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Volume 10 Issue 5
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Original Articles
Abundant Symmetry Structure of the Kaup-Kupershmidt Hierarchies
HAN Pin*, LOU Senyue
Chin. Phys. Lett. 1993, 10 (5): 257-260 .  
Abstract   PDF(pc) (169KB) ( 493 )
Explicit computation for the Kaup-Kupershmidt (KK) equation shows that there exists an abundant symmetry structure of the KK hierarchy. The recursion operator, inverse recursion operator and the symmetries all can be expressed explicitly by the pseudopotential of the KK equation.
Lee’s Theorem in η-ξ Spacetime
GUI Yuanxing
Chin. Phys. Lett. 1993, 10 (5): 261-264 .  
Abstract   PDF(pc) (160KB) ( 417 )
Lee’s theorem in η-ξ spacetime is discussed. For massless free scalar field, Lee’s theorem is derived from thermal Bogoliubov transformation in η-ξ field theory. For scarlar fields with an arbitrary interaction in η-ξ spacetime, Lee’s theorem is proven by Feynman path-integral method.

Production of 1991r via Exotic Nucleon Transfer Reaction
ZHAO Kui, J. S. Lilley, P. V. Drumm, D. D. Warner, R. A. Cunningham, J. N. Mo
Chin. Phys. Lett. 1993, 10 (5): 265-266 .  
Abstract   PDF(pc) (130KB) ( 285 )
A new nucleus 1991r has been produced using the exotic transfer reaction 198Pt(18O, 17F) 1991r at 140MeV. The mass of 1991r has been measured by the determination of the reaction Q value. Its mass excess is -24.424±0.034 MeV.
Nuclide 202Pt Properties Extrapolated from the Systematic Studies in Pt Chain
FU Deji*, ZHU Zhiyuan, LI Yan
Chin. Phys. Lett. 1993, 10 (5): 267-270 .  
Abstract   PDF(pc) (243KB) ( 371 )
By using a) NpNn scheme systematics, b) algebraic as well as geometrical IBMI calculations and c) the angular momentum projected method the properties of the nuclei in Pt chain are studied. Based on the satisfactory agreements with the existing experimental data, the energy spectra and the groundstate deformation of recent identified neutron-rich nuclide 202Pt are reasonab1y obtained by extrapolating procedure.

Explosion and Limiting Excitation Energy for 20Ne+20Ne Central Collision at Intermediate Energy
GE Lingxiao, ZUO Wei, ZHANG Fengshou
Chin. Phys. Lett. 1993, 10 (5): 271-274 .  
Abstract   PDF(pc) (219KB) ( 425 )
The incomplete fusion-explosion/multifragmentation transition in in termediate energy heavy ion collision has heen investigated within the framework of the Boltzmann- Uehling-Uhlenbeck theory. A detailed analysis for central 20Ne+20Ne collision from 10 MeV/u to 100MeV/u is performed. Quantitative estimates of the excitation energy limit and the explosion threshold are given for 20Ne+20Ne central collision.
Peripheral Collisions on 20Ne+20Ne at 25 MeV/A
GE Lingxiao, ZHU Quanling
Chin. Phys. Lett. 1993, 10 (5): 275-278 .  
Abstract   PDF(pc) (216KB) ( 376 )
Peripheral collisions for 20Ne+20Ne system at 25 MeV/A were analysed in detail by means of quantum molecular dynamics model. Its characteristics, coexistences and competitions between deep inelastic collision and fragmentation were discussed, the rnechanism giving rise to intermediate mass fragments were also explored.
Dynamical Study of the Radiation Environment at the Interaction Region of BEPC
CHEN Yu, GU Yifan, LI Jianping, TANG Yueli
Chin. Phys. Lett. 1993, 10 (5): 279-281 .  
Abstract   PDF(pc) (188KB) ( 442 )
A method to study dynamically the radiation environment at the interaction region of the Beijing Electron-Positron Collider is described. It is shown that the radiation levels are closely correlated to the beam conditions of the collider: most radiation occurs during injection and sudden loss (or dump) of beam, while Colliding beams produce at least an order of magnitude less radiation background which decreases gradually with time. By using this method, an extra source of background for the Beijing Spectrometer experiment at the collider has been found and eliminated.
Field Ionization Thresholds of (17, n1, n2, 0) and (17, n1, n2, 1) Stark States of Sr Atom
LI Jing, ZHANG Sen, CHU Xiaofeng
Chin. Phys. Lett. 1993, 10 (5): 282-285 .  
Abstract   PDF(pc) (239KB) ( 485 )
The field ionization thresholds of n=17, |m|=0,1 Stark states of Sr atoms have been investigated by two-step excitation using ππ, πσ polarized lasers and both uniform and pulse electric fields. The results showed, contrary to the hydrogen 's, higher-energy states generally have lower ionization thresholds, and that the |m|=0,1 Sr atoms exhibit partly adiabatic behavior at several avoided crossings in the passage to ionization.

Relativistic Effects in Electron Capture of Ion-Atom Collision at High Energies
Chin. Phys. Lett. 1993, 10 (5): 286-289 .  
Abstract   PDF(pc) (176KB) ( 361 )
A relativistic extension for Blankenbecler-Goldberger approximation to the calculation of the electron capture processes in ion-atom collisions is developed. The results are compared with other methods and the relativistic effects are discussed. Some new conclusions are obtained.
Electronic Structure of C70 Within the Tight-Binding Approximation
GU Binglin, LIU Jingnan, HUANG Mingwei, ZHU Jialin
Chin. Phys. Lett. 1993, 10 (5): 290-293 .  
Abstract   PDF(pc) (215KB) ( 623 )
The electronic structure of C70 molecule with D5h symmetry has been studied using a simple tight-binding approximation. Comparing the results with those of local -density approximation calculation and experiment, we have determined the hopping matrix element. We have also compared the electronic structure and charge density over cluster of C70 with the results of ellipsoid model, and found the angular momentum and magnetic quantum number (1 and m) of each bunch and level.
Effects of H+-Implantation on the Formation of Secondary Defects in Self-Implanted Si(100)
TIAN Renhe
Chin. Phys. Lett. 1993, 10 (5): 294-297 .  
Abstract   PDF(pc) (529KB) ( 466 )
By using the plan-view transmission electron microscopy, cross-sectional transmission electron microscopy, and Rutherford backscattering (and channeling) spectrometry technology, the effects of H+-implantation on the formation of secondary defects in self-implanted Si(100) were investigated. Experiments indicate that the H+-implantation can reduce the formation of secondary defects and improve the perfection of crystal in self-implanted Si(100).
A Study of 90°Ferroelectric Domains in Potassium Tantalate Niobate Crystals by Means of Transmission Electron Microscopy
XU Huiping, LI Qi, SHEN Guangjun, WANG Luchun, SHA Zhenshun, ZHU Jianming, FENG Duan, WANG Jiyang
Chin. Phys. Lett. 1993, 10 (5): 298-301 .  
Abstract   PDF(pc) (316KB) ( 469 )
By flux method, potassium tantalate niobate crystals with 46% Nb contents were prepared. In this material 90°a-type domains with (011) and (01 ī) walls were observed by a transmission electron microscope, and the nature of fringe patterns associated with these domain walls was analysed. According to the extinction rules for the domain walls, the displacement vector R along < 01 ī > direction can be determined. Finally, using a selected area electron diffraction method, we examined the crystallographic character of these 90°domains and defined the ratio of lattice parameters c to a.

Proton Transport in Hydrogen-bonded Systems in Anharmonic Interaction Approximation : an Analytical Approach
MEI Yuping, YAN Jiaren
Chin. Phys. Lett. 1993, 10 (5): 302-305 .  
Abstract   PDF(pc) (208KB) ( 428 )
We study the collective proton motion in hydrogen-bonded systems in anharmonic interaction approximation, and obtain analytical solutions of kinkantikink solitons. The asymmetric feature of kink-antikink solitons can be clearly seen from the solutions. Some basic physical quantities of the kink and antikink solitons are calculated in anharmonic interaction approximation.
Lens-Like Effect in LiNbO3 : Fe Photorefractive Crystal
XU Jingjun, LIU Junmin, ZHANG Guangyin, LIU Simin
Chin. Phys. Lett. 1993, 10 (5): 306-309 .  
Abstract   PDF(pc) (200KB) ( 520 )
The lens-like effects, both photorefractive effect and thermo-optical effect, were studied in the LiNbO3 : Fe sheet. The threshold light intensity above which the photorefractive effect was overwhelmed b-v the thermal effect was determined and the thermo-optical coefficient dn/dT is evaluated by the Z-scanning method. The limiting characteristics of LiNbO3 : Fe sheet is examined.
Formation and Growth of Stacking Fault in YBCO by Electron Irradiation
SHEN Guangjun, HAN Yongsheng, JIN Jirong, JIN Xin, JI Helin, YAO Xixian, FAN Zhanguo
Chin. Phys. Lett. 1993, 10 (5): 310-312 .  
Abstract   PDF(pc) (234KB) ( 473 )
This paper studies a new electron irradiation effect of the formation, movement and growth of stacking fault in YBa2 Cu3 O6+x. The energy of electron irradiation is about 160keV. It would be a promising way to enhance the density of pinning centers.
Distribution of Magnetic Flux in Powder-Melting-Processed YBCO Superconductors
TONG Litai, CHEN Haiying, YAN Shousheng, ZHANG Cungui, ZHOU Lian, WANG Keguang
Chin. Phys. Lett. 1993, 10 (5): 313-316 .  
Abstract   PDF(pc) (331KB) ( 462 )
Using magnetic decoration technique, the distribution of magnetic flux in power-melting-processed Y-Ba-Cu-O superconductor has been studied in an applied field of 200G at 64K. The decoration patterns indicate that twin boundaries act as strong flux pinning sites and the nonsuperconducting Y2BaCuO5 (211) inclusions provide pinning sites in their vicinity by inducing lattice distortion. Chain-like vortex distribution, distorted hexagonal flux line lattice and anisotropic vortices have been observed.

Phonon Participation in the Light Emission Process of Porous GeSi Layer
SHI Hongtao, ZHENG Youdou, YUAN Renkuan
Chin. Phys. Lett. 1993, 10 (5): 317-320 .  
Abstract   PDF(pc) (212KB) ( 484 )
Relaxed Ge0.5Si0.5/Si heterostructure was grown by the rapid radiant heating, very low pressure chemical vapor deposition (RRH-VLP/CVD). We report the anomalous temperature dependence of photoluminescence (PL) from porous GeSi layer at 77-300K. The peak-emission energy of PL spectra from porous GeSi layer decreases with increasing temperature while its peak intensity rises, which is quite different from the temperature dependence of porous Si layer. Such dependencies are reversible and independent of temperature-change directions. No obvious 480cm-1 peak was observed in Raman spectrum, indicating that no substantial amorphous phase contributes the intense light emission from the porous materials. We attribute such anomalous behavior of porous GeSi layer to phonon participation in the light-emission process of porous GeSi layer.
17 articles