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Volume 9 Issue 10
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Original Articles
Imaginary-Time Periodicity in ŋ-ξ Spacetime
GUI Yuanxing
Chin. Phys. Lett. 1992, 9 (10): 505-507 .  
Abstract   PDF(pc) (112KB) ( 665 )
The relations between the imaginary-time periodicity and the thermal Bogoliubov transformation in ŋ-ξ field theory are discussed. It has been shown that the thermal Bogoliubov transformation leads to the imaginary- time periodicity of the Green function in ŋ-ξ spacetime and to the KMS condition.

New Upper Limit of γ-Rays Emitted by Tritium Nucleus
TANG Xiaowei, WU Yigen, ZHANG Su, CHEN Qingwang*, XIE Xiangqian*
Chin. Phys. Lett. 1992, 9 (10): 508-510 .  
Abstract   PDF(pc) (158KB) ( 410 )
Using a strong tritium source and a low background HPGe spectrometer a new upper limit of γ-rays emitted by tritium nucleus, less than 3.4X10-13, is obtained.
A Molecular Dynamics Study of Silver Microclusters
ZHU Lei, CHEN Kaitai, LI Yufen
Chin. Phys. Lett. 1992, 9 (10): 511-514 .  
Abstract   PDF(pc) (199KB) ( 432 )
Employing a recently developed empirical many-body potential energy function, we obtained the ground-state structures of silver microclusters (N=3-9, 13) using molecular dynamics and quenching method. The present configurations for clusters (N=3-6) agree well with the available literature values, while the structures for clusters (N=7-9, 13) are newly reported. Also, we find that there is a distinct alternation between even and odd numbered neutral silver clusters with growing cluster size.
Chaotic Phenomena Produced by the Spherical Vortices in the Beltrami Flows
SHl Changchun, HUANG Yongnian, ZHU Zhaoxuan, SU Weidong, DONG Yufei
Chin. Phys. Lett. 1992, 9 (10): 515-518 .  
Abstract   PDF(pc) (217KB) ( 387 )
We find a special type of Beltrami flows which has chaotic trajectories confined within a sphere or between two concentric spherical shells. We also find there exists the structure of chaotic manifold made from double-torus in some special cases.
Tunable Femtosecond Soliton Propagation in Optical Fibers
BAI Yingxin, ZHANG Guoqing*, SU Dachun**
Chin. Phys. Lett. 1992, 9 (10): 519-522 .  
Abstract   PDF(pc) (191KB) ( 434 )
We achieve a tunable femtosecond soliton solution of the extended nonlinear Schrodinger (ENLS) equation. Such a soliton can stably propagate in an optical fiber with negative third-order dispersion (β0< 0) and it would not collapse even if the fiber loss is considered. All of these show that it is possible to realize the femiosecond soliton propagation in special optical fibers. Besides, it will be applied that the group velocity of the soliton varies with its intensity in some measurements.

Nonlinear Fabry-Perot Etalon and Optical Bistability in CdHgTe at 77K
WU Xiaoguang, HU Xierong, YANG Yawen*, SU Jingwen**, CHEN Jishu***
Chin. Phys. Lett. 1992, 9 (10): 523-526 .  
Abstract   PDF(pc) (185KB) ( 460 )
We report the first observations of nonlinear feature and optical bistability in n-CdHgTe at 77K and obtained computer simulated curves, then discuss contribution due to thermal effect.
Model on Inducing H-Mode by Biased Electrode in Tokamaks
X.M.Qiu, L.Bai, L.B.Ran
Chin. Phys. Lett. 1992, 9 (10): 527-529 .  
Abstract   PDF(pc) (134KB) ( 481 )
In this letter, a model on inducing H-mode by biased electrode in tokamaks is put forward, it successfully explains the experiments in CCT, TEXTOR, and HL-1 with bias.
Evaluation of Atomic Correlation Functions for Stepped Inhomogeneous Surfaces
Chin. Phys. Lett. 1992, 9 (10): 530-533 .  
Abstract   PDF(pc) (192KB) ( 395 )
The atomic correlation functions of inhomogeneities are exactly evaluated for three-level stepped inhomogeneous surfaces with three sorts of randomly distributed domains. An analytical expression is derived for the intensity of the diffraction electron beam. It is shown that for this surface the diffraction spot is split into a central spike and a diffused profile, which consists of three kinds of Lorentzian-like broadenings produced by both the steps and inhomogeneities.
Separation of NMR Spin-Spin Multi-relaxation Process and Imaging - Phantom Investigation
FENG Yilian, QIN Songmao, Y. Huang*, ZHOU Zhiying**, LIANG Xiuhui***
Chin. Phys. Lett. 1992, 9 (10): 534-536 .  
Abstract   PDF(pc) (163KB) ( 443 )
A physical-mathematical model was proposed for the NMR relaxation processes, which can automatically identify the multi-relaxation process; the automatic separation of the spin-spin relaxation processes of water sample in a home made phantom was carried out; two kinds of proton pure spin-spin relaxation time images and two kinds of proton computed pure density images have been obtained on a 1.0T supercondlrtive magnet MR-Scanner.

A Fractal Lattice Ising Model with Pair and Triplet Interactions
QIN Yong
Chin. Phys. Lett. 1992, 9 (10): 537-540 .  
Abstract   PDF(pc) (202KB) ( 412 )
The equivalence of the Ising model on a fractal lattice having two- and three-site couplings with the Ising model having only two-site interaction in a non-zero magnetic field on the same lattice is derived by a partial tracing which effectively decimates triplet interaction. It is shown that the system is in ordered phase and no phase transition exists at any finite temperature. Only trivial transition occurs at T = ∞. In particular, we find that the pure triplet interaction Ising model is equivalent to one with pure nearest-neighbor pair interaction on the lattice, and the two systems have the same critical behavior. This is in contrast with that of triangular lattice and Sierpinski gasket fractal.

Layer Structure of Doped C60
FU Rongtang, CHEN Zhang, FU Rouli*, SUN Xin**
Chin. Phys. Lett. 1992, 9 (10): 541-544 .  
Abstract   PDF(pc) (171KB) ( 399 )
It is found in this letter that the doped C60 possesses layer-structure in both bond distortions and electronic states. There are eight layers of carbon atoms in the charged C60, and its symmetry is reduced from Ih to D5d. This layer-structure indicates that there exist four nonequivalent groups of carbon atoms in the doped C60. It contrasts with the pristine C60, in which all the sixty carbon atoms are equivalent. One observable consequence of such layer-structure is the split of its NMR spectrum with the ratio 1:1:2:2.

Break-Down of Vertical-Bloch-Line Chains in Ordinary Hard Bubble Walls Subjected to an In-plane Field
HUO Suguo*, LI Bozang, HAN Baoshan
Chin. Phys. Lett. 1992, 9 (10): 545-548 .  
Abstract   PDF(pc) (207KB) ( 450 )
An experimental and theoretical study was carried out on the break-down of vertical-Bloch-line (VBL) chains in ordinary hard bubble walls subjected to an in-plane field, Hip. Other than a single critical value, a critical range of in-plane field, from H(1)ip to H(2)ip, was found. When Hip< H(1)ip the VBL chains keep unchanged; whereas when H(1)ip < Hip < H(2)ip, more and more hard domains are softened. Above H(2)ip all VBL chains are broken-down. A theoretical analysis showed that the critical range of Hip is originated from the serpentine curving of domain walls, and a relation H(2)ip / H(1)ip=√2, was obtained, which is in good agreement with the experiments.

Investigation of Nanocrystalline SnO2 by Electron Spin Resonance
JIN Tongzheng, WANG Dazhi, HAN Shiying, SUI Yunxia, ZHAO Xiaoning, JIN Sizhao*
Chin. Phys. Lett. 1992, 9 (10): 549-551 .  
Abstract   PDF(pc) (132KB) ( 492 )
Electron spin resonance studies of nanocrystalline SnO2 indicated that the experimental spectrum can be decomposed into two spectra attributed to crystalline and interfacial components respectively. The results confirmed the proposed two components model of nanocrystalline materials.

Superconductivity at 50K in (Pb0.5Cd0.5)Sr2(LuxCa1-x)Cu2Oz
QIAN Yitai, HUANG He, TANG Kaibin, CAO Guanghan, CHEN Zuyao, ZHOU Guien*, WANG Nanlin**
Chin. Phys. Lett. 1992, 9 (10): 552-554 .  
Abstract   PDF(pc) (134KB) ( 393 )
Superconducting copper oxide (Pb0.5Cd0.5)Sr2(LuxCa1-x)Cu2Oz has been prepared in oxygen atmosphere. The zero resistivity temperature is 50K for the x=0.5 sample and 43K for the x=0.7 sample. The lattice constants are a=0.3805nm, c=1.2008nm. Phase and superconductivity are discussed in this paper.

Current-Induced Light Emission from a Laterally Anodizing Porous Silicon Device
SHI Hongtao, ZHENG Youdou, WAND Yongbin, YUAN Renkuan
Chin. Phys. Lett. 1992, 9 (10): 555-557 .  
Abstract   PDF(pc) (165KB) ( 467 )
We report the current-induced light emission (CILE) at RT from a porous silicon (PS) Schottky device exhibiting good rectifying characteristics with the ideal factor of 14. The photoluminescence spectrum from the PS layer fabricate by laterally anodization peaks at 668 nm. The intensity of CILE increases with increasing current. It has run for more than two hours and still keeps stable. Possible mechanism of CILE is discussed.
Real-Time Thermal Green’s Functions in Rindler Space
GUI Yuanxing
Chin. Phys. Lett. 1992, 9 (10): 558-560 .  
Abstract   PDF(pc) (102KB) ( 424 )
The real-time thermal Green’s functions with 2x2 matrix in Rindler field theory are derived for massless scalar fields by using both the Bogoliubov transformation method and path-integral formulation.
Tunneling Wave Function with Induced Gravity
WANG Wenfu, TAO Caide*
Chin. Phys. Lett. 1992, 9 (10): 561-564 .  
Abstract   PDF(pc) (164KB) ( 403 )
A Tunneling wave function of the universe with induced gravity in the WKB approximation is discussed and using Vilenkin’s boundary condition we obtain the probability density for the scale factor a at a given value of the scalar field. It is shown that when the universe spontaneously nucleates, the minimum value of the scale factor of the classical universe is of the order of Planck length.

17 articles