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Volume 8 Issue 6
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Original Articles
D and B Meson Decays into Vlv and PV
GUO Xinheng, HUANG Tao
Chin. Phys. Lett. 1991, 8 (6): 274-277 .  
Abstract   PDF(pc) (181KB) ( 432 )
The reasonable wavefunctions of the vector mesons ρ, K* and D* are pro-posed and their properties are discussed. We calculated the decay processes D, B → Vlv and PV. Comparison of the results of our model with those of the Bauer-Stech- Wirbel (BSW) model and the experimental data are given. We also obtained the upper limit of Vub which is smaller than that of BSW model.
Mechanism of Separate Neutron and Proton Excitations in Interacting Neutron and Proton Boson Model and 168Er Spectrum
DENG Weizhen*, YANG Tsesen, Qi Hui
Chin. Phys. Lett. 1991, 8 (6): 278-281 .  
Abstract   PDF(pc) (158KB) ( 377 )
We study the interacting neutron and proton boson model (IBM2) model without the assumption of the maxium F-spin truncation. Then we make a complete IBM2 calculation of the spectrum and E2 transitions to the 168Er nucleus. Also from our simple condensate wavefunctions, we investigate a new mechanism of separate excitations of neutron and proton boson degrees.

Mass-effect of Quarks in Freeze-out from Quark-gluon Plasma
ZHOU Xiaobing, HU Shike*, ZHANG Lin, ZHAO Changlin
Chin. Phys. Lett. 1991, 8 (6): 282-285 .  
Abstract   PDF(pc) (165KB) ( 395 )
The effects of masses of quarks and light gluions on the temperature of Quark-Gluon Plasma (QGP) is taken into account in Massachusetts Institute of Technology (MIT) bag model while freeze-out of quarks from QGP is discussed in the break-up model. It turns out that in the last stage of development of QGP, quark species will freeze-out in the heavier to lighter order, which may not be changed by unavoidable production of other particles (e. g., gluions).
Observation of Optical Bistability Hysteresis Loop with Surface Waves in Doped Polymer Film
YE Peixian, YU Zuhe, ZHANG Zhanxiang, SHEN Yuquan*, FU Xingfa*
Chin. Phys. Lett. 1991, 8 (6): 286-289 .  
Abstract   PDF(pc) (233KB) ( 478 )
Optical bistability hysteresis loop has been observed experimentally with a setup using prism excitation of surface wave in a doped polymer thin film. A simple model has been developed to analyze its operation. The observed bistability hysteresis loop can be explained in terms of surface plasmon excitation and laser induced refractive index variations.
Room Temperature 1.06-0.53 μm Second Harmonic Generation with MgO:LiNbO3
YAO Jianquan, SHI weiqiang, J. E. Millerd, XU Guangfeng, E. Garmire, M. Birnbaum
Chin. Phys. Lett. 1991, 8 (6): 290-291 .  
Abstract   PDF(pc) (103KB) ( 353 )
Second harmonic generation conversion efficiency of 45% was obtained with a 12 mm long specially grown and cut MgO:LiNbO3 crystal and fundamental peak power density of 140MW/cm2.
Various Progressive Waves as solutions to the Modified KdV Equation
TANG Shimin
Chin. Phys. Lett. 1991, 8 (6): 292-295 .  
Abstract   PDF(pc) (148KB) ( 460 )
Various progressive waves expressed by rational combination of Jacobian elliptic functions in general are found as solutions to the modified KdV equation. They reduce to cnoidal, dnoidal, snoidd, solitary waves or solitons and kinks in some special cases.
Structure and Crystallization Process of (Fel-xCrx)83B17 Metallic Glass
WEI Qin, YANG Bingchu, JIANG Ansheng
Chin. Phys. Lett. 1991, 8 (6): 296-299 .  
Abstract   PDF(pc) (209KB) ( 460 )
The crystllization process of metallic glass (Fel-xCrx)83B17 (x=0.05, 0.10,0.15, 0.25) was studied by differential thermal analysis, X-ray diffraction technology. Experiment proved the atomic bond force as an important driving force in the phase transition. The crystallization peak shifts towards high temperature with the increase in the concentration of high melting point Cr atom. The main structural unit of as-quenched state of (Fel-xCrx)83B17 metallic glass contains atomic cluster of local nine-atom structure.

Flux Relaxation and Pinning Potential in Weak Links of Sintered T12Ba2Ca2Cu3O10+x
CAO Xiaowen*, FENG Shangshen*, LONG Xiangyun, WU Yusheng, PENG Huotain, QI Zhiwei, PENG Qiyun, FANG Junren
Chin. Phys. Lett. 1991, 8 (6): 300-302 .  
Abstract   PDF(pc) (142KB) ( 385 )
We have measured directly the low field magnetization and its time decay of weak link superconductor in the sintered T12Ba2Ca2Cu3O10+x. The decay of magnetization with time at the field intensities of 5, 10, 15, 20 and 50 Oe was observed to follow the law of logarithm, M ∝ Int . The pinning potential derived from the slope of the magnetization decay is about 0.045~0.075eV.
Sn Substitution of TlBaCaCuO Superconductors
ZHOU Yisheng, MENG Xianren, LIN Mingzhu, LIN Zhenjin ZHOU Shanyuan, SANG Lihua, TU Qingyun, LIU Zhenxing
Chin. Phys. Lett. 1991, 8 (6): 303-306 .  
Abstract   PDF(pc) (238KB) ( 451 )
In order to study how the Sn substitution for Tl changes the superconducting properties of the TlBaCaCuO compound, we have prepared samples with Sn in place of Tl by solid state reactions. Measurements of resistance and magnetic susceptibility show that partial substitution of Tl with Sn is helpful to form the superconducting 2223 phase (for T1:Ba:Ca:Cu). It has been found that samples mainly contain tetragonal phase 2223, but there also exist a few additional maxed phases like 1223, 1234 and nonsuperconducting phase BaSnO3.
Relationship between Tc and σ J in Doped Superconducting Copper Oxides
QIAO Rongwen, ZHAO Zhongxian
Chin. Phys. Lett. 1991, 8 (6): 307-309 .  
Abstract   PDF(pc) (152KB) ( 457 )
A relation of Tc ~σ.Jn proposed after analysing the phase diagram and magnetic susceptibility experiments for La2-xSrxCuO4 and Bi2+xSr2Ca1-xCu2Oy . This empirical rule agrees with the phase diagram for La2-xSrxCuO4. We suggest that it should also hold for other superconducting cuprites.
Studies of the Anomaly of Hall Coefficient in High Tc Superconducting Thin Films
HE Zhenhui, SHA Jian, SU Zhenpeng, CHENG Xiang ai, WANG Shunxi, FANG Minghu, ZHANG Qirui, ZHOU Xianyi, YAO Weiguo, QI Zhenzhong, YI Huairen, LI Hongcheng
Chin. Phys. Lett. 1991, 8 (6): 310-313 .  
Abstract   PDF(pc) (212KB) ( 448 )
Measurements of the Hall coefficient (RH) were carried out for a polycrystalline YBa2Cu3O7-y film, a well oriented YBa2Cu3O7-y film and an oriented GdBa2Cu3O7-y film. Sign change of RH was observed for the two YBa2Cu3O7-y films near Tc, but not for the GdBa2Cu3O7-y film which contains partly the component of (110) orientation. The RH anisotropy model proposed previously turns out to be incorrect. Why the YBa2Cu3O7-y films experience sign change of RH while the GdBa2Cu3O7-y film does not is tentatively investigated.
X-ray Photoelectron Spectroscopy on Superconducting T12CaBa2Cu2O8 Thin Film
ZENG Wensheng, QIU ping, YAN Shaolin, LI Zengfa, ZHANG Guangyin
Chin. Phys. Lett. 1991, 8 (6): 314-317 .  
Abstract   PDF(pc) (211KB) ( 452 )
We have prepared single-phase superconducting T12CaBa2Cu2O8 thin film by dc magnetron sputtering process and measured X-ray photoelectron spectra of the film at room and liquid nitrogen temperatures. From the relative intensities of the Ba3d, Tl4f. O1 s and Cu2p spectra taken at different take-off angles, we have concluded that there is an adventitious contamination (nonsupercon-ducting phase) surface layer. After excluding contributions from these spurious phases, we have tentatively assigned which core-level shifts should be caused by the superconducting phase transition.
Magnetic Properties of Sm2 Fe17 N2 and Y2 Fe17 N2
YANG Yingchang, ZHANG Xiaodong, KONG Linshu, PAN Qi
Chin. Phys. Lett. 1991, 8 (6): 318-321 .  
Abstract   PDF(pc) (194KB) ( 334 )
The crystallographic and magnetic properties of Sm2 Fe17 N2 and Y2 Fe17 N2 have been investigated by using X-ray diffraction techniques and magnetic measurements. The effects of the interstitial nitrogen atoms on the Fe-Fe and R-Fe exchange interactions, iron 3d band structure and magnetocrystalline anisotropy induced by crystal field interactions in these nitride compounds are discussed.
Pair Produced Positron Annihilation Technique
TANG Xiaowei, LIN Xianghong, BIAN Zuhe
Chin. Phys. Lett. 1991, 8 (6): 322-324 .  
Abstract   PDF(pc) (148KB) ( 735 )
The feasibility of pair produced positron annihilation technique, which provides the electron momentum information of materials by analyzing the spectrum from pair produced positron annihilation, is studied. In this technique the positrons produced by low energy r-ray in a sample are moderated and annihilated and the Doppler broadening annihilation spectrum is measured and analyzed.
Boron Isotope Fractionation During Prolonged Ion Bombardment
ZHENG Liping, LI Risheng*, LI Mingyao, CHENG Yulin
Chin. Phys. Lett. 1991, 8 (6): 325-328 .  
Abstract   PDF(pc) (192KB) ( 448 )
Dynamic Monte Carlo simulation is used to explore the B isotope sputtering during 1 keV Kr ion irradiation. It is found that at both zero and high fluences the light isotope is preferentially ejected in the near-normal direction; meanwhile, there is a low fluence (1.4x1015 ions/cm2), at which the isotope fractionation is independent of the emission angle in the nearly whole angular range.
15 articles