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Volume 5 Issue 10
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Original Articles
A MODEL FOR THE PERIPHERAL PROCESS IN ULTRARELATIVISTIC NUCLEUS-NUCLEUS COLLISIONS
TANG Xiaowei, CHAO Weiqin
Chin. Phys. Lett. 1988, 5 (10): 433-436 .  
Abstract   PDF(pc) (42KB) ( 366 )
A model for the peripheral process in ultrarelativistic nucleus-nucleus collisions is proposed to explain the first experimental results of interactions of oxygen nuclei in nuclear emulsions at the highest energy now available. The fraction of the interactions producing 'white' stars and the mean value of NH for different incident energies and colliding nuclei are given.
COMPACTIFICATION OF STRING THEORY ON COSET SPACE
TANG Jufei, ZHU Chuanjie
Chin. Phys. Lett. 1988, 5 (10): 437-440 .  
Abstract   PDF(pc) (41KB) ( 359 )
String theory is constructed on group manifold which is locally neither a Minkovski nor a Euclidean space. It is shown that Lorentz algebra is satisfied and ghost states can all be eliminated. The string theory constructed is just like a string theory in four dimensions.
SELF-FOCUSING AND SELF-DEFOCUSING DUE TO COLLISION-INDUCED ZEEMAN COHERENCE
GONG Qihuang, WANG Xiangmei, Y.H.Zou
Chin. Phys. Lett. 1988, 5 (10): 441-444 .  
Abstract   PDF(pc) (44KB) ( 417 )
The continuous wave self-focusing and self-defocusing in sodium vapor have been observed at zero magnetic field. The effects are enhanced by collisions and can be observed in low light intensity and large frequency detuning from the resonance transition. All experimental results can be well explained by collision-induced Zeeman coherence.
FRACTAL STRUCTURE APPEARED IN ION-IMPLANTED a-Ge/Ag BILAYER FILMS AFTER ANNEALING
HOU Jianguo, WU Ziqin
Chin. Phys. Lett. 1988, 5 (10): 445-448 .  
Abstract   PDF(pc) (54KB) ( 379 )
The agglomeration in ion-implanted a-Ge/Ag bilayer films has been investigated by use of transmission electron microscopy (TEM). There are two kinds of fractal structures, one of which is soot - like with fractal dimension (FD) of 1.515, the other is snow - flake - like with FD of 1.797. The result is compared with that of the unimplanted film, and the mechanism of the occurrence of fractal regions is also discussed.
PHOTOREFRACTION IN Li-RICH LiNbO3:Mg:Fe CRYSTALS
CHANG Tiejun, WEN Jinke, ZHU Yaping, WANG Zhefu, TANG Yansheng, WANG Huafu
Chin. Phys. Lett. 1988, 5 (10): 449-452 .  
Abstract   PDF(pc) (62KB) ( 366 )
The ability of Li-rich LiNbO3:Mg(5mol%):Fe(0.lwt%) to resist photorefraction is found to be comparable to that of LiNbO3:Mg(5mol%), even though the photorefraction sensitive dopant Fe is added. The nuclear quadrupole splitting and isomer shift of 57Fe in Li-rich LiNbO3: Mg57Fe and LiNbO3:57Fe are quite different. The electron spin resonance spectra of the two kinds of crystals are significantly different, too. The enhanced resistance to photorefraction may be due to the change in occupation sites of Fe ions.

HEAT TREATMENT EFFECTS ON POSITRON DOPPLER BROADENING IN YBa2Cu3O7-x
ZHANG Hong, WANG Xiaogang
Chin. Phys. Lett. 1988, 5 (10): 453-456 .  
Abstract   PDF(pc) (47KB) ( 370 )
Positron annihilation Doppler lineshape parameters for YBa2Cu3O7-x have been demonstrated experimentally to be sensitive to heat treatment conditions and to vary almost linearly with oxygen vacancy concentration. positron annihilation spectroscopy (PAS) can be used to monitor the beheviors of oxygen vacancies in YBaCuO-like ceramic.
ANALYTICAL METHOD IN LATTICE GAUGE THEORY AT FINITE TEMPERATURE
ZHENG Xite, CHUNGI Tan*
Chin. Phys. Lett. 1988, 5 (10): 457-460 .  
Abstract   PDF(pc) (43KB) ( 366 )
A variational-cumulant expansion method at finite temperature is developed in the lattice gauge theory. The order parameter < L > (the statistical average of the thermal loop) is analytically calculated to the 3rd order cumulant expansion. The change of < L > = 0 to < L > ≠ 0 clearly shows the existence of a deconfine phase transition of 2nd order in agreement with the latest Monte Carlo simulations.








ULTRASONIC STUDIES ON HIGH Tc SUPERCONDUCTOR YBa2Cu3O7-x
DENG Tingzhang, ZHANG Liangkun, GU Huicheng, XIAO Zhili, CHEN Liquan
Chin. Phys. Lett. 1988, 5 (10): 461-464 .  
Abstract   PDF(pc) (48KB) ( 380 )
Ultrasonic attenuation and velocity measurements down to 77K were performed on high Tc superconductor Y-Ba-Cu-O samples with different sintering procedures. The change of sound velocity was found near Tc in two samples which have density of 94% of the theoretical density and excellent diamagnetism. In one of the samples an anomaly related to ultrasonic frequency was observed around Tc in the ultrasonic attenuation. Another sample also possesses an excellent diamagnetism, but no anomaly in ultrasonic attenuation was found near Tc. We did not observe anomaly in attenuation resulted from electron-phonon interaction in these two samples.
HIGH Tc SUPERCONDUCTIVITY IN LnBa2Cu3O7-y(Ln=Yb, Er ) SINGLE CRYSTAL WITH LARGE SIZE
FANG Minghu, XIA Jiansheng, ZHAO Zhanchun, SUN Dunming, CHEN Zuyao*, ZHANG Qirui**
Chin. Phys. Lett. 1988, 5 (10): 465-468 .  
Abstract   PDF(pc) (44KB) ( 366 )
Two kinds of single crystal YbBa2Cu3O7-y and ErBa2Cu3O7-y have been grown by the fluxed method. They are orthorhombic structure with space group Pmmm, cell parameters are a=3.88Å, b=3.82Å, c=11.68Å and their typical size are 3x2x2mm3. The superconducting critical temperature is over 90K. Their superconductivity is discussed.
SPATIAL RESOLUTION HARD X-RAY MEASUREMENT ON CT-68 TOKAMAK
QI Xiazhi, WANG Long
Chin. Phys. Lett. 1988, 5 (10): 469-472 .  
Abstract   PDF(pc) (52KB) ( 386 )
The hard X-ray emissions from different chords of plasma column and at the limiter have been detected by a detector array on CT-6B tokamak. The experimental results show that the hard X-ray emission is correlative with MHD activity in the plasma. The measured signals are in the same phase as that of soft X-ray from the outer region near q=I resonant surface when sawtooth oscillation occus, indicating that the most part of runway electrons is generated in the region.
LOW-LYING GLUEBALL PRODUCTION IN POLARIZED PHOTON-PHOTON COLLISION
XU Zaixin, HU Chengguo
Chin. Phys. Lett. 1988, 5 (10): 473-476 .  
Abstract   PDF(pc) (51KB) ( 322 )
Inclusive glueball production via polarized photon-photon collision is discussed. The cross section and asymmetry are calculated. The results show that this kind of process is favorable to the glueball search and identification.
IS THE LARGE OXYGEN ISOTOPIC Tc SHIFT IN YBa2Cu3OX INTRINSIC?
LEI Xiaolin, XIE Leiming, CHEN Jianmin
Chin. Phys. Lett. 1988, 5 (10): 477-479 .  
Abstract   PDF(pc) (37KB) ( 425 )
It is suggested that the extremely large oxygen isotopic Tc shift recently reported in YBa2Cu3O7 may not be an intrinsic mass effect related to the mechanism but due to the small difference of the oxygen contents.
12 articles