchange splittings due to the anisotropic exchange potential induce an antiferromagnetic and insulating solution improved upon the previous nonmagnetic and metallic one.
A Continuous Model for Molecular Vibrations in C60
WANG Hong-mei, GAN Zi-zhao
Chin. Phys. Lett. 1999, 16 (3): 205-207 .  
Abstract   PDF(pc) (238KB) ( 325 )
A continuous model for molecular vibration in C60 is developed which presents a physical picture easy to understand. The molecular vibration modes are expanded by vector spherical harmonics. With the choice of suitable parameters, the calculated frequencies are fit the experimental values very well. In combination with the pseudopotential model for the valence electrons in C60, the interaction between the electron and intramolecular phonon in solid C60 can be analysed and calculated based on our model.
Growth and Morphology of β–FeSi2 Single Crystal with Chemical Vapor Transport
ZHAO Jian-hua, LI Yan-chun, LIU Ri-ping, ZHANG Xiang-yi, ZHOU Zhen-hua, WANG Chao-ying, XU Ying-fan, WANG Wen-kui,
Chin. Phys. Lett. 1999, 16 (3): 208-210 .  
Abstract   PDF(pc) (430KB) ( 488 )
Single crystals of β–FeSi2 have been grown from vapor by employing chemical vapor transport technique and using iodine as transport agent in a closed ampoule. In the experiment, β–FeSi2 single crystals with well-developed faces and edges have been observed on the silicon substrate, but no needlelike ones have been found. The changes in the size and the geometric shape of the growth ampoule and temperature gradient are primary factors which result in the variation on β–FeSi2 single crystal morphology.
Magnetic Properties of Nanostructured Fe40Ni38Mo4Bl8
LI Jian-gong, SU Zhi-bin, WEI Fu-lin, YANG Zheng, Horst Hahn, WANG Tian-min, GE Shi-hui
Chin. Phys. Lett. 1999, 16 (3): 211-213 .  
Abstract   PDF(pc) (225KB) ( 425 )
Nanostructured Fe40Ni38Mo4Bl8 prepared by crystallization technique has a microstructure of nanometer-sized fcc (Fe, Ni) solid solution crystallites embedded in a nanometer-thick amorphous matrix. The nanostructured Fe40Ni38MO4Bl8 obtained at 740K has the optimal soft magnetic properties. The maximal magnetic softening can be understood by considering the combination of the zero anisotropy and the lowest saturation magnetostriction.
A Relation Between Energy Barrier and Ferroelectricity in BaxSrl-xTiO3
WANG Feng-xiang, ZHANG Lei, PENG Yi-ping, WNAG Chun-lei, WANG Qun
Chin. Phys. Lett. 1999, 16 (3): 214-216 .  
Abstract   PDF(pc) (268KB) ( 432 )
In the BaxSrl-xTiO3 system, the decrease of the grain size causes the suppression of the ferroelectricity and the increase of the relaxation frequency. Barrier heights increase with the increasing grain size. The result is analogous to magnetic phase transitions in nanocrystals and the solid-solid phase transitions in nanocrystals.

Electron Aceleration Process in ZnS-Type Thin Film Electroluminescence Devices
ZHAO Hui, WANG Yong-sheng, XU Zheng, XU Xu-rong
Chin. Phys. Lett. 1999, 16 (3): 217-219 .  
Abstract   PDF(pc) (262KB) ( 383 )
Based on the calculations about scattering rates, the electron acceleration process of ZnS-type thin film electroluminescent devices is studied in detail through Monte Carlo method. The acceleration time and drift length before the balance of acceleration and Scattering are about 200 fs and 30-40nm, respectively. The steady average kinetic energy of electrons increases with electric field. Field emission process of electrons trapped at interface states only affects the acceleration process of electron transport and makes no influence on steady state. New explanations about the “dead layer” phenomenon and the overshoot in the averge drift velocity are proposed based on the calculations.
Ternary Eutectic Growth in Microgravity Environment
WANG Nan, CAO Chong-de, WEI Bing-bo
Chin. Phys. Lett. 1999, 16 (3): 220-222 .  
Abstract   PDF(pc) (408KB) ( 851 )
Rapid growth of Ag38.5Cu33.4Ge28.l ternary eutectic alloy was accomplished in a 3m drop tube and its phase selection and growth mechanism were investigated. The experimental results revealed that the semiconductor phase (Ge) was the primary nucleating phase during solidification, which agrees with the calculated results of nucleation rate. The solid solution phase (Ag) and intermetallic compound phase η(Cu5Ge2) grew cooperatively and lamellar structures similar to binary eutectic formed. Moreover, with the decreasing of droplet size, the growth morphology of primary (Ge) phase transformed from platelike to granular shape and a kind of anomalous ternary eutectic formed. The microgravity environment has a significant effect on the crystal growth process, which makes the (Ge) phase distribute homogeneously and the anomalous eutectic grains show good geometrical symmetry. The calculation of cooling rate versus droplet diameter showed that it was the high cooling rate and large undercooling that brought about the eutectic growth morphology transition.

A Method of Calculation of the Solar Radio Flux Density for High Spatial Resolution Observations
ZHOU Shu-rong, HUANG Guang-li
Chin. Phys. Lett. 1999, 16 (3): 223-225 .  
Abstract   PDF(pc) (220KB) ( 451 )
In this paper we present a method of calculation of the flux density of radio source for high spatial resolution solar radio observations, i.e., according to the observed solar antenna temperature, we make a correction for the K factor of antenna power pattern, then we can obtain values of solar radio flux. According to models of different brightness temperature distributions of the quiet sun and radio sources, we deduced the expression of the K factor of antenna power pattern, and calculated the fluxes of the quiet sun and slowly varying component emission of radio sources at 22 GHz.
High Brightness and Efficiency Yellow-Emitting Organic Electroluminescent Device
HUANG Jing-song, XIE Zhi-yuan, YANG Kai-xia, LI Chuan-nan, HOU Jing-ying, LIU Shi-yong
Chin. Phys. Lett. 1999, 16 (3): 226-228 .  
Abstract   PDF(pc) (204KB) ( 575 )
Yellow-light-emitting organic electroluminescent device with multilayer thin-film structure, which shows high brightness and efficiency, is constructed. The hole-transport layer is an N,N'-bis(3-methyphenyl)-N,N'-diphenylbe-nzidine film. The electron-transport layer is an 8-(quinolinolate)-aluminum(A1q) film. The luminescent layer consists of a host material Alq and an emitting dopant 5,6,11,12-petraphenyInaphthacene. The doped device exhibited the maximum emission 40000cd/m2 at 19V, and the maximum efficiency of 3.141m/W, which have been improved by about six and three times, respectively, in comparison with that in undoped device. For the unpackaged device, a luminance half-life on the order of about 230 h has been achieved with a constant current density of 15mA/cm2, starting at 500cd/m2 at the room temperature under ambient atmosphere.
Wound-Ribbon Helix Structure of Tilted Chiral Lipid Bilayers
XIE Yu-zhang
Chin. Phys. Lett. 1999, 16 (3): 229-231 .  
Abstract   PDF(pc) (210KB) ( 600 )
With the equation of helicoid, it is found that for wound-ribbon helix of chiral lipid bilayers the edge line of the helix can only be parallel to the azimuthal direction of the director. This clears the dilemma of the existence of both the parallel and the perpendicular case under the treatment of a chiral bilayer around a circular cylinder by Ou-Yang and Liu [Phys. Rev. Lett. 65 (1990) 1679; Phys. Rev. A43 (1991) 6826]. The present calculation also explains the self-transformation of the wound-ribbon helix into a prolate tube and the prolate tube into a multilayer soda straw structure.
Is the 0.36keV X-ray a Sign of the Existence of Antimatter Domains ? *
XU Chong-ming, WANG Xiang-yu, ZHAO Yong-heng, WU Xue-jun
Chin. Phys. Lett. 1999, 16 (3): 232-234 .  
Abstract   PDF(pc) (290KB) ( 377 )
If the universe consisted of domains of matter and antimatter, annihilations of e+-e- at the domain interface in the recombination time would leave an imprint on the x-ray band due to the high redshift. We found five ROSAT sources with the 0.36keV spectral line, especially the source lRXP J005510-3738.8 has a single sharp spectral line almost without a continuous spectrum. It is hard to be produced by any mechanism except the annihilations of e+-e-.
27 articles