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Volume 10 Issue 1
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Original Articles
Proportions of Different Unit-Cells in a Projection Lattice
SUN Jirong
Chin. Phys. Lett. 1993, 10 (1): 1-4 .  
Abstract   PDF(pc) (195KB) ( 599 )
A general formula for determinating the proportions of different unit-cells in a projection lattice is given. It is found that there exist certain relations between the occurrence frequency of a specified unit-cell in the aperiodic lattice and the projection (in a special subspace E2') of the corresponding facets of the hyper-unit-cell of the n-dimensional periodic lattice. Based upon these, some special cases are discussed.

Faddeev-Jackiw Quantization of the Gauge Invariant Version of the Linear Self-Dual constrained Theory
MIAO Yangang, LIU Yaoyang*
Chin. Phys. Lett. 1993, 10 (1): 5-7 .  
Abstract   PDF(pc) (144KB) ( 438 )
The Faddeev-Jackiw quantization procedure is applied to the gauge invariant version of the linear self-dual constrained theory. The equivalence of the gauge invariant and the gauge noninvariant versions is discussed.

Variational Calculation of the Excited States in the Sing-Gordon and Sine-Gordon Field Theories
LU Wenfa, XU Bowei
Chin. Phys. Lett. 1993, 10 (1): 8-10 .  
Abstract   PDF(pc) (117KB) ( 495 )
The one- and two-particle states in the sinh-Gordon and sine-Gordon models in (1+1) dimensions are investigated by using the gaussian wave-functional approach. We find that (i) the renormalized mass parameter is just the variational one particle mass, and (ii) there are no two-particle bound states in the sinh-Gordon model, but in the sine-Gordon model, there exist two-particle bound states.

Theoretical Calculation of Differential Cross Section for e+-Ar and e--Ar Elastic Scattering
HOU Qing, LIU Lei*, LI Jiaming**
Chin. Phys. Lett. 1993, 10 (1): 11-14 .  
Abstract   PDF(pc) (236KB) ( 533 )
The differential cross sections for e--Ar and e+-Ar elastic scattering are calculated by relativistic partial wave expansion method. In the processes an incident particle (electron or positron) is treated as moving relativistically in an effective central potential. For electron-atom scattering, the effective potential is calculated by relativistic self-consistent-field (SCF) method with the Slater local exchange approximation. For the positron scattering, the effective potential is the electrostatic potential determined by the ground-state electron charge density calculated by the SCF method. For atomic target polarization due to the incident charge particle(e1ectron or pwitron), the effect is treated approximately by adding a static polarization potential to the SCF potentials. The calculated results show that the polarization effect is very important for the low energy positron-atom scattering.

Pinhole Technique Tunable VUV Generation by Nonresonant Four-Wave Sum-Mixing in Xenon
TIAN Cechan, SUN Taoheng
Chin. Phys. Lett. 1993, 10 (1): 15-17 .  
Abstract   PDF(pc) (183KB) ( 482 )
A pinhole structure has been adopted to serve as the exit window in efficient generation of tunable vacuum ultraviolet (VUV) radiation (115.0-119.0nm) by nonresonant four-wave sum-mixing in Xe. The generated VUV intensity is greatly enhanced when Xe is matched with Ar. Calculations have been done to analyse the roles of phase-matching and to predict the optimum pressure ratio of Xe to Ar.

Effective Visible Emission from Porous Silicon
WENG Yumin, FAN Zhineng, ZONG Xiangfu
Chin. Phys. Lett. 1993, 10 (1): 18-20 .  
Abstract   PDF(pc) (179KB) ( 683 )
Concentration of Si-H2 bond in porous silicon layer (PSL) affects its photolu-minescence (PL) intensity and peak wavelength PL emission characters of PSL associate with not only its micro-structure, but also the Si-H2 band. So a stabilization of the emission intensity and the peak wavelength can be achieved by proper photochemical processing. A stable effective PL emission at wavelength as short as 570nm can be observed on PSL made by anodization method.

Bipartition Model Studies of the Particle and Energy Reflection Coefficients of Fusion α-Particles from the First Wall
LUO Zhengming*, JIANG Bin
Chin. Phys. Lett. 1993, 10 (1): 21-24 .  
Abstract   PDF(pc) (188KB) ( 395 )
The particle and energy reflection coefficients of fusion α-particles which leak out from the plasma boundary in a fusion device and bombard the first wall with various incident directions are calculated by the newly-improved bipartition model for light ion transport. The influence of surface barrier upon the reflection of α-particles with low energy is investigated as well. The validity of bipartition model can be shown by the comparison of computational results with relevant experimental data.

Initial Evolution of a Laser Wake-Field in Plasmas
SHENG Zhengming, MA Jinxiu, YU Wei, XU Zhizhan,
Chin. Phys. Lett. 1993, 10 (1): 25-28 .  
Abstract   PDF(pc) (229KB) ( 459 )
Numerical calculations are used to study the initial temporal evolution of the wake-field produced by a short laser pulse. Results are compared to the previous quasi-static solutions. The usually adopted quasi-static approximation is found not appropriate for describing the wake-field generation at initial stages.

Sduties on Modification of Pb1-xBaxNb2O6 Crystals
SONG Yongyuan, CHEN Huanchu, ZHANG Peilin*, ZHONG Weilie*
Chin. Phys. Lett. 1993, 10 (1): 29-32 .  
Abstract   PDF(pc) (203KB) ( 411 )
This paper reports the growth of pqre and Na, K modified lead barium niobate crystals and the measurement of their dielectric and structure properties. Exprimental results show that both pure and Na, K modified lead barium niobate crystals have growth striations. All the crystals belong to 4mm point group of
tetragonal system at room temperature. Their Curie temperature are 379°C, 389°C and 473°C, respectively.

Growth and Properties of Tungsten Bronze-Type Second Harmonic Generation Crystal LiBa2Nb5O15
CHENG Ruiping, DONG Shengming, SONG Yongyuan, ZHANG Peilin*, ZHONG Weilie*
Chin. Phys. Lett. 1993, 10 (1): 33-36 .  
Abstract   PDF(pc) (198KB) ( 492 )
Striation-free LiBa2Nb5O15 (LBN) single crystal of good optical quality has been grown by Czochralski method. The crystal growth and dielectric, structural, spectral properties of LBN were measured. Experimental results show that LBN single crystal belongs to tetragonal tungsten bronze structure at room temperature. Experiments carried out with LBN powder samples have shown that this crystal has good second harmonic generation effect. At room temperature, the dielectric constant 33 is about 87 and Curie temperature Tc, is about 586°C. A very ideal uniaxial conoscope image can be observed in LBN single crystal under polarizing microscope. In the range of 600 to 2600nm, the transmission of single crystal is about 75%.

Positron Annihilation During Pre-crystallizat ion Process in an Amorphous Silver Ionic Conductor
CAO Shixun*, CHEN Liquan**, XUE Rongjian**, HE Yusheng, YU Weizhong
Chin. Phys. Lett. 1993, 10 (1): 37-40 .  
Abstract   PDF(pc) (228KB) ( 568 )
The study of positron annihilation on amorphous 0.60AgI-O.25Ag2O-0.15P2O5 has been carried out in the temperature range from 100 to 350K. The temperature dependence of average lifetime shows anomalous peaks at 208, 228, 325, 338 K indicating possible structure relaxation. Especially the last two peaks reflect the structural changes during pre-crystallization process of the amorphous ionic conductor. These results are consistent with that of ultrasonic attenuation and ionic conductivity experiments on the same samples.

Electronic Structure Calculation of NbCx
SHEN Yaowen, CHEN Lixuan, LI Junda, HUANG Meichun
Chin. Phys. Lett. 1993, 10 (1): 41-44 .  
Abstract   PDF(pc) (196KB) ( 435 )
The changes of electronic structure with the concentration x in BI structure NbCx, are calculated by means of the LDF-LMTO-ASA supercell statistical method. It is shown that the trend of total density of states on the fermi Surface(EF)changing with x is consistent with the results of experiments on the whole.

Microstructure Study in Slow Neutron Irradiated Bi-2223
SHEN Guangjun*, JI Helin, JIN Jirong, JIN Xin, ZHANG Yitong, XU Xiaonong, YAO Xixian
Chin. Phys. Lett. 1993, 10 (1): 45-48 .  
Abstract   PDF(pc) (466KB) ( 698 )
The effect of slow neutron irradiation at a low Auence of about 108n/cm2 on the microstructures of Bi-2223 polycrystalline samples was observed by transmission electron microscopy. By comparative study of the defect structures in a given area in one sample, we get evidence for the flux pinning enhancement by low Auence slow neutron irradiation.

New 1222-Type Thallium-Indium Layered Cuprates (Tl, In)Sr2(Nd, Ce)2Cu2Oz and Their Superconductivity
CHEN Zuyao*, TANG Yongqiu**, Z. Z. Sheng, Y . F. Li, D. O. Pederson,
Chin. Phys. Lett. 1993, 10 (1): 49-52 .  
Abstract   PDF(pc) (237KB) ( 425 )
A new series of 1222-type thallium-indium layered cuprate compounds (Tl, In)Sr2(Nd, Ce)2Cu2Oz have been successfully synthesized in the pure or nearly pure form and identified by powder x-ray diffraction analyses. The structure of the compounds is directly related to that of Nb-1222 NbSr2(Nd, Ce)2Cu2Oz, with a tetragonal body-center lattice. The lattice parameters are a=3.85Å, c=29.56Å for (Tl0.7ln0.3)Srz(Nd0.5Ce0.5)2Cu2Oz, and a=3.85Å, c=29.28Å for lnSr2(Nd0.75Ce0.25)2Cu2Oz. Resistance measurements showed that (T11-xInx)Sr2(Nd0.75Ce0.25)2Cu2Oz(x ≤ 0.8) are superconducting with Tc(onset)=30-40K .

Formation of Superconducting Phases in Electron-Doped Nd1.85Ce0.15CuO4-y
YAO Yushu, JIN Changqing, WU Bingqing, WANG Wenkui, ZHAO Zhongxian
Chin. Phys. Lett. 1993, 10 (1): 53-56 .  
Abstract   PDF(pc) (228KB) ( 444 )
The effect of annealing process in flowing nitrogen on the formation of super-conducting phases in Nd1.85Ce0.15CuO4-y has been investigated. Two super-conductingphases with onset temperature Tcons of about 15 and 25K might be formed when the samples were annealed at various temperatures ranging from
850°C to 870°C and from 880°C to 920°C, respectively. The dependence of Tcons on the annealing temperature was reported.

Parabolic Equation Modeling of Microwave Propagation over Irregular Terrain
YUAN Xiaojun, LIN Weigan
Chin. Phys. Lett. 1993, 10 (1): 57-60 .  
Abstract   PDF(pc) (146KB) ( 686 )
A new method in the parabolic equation modeling of microwave propagation is developed to cope with the problem of radiowave propagation over irregular terrain in the presence of atmospheric refraction effects.

Photogravitationally Restricted Three-Body Problem and Coplanar Libration Point
ZHENG Xuetang, YU Lizhong
Chin. Phys. Lett. 1993, 10 (1): 61-64 .  
Abstract   PDF(pc) (200KB) ( 511 )
The photogravitationally restricted three-body problem in which the mass reduction factors of two primaries q1, q2 ∈ (-∞,1] is studied and the calculating formula of the location of coplanar libration points is given in this paper. As an application, the motion of cometary dust in the solar system and dust grain in binary AR Cas is also discussed.

17 articles