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Volume 13 Issue 1
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Original Articles
Role of Self-Coupling in Dynamics of Diluted Hopfield Neural Networks
HU Bei-lai, ZHANG Yan-xin
Chin. Phys. Lett. 1996, 13 (1): 1-4 .  
Abstract   PDF(pc) (165KB) ( 448 )
The dynamical equation of diluted Hopfield neural networks with self-couplings is calculated by analytical approach. The presented results show that the self-coupling strongly influences the dynamical behavior of the network, making the critical loading value αc smaller remarkably and the size of basin of attraction decrease.
Compton Profiles of Graphite and Nanocrystalline Graphite
MO Hai-ding, GUO Ying, GONG Zhu-fang, YANG Bao-zhong, WU Tie-jun, BIAN Zu-lie
Chin. Phys. Lett. 1996, 13 (1): 5-8 .  
Abstract   PDF(pc) (179KB) ( 428 )
The Compton profiles of Polycrystalline graphite and nanometeric graphite produced by mill grinding were measured and the Compton profile of polycrystalline graphite was calculated. The theoretical and the experimental Compton profiles of polycrystalline graphite, the experimental Compton profiles of nanometeric graphite were compared.

A New Half-Life Value of 79Se
JIANG Song-sheng, GUO Jing-ru, JIANG Shan, LI Chun-sheng, CUI An-zhi, HE Ming
Chin. Phys. Lett. 1996, 13 (1): 9-12 .  
Abstract   PDF(pc) (249KB) ( 460 )
In the recent charts of the nuclides an accepted half-life of 79Se is only an upper limit, < 6.5 x 104 a. In this letter, A new half-life of 79Se has been measured to be (1.13 ± 0.17) x 106a. The number of 79Se atoms was determined from measured 79Se /Se ratios with the accelerator mass spectrometry technique and the decay rate of 79Se was determined by counting the emitted β rays with a liquid scintillation spectrometer.
New Isomeric States in 197Bi
ZHOU Xiao-hong, SUN Xiang-fu, GUO Ying-xiang, LEI Xiang-guo, CHEN Xin-feng, LIU Zhong, ZHANG Yu-hu, JIN Han-juan, LUO Yi-xiao WEN Shu-xian, YUAN Guan-jun, LI Guang-sheng, YANG Chun-xiang
Chin. Phys. Lett. 1996, 13 (1): 13-16 .  
Abstract   PDF(pc) (217KB) ( 466 )
The high-spin states in 197Bi have been studied with the 187Re(16O,6n) reaction at 16O energies from 85 to 105MeV. In-beam measurements of γ-ray excitation functions, γ -γ -t coincidences and γ-ray angular distributions were carried out with six BGO(AC)HPGe detectors and one intrinsic Ge planar detector. Eleven new transitions and three new isomers were observed, and a level scheme for 197Bi was established. Some differences between the present work and the previous results were found.
A Two-Soliton Solution of Cubic Schrödinger Equation
YAN Jia-ren, CHOU Guang-hui, WANG Xiao-gang
Chin. Phys. Lett. 1996, 13 (1): 17-19 .  
Abstract   PDF(pc) (118KB) ( 402 )
An exact two-soliton solution of cubic Schrödinger equation is derived by using the inverse scattering method, where the transmission coefficient has one pole of second order instead of two simple poles. This solution describes such a process that two infinitely separated solitons approach and then pass through each other and keep straight on infinitely.

Elastic Wave Scattering from Cylindrical Multilayered Solid Media
WANG Yao-jun, ZHU Wei-yong
Chin. Phys. Lett. 1996, 13 (1): 20-23 .  
Abstract   PDF(pc) (174KB) ( 583 )
By using the transfer matrix method, we present a general model for evaluating the ultrasonic scattering cross-section from a cylindrical multilayered medium. A numerical computation is given for an SCS-6/Ti fiber. This model can be conveniently used to estimate the ultrasonic scattering from a cylinder consisting of any number of layers.
Laser-Generated Transient Lamb Wave in Thin Plates
WU Lei, CHENG Jian-chun, ZHANG Shu-yi
Chin. Phys. Lett. 1996, 13 (1): 24-27 .  
Abstract   PDF(pc) (175KB) ( 427 )
The laser-generated transient Lamb wave in thin isotropic plates is studied theoretically by employing the method of eigenfunction expansion. The thermoelastic displacement field is expressed by symmetric and antisymmetric Lamb wave modes, so that it is convenient to investigate the transient excitation of the lowest and higher order Lamb wave modes. The characteristics of transient Lamb waves in thin materials
with different thicknesses are discussed in details.
Three Wave Mixing and Four Wave Scattering Processes in Laser-Plasma Interaction
HU Xi-wei
Chin. Phys. Lett. 1996, 13 (1): 28-30 .  
Abstract   PDF(pc) (135KB) ( 497 )
A nonlinear fluid description for the parameter processes has been derived. The linear instability analyses about three wave mixing process ω0 →ωs1 + ωs2 and four wave scattering process ω0→ωs + ωP1 + ωP2 have been made. Correspondent backward or side scattering light waves emitted from mentioned processes may provide valuable information for the diagnostic of plasma parameters.
Growth and Saturation of the Relativistic Harmonic Radiation
ZENG Gui-hua, YU Wei, SHEN Bai-fei, XU Zhi-zhan
Chin. Phys. Lett. 1996, 13 (1): 31-34 .  
Abstract   PDF(pc) (197KB) ( 359 )
A series of coupling equations for the relativistic coherent harmonic generation is derived taking account of the coupling effect among the harmonic contents and plasmas wave. Using these equations, the growth and saturation of amplitude of the third harmonic wave is investigated. Results show that the coupling effect induces the saturation of harmonics, which is identical with ones of the Lagrangian description.
Microstructure Study of Photoluminescent Porous Silicon
WENG Yu-min, ZONG Xiang-fu
Chin. Phys. Lett. 1996, 13 (1): 35-38 .  
Abstract   PDF(pc) (238KB) ( 656 )
We have studied the microstructure and photoluminescent properties of porous Si. High resolution observations revealed that the microstructure of porous Si consists with nano-crystallites Si embedded in the surrounding amorphous matrix. The structure of nano-crystallites of porous Si is not consistent with the usual diamond structure of bulk Si. The photoluminescence from porous Si is due to the quantum confinement of carriers in this structure.
New Potentials of Silicon and Germanium Crystals
LIU Xin-hou
Chin. Phys. Lett. 1996, 13 (1): 39-41 .  
Abstract   PDF(pc) (138KB) ( 408 )
In this paper, a new model of potential energy functions for atomic solids is given and applied to silicon and germanium crystals. Obtained potentials of Si and Ge crystals accurately reproduce experimental elastic constants and phonon dispersion curves.
Growth of GaAs on Si by Using a Thin Si Film as Buffer Layer
HAO Mao-sheng, LIANG Jun-wu, JIN Xiao-jun, WANG Yu-tian, DENG Li-sheng, XIAO Zhi-bo, ZHENG Lian-xi, HU Xiong-wei
Chin. Phys. Lett. 1996, 13 (1): 42-45 .  
Abstract   PDF(pc) (248KB) ( 659 )
We report a novel technique for growing high-quality GaAs on Si substrate. The process involves deposition of a thin amorphous Si film prior to the conventional two-step growth. The GaAs layers grown on Si by this technique using metalorganic chemical vapor deposition exhibit a better surface morphology and higher crystallinity as compared to the samples grown by conventional two-step method. The full width at half maximum (FWHM) of the x-ray (004) rocking curve for 2.2 μm thick GaAs/Si epilayer grown by using this new method is 160arcsec. The FWHM of the photo-Luminescence spectrum main peak for this sample is 2.1 meV. These are among the best results reported so far. In addition, the mechanism of this new growth method was studied using high-resolution transmission electron microscopy.
Van Hove Scenario in Two-Layer BCS Model
SHI Da-ning
Chin. Phys. Lett. 1996, 13 (1): 46-49 .  
Abstract   PDF(pc) (152KB) ( 369 )
In this letter, we study the effects of the interlayer hopping and pairing of the layered high-Tc superconductors within the framework of BCS-van Hove singularity model. The obtained results are in qualitative agreement with the experiments.
Temperature Effect on Giant Magnetoresistance in Magnetic Multilayers
ZHANG Ling-yun, YANG Guo-lin, LI Bo-zang, PU Fu-ke
Chin. Phys. Lett. 1996, 13 (1): 50-53 .  
Abstract   PDF(pc) (196KB) ( 453 )
We have presented the electronic free energy with respect to the magnetization and the model of the electronic density of states. The expression of the giant magnetoresistance has been obtained by considering the spin splitting of the electronic energy band. Our approach explained the temperature effect on the giant magnetoresistance in magnetic multilayers.
Resonant Raman Scattering in GaAs1-xPx:N
YU Rong-wen, ZHENG Jian-sheng, XIAO Mei-jie, LIN Zhi-rong, YAN Bing-zhang
Chin. Phys. Lett. 1996, 13 (1): 54-57 .  
Abstract   PDF(pc) (168KB) ( 469 )
We report a study of the resonant Raman scattering (RRS) by optical phonons that is induced by excitons bound to isoelectronic nitrogen impurities in GaAs1-xPx:N alloys. Under resonant excitation into Nx band, strong Raman lines involving allowed LO and “forbidden” TO for backscattering configuration from (100) surface are observed. This is interpreted as the breakdown of normal selection rule in the RRS process. By following the temperature dependence of the Nx luminescence and its phonon sidebands, we also separate RRS from sharp line due to luminescence.

Ammonium Ion Motion and Phase Transitions in (ND4)2TeCl6 Studied by Raman Scattering
SHI Jin-rong, MÜ, LLER S, ARNSCHEIDT B, PELZL J, XU Yong-chen, WU Xian,
Chin. Phys. Lett. 1996, 13 (1): 58-61 .  
Abstract   PDF(pc) (204KB) ( 394 )
The internal vibrations of the ammonium ion in (ND4)2TeCl6 have been studied by Raman scattering in the temperature range 4.2-300K. Splittings of A1-, E-, and T2-modes have been observed at Tc2 = 48 K and Tc3 = 28 K. These splittings were well interpreted by group theoretical correlation method. The reason for the transitions at Tc2 and Tc3 may be the decrease of the force constant in the deuterated ammoniumion.
Photoluminescence and Photoluminescence Excitation of Si Aerogels Prepared by Supercritical Drying
GUO Guo-lin, XU Dong-sheng, YAO Guang-qing, TANG You-qi, ZHANG Li-dong, LIN Jun, MA Shu-yi, DUAN Jia-qi, ZHANG Bo-rui, QIN Guo-gang
Chin. Phys. Lett. 1996, 13 (1): 62-64 .  
Abstract   PDF(pc) (152KB) ( 468 )
Si aerogel, the porous silicon with ultra high porosity, has been prepared by the technique of anodization followed by supercritical drying. Its photoluminescence, photoluminescence excitation and morphological features exhibit novel characteristics from those of the conventionally anodized porous silicon. We observed the differences between the Si aerogels made from <100> and <111> crystalline Si.
Adsorptidn of Sm on C60 Film
PAN Hai-bin, XU Shi-hong, XU Chang-shan, LU Er-dong, XIA An-dong, ZHANG Guo-shang, XU Peng-shou, ZHANG Xin-yi
Chin. Phys. Lett. 1996, 13 (1): 65-68 .  
Abstract   PDF(pc) (178KB) ( 401 )
Using photoemission spectroscopy, we have studied the adsorption of Sm on C60 film. At the first stage of Sm adsorption, the C60 valence band shifts to the high binding energy side. The maximum shift is about 0.4eV. In the meantime, there appears a new structure at the upper side of the highest occupied molecule orbit (HOMO) band, which comes from the hybrid of the Sm 4f 5 state and C60 HOMO band. As Sm coverage increases the Sm electron is in a kind of Sm2+ state due to the forming of Sm cluster on the surface.

Polycrystalline β-C3N4 Thin Films Deposited on Single-Crystal KCl(100) Using rf Sputtering
ZHANG Ze-bo, LI Yin-an, XIE Si-shen, YANG Guo-zhen
Chin. Phys. Lett. 1996, 13 (1): 69-72 .  
Abstract   PDF(pc) (207KB) ( 453 )
The carbon-nitride thin films were deposited on the (100) oriented single-crystal KCl wafers at ambient temperatures by using rf-plasma sputtering. The IR spectrum showed that the films contained carbon-nitride bonds. The transmission electron microscopy (TEM) and x.-ray diffraction (XRD) measurements indicated the existence of predicted polycrystalline β-C3N4 films on the KCl(I00) wafers. And the TEM and XRD measured lattice spacings well match the calculated data.
Phonon and Spin Wave Spectra Study on “in situ Oxidizing Sputtered” Ni/NiO Multilayers
WANG Wen-nai, JIANG Zheng-sheng, CHENG Guang-xu, DU You-wei
Chin. Phys. Lett. 1996, 13 (1): 73-76 .  
Abstract   PDF(pc) (202KB) ( 420 )
An improved sputtering method, which is named “in situ oxidizing sputtering”, was used to prepare periodic Ni/NiO multilayers. Samples studied in this letter contains 20 pairs of Ni/NiO with period about 100Å. In Raman scattering, the low frequency phonon modes are interpreted as LA phonon folding effect, which is usually measured in superlattices with a strict periodic structure. The ferromagnetic resonance spectra were also recorded at room temperature with microwave frequency 9.777GHz. The analysis of spin wave resonance indicates that Ni sublayers are coupled with each other, which is the mechanism that surely relates to the amorphous-like NiO spacers.

Experimental Study of Molecular Fluctuation in the Living Cells
TANG Xiao-wei, LIU Jin-bo, WU Bi-chu
Chin. Phys. Lett. 1996, 13 (1): 77-80 .  
Abstract   PDF(pc) (172KB) ( 423 )
The velocity non-uniformity of the particle movement in the living cells is investigated. Introducing the concept of molecular fluctuation in the living cells, the phenomenon of the velocity non-uniformity is explained. A quantitative relation between molecular fluctuation and velocity non-uniformity of the particle movement is derived.
21 articles