Current Issue

Volume 15 Issue 11
Online Date:
Previous Issue    Next Issue
Original Articles
Topological Quantization of Linear Defects
DUAN Yi-shi, JIANG Ying, YANG Guo-hong
Chin. Phys. Lett. 1998, 15 (11): 781-783 .  
Abstract   PDF(pc) (223KB) ( 409 )
Using Ф-mapping method and topological current theory, we get the topological structure and the topological quantization of topological linear defects and point out that the topological quantum numbers of the linear defects are described by the Winding numbers of Ф-mapping which are determined in terms of the Hopf indices and the Brouwer degrees. All the topological linear defects are generated from the zero points of the Ф-mapping.
The 2++ Three-Gluon Tensor Glueball in Quantum Chromodynamics Sum Rules
LIU Jue-ping
Chin. Phys. Lett. 1998, 15 (11): 784-786 .  
Abstract   PDF(pc) (190KB) ( 335 )
The three-gluon tensor current of quantum numbers Jpc = 2++ is constructed. The corresponding two-point function is calculated by including not only the perturbative contribution but also the non-perturbative ones resulting from condensates of dimensions up to six. In a usual “resonance plus continuum ”model of the spectral function of the current, the quantum chromodynamics sum rules for the 2++three-gluon tensor glueball are deduced, and the mass of that glueball is determined to be 2.0 GeV approximately.
Debye Screening Mass at Next-to-Leading Order and Charmonium Deconfinement in the Quark-Gluon Plasma
CHEN Hong, LIU BO, HE Ze-jun
Chin. Phys. Lett. 1998, 15 (11): 787-789 .  
Abstract   PDF(pc) (199KB) ( 378 )
Debye screening mass at the next-to-leading order is studied by the resummation method based on perturbation theory at finite temperature. We find that the critical temperature for the J/ψ dissociation is 0.211 GeV. The contributions from the next-to-leading order are important, and critical temperature and chemical potential are shifted lower values.
Separation and Identification of Isotopes Produced from 20Ne+Be Reaction by Radioactive Ion Beam Line in Lanzhou
SUN Zhi-yu, ZHAN Wen-long, GUO Zhong-yan, XIAO Guo-qing, WANG Jin-chuan, LI Jia-xing, JIANG Shan-hong, MENG Xiang-wei, QIN Li-jun, WANG Quan-jin
Chin. Phys. Lett. 1998, 15 (11): 790-792 .  
Abstract   PDF(pc) (206KB) ( 584 )
The separation and identification of isotopes emitted from the projectile fragmentation reaction of 80 MeV/u 20Ne on 9Be target were carried out by using the radioactive ion beam line in Lanzhou (RIBLL). Many proton rich isotopes are obtained. Their intensity and purity fit the theoretical calculations. Good separation and identification abilities of RIBLL A/ΔA > 300 and Q/ΔQ > 150, are obtained.
Collective Band Structures in the Neutron-Rich 107,109Ru Nuclei
ZHU Sheng-jiang, GAN Cui-yun, J. H. Hamilton, A. V. Ramayya, B. R. S. Babu, M. Sakhaee, W. C. Ma, LONG Gui-lu, DENG Jing-kang, ZHU Ling-yan, LI Ming, YANG Li-ming, J. Komicki, J. D. Cole, R. Aryaeinejad, Y. K. Dardenne, M. W. Drigert, J. O. Rasmussen, M. A. Stoyer, S. Y. Chu, K. E. Gregorich, M. F. Mohar, S. G. Prussin, I. Y. Lee, N. R. Johnson, F. K. McGowan
Chin. Phys. Lett. 1998, 15 (11): 793-796 .  
Abstract   PDF(pc) (197KB) ( 502 )
The levels in neutron-rich odd-A 107,109Ru nuclei have been investigated by using γ -γ -and γ -γ -γ-coincidence studies of the prompt γ-rays from the spontaneous fission of 252Cf. The ground state bands and the negative parity bands are identified and expanded in both nuclei. Triaxial rotor plus particle model calculations indicate the ground state bands originate from v(d5/2+g7/2) quasiparticle configurations and the negative parity bands are from vh11/2 orbital.
Experimental Study of p-llB Reaction Related to the Clean Fusion Fuel
LIN Erh-kang, WANG Chang-wan, YUAN Jian, LIU Xiao-dong, LI Cheng-bo, SUN Zu-xun, ZHANG Pei-hua, CHEN Jin-xiang, YANG Qi-xiang, WANG Jian-yong, Gong Ling-hua
Chin. Phys. Lett. 1998, 15 (11): 796-798 .  
Abstract   PDF(pc) (238KB) ( 415 )
Whole continuous a spectra of the p-llB three-body sequential decay reaction have been measured by using a charge particle time-of-flight (TOF) spectrometer with the high-resolution passivated implanted planar silicon detector. A characteristic shape of the saddle-type distribution was obtained. The Monte Carlo calculations show that observed a spectra can be interpreted by anisotropy sequential decay process of the intermediate nucleus 8Be (1) for the p-llB reaction. In the measurement, angular distributions were obtained for proton energies at 667 and 1370keV, respectively. Total cross-sections for the llB(p, α)8Be (2α) reaction related to the clean fusion fuel were also reported at two bombarding energies.
Modulated Transmission Property of Bacteriorhodopsin Film and Its Application on Thresholding Operation
LI Yu-dong, SUN Qian, ZHANG Chun-ping, LU Rui, FU Guang-hua, ZHANG Guang-yin, SONG Q.Wang, Bruce Parsons, Robert R. Birge
Chin. Phys. Lett. 1998, 15 (11): 799-801 .  
Abstract   PDF(pc) (249KB) ( 740 )
In this paper, the modulated transmission property of bacteriorhodopsin (bR) film is analyzed theoretically when two beams of light, yellow light and purple light, illuminate the bR film simultaneously. By using the transmission property of bR film, the winner-take-all thresholding operation can be realized.
Unified Solution Formulas to Jaynes-Cummings Models with Field Nonlinearity and Strong Atom-Field Coupling
YANG Xiao-xue, WU Ying, GAO Ke-lin
Chin. Phys. Lett. 1998, 15 (11): 802-804 .  
Abstract   PDF(pc) (223KB) ( 598 )
Unified and standardized solving formulas for eigenvalues, eigenvectors, evolution operators, time-varying atomic inversion and photon numbers are given to single-mode Jaynes-Cummings models with any forms of intensity-dependent atom-field coupling and the nonlinearity of the quantized photonic field itself such as the Kerr effect.
Perturbation Theory for Optical Soliton
TANG Yi, YAN Jia-ren, ZHANG Kai-wang
Chin. Phys. Lett. 1998, 15 (11): 805-806 .  
Abstract   PDF(pc) (111KB) ( 373 )
Based on the main idea of the derivative expansion method, a perturbation approach is proposed for the investigation of single soliton propagating down a nonideal monomode optical fiber. This approach is totally independent of inverse scattering theory, which has substantial difference from the past methods. In this scheme, the first-order correction is derived by the method of eigenfunction expansion, and the parameters change is directly obtained from the secularity conditions for some cases.
Diode Pumped Nd:YVO4 Laser Emitting 671 nm Through Intracavity Frequency Doubling with LiB3O5
ZHANG Heng-li, HE Jing-liang, HOU Wei, FANG Xiao-jun, WU Ling-an, XU Zu-yan, WANG Jian-ming, ZHAO Zong-yuan, WU Xing, WU Bai-chang, CHEN Chuang-tian
Chin. Phys. Lett. 1998, 15 (11): 807-809 .  
Abstract   PDF(pc) (206KB) ( 482 )
With a type-I noncritically phase-matched LiB3O5 crystal as the intracavity frequency doubler in a diode pumped Nd:YVO4 laser, 440mW of 671 nm light was obtained at 5.5W of incident pump power, the optical-optical conversion efficiency being 8.0%.
Third-Order Optical Nonlinearities in the Poly(2-Chloro-1,4-Phenylene Vinylene) Thin Film
SUN Zhen-rong, YANG Xi-hua, HUANG Yan-ping, DING Liang-en, QIN Li-juan, WANG Zu-geng
Chin. Phys. Lett. 1998, 15 (11): 810-812 .  
Abstract   PDF(pc) (199KB) ( 457 )
A new polymer thin film, ploy (2-chloro-1,4-phenylene vinylene) (ClPPV), with high environmental and thermal stability, high optical damage threshold, and good film quality, was successfully prepared by the “precursor-route” method. Its third-order optical nonlinearities were measured by picosecond forward three-dimensional degenerate four-wave mixing technique. In the near resonance region (532nm), the measured third-order nonlinear optical coefficients x(3)zzzz and x(3)yzzy are 9.1 x 10-l0 and 7.2 x 10-11 esu, respectively, and its response time is quite fast, estimated to be less than picosecond. The Kerr effect, which arises from the distortion of the large quasi-one-dimensional π-conjugated electronic charge distribution of ClPPV, is the main reason for generating third-order optical nonlinearities.


Calculation of a Nonuniform and Nonadiabatic Model of Sonoluminescence
XIE Zhi-Xing, CHEN Wei-zhong, WEI Rong-jue
Chin. Phys. Lett. 1998, 15 (11): 813-815 .  
Abstract   PDF(pc) (270KB) ( 330 )
A nonuniform and nonadiabatic model has been developed to research the gas dynamics within a bubble of sonoluminescence. The model includes three diffusive effects of gas viscosity, thermal conduction and radiative transport simultaneously, and calculations prove that they have important influences on the characteristics of sonoluminescence. The model has been solved numerically and gives the results of about 104 K peak temperature and l00ps pulse duration which are consistent with recent experiments.

Gamma-Rays Generated from Plasmas in the Interaction of Solid Targets with Femtosecond Laser Pulses
HE Jing-tang, ZHANG Ping, CHEN Duan-bao, LI Zu-hao, ZHANG Ying, WANG Long, FENG Bao-hua, ZHANG Xiu-lan, WEI Zhi-yi, LI Zan-liang, TANG Xiao-wei, ZHANG Jie,
Chin. Phys. Lett. 1998, 15 (11): 816-818 .  
Abstract   PDF(pc) (299KB) ( 455 )
The γ-rays with energies up to 300keV have been observed from plasmas produced by femtosecond laser pulses at a focused intensity of 5 x 1015 W.cm-2.μm2 irradiating Ta, Mo, and Cu targets. By introducing an 8% prepulse of 70ps before the main pulse, the fraction of high energy γ-ray photons (hv >l00keV) was significantly enhanced relative to low energy photons (hv < 100 keV).
Heteroepitaxial Growth of Single-Crystalline Diamond Film
WANG Qi-min, CHEN Qing-gui, SHI Ri-hua, DONG Rong-kang, NI Ru-shan, ZHU Ji-qian
Chin. Phys. Lett. 1998, 15 (11): 819-821 .  
Abstract   PDF(pc) (219KB) ( 441 )
Using high temperature heteroepitaxial growth method the single-crystalline diamond film growth conditions have been studied by Raman spectrum and transmission electron diffraction. High temperature, low alcohol concentration, slow gas flow velocity, long epitaxial time and substrate located near the gas exit side on the susceptor are the favourable conditions for growing single-crystalline diamond film.
Highly Oriented Diamond Film Growth by Atomic Force Microscopy
LI Jian-long, MENG Ge, WU Ke-hui, WANG En-ge
Chin. Phys. Lett. 1998, 15 (11): 822-824 .  
Abstract   PDF(pc) (396KB) ( 370 )
Diamond thin films are grown with microwave plasma chemical vapor deposition method on silicon (100) substrates from methane/hydrogen gas mixture, and characterized with atomic force microscopy The results show that most of the diamond crystallites are highly oriented with the (100) planes parallel to the silicon substrate. Layer structures are found in the film, indicating a combination of layer-by-layer and island growth. Raman spectrum and x-ray diffraction also confirm the present results.
Theoretical Study of Extraction of a Single Al Atom from Al(111) Surface by Scanning Tunneling Microscopy W Tip
WANG Fu-he, YANG Jin-long, LI Jia-ming,
Chin. Phys. Lett. 1998, 15 (11): 825-827 .  
Abstract   PDF(pc) (256KB) ( 488 )
Based on the discrete variational method with the local-density-functional approximation, the cluster models were chosen to simulate the extraction of a single Al atom from Al(111) sample surface by a scanning tunneling microscopy W tip with and without external bias voltages. The calculated results show that the tip-sample effects of W tip on the extraction of an Al atom are very important. The Al atom can be extracted from the Al(111) surface by the pure W tip without external bias, as the tip approaches the sample within 10 a.u. (5.3Å). When the separation between the tip and the sample is larger than 10 a.u., a positive bias must be applied to the sample. The extracted Al atom is expected to have net positive charge when it escapes from the Al(111) sample surface. The corresponding critical field is about 0.6V/Å. This value is in good agreement with experimental results.
Effect of Non-Muffin-Tin Potential on Electronic Structure of NiO
QIAN Mei-cun, HU Wen-ying, ZHENG Qing-qi
Chin. Phys. Lett. 1998, 15 (11): 828-830 .  
Abstract   PDF(pc) (258KB) ( 378 )
The electronic structure of NiO has been calculated within the self-consistent local spin density approximation(LSDA) as well as with on-site Coulomb interaction(LSDA+U) method. Considering NiO as a typical ionic crystal, the linear muffin-tin orbitals with the ionic sphere approximation method is used. The effect of non-spherical crystalline field is taken into account precisely. The obtained energy-dispersion bands are in agreement with the recent angle-resolved-photoemission spectra.
Magnetic Hardening Mechanism in Nanocrystalline Sm2Fe15-xMxGa2C
ZHANG Shao-ying, ZHANG Hong-wei, SHEN Bao-gen, ZHAN Wen-shan, CHIN Tsung-shune
Chin. Phys. Lett. 1998, 15 (11): 831-833 .  
Abstract   PDF(pc) (242KB) ( 526 )

Coherent Phonons in Ag-BaO Thin Films
QIAN Wei, YAN Hong, WANG Jing-jing, ZOU Ying-hua, LIN Lin, WU Jin-lei
Chin. Phys. Lett. 1998, 15 (11): 834-836 .  
Abstract   PDF(pc) (205KB) ( 461 )
Coherent acoustic phonons have been observed in Ag nanoscale particles (NSPs) embedded in BaO thin film by means of the femtosecond time-resolved pump-probe technique. The oscillatory component in the signal corresponds to a very low-frequency acoustic phonon mode of Ag NSPs. The generation of coherent acoustic phonons is attributed to the resonant excitation of localized surface plasmon.
Photoluminescence Properties of a-SiC:H Films Grown by Plasma Enhanced Chemical Vapor Deposition from SiH4+C2H2 Gas Mixtures
LIU Yi-chun, LIU Chun-guang, CHEN Da-wei, LIU Yu-xue, BAI Yu-bai, LI Tie-jin
Chin. Phys. Lett. 1998, 15 (11): 837-839 .  
Abstract   PDF(pc) (281KB) ( 418 )
The films of a-SiC:H were deposited by plasma enhanced chemical vapor deposition system from SiH4+ C2H2 gas mixtures. The C-rich a-SiC:H films were easily obtained by using C2H2 gases due to the low dissociation energy of C2H2 molecule in the plasma. Thus, the carbon was effectively incorporated into a-Si:H network. Although the defect state densities were proportional to carbon content in a-SiC:H films, the photoluminescence intensities were not directly related with defect density, yet increased with the carbon content increasing. The infrared spectra indicated that CHn groups as clusters were incorporated mainly into a-SiC:H network. The little correlation of the PL integrated intensity with defect state density suggested that luminescence was associated with clusters as a largely intracluster process.
Solute Diffusion Controlled Dendritic Growth Under High Undercooling Conditions
CAO Chong-de, LU Xiao-yu, WEI Bing-bo
Chin. Phys. Lett. 1998, 15 (11): 840-842 .  
Abstract   PDF(pc) (310KB) ( 615 )
Liquid Cu70Co30 alloy is undercooled up to 363 K (0.22TL) by using glass-fluxing technique. The LKT/BCT dendritic growth theory is modified and made applicable to predict the kinetic characteristics of dendritic growth in those alloy systems which have extremely curved liquidus and solidus lines. Actual calculations reveal that the dendritic growth of primary α-Co phase in Cu70Co30 alloy is constantly controlled by solute diffusion. The growth velocity of α-Co dendrite has a maximum value of 54.5mm/s at an undercooling of 333K. The calculated solubility of Cu in α-Co dendrite decreases with the increase of undercooling, which agrees well with the experimental data. Prior to peritectic transformation, the growth of α-Co dendrite is close to equilibrium solidification.
Orthogonal Alignment InAs Islands Formation on GaAs Tensile Strained Layer Grown on (001) InP Substrate by Low Pressure Metal-Organic Chemical Vapor Deposition
GAO Chun-xiao, WANG Ben-zhong, LIU Bing-bing, LIU Shi-yong, ZOU Guang-tian
Chin. Phys. Lett. 1998, 15 (11): 843-845 .  
Abstract   PDF(pc) (257KB) ( 466 )
Nucleation control is one of the key questions in quantum dots preparation and application. This paper reports the experimental results of orthogonal alignment InAs islands formed on (001) InP substrate by low-pressure metal-organic chemical vapor deposition. As a nucleation control layer, the tensile strained GaAs epilayer with orthogonal trench structure was grown firstly on (001) InP substrate under Stranski-Krastanov growth mode. Then, the InAs islands were grown selectively on the trench edges by using strain effect. This growth technique results in the formation of orthogonal alignment InAs islands without any preprocessing technique prior to the growth.
Solitary Wave Propagation in Deoxyribonucleic Acid Double Helices
ZHANG Ling-yun, SUN Hong
Chin. Phys. Lett. 1998, 15 (11): 846-848 .  
Abstract   PDF(pc) (180KB) ( 430 )
A solitary wave propagation of deoxyribonucleic acid (DNA) double helices has been discussed. The stretch of the hydrogen bonds is considered as a nonlinear chain with cubic and quartic potential. The solitary wave solution can be obtained by using a homogeneous balance method. The characteristic parameters of solitary wave, such as the stretch amplitude and width are estimated. It is shown that the conformational transitions from B-DNA to A-DNA can occur in a certain condition.
Hypothesis of Intracellular Signaling Based on the Cytoskeleton Network
TANG Xiao-wei, DING Ming-xiao
Chin. Phys. Lett. 1998, 15 (11): 849-850 .  
Abstract   PDF(pc) (147KB) ( 345 )
In order to explain the direction, speed and specificity of cell signaling a dual pathway hypothesis is proposed. In this hypothesis the physical pathway is coupled to the biochemical pathway. As an example, the propagation of a mechanical wave along the cytoskeleton components is discussed.
Revisions of Convolution Model of Reflected Seismic Wave
HUANG Guang-yuan
Chin. Phys. Lett. 1998, 15 (11): 851-853 .  
Abstract   PDF(pc) (363KB) ( 452 )
The convolution model of reflected wave used in exploration physics has no serious physical concept and mathematical proof. Wave phenomena should be characterized by instantaneous spectrum in physics and a complex function of three real variables (time. Place frequency) in mathematics. Reflection coefficient is also a complex function of place and frequency. Several new formulas instead of convolution model are given. Based on wavelet transform and a method of “3 basis colors”, new color sectional image is obtained from practical data.
Acceleration and Emission Mechanism for Wisps in the Crab Nebula
JING Hai-rong, TONG Yi, MAO Xin-jie
Chin. Phys. Lett. 1998, 15 (11): 854-855 .  
Abstract   PDF(pc) (174KB) ( 384 )
A new acceleration and emission mechanism is presented for wisps in the crab nebula. It is suggested that the energy of ultra-relativistic electrons comes mainly from Langmuir wave turbulence acceleration and synchrotron absorption acceleration, then they give rise to synchrotron emission. Langmuir wave turbulence acceleration is the dominant mechanism at ε ≤ ε* , while synchrotron absorption acceleration is more important at ε > ε*. The energy diffusion equation is investigated for ultra-relativistic electrons undergoing different acceleration and derive power-law solution. In wisp 1 region, the synchrotron emission spectra are obtained, and they are x-rays, optical but not radio. The results are consistent with observations.

Relation Between Millimeter Wavelengths Emission and High-Energy Emission for Active Galactic Nuclei
HUANG Li-hua, JIANG Dong-rong, CAO Xin-wu
Chin. Phys. Lett. 1998, 15 (11): 856-858 .  
Abstract   PDF(pc) (245KB) ( 363 )
After comparing the flux densities of a sample of active galactic nuclei detected by energetic gamma-ray experiment telescope at 90 and 230 GHz with the γ-ray emissions detected by Compton Gamma-Ray Observatory and x-ray emission, a strong correlation between the emission at the millimeter wavelength and the γ-ray emission is found. The average flux density of x-ray is almost proportional to the average flux density at the millimeter wave-length for quasars detected by energetic gamma-ray experiment telescope, which strongly supports the previous idea that the x-ray emissions of this kind sources are mainly produced by synchrotron self-Compton process.
27 articles