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Volume 17 Issue 9
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Original Articles
Soliton Perturbations for a Combined KdV-MKdV Equation
YAN Jia-Ren, PAN Liu-Xian, ZHOU Guang-Hui
Chin. Phys. Lett. 2000, 17 (9): 625-627 .  
Abstract   PDF(pc) (172KB) ( 399 )
The soliton perturbations for the combined Korteweg de Vries and modified Korteweg de Vries (KdV-MKdV) equation are studied. The first-order effects of perturbation on a soliton, namely both the slow time-dependence of the soliton parameters and the first-order correction are derived through constructing the appropriate Green's function.
Excitation Spectrum of Three Dressed Bose-Einstein Condensates
OU-YANG Zhong-Wen, KUANG Le-Man
Chin. Phys. Lett. 2000, 17 (9): 628-630 .  
Abstract   PDF(pc) (237KB) ( 385 )
We study quantum dynamics of three dressed Bose-Einstein condensates in a high-Q cavity. The quasiparticle excitation spectrum of this system is found numerically. The stability of the quasiparticle excitation is analyzed. It is shown that there exist instabilities in the excitation spectrum.
A Model for Macroscopic Quantum Tunneling of Bose-Einstein Condensate with Attractive Interaction
YAN Ke-Zhu, TAN Wei-Han
Chin. Phys. Lett. 2000, 17 (9): 631-633 .  
Abstract   PDF(pc) (208KB) ( 584 )
Based on the numerical wave function solutions of neutral atoms with attractive interaction in a harmonic trap, we propose an exactly solvable model for macroscopic quantum tunneling of a Bose condensate with attractive interaction. We calculate the rate of macroscopic quantum tunneling from a metastable condensate state to the collapse state and analyze the stability of the attractive Bose-Einstein condensation.
A New Noncontact Probe for Thermophysical Properties of Solid Surfaces
FANG Jian-Wen, YIN Qing-Rui, ZHANG Shu-Yi, ZHANG Zhong-Ning, SHUI Xiu-Ji
Chin. Phys. Lett. 2000, 17 (9): 634-636 .  
Abstract   PDF(pc) (268KB) ( 337 )
Based on the photothermal displacement effect and the optical diffraction effect, an alternative pulsed photothermal technique has been developed. This technique overcomes some disadvantages of conventional methods and provides a sensitive, noncontact and nondestructive probe of the transient thermal and mechanical process at solid and thin film surfaces. Meanwhile, a three-dimensional theoretical model has also been presented to describe the experimental phenomena. Excellent agreement between the theory and the experiment is obtained. As an example, the technique is demonstrated by measuring the thermal diffusivity of aluminum and brass thin plates.
Energy Filtering and Coaxial Detection of the Backscattered Electrons in Scanning Electron Microscope
JIANG Chang-Zhong, P. Morin, N. Rosenberg
Chin. Phys. Lett. 2000, 17 (9): 637-639 .  
Abstract   PDF(pc) (305KB) ( 478 )
A new detection system in scanning electron microscope, which filters in energy and detects the backscattered electrons close to the microscope axis, is described. This technique ameliorates the dependence of the backscattering coefficient on atomic number, and suppresses effectively the relief contrast at the same time. Therefore this new method is very suitable to the composition analysis.
Topology of SU(2) Vacuum Through Improved Coolings
CHEN Ying, HE Bing, LIU Da-Qing, WU Ji-Min
Chin. Phys. Lett. 2000, 17 (9): 640-642 .  
Abstract   PDF(pc) (224KB) ( 606 )
The Wilson and the improved cooling methods are used to explore the topological properties of SU (2) gauge field on lattice. Topological charge values which are close to integers are obtained. The measured charges through the Wilson cooling are within about 15% discrepancy to integers, and most of the configurations tend rapidly to 0-charged flat vacuum, while the charges through improved cooling are refined to almost integers within a few percentage of error and the corresponding plateaus last longer. The final charges and the evolutions of the same configuration cooled from various improved actions are different from each other due to the lattice artifact.
Non-abelian Collective Excitations in Nonlinear Quark-Gluon Plasma Media
ZHENG Xiao-Ping, HOU De-Fu, LIU Liang-Gang, LI Jia-Rong
Chin. Phys. Lett. 2000, 17 (9): 643-645 .  
Abstract   PDF(pc) (234KB) ( 318 )
We have studied the effect of the third-order density fluctuations in the medium on the collective excitations in quark-gluon plasma. We show that the nonlinear response of a quark-gluon plasma medium leads to non-Abelian collective excitations. We present two kinds of non-Abelian oscillation solutions which respectively correspond to weakly and strongly nonlinear coupling of field components in the color space. We also show that the weakly nonlinear solution is similar to the Abelian-like one but has a frequency shift, which is of order g2T, from the eigenfrequency.
Calculation of the Nuclear Transition Charge Density in a Microscopic sdgIBM-1
ZHANG Zhan-Jun, SANG Jian-ping, LIU Yong
Chin. Phys. Lett. 2000, 17 (9): 646-648 .  
Abstract   PDF(pc) (271KB) ( 467 )
Formulae of proton and neutron boson structure functions (BSF’s) are deduced in terms of a microscopic approach of sdgIBM (namely, microscopic sdgIBM). For the nucleus 190Os, the value of BSF’s is worked out. Due to the high similarity, the maximum F-spin truncation is made under the full-symmetry approximation. Thereafter, calculations of E2 and E4 transition charge densities (TCD’s) are performed in the sdglBM-1. It is found that the E2 and E4 TCD’s can be reproduced quite satisfactorily in the uniform frame of microscopic sdglBM-1.

Finite-Temperature Phase Structure in the Chiral σ-ω Model with Dilatons
ZHANG Xiao-Bing, LI Xue-Qian, NING Ping-Zhi
Chin. Phys. Lett. 2000, 17 (9): 649-651 .  
Abstract   PDF(pc) (253KB) ( 450 )
We investigate the finite-temperature phase structure in a scaled chiral model which includes the dilaton (glueball) field. It is shown that hot nuclear matter undergoes a discontinuous transition in the mean field of scalar mesons as well as the Lee-Wick abnormal transition. The corresponding behavior of the gluon condensate during the chiral phase transition is also studied.
Relativistic Spin-Isospin Dependent Response Function of Nucleus
LIU Liang-Gang, CHEN Wei, AI Bao-Quan, ZHENG Xiao-Ping, Masahiro Nakano*
Chin. Phys. Lett. 2000, 17 (9): 652-654 .  
Abstract   PDF(pc) (245KB) ( 287 )
A full relativistic formalism is employed to derive the relativistic particle-hole and delta-hole excitation polarization insertion of pion propagator in nuclear matter. The spin-isospin-dependent response function of nucleus at high energy-momentum transfer is calculated with the nuclear matter approximation. The short range correlation effect, two-nucleon absorption and nucleus form factor effects are included in the calculation. The position and width of the resonance peak of the spin-isospin mode are reproduced and found to be coincident with experiment data. The position of the peak and its width is sensitive to Landau-Migdal parameter g’ which is about 0.6.
Measurements of Total Reaction Cross Section for Light Nuclei and Evidence for the Anomalous Nuclear Structure in 15C
FANG De-Qing, SHEN Wen-Qing, FENG Jun, CAI Xiang-Zhou, WANG Jian-Song, SU Qian-Min, ZHANG Hu-Yong, HU Peng-Yun, MA Yu-Gang, ZHU Yong-Tai, LI Song-Lin, WU He-Yu, GOU Quan-Bu, JIN Gen-Ming, ZHAN Wen-Long, GUO Zhong-Yan, XIAO Guo-Qing
Chin. Phys. Lett. 2000, 17 (9): 655-657 .  
Abstract   PDF(pc) (282KB) ( 521 )
Measurements of the total reaction cross section for 12-16C, 14-17N and 16-18O on carbon target at intermediate energies were performed on RIBLL of HIRFL. A larger enhancement of σR for 15C was observed than that for its neighbors. The analysis of these data indicates possible existence of an anomalous nuclear structure in 15C. A new quantity was suggested as the criterion to distinguish anomalous structure nuclei from normal nuclei.

Observation of Electronic shells and Characteristic Products from Mass Abundance Spectra of AI Cluster and AI-C Cluster Anions
LIU Bing-Chen, ZHAI Hua-Jin, ZHOU Ru-Fang, NI Guo-Quan, XU Zhi—Zhan
Chin. Phys. Lett. 2000, 17 (9): 658-660 .  
Abstract   PDF(pc) (269KB) ( 375 )
Using a laser vaporization/pulsed molecular beam cluster source, AI cluster anions and A1-C mixed cluster anions are produced and recorded by a time of flight mass spectrometer. Mass abundance spectra of the AI cluster anions in the size range from AI-2 to AI-42 show that AI-13, AI-23, AI-35, and slightly, AI-37 are local maxima, as predicted by the electronic jellium model. Mixed cluster AInC- and AInC-2 are also shown, among which the most abundant species are AI3C-2, AI6C-2,AI7C- and AI7C-2in the small size range. The formation mechanism of these products is discussed.

Size Determination of Argon Clusters from a Rayleigh Scattering Experiment
LEI An-Le, ZHAI Hua-Jin, LIU Bing-Chen, LI Zhong, NI Guo-Yuan, XU Zhi-Zhan
Chin. Phys. Lett. 2000, 17 (9): 661-662 .  
Abstract   PDF(pc) (183KB) ( 390 )
Argon clusters are produced in the process of adiabatic expansion of a high backing pressure gas into vacuum through a nozzle. The cluster size is determined by a Rayleigh scattering measurement. The scattered signal measured is proportional to the 2.78th power of gas stagnation pressure. The average cluster sizes vary from 100 to more than 12000 atoms/cluster with the argon gas backing pressures ranging between 3 to 45atm.
Reduction of the Resolution Losses in Dual-Wavelength Storage
ZHANG Xin-Zheng, XU Jing-Jun, SUN Qian, Nouel Y. Kamber, LIU Si-Min, LI Fei-Fei, HUANG Hui, ZHGNG Guang-Yin
Chin. Phys. Lett. 2000, 17 (9): 663-665 .  
Abstract   PDF(pc) (252KB) ( 365 )
The dual-wavelength storage for multi-page storage with the nondestructive readout is investigated in the double-doped lithium niobate crystals. The image field losses are minimized by adjusting the readout wave vectors, and the resolution is improved by optimizing the storage setup.
Scaling Law of Nonlinear Compton Scattering
WANG Ping-Xiao, HUO Yu-Kun, WANG Jia-Xiang, FENG Liang, KONG Qing
Chin. Phys. Lett. 2000, 17 (9): 666-668 .  
Abstract   PDF(pc) (261KB) ( 443 )
We show that there are two mechanisms responsible for the net energy exchange between an intense pulsed laser and an electron in vacuum, namely, stimulated Compton scattering and nonlinear Compton scattering(NLCS). For NLCS, being the only effect in a mono-frequency continuous laser beam, its contribution is also independently determined. The characteristics of these two mechanisms in connection with the net energy exchange are studied. For the case of a pulsed laser field, it is found that the maximum net energy exchange by NLCS is approximately proportional to Q20(Q0 ≡ eE0/(me ωc)) for Q0 ≥100. In addition, the relative importance of these two mechanisms to the net energy exchange at different intensities is explored.

Thermal and Mechanical Properties of a Complex Nonlinear Optical Material: Cadmium Mercury Thiocyanate Crystal
YUAN Duo-Rong, XU Dong, ZHANG Guang-Hui, LIU Ming-Guo, GUO Shi-Yi, MENG Fan-Qing, LÜ, Meng-Kai, FANG Qi, JIANG Min-Hua
Chin. Phys. Lett. 2000, 17 (9): 669-671 .  
Abstract   PDF(pc) (223KB) ( 411 )
The data of the thermal expansion and specific heat of cadmium mercury thiocyanate crystal have been obtained. The specific heat is 0.7588 J/g.oC at room temperature. The thermal expansion occurs in the direction parallel to the c-axis, and the thermal contraction occurs in the direction parallel to the a-axis. The thermal expansion is the same as the thermal contraction at 353 K. The relationship between thermal properties and crystal structure is discussed.

Stimulated Emission at 722.9nm by Laser Photodissociation of PbI2 Vapor
MAN Bao-Yuan, ZHANG Jie, NI Pei-Gen, ZHANG Dao-Zhong
Chin. Phys. Lett. 2000, 17 (9): 672-674 .  
Abstract   PDF(pc) (248KB) ( 494 )
The stimulated emission at 722.9nm is observed by a direct photodissociation of the PbI2 molecules with a 266nm pulse laser. The possible dissociation channels are discussed. Two-photon resonant photodissociation mechanism is used to explain the generation of the 722.9nm emission. The emission is measured at different incident laser energy and heat-pipe temperature. The obtained experimental result is well supported by the photodissociation mechanism given by us.
Multi-track Storage of 10000 Holograms in a Disk-Type Photorefractive Crystal
TAO Shi-Quan, JIANG Zhu-Qing, YUAN Quan, LIU Guo-Qing, XU Min
Chin. Phys. Lett. 2000, 17 (9): 675-677 .  
Abstract   PDF(pc) (218KB) ( 495 )
Three-dimensional disk-type holographic storage using spatioangular multiplexing with a spherical reference beam is analyzed and experimentally demonstrated. The overlapping factors between adjacent holograms in a track and between adjacent tracks in a disk are determined based on the selective angles calculated by coupled-wave theory. There are 10000 holograms stored along 5 tracks in a sector of a single iron-doped lithium niobate crystal.
Propagation Properties of Quasi-longitudinal Leaky Surface Acoustic Wave on Y-Rotated Cut Quartz Substrates
TONG Xiao-Jun, WANG Wei-Biao, ZHOU Ran, ZHANG De, QIN Hou-Rong
Chin. Phys. Lett. 2000, 17 (9): 678-679 .  
Abstract   PDF(pc) (183KB) ( 377 )
Propagation properties of the quasi-longitudinal leaky surface acoustic wave (QLLSAW) along different directions on Y-rotated cut quartz substrates, such as on the 34o, 36o, 42o Y-rotated cut, are investigated. The advantages of the QLLSAW along some directions include low propagation attenuation (less than 10-4dB/λ), small power flow deviation and high phase velocity which can be up to 7000 m/s. A novel propagation direction of the quasi-longitudinal leaky surface acoustic wave with the theoretical temperature coefficient of delay of 0.508 ppm/oC is proposed.

Eigenfrequencies of Ion-Acoustic Waves in the Presence of Electron-Ion Collisions
ZHEHG Jian, YU Chang-Xuan
Chin. Phys. Lett. 2000, 17 (9): 680-682 .  
Abstract   PDF(pc) (200KB) ( 364 )
Frequencies and damping rate of ion-acoustic waves in the presence of electron-ion collisions are computed by reducing the linearized electron Fokker-Planck equation and cold-ion fluid equations to an eigenvalue equation via moment expansion of the perturbation of electron distribution function. As electrons becomes less collisional, a great number of Sonine modes are needed for convergence to a desired accuracy in the calculation, which may be ascribed to the neglected electron-electron collisions.
Microstructures of Fe77-xNixCu1Nb2P14B6 Soft Magnetic Alloys Studied by X-Ray Absorption Fine Structure
YIN Shi-Long, BIAN Qing, WE Shi-Qiang
Chin. Phys. Lett. 2000, 17 (9): 683-685 .  
Abstract   PDF(pc) (252KB) ( 374 )
Local structures of the mechanically alloyed Fe77-xNixCu1Nb2P14B6soft magnetic materials have been investigated by x-ray absorption fine structure. The results show that mechanical alloying (MA) can drive the Fe77-xNixCu1Nb2P14B6powder mixture to produce amorphous alloy when the atomic concentration of Fe element is about and over 40%. On the contrary, the MA Fe77-xNixCu1Nb2P14B6is a solid solution with an fcc-like structure in the region o f lower Fe at Fe77-xNixCu1Nb2P14B6 omic concentration (< 22%), preserving a medium-range order around Ni and Fe atoms. Moreover, we have found that the local structure geometry of Fe atom is similar to that of Ni atom for all the MA Fe77-xNixCu1Nb2P14B6 samples. It indicates that the local structures of Fe and Ni atoms in a Fe77-xNixCu1Nb2P14B6 sample only depend on the x value of element Ni after ball milling.
Influences of H+ Implantation on the Boron-Doped Synthesized by Chemical Vapor Deposition Diamond Films
WANG Shuang-Bao, ZHU Pei-Ran, WANG Yu-Guang, FENG Ke-An
Chin. Phys. Lett. 2000, 17 (9): 686-688 .  
Abstract   PDF(pc) (315KB) ( 447 )
Diamond films (DF) were preliminarily B doped in situ during chemical vapor deposition. Subsequently, the films were implanted with 120 keV H+ to dose of 5 x 1014 ~ 5 x 1016cm-2. After the implantation, the B doped DF become insulating and Raman measurements indicate that the implantation has amorphous carbon and graphite etched. It is known that the formation of H-B pairs plays an important pole in property changes. However, for larger dose cases, the electrical resistance of DF is influenced by radiation damage and/or non-diamond phases. In addition to them, annealing makes the specimens conducting again. This phenomenon maybe has potential for application in designing DF device.
Frenkel-Kontorova Model of the Dimerized Overlayer System with Vacancies
XU Hai-Bo, WANG Guang-Rui, CHEN Shi-Gang
Chin. Phys. Lett. 2000, 17 (9): 689-690 .  
Abstract   PDF(pc) (188KB) ( 353 )
The reconstruction of the dimerized overlayer system with vacancies is studied via a diatomic chain Frenkel-Kontorova model. We present the details of the exactly solvable model and the analytical solution of the atomic displacements in the ground state. Our calculations explain the 2 x N reconstruction observed in Ge/Si(100) and Ga/Si(112).
Backward Secondary Electron Emission Yield of Thick Targets Induced by MeV Ions
JIANG Lei, ZHOU Zhu-Ying, ZHAO Guo-Qing
Chin. Phys. Lett. 2000, 17 (9): 691-693 .  
Abstract   PDF(pc) (265KB) ( 363 )
The backward secondary electron emission yields of MeV ions (H+, He+, He++, Cl, Si, and Cu ) impinging on thick carbon and gold targets are studied. The measured results for H+ (1 MeV≤ E≤ 5MeV) on carbon are proportional to the electronic stopping power. Our experimental data and fitting formula of yields for H+ (1 MeV≤ E≤ 4.5 MeV) impacting Au are compared with the theoretical expectation. The influence of the collective field and the charge state of ions on the secondary electron emission yield is discussed.

Structural and Optical Characterizations of ZnO Films Grown by Reactive Electron Beam Evaporation
WU Hui-Zhen, XU Xiao-Ling, QIU Dong-Jiang, HE Ke-Ming, SHOU Xiang
Chin. Phys. Lett. 2000, 17 (9): 694-696 .  
Abstract   PDF(pc) (378KB) ( 696 )
Low temperature epitaxial growth of ZnO films is achieved on Si(001) substrates by reactive electron beam evaporation. Growth temperature is varied from 125°C to 420°C and the optimum temperature is found between 200°C and 300°C. X-ray diffraction shows that the ZnO films are highly c-axis oriented and the line width of (002) diffraction peak is significantly smaller than that measured from the ZnO films deposited by magnetron sputtering. The combined photoluminescence and photoluminescence excitation (PLE) spectroscopic measurements demonstrate the sharp band-absorption edge and exciton absorption in the ZnO films. PLE has also revealed that the absorption characteristic near the band edge is remarkably improved with the increase of oxygen content in the ZnO films, although x-ray diffraction analysis shows that the crystalline structure of ZnO films grown under different oxygen pressures remains unchanged.
Studies on the Surface Interaction and Dispersity of Silver Nanoparticles in Organic Solvents
ZENG Rong, RONG Min-Zhi, ZHANG Ming-Qiu, ZENG Han-Min
Chin. Phys. Lett. 2000, 17 (9): 697-699 .  
Abstract   PDF(pc) (428KB) ( 697 )
Silver nanoparticles with different sizes have been prepared by microemulsion and have been surface-modified with C12H25SH. Electron spin resonance results indicate that there exist some kinds of surface local paramagnetic sites in capped Ag nanoparticles, which leads to the relation between electron spin resonance parameters and particle size deviating from Kawabata's description. There is a strong interaction between nanosilver and chloroform. The smaller the particles, the stronger the interaction. Transmission electron microscopy and ultravilolet-visible absorption spectra confirmed that Ag nanoparticles are well dispersed in chloroform, implying that a good dispersity of Ag nanoparticles in polymers could be obtained by means of solution mixing by using chloroform as the solvent.

New Age Indicators for Stellar Populations
KONG Xu, , CHENG Fu-Zhen,
Chin. Phys. Lett. 2000, 17 (9): 700-702 .  
Abstract   PDF(pc) (305KB) ( 332 )
We apply the method of principal component analysis to a sample of simple stellar populations to select some age sensitive spectral indices. Besides the well-known age sensitive index Hβ, we also find some new age sensitive indices, G4300 and Fe4383, C24668, and Mgb. In addition, we find that these spectral indices sensitive to age depend on the metallicity of stellar population, Hβ and G4300 are more suitable to determine the age of low metallicity stellar population, while C24668 and Mgb are more suitable to the high metallicity stellar population.
27 articles