Table of contents

20 February 1993, Volume 2 Issue 2 Previous issue    Next issue

GENERAL

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BALLOONING INSTABILITY IN HIGH $\beta$ TOKAMAK LIN JIAN-LONG (林建龙), SHI BING-REN (石秉仁), LI FANG-ZHU (李芳著) Acta Physica Sinica (Overseas Edition), 1993, 2 (2):  81-88.  DOI: 10.1088/1004-423X/2/2/001 Abstract ( 1244 )   PDF (274KB) ( 326 )   In this paper we show that $\Delta$′B is negative over parts of the second region, and that plasmas are stable to $\Delta$′B -driven resistive modes for realistic equilibria in which characteristics of finite-$\beta$ configurations are retained. We have found that ideal instability is very sensitive to the ratio T=r$\Delta$″/$\Delta$′ in the second region. In comparison with previous works. results obtained by present authors show that the shift gradient $\Delta$′ has a significant stabilizing effect on the second stable boundary, and this effect increases as the shear s becomes larger.

ATOMIC AND MOLECULAR PHYSICS

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CROSS SECTIONS OF ANTIHYDROGEN FORMATION IN COLLISIONS OF ANTIPROTONS WITH POSITRONIUM CHEN XUE-JUN (陈学俊), CHEN ZI-TAO (陈子韬), QIAN QING (钱青), FU YUN-CHANG (伏云昌) Acta Physica Sinica (Overseas Edition), 1993, 2 (2):  89-99.  DOI: 10.1088/1004-423X/2/2/002 Abstract ( 1357 )   PDF (315KB) ( 350 )   New calculations of the cross sections for antihydrogen formation in collisions of antiprotons with positronium are reported in the present paper. A multiple-scattering expansion method has been used for getting reliable results. Discussion and comparison of the present results are made with other theoretical calculations.

CLASSICAL AREAS OF PHENOMENOLOGY

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MULTIGRATING NONDEGENERATE OSCILLATION AND PHASE SHIFT IN THE LINEAR SPPCM XIE PING (谢平), DAI JIAN-HUA (戴建华), ZHANG HONG-JUN (张洪钧) Acta Physica Sinica (Overseas Edition), 1993, 2 (2):  100-112.  DOI: 10.1088/1004-423X/2/2/003 Abstract ( 1231 )   PDF (427KB) ( 347 )   The nondegenerate four-wave mixing in a linear self-pumped phase-conjugate mirror with arbitrary-chosen complex coupling constants has been studied by numerical methods. The frequency detuning and the phase-conjugate reflectivity versus cavity path length detuning for different complex coupling constants are discussed in detail. It is found that multigrating operation in some cases can enlarge the interval of cavity path length detuning to be compensated for by frequency detuning and improve the phase-conjugate beam generation. The phase relation between the output phase-conjugate beam and the input beam is calculated and the result is in agreement with the experimental results.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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INVESTIGATIONS ABOUT THE DYNAMICAL ELECTRON SCATTERING BY A HEXAGON-PRISM $\beta$-Si3N4 WHISKER NING XIAO-GUANG (宁小光), PAN JIN (潘进), HU KUI-YI (胡魁毅), YE HENG-QIANG (叶恒强) Acta Physica Sinica (Overseas Edition), 1993, 2 (2):  113-119.  DOI: 10.1088/1004-423X/2/2/004 Abstract ( 1212 )   PDF (299KB) ( 405 )   The dynamical electron scattering effects by a hexagon-prism $\beta$-Si3N4 whisker were investigated. The 002 dark field images of the wedges of the whisker along [1$\bar{1}$0] direction showed sinusoidal fringes, in which there existed great differences in fringe period under two- and N-beam conditions. Fine structures of the corresponding diffraction spots under two-beam condition were also very different from those under many-beam condition. Such dynamical scattering effects were analyzed quantitatively.

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RAMAN STUDY ON  $X_i^-$(Pb) CENTERS IN SINGLE CRYSTALS OF ALKALI HALIDES DOPED WITH LEAD WANG YING-ZONG (王应宗) Acta Physica Sinica (Overseas Edition), 1993, 2 (2):  120-127.  DOI: 10.1088/1004-423X/2/2/005 Abstract ( 1198 )   PDF (281KB) ( 374 )   Low frequency modes were observed in a series of alkali halides doped with lead after X-irradiation at 77K. The peak positions of the Raman signals are at 34cm-1 for NaCl:Pb2+, 30cm-1 for KCl:Pb2+,28cm-1 for RbCl:Pb2+ and 22cm-1 for KBr:Pb2+. They are assigned to the inelastic light scattering caused by the local vibration of $X^-_i$(Pb+) center, which consists of an interstitial halogen ion stabilized by a substitutional ion Pb+ . Polarized Raman measurements and Behavior Typer(BT) analysis show that the symmetry of the $X^-_i$ (Pb+) center belongs to the point group C3v. A structure model of the $X^-_i$ (Pb+) center is proposed based on the Raman data and the result of BT analysis.

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ATOMIC CHARGE SUPERPOSITION CALCULATIONS OF STM IMAGES OF 2D-ORDERED AMINO ACID ADSORBATES(Ⅰ) LI YAN-FANG (李燕芳), MOU JIAN-XUN (牟建勋), YAN JUN-JUE (严隽珏), YANG WEI-SHENG (杨威生) Acta Physica Sinica (Overseas Edition), 1993, 2 (2):  128-138.  DOI: 10.1088/1004-423X/2/2/006 Abstract ( 1255 )   PDF (501KB) ( 399 )   In a previous STM investigation by Yang and co-workers a variety of 2D ordered atomic-scale features of glycine molecules adsorbed on graphite were observed and several models have been proposed to interpret these features. In the present work, atomic charge superposition(ACS) calculations of STM images of their models were carried out. The calculated images match the experimental ones fairly well, indicating the general validity of the ACS method to the glycine/graphite system and the correctness of their interpretations. The reason of the validity, the origin of the atomic resolution, and the proper tip-sample distance are also discussed.

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ATOMIC CHARGE SUPERPOSITION CALCULATIONS OF STM IMAGES OF 2D-ORDERED AMINO ACID ADSORBATES(Ⅱ) LI YAN-FANG (李燕芳), MOU JIAN-XUN (牟建勋), YAN JUN-JUE (严隽珏), YANG WEI-SHENG (杨威生) Acta Physica Sinica (Overseas Edition), 1993, 2 (2):  139-146.  DOI: 10.1088/1004-423X/2/2/007 Abstract ( 1241 )   PDF (358KB) ( 410 )   In the preceding paper[1], we have successfully used the atomic charge superposition (ACS) method to calculate STM images of 2D-ordered structures of glycine molecules adsorbed on graphite (HOPG). In this work we focus on alanine/HOPG system. Firstly, we make a thorough searching for all of the possible 2D-ordered aggregation structures that can form linear chains or 2D nets of hydrogen bonds between the molecules and simultaneously satisfy the Van der Waal's radii of the condtituent atoms, just like in the case of 3D crystal of the molecules. Secondly, in order to interpret the experimental images, we use the ACS method to calculate STM images of the possible structures. It turns out that many of the experimental images can be interpreted satisfactorily with their calculated counterparts. This result further exhibits the great potential of using STM to study organic and biological molecules.

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

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THE STUDY OF SERS EFFECT AND ADSORPTION PROPERTY ON Cu SURFACE FOR PNBA ZHENG HAI-CAI (郑海菜), MO YU-JUN (莫育俊), ZHU KE (朱恪), GOU ZENG-GUANG (苟增光) Acta Physica Sinica (Overseas Edition), 1993, 2 (2):  147-150.  DOI: 10.1088/1004-423X/2/2/008 Abstract ( 1089 )   PDF (193KB) ( 361 )   With different amounts of KCl added in the PNBA (p- nitro benzoic acid) aqueous solution, the factors affecting the SERS (Surface Enhanced Raman Scattering) are studied systematically on the surface of Copper. The results show that in PNBA aqueous solution the occurrence of SERS effect stongly depends on the existence of Cl-. The amount of KCl added affects not only the emergence and the intensity of SERS effect, but also the adsorption properties such as the adsorption manner,etc.