Table of contents

20 October 1994, Volume 3 Issue 10 Previous issue    Next issue

THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

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TWO-PARTICLE BOUND STATES IN THE QUANTUM SINE-GORDON FIELD THEORY IN (D+1) DIMENSIONS LU WEN-FA (卢文发), XU BO-WEI (许伯威), ZHANG YU-MEI (章豫梅) Acta Physica Sinica (Overseas Edition), 1994, 3 (10):  721-729.  DOI: 10.1088/1004-423X/3/10/001 Abstract ( 1259 )   PDF (225KB) ( 438 )   The two-particle states of the quantum sine-Gordon fields are studied variationally in (D+1) dimensions using the Gaussian wave functional approach. In both (1+1) and (2+1) dimensions, there exist two-particle bound states for certain ranges of coupling constant, where the vacuum states are stable. In the higher dimensions (D > 2), this approximation indicates that the two-particle states may be only the states consisting of two free particles, which is conformable to the triviality of the sine-Gordon field theory previously obtained in recent literatures.

NUCLEAR PHYSICS

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NMR STUDIES OF HYDROGEN MICROSTURUCTURES IN HYDROGENATED AMORPHOUS SILICON FILMS QU XUE-XUAN (瞿学选), CHEN KUN-JI (陈坤基), CHEN MAO-RUI (陈茂瑞), HU CHENG (胡澄), LI ZHI-FENG (李志锋), FENG DUAN (冯端) Acta Physica Sinica (Overseas Edition), 1994, 3 (10):  730-735.  DOI: 10.1088/1004-423X/3/10/002 Abstract ( 1404 )   PDF (167KB) ( 388 )   Four kinds of a-Si: H films deposited in the PECVD system with different Ts are studied by 1H NMR technique. Direct evidence is given to confirm hydrogen atoms in the diluted and clustered phases. The local bonding configurations for hydrogen and the density of dangling bonds are analyzed by ESR and infrared absorption spectroscopy. The behaviour of hydrogen in a-Si; H films is discussed.

CLASSICAL AREAS OF PHENOMENOLOGY

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THEORETICAL STUDY ON THE DIRECT RECONSTRUCTION OF LLFT X-RAY HOLOGRAM WITH VISIBLE LIGHT XIAO TI-QIAO (肖体乔), CHEN JIAN-WEN (陈建文), XU ZHI-ZHAN (徐至展), ZHU PEI-PING (朱佩平), KOU LEI-GANG (寇雷刚), WANG ZHI-JIANG (王之江) Acta Physica Sinica (Overseas Edition), 1994, 3 (10):  736-745.  DOI: 10.1088/1004-423X/3/10/003 Abstract ( 1271 )   PDF (284KB) ( 452 )   Reconstructing X-ray hologram with visible light, without enlargement of it, can sim-plify the process of its reconstrution greatly. For lensless Fourier transform (LLFT) X-ray holography, there is no spherical aberration in it and the spacing of its interference fringes is relatively large. Therefore, it is possible to reconstruct hologram of this type directly with visible light. The effects of aberrations and emulsion shrinkage on the resolution of LLFT X-ray hologram, the conditions for perfect reconstructing of the recorded information are analyzed, and the results of corresponding numerical analyses are also given. As a result, the legibility for direct reconstructing of LLFT X-ray hologram with visible light is verified theoretically, In addition, the longitudinal resolution in X-ray holography is analyzed, and the conditione for longitudinal resolving in X-ray holography are given from the relationship between longitudinal and transverse resolution.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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BEHAVIOR OF Ar PLASMA FORMED IN A HIGH DENSITY PLASMA SOURCE-AN ECR REACTOR WU HAN-MING (吴汉明), D.B. GRAVES, R.K PORTEOUS, LI MING (李明) Acta Physica Sinica (Overseas Edition), 1994, 3 (10):  746-757.  DOI: 10.1088/1004-423X/3/10/004 Abstract ( 1218 )   PDF (349KB) ( 454 )   In order to develop the ultra-large scale integration(ULSI), low pressure and high density plasma apparatus are required for etching and deposit of thin films. To understand critical parameters such as the pressure, temperature, electrostatic potential and energy distribution of ions impacting on the wafer, it is necessary to understand how these parameters are influenced by the power input and neutral gas pressure. In the present work, a 2-D hybrid electron fluid-particle ion model has been developed to simulate one of the high density plasma sources-an Electron Cyclotron Resonance (ECR) plasma system with various pressures and power inputs in a non-uniform magnetic field. By means of numerical simulation, the energy distributions of argon ion impacting on the wafer are obtained and the plasma density, electron temperature and plasma electrostatic potential are plotted in 3-D. It is concluded that the plasma density depends mainly on both the power input and neutral gas pressure. However, the plasma potential and electron temperature can hardly be affected by the power input, they seem to be primarily dependent on the neutral gas pressure. The comparison shows that the simulation results are qualitatively in good agreement with the experiment measurements.

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THE ION CURRENT BEHAVIOR IN ECR ARGON PLASMA YAO XIN-ZI (姚鑫兹), JIANG DE-YI (江德仪), REN YU-FENG (任育峰) Acta Physica Sinica (Overseas Edition), 1994, 3 (10):  758-763.  DOI: 10.1088/1004-423X/3/10/005 Abstract ( 1097 )   PDF (184KB) ( 367 )   The ion current density as a function of various system parameters, such as pressure, magnetic field, and microwave power, has been studied by using Faraday cup. The bistability of plasma was observed and discussed.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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A NEUTRON POWDER DIFFRACTION STUDY OF THE STRUCTURE IN Nd2Fe17Nx(x = 2.5, 3.0, 5.5) YAN QI-WEI (严启伟), ZHANG PAN-LIN (张泮霖), SUN XIANG-DONG (孙向东), WEI YU-NIAN (魏玉年), SUN KE (孙克), HU BO-PING (胡伯平), WANG YI-ZHONG (王亦忠), LIU GUI-CHUAN (刘贵川), GOU CHENG (勾成), CHENC YU-FEN (程玉芬), CHEN DONG-FENG (陈东风), Acta Physica Sinica (Overseas Edition), 1994, 3 (10):  764-768.  DOI: 10.1088/1004-423X/3/10/006 Abstract ( 1242 )   PDF (118KB) ( 357 )   The crystallographic and magnetic structures of Nd2Fe17Nx(x = 2.5, 3.0, 5.5) at room temperature were refined by Rietveld analysis of neutron powder diffraction data. We found that Nd2Fe17Nx has a Th2Zn17 type structure (S.G. R3m) and the nitrogen atoms occupy both 9e and 18g sites simultaneously and at different rates.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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QUANTUM PERCOLATION AND BALLISTIC CONDUCTANCE IN A SYSTEM OF DOUBLE-COUPLED CHAINS FAN XU-DONG (范旭东), GU BEN-YUAN (顾本源), YANG GUO-ZHEN (杨国桢), LIN ZONG-HAN (林宗涵) Acta Physica Sinica (Overseas Edition), 1994, 3 (10):  769-779.  DOI: 10.1088/1004-423X/3/10/007 Abstract ( 1219 )   PDF (321KB) ( 395 )   The quantum-mechanical calculation of electronic conductance in double-coupled chains as a function of the interchain bonding probability p is presented. The calculated results show that one still can see the basic plateaus in the ensemble-averaged conductance curves as a function of the Fermi energy for the weak disorder. In addition, dense irregularly oscillating structures are superimposed upon each plateau. The characteristics of the conductance are very sensitive to the presence of the interchain broken bonds. For the strong disorder (p≈0.5) the conductance quantization breaks down. The accuracy of the quantization conductance rapidly drops down as the value of p approaches 0.5. The ensemble-averaged value of the logarithmic conductance as a function of the sample length exhibits a linear variation, determining a localization length. Both the localization length and the root-mean- square (RMS) value of the conductance fluctuations depend on p and the Fermi energy of electrons. The variations of the localization length and RMS with p are both of an approximate parabolic function around p≈0.5. No percolation transition is found for this quasi-one-dimensional system, as expected.

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TEMPERATURE DEPENDENCE OF ANISOTROPY IN Co/X(Pt, Au, Ag, Ni) MULTILAYER FILMS ZHANG HUI-YUN (张慧云), WANG YIN-JUN (王荫君) Acta Physica Sinica (Overseas Edition), 1994, 3 (10):  780-787.  DOI: 10.1088/1004-423X/3/10/008 Abstract ( 1446 )   PDF (260KB) ( 383 )   Temperature dependences of effective perpendicular anisotropy (PA) Ku and inter-face energy Ks for Co/X(Pt, Au, Ag, Ni) multilayer films(MFs) as well as of spontaneous magnetization Ms for Co/Pt and Co/Au MFs are reported. The dependence of Ks on T dis-tinguishes between Go/Au, Co/Ni and Co/Pt, Co/Ag MFs, i.e., Ks of the former decreases with the increase of T, but it increases for the latter. Co/Pt MFs with the perpendicular anisotropy possess a large enhancement of Ms at low temperature, but there is not any en-hancement for Co/Au MFs. We have discussed the source of PA in Co/Au and Co/Pt MFs and speculated that the strain due to the lattice mismatch may be the main cause of PA in Co/Au MFs, but it is not for Co/Pt MFs.

CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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A MODIFIED METHOD OF DETERMINING FRACTAL DIMENSIONS OF POLYMERS AND BIOPOLYMERS XIAO YI (肖奕), YAO KAI-LUN (姚凯伦) Acta Physica Sinica (Overseas Edition), 1994, 3 (10):  788-792.  DOI: 10.1088/1004-423X/3/10/009 Abstract ( 801 )   PDF (136KB) ( 311 )   A modified method of calculating the end-to-end distance of segments with a given number of units in a single polymer chain is presented and numerical studies of some fractals by using Havlin and Ben-Avraham's and our methods are given. The results show that our method can remove the fluctuations in the end-to-end distances of the segments arising in Havlin and Ben-Avraham's method.