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Volume 15 Issue 2
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Original Articles
Foam-Like Structure Created From (1+1) Dimensional Vacuum Fluctuation
LIU Liao, XU Dian-yan
Chin. Phys. Lett. 1998, 15 (2): 79-80 .  
Abstract   PDF(pc) (123KB) ( 411 )
As is known, the two-dimensional (2D) gravitational theory is a very good toy model for studying the four-dimensional gravitational theory. Now in this paper, it is shown that the vacuum fluctuation in 2D gravity can create a foam-like structure of space-time, which is constructed from wormhole.
A More Restrictive Upper Bound for the Bare Pomeron Intercept
HE Bo, PENG Fei, ZHU Wei
Chin. Phys. Lett. 1998, 15 (2): 81-82 .  
Abstract   PDF(pc) (141KB) ( 334 )
By studying the properties of the modified Gribov-Levin-Ryskin evolution equation which incorporates both shadowing and antishadowing effects, the more restrict upper bound is set for the bare pomeron intercept in the case when gluons uniformly distribute within the proton.
Colored Particle Acceleration by Fluctuations in Quark-Gluon Plasma
ZHENG Xiao-ping, LI Jia-rong
Chin. Phys. Lett. 1998, 15 (2): 83-85 .  
Abstract   PDF(pc) (181KB) ( 447 )
The energy variation of a parton passing through a quark-gluon plasma(QGP) is discussed by taking into account nonlinear polarization effect. It is found that the parton can be accelerated by fluctuations in QGP, which gives a new physical insight about the response of QGP to such external current.
Correlation of final state Interaction with the Detection Phase Space
YANG Chun, CHEN Tao, YE Yan-lin, YING Jun, XU Chun-cheng, LIU Hong-tao
Chin. Phys. Lett. 1998, 15 (2): 86-88 .  
Abstract   PDF(pc) (204KB) ( 553 )
The final state interaction between the emitting particles has been expected to play an important role to discriminate the signal and background channels in the experiment which detects low mass dibaryon. Theoretically this effect is shown most clearly in the invariant mass spectrum which display a narrow peak for the dibaryon decaying particles and a flat distribution for the background particles. But our detailed simulation study indicates that the detection phase space will largely change the shape of the spectra. The calculation for TRIUMF-E772, which is designed to search for d* dibaryon, shows that the spectra of signal and background become similar to each other and therefore the discrimination is certainly ineffective.
Single Minimal Supersymmetric Extension of Standard Model Higgs Production in γγ Collision
ZHU Shou-hua, LI Chong-sheng, GAO Chong-shou
Chin. Phys. Lett. 1998, 15 (2): 89-91 .  
Abstract   PDF(pc) (201KB) ( 446 )
The cross sections of the single minimal supersymmetric extension of standard model(MSSM) Higgs production in γγ collision based on next linear collider with the e+e- center-of-mass energy 500 GeV have been calculated. Contributions to the cross sections arising from stops mixing are significant and have been emphasized. And the MSSM single Higgs production cross sections, which are typically in the range of 0.01 fb to several hundreds of fbs, can be comparable to that of standard model at appropriate parameters values.
Half-Lives of Low-Lying Isomeric States in 169Ta
ZHANG Yu-hu, ZHAO Qing-zhong, ZHU Shao-fei, XU Hu-shan, ZHOU Xiao-hong, GUO Ying-xiang, LEI Xiang-guo, LU Jun, GOU Quan-bu, LIU Zhong, JIN Han-juan, LUO Yi-xiao, SUN Xiang-fu, ZHU Yong-tai
Chin. Phys. Lett. 1998, 15 (2): 92-94 .  
Abstract   PDF(pc) (222KB) ( 436 )
Two low-lying isomeric states in 169Ta have been identified via 159Tb(l6O, 6n γ )169Ta reaction. Their half-lives are measured to be 28 ± 5ns for the 9/2- level and 17 ± 4 ns for the 5/2- level by using the delayed γ-γ coincidence method. These two isomeric states are considered to be the bandheads with 9/2-[514] and 1/2-[541] configurations, respectively. Possible neutron quasiparticle configuration for the ground state of 169W is discussed.
Fission-Like and Reaction Time in 8.5 MeV/u 84Kr+27A1 Reaction
JIANG Dong-Xing, LIU Xin
Chin. Phys. Lett. 1998, 15 (2): 95-97 .  
Abstract   PDF(pc) (230KB) ( 537 )
Reaction time of the deeply inelastic reaction in 8.5MeV/u 84Kr+27A1 was estimated to be 8 ×10-21s by extracting pre-scission α and proton multiplicities and by statistical model (PACE4) calculations. By using this reaction time value, the diffusion model calculations for the charge number distribution of fragments nicely explained the experimental results for the reactions at three incident energies 5.8, 8.5 and 10.6MeV/u. It is indicated that a considerable fission-like component has contributed to the symmetric splitting fragments in the reactions, especially at 8.5 and 10.6 MeV/u.
Energy Level for a Type of Three-Particle Hamiltonian with Kinetic Couplings
FAN Hong-yi, ZHANG Ying
Chin. Phys. Lett. 1998, 15 (2): 98-100 .  
Abstract   PDF(pc) (172KB) ( 433 )
For a triatomic molecule described by the Harniltonian with kinetic energy couplings, H = P21/(2m) +P22/(2m) + P23/(2M) + kP1P2 + KP1P3 + KP2P3 + V1(X2–X1 ) + V2[x3 - ( X1+ X2) / 2 ] , its energy level formula is derived. The cases are consider when the potentials Vi (i = 1,2) are harmonic oscillator, or Morse potential, separately. Squeezing mechanism involved in the approach for solving this dynamic problem is revealed.
Calculation of the High-n Dielectronic Satellites of Kα Resonance Lines for Heliumlike Iron
WANG Jian-guo, CHANG Tie-qiang, DONG Chen-zhong
Chin. Phys. Lett. 1998, 15 (2): 101-102 .  
Abstract   PDF(pc) (186KB) ( 374 )
A simplified relativistic configuration interaction method is used to study the dielectronic satellite transition processes, in which the whole high-n dielectronic satellite transition processes can be treated conveniently in the frame of quantum defect theory. The theoretical results for heliumlike iron are in good agreement with the experimental measurements.

Electronic Properties of Solid Composed of Al12Ge Clusters
ZHU Zi-zhong, TIAN Bo, HUANG Mei-chun
Chin. Phys. Lett. 1998, 15 (2): 103-105 .  
Abstract   PDF(pc) (225KB) ( 339 )
The ab initio pseudopotential local-density studies on the electronic structure and geometry of a theoretical solid are presented with Al12Ge cluster serving as the building block of the material. The results show that bulk material formed from cubic close-packing of All2Ge clusters will eventually be an aluminum-like metal when lattice parameter of the solid and atomic geometry of the clusters are optimized by the crystal field.
Properties of Boron-Substituted Heterofullerenes
ZOU Ying, LUO Min-xing, WANG Zhi-jian, LI Wen-zhu
Chin. Phys. Lett. 1998, 15 (2): 106-108 .  
Abstract   PDF(pc) (214KB) ( 416 )
On the basis of a succinct description of geometrical configurations for giant fullerenes, the electronic properties and structural distortions of heterofullerenes CN-1B ( N = 60,180,240,420,540,720,780) are analyzed by the extended Su-Schrieffer-Heeger model. In comparison with their pristine fullerenes CN, local distortions and mid-gap states are found to occur in boron-doped giant fullerenes.
Generation of Squeezed States in Forward Three-Wave Mixing
LÜ, Ya-jun, WU Ling-an, WU Mei-juan, LI Shi-qun
Chin. Phys. Lett. 1998, 15 (2): 109-111 .  
Abstract   PDF(pc) (226KB) ( 447 )
We present a study of the generation of squeezed states through nonlinear three-wave mixing in media with an intensity-dependent index of refraction. In the semiclassical model, perfect squeezing for combination modes can be generated. Using the Fokker-Planck equation approach, the effects of pump (including squeezed pump) and loss are discussed. It is shown that the fluctuations of the pump place no fundamental limit to the degree of squeezing obtainable but losses do give an absolute limit.
Narrow Linewidth, Nanosecond Pulsed Optical Parametric Oscillator with a Compound Cavity
XU Zu-yan, KONG Yu-fei, ZHOU Yi, DENG Dao-qun, ZHU Xiang-an, WU Ling-an
Chin. Phys. Lett. 1998, 15 (2): 112-114 .  
Abstract   PDF(pc) (300KB) ( 553 )
We report a new type of optical parametric oscillator (OPO) cavity, i.e., a compound cavity OPO. Both the numerical simulation and experimental results show that this type of cavity is superior, in that its threshold is lower than that of a simple narrow-band cavity with dispersive elements, and its external efficiency is increased while its narrow linewidth remains nearly the same across the tunable range of the nonlinear crystals used.
Experimental Study of Sterilizing Molds by Ultrasound
REN Jin-lian, NIU Yong
Chin. Phys. Lett. 1998, 15 (2): 115-116 .  
Abstract   PDF(pc) (238KB) ( 603 )
An ultrasound method of sterilizing aspergillus flavus and fusarium is proposed and demonstrated. The dependence of sterilizing effect on ultrasonic intensity, frequency, and treatment time is experimentally investigated. The density of surviving spores decreases first with increasing ultrasonic frequency and then increases with the further increase of the frequency, that is to say, there exists the optimum frequency 26 kHz at which the killing rate is near 100%. The killing rate seems proportional to the intensity and the time.

Analytic Solution of an Asymmetrical Crack in a Strip
YANG Xiao-chun, WANG Lu, FAN Tian-you
Chin. Phys. Lett. 1998, 15 (2): 117-119 .  
Abstract   PDF(pc) (132KB) ( 440 )
We present the analytic solution of an asymmetrical crack in a strip from which the stress intensity factors are determined. The results have important application in earthquake source physics and provide information concerning the instability of faults and the detection of earthquake precursors.
Characterization of Magnetron Sputter CNx Thin Films
ZHENG Wei-tao, J. E. Sundgren
Chin. Phys. Lett. 1998, 15 (2): 120-122 .  
Abstract   PDF(pc) (236KB) ( 532 )
Carbon nitride thin films were deposited at different substrate temperature (ST) by using reactive magnetron sputtering in a pure N2 discharge, and studied by laser Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometer. The Raman spectra of the films show that I(D)/I(G) decreased with the increase of ST. The D bandposition shifted towards lower frequency, while the G bandposition shifted towards higher frequency as the ST increased. The XPS data exhibit that Nls binding states also depend on ST. The optical band gap of the films is found dropped from 0.22eV to 0.10eV with the increase of ST.
Charge-Density Wave in 2H-NbSe2 Observed by Scanning Tunneling Microscopy at 4.3K
YANG Hai-tao, TAO Hong-jie, ZHAO Zhong-xian
Chin. Phys. Lett. 1998, 15 (2): 123-124 .  
Abstract   PDF(pc) (0KB) ( 424 )
Charge-density waves (CDWs) on a cleaved surface of 2H-NbSa2 have been observed at 4.3 K with a home-built low temperature scanning tunneling microscope(STM). The STM images revealed well-resolved atomic modulation, CDW modulation, and combined periodic lattice distortion resulting from the CDW.
Charge States of DX Centers and Electronic Raman Scattering in n-Ga1-xAIxAs
LIAN Shi-yang
Chin. Phys. Lett. 1998, 15 (2): 125-127 .  
Abstract   PDF(pc) (202KB) ( 409 )
The observation of the electronic Raman scattering in n-Gal-xAIxAs (x > 0.45) is reported and the charge state of DX centers in III-V alloy semiconductors is discussed. The result shows clearly that the electronic Raman scattering in n-Gal-xAIxAs of indirect band-gap and the persistent photoconductivity in n-Gal-xAIxAs of direct band-gap are equivalent to each other. Both of them originate from the optical induced metastable state of donors in n-Gal-xAIxAs (x > 0.22) at low temperatures. At higher temperatures, this hydrogen-like level is depopulated to the benefit of a stable DX-like deep state.


Fano Resonance and Persistent Currents in a Mesoscopic Open Ring with a Flux Loop in Side-Branch
WEI Lian-fu, WANG Shun-jin, JIA Huan-yu, JIE Quan-lin
Chin. Phys. Lett. 1998, 15 (2): 128-130 .  
Abstract   PDF(pc) (234KB) ( 439 )
Persistent circulating currents in a mesoscopic open ring with side-branch structures are derived by transfer matrix method in the framework of quantum waveguide theory on networks. The behavior of transmission probability may show the Fano resonance in the presence of geometric scattering of side-branch structures. It is shown that persistent circulating currents in the main loop with equal length of both arms in the absence of magnetic Aux occur near the Fermi wave vectors where the Fano resonance appears. The numerical results show that a larger persistent current is associated with a stronger Fano resonance. The persistent circulating currents can be controlled by the Aux of side-branch structure.
Magnetic Study on Kondo Semiconductor CeNiSn
HOU Yu-min, JIN Duo, YANG Fu-ming, RAN Qi-ze, WANG Yu-peng, CHEN Zhao-jia, HE Yu-sheng
Chin. Phys. Lett. 1998, 15 (2): 131-133 .  
Abstract   PDF(pc) (230KB) ( 417 )
There are two standpoints to explain the formation of the peak of magnetic susceptibility versus temperature in CeNiSn. One is the presence of the pseudo-gapped density of states (DOS) while the other is the development of an antiferromagnetic correlation. To check which one is more reasonable, an experiment is designed on measuring magnetic susceptibility under different magnetic fields. It is found that magnetic field can shift the peak of the magnetic susceptibility to lower temperatures while by calculation the presence of the pseudo-gapped DOS cannot shift the peak, which gives another evidence of the existence of antiferromagnetic correlations and is discussed in the light of some recent theoretical model.
Structure and Magnetocaloric Properties in Perovskitelike Lal-xNaxMnOz Powders
CHEN Wei, ZHONG Wei, HOU Deng-lu, DING Wei-ping, DU You-wei, YAN Qi-jie
Chin. Phys. Lett. 1998, 15 (2): 134-136 .  
Abstract   PDF(pc) (214KB) ( 382 )
Perovskitelike manganese oxides Lal-xNaxMnOz (x = 0.075, 0.100, 0.165, 0.200) have been fabricated using sol-gel technique. Structure analysis, temperature programmed reduction (TPR) technique and magnetic measurement have been used to study the effect of Na ion substituted amount on Mn-O distance, the oxygen content, and the magnetocaloric properties of these materials. Results show there is no clear correlation between the substituted amount and mean Mn valence, but a close relationship is observed between Tc and the bond distance of Mn-O. These materials have quite large magnetic entropy changes upon an application of a low magnetic field and can be utilized as more suitable candidates for magnetic refrigerants with wide temperature span.



Color Tunable Light-Emitting Diodes Based on Polymer/Inorganic Heterojunction
TAN Hai-shu, CHEN Li-chun, WANG Xiang-jun, YAO Jian-quan, JU Chuan-xi, XIE Hong-quan, GAO Guang-hua
Chin. Phys. Lett. 1998, 15 (2): 137-139 .  
Abstract   PDF(pc) (253KB) ( 471 )
By using p-type polymer poly(2,5-Didodecyloxy-1, 4-Phenylenylenevinylene) (PDDOPV) and n-type inorganic material ZnO:Zn, the electronluminescent (EL) emission from bilayer device based on polymer/inorganic hetero-junction was successfully demonstrated. In comparison with single layer polymer device, with dc voltage of 10V, the brightness and luminous efficiency of bilayer device were enhanced 14 and 26 times, respectively. The EL spectrum of bilayer device is not identical to the characteristic emission spectrum of either PDDOPV or ZnO:Zn, and shifts continuously towards to short wavelength direction as the applied voltage increases.
Fractal Linear Arrays
XU Liang, WU Zhen-sen, WANG Wen-bing
Chin. Phys. Lett. 1998, 15 (2): 140-142 .  
Abstract   PDF(pc) (175KB) ( 547 )
The general expression of the fractal linear array factors is derived. The similarity of the patterns and their fractal features are examined. The relation between the maximum side-lobe and the fractal dimension is shown.

Quantum Confinement in InSb Microcrystallites Embedded in SiO2 Thin Films
ZHU Kai-gui, SHI Jian-zhong, ZHANG Li-de
Chin. Phys. Lett. 1998, 15 (2): 143-145 .  
Abstract   PDF(pc) (334KB) ( 761 )
Semiconductor InSb microcrystallites were embedded in SiO2 thin films by rf cosputtering technique. Structures of the thin films were characterized by transmission electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. Average size of the microcrystallites, depending on post-annealing temperature and time, is on the order of magnitude of nanometer. Absorption spectra of the films were measured and large blue shifts of absorption edge were observed in a wide range from 300 to 1500nm. The blue shifts were attributed to the quantum confinement effect and explained in the model of effective-mass approximation.
Investigation of Diamond Films Deposited on LaAIO3 Single Crystal Substrates by Hot Filament Chemical Vapor Deposition
SHANG Nai-gui, FANG Rong-chuan, HANG Yin, LI Jin-qiu, HAN Si-jin, SHAO Qing-yi, CUI Jing-biao, XU Cun-yi
Chin. Phys. Lett. 1998, 15 (2): 146-148 .  
Abstract   PDF(pc) (402KB) ( 396 )
Diamond nucleation and growth on a LaAIO3 single crystal substrate, whose lattice mismatch with diamond is only 7.2% at high temperature, were investigated for the first time. As an insulating substrate, a nucleation density of more than 108 cm-2 was achieved on ultrasonically cleaned wafers. A free-standing diamond film was obtained for 65 h growth and characterized by scanning electron microscopy, Raman and x-ray photoelectron spectroscopy. The results show that LaAIO3 single crystal is a good candidate substrate for diamond film growth.
Solidification of Undercooled Ge73.7Ni26.3 Alloy Subjected to Sputtering-Deposition of Ni Clusters
LIU Ri-ping, JING Qin, CAO Li-min, ZHANG Ming, ZHANG Fu-xiang, ZHANG Xiang-yi, ZHAO Jian-hua, HE Duan-wei, XU Ying-fan, WANG Wen-kui,
Chin. Phys. Lett. 1998, 15 (2): 149-151 .  
Abstract   PDF(pc) (466KB) ( 615 )
Undercooled melt of Ge73.7Ni26.3 alloy sample floated on B2O3 melt was subjected to sputtering-deposition of Ni clusters on cooling to induce solidification. The initial temperature of solidification was 975 K. Its undercooling ΔT was 134 K with respect to the melting temperature of the primary phase Ge. On the cooling curve existed dual recalescences representing the transformation of the primary phase (Ge) and the eutectics (Ge+GeNi) respectively. But for the sample unsputtered, only a single exothermic peak presented on the cooling curve with the initial solidification temperature of 904K and undercooling of 205K. Careful observation of the microstructure proved that the Ge phase primarily formed in the sputtering experiment was now formed together with the formation of the eutectics in the experiment without sputtering.
Stochastic Resonance in a Coupled Neuronal Network
LIU Feng, WANG Wei
Chin. Phys. Lett. 1998, 15 (2): 152-154 .  
Abstract   PDF(pc) (235KB) ( 358 )
Stochastic resonance in a globally coupled neuronal network has been studied via numerical simulation. The ability of the network to detect a weak (subthreshold) periodic signal can be optimized to a high signal-to-noise ratio with a long plateau as the noise intensity increases. This may interpret the strong ability of neurons to process information in biological system.
Disruption of Charged Dust Grains in Cometary Plasma Environments
SHI Zhi-dong, LI Zhong-yuan, CHEN Yao
Chin. Phys. Lett. 1998, 15 (2): 155-156 .  
Abstract   PDF(pc) (159KB) ( 656 )
The equilibrium potential and dust fragmentation criterion of fluffy dust grains in plasma are calculated for comet P/Halley. It is found that the dust grain acquires its largest negative potential and disruptive probability about 50000km from the comet where the dust mass spectrum measured by the spacecraft took a great change.
28 articles