Table of contents

20 March 1997, Volume 6 Issue 3 Previous issue    Next issue

GENERAL

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HIGH FREQUENCY GRAVITATIONAL WAVE OF A COMPOSITE TOROIDAL ELECTROMAGNETIC RESONANT SYSTEM TANG MENG-XI (唐孟希), LI FANG-YU (李芳昱), LUO JUN (罗俊) Acta Physica Sinica (Overseas Edition), 1997, 6 (3):  161-171.  DOI: 10.1088/1004-423X/6/3/001 Abstract ( 1076 )   PDF (245KB) ( 981 )   Starting with the Einstein equation of weak gravitational field, a new scheme of generating high frequency gravitational wave by composite toroidal electromagnetic resonant system is discussed. The system is a composite toroidal electromagnetic resonant cavity consisting of a vacuum and a dielectric regions. In the focal region of the cavity under the condition of allowable ohmic losses in the cavity walls, the amplitude of the standing gravitational wave is almost two orders of magnitude higher than that in usual cavity with the same volume. A concrete numerical calculation shows that a composite toroidal electromagnetic resonant system with a volume 2×108cm3 could generate the standing gravitational wave with an amplitude h=10-33, wavelength $\lambda$g = 40 cm in its focal region. This is comparable to the typical order of magnitude of several astrophysical sources, and it would be displayed by electromagnetic detection due to very high frequency.

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ANALYSIS ON THE EMBEDDING CHARACTER OF TIME SERIES RECONSTRUCTION YANG ZHI-AN (杨志安), CHEN SHI-GANG (陈式刚) Acta Physica Sinica (Overseas Edition), 1997, 6 (3):  172-182.  DOI: 10.1088/1004-423X/6/3/002 Abstract ( 1565 )   PDF (236KB) ( 313 )   A method is proposed to analyze embedding character of the reconstruction by calculating the ratio of two volumes in two reconstructed phase spaces. By this method the embedding dimension and the delay time are found. The R$\ddot{\rm o}$ssler system is discussed as a special model.

ATOMIC AND MOLECULAR PHYSICS

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SURFACE-ENHANCED RAMAN SCATTERING STUDY ON NON-ACTIVITY OF Ag-Cl CLUSTERS FANG YAN (方炎), LI QIN (李勤) Acta Physica Sinica (Overseas Edition), 1997, 6 (3):  183-188.  DOI: 10.1088/1004-423X/6/3/003 Abstract ( 1093 )   PDF (176KB) ( 494 )   The non-active mechanism of Ag-Cl clusters in surface-enhanced Raman scattering (SERS) was discussed on the basis of the study of the interaction and adsorption competition of chlorions with a series of compounds: benzoic acid, p-hydroxybenzoic acid, and m-hydroxybenzoic acid on silver surface. As a result of the addition of chlorions, the SERS signals of these molecules were sharply and rapidly reduced and quenched in intensity. The change of Raman bands at 1644 cm-1 for benzoic acid, and at 1636 cm-1 for p-hydroxybenzoic acid and m-hydroxybenzoic acid, before and after the addition of chlorions, indicated the desorption process of these adsorbed molecules, and the adsorption behavior of the molecules remaining adsorbed on the silver surface.

CLASSICAL AREAS OF PHENOMENOLOGY

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A THEORETICAL SIMULATION FOR ACHIEVING HIGH SPATIAL COHERENCE OF LABORATORY X-RAY LASERS LI JING-HONG (李敬宏), PENG HUI-MIN (彭惠民), ZHANG GUO-PING (张国平), YANG MING-LUN (杨明伦) Acta Physica Sinica (Overseas Edition), 1997, 6 (3):  189-196.  DOI: 10.1088/1004-423X/6/3/004 Abstract ( 1176 )   PDF (249KB) ( 743 )   An efficient method to achieve high spatial coherence of laboratory soft-X-ray laser is presented, in which a pinhole can be used in "four-target series coupling" experiment to obtain a fully coherent X-ray laser. The model of amplified spontaneous emission is used to describe the characteristics and spatial coherence properties of a soft-X-ray laser beam. The simulation results show that the method is feasible.

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HIGH HARMONIC GENERATION OF TWO-COLOUR FIELDS WITH ORTHOGONAL LINEAR POLARIZATION LI XUE-XIN (李学信), XU ZHI-ZHAN (徐至展), MAO LI-QUN (毛利群) Acta Physica Sinica (Overseas Edition), 1997, 6 (3):  197-204.  DOI: 10.1088/1004-423X/6/3/005 Abstract ( 1126 )   PDF (260KB) ( 418 )   We studied the high-order harmonic generation of two linearly-polarized orthogonal fields.The results showed that the frequency of the harmonics can be controlled by controlling the relative frequency of the two incident fields,especially, when the frequency of one field is an integral mutiple of the frequency difference between the two incident fields,the fractional times of harmonic can be obtained.

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

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STUDY OF DOPING EFFECT ON THE Bi2Sr2Ca2Cu3Oy SUPERCONDUCTOR HU YU-CAI (胡玉才), LIU JIAN (刘建), LI REN-CHENG (李仁宸), BAI PEI-GUANG (白培光) Acta Physica Sinica (Overseas Edition), 1997, 6 (3):  205-211.  DOI: 10.1088/1004-423X/6/3/006 Abstract ( 1317 )   PDF (276KB) ( 348 )   We have systematically investigated the doping effect on the Bi2Sr2Ca2Cu3Oy superconductive material. After entering into the crystal lattice, Pb and/or Sb atoms cause not only variations of the temperature condition during the sample preparation process, but also variations of structures and superconductivity. By analyzing the experimental results, we have come to the conclusion that the Pb and/or Sb atoms enter into the Bi-O planes, preferably occupy the sites of Bi ions, regulate the crystal structures and the distribution of oxygen ions in Bi-O planes and nearby lattice sites, thus benefiting the formation of the high-Tc phase and improving the superconductivity.

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THEORETICAL CALCULATION OF THE MAGNETIC PROPERTIES IN DISORDERED GROUND STATE FOR SPIN-1/2 ANTIFERROMAGNET DU AN (杜安), WEI GUO-ZHU (魏国柱) Acta Physica Sinica (Overseas Edition), 1997, 6 (3):  212-222.  DOI: 10.1088/1004-423X/6/3/007 Abstract ( 1228 )   PDF (248KB) ( 358 )   The spin-1/2 quantum antiferromagnet in three-dimensional space can be described by Heisenberg model:two nearest-neighbor spins with strong interaction in z direction consistitute a dimer, every dimer can be considered as a lattice site in the tetragonal lattice. In z direction, the exchange interaction between two nearest-neighbor dimers is $\lambda '$J, and in xy plane it is 2$\lambda$J. In bond-operator representation, within the mean-field decoupling approximation, we have calculated the phase diagram for order-disorder phase transition about $\lambda $ and $\lambda '$  at 0 K, obtained the critical value, $\lambda$c = 0.292, within which the disordered phase is stable in two-dimensional case($\lambda$ = 0), and found that the disordered phase is always stable for $\lambda'$<1 in one-dimensional case($\lambda$ = 0). For the disordered phase, the physical quantities, such as energy gap, ground-state energy, two-point correlation functions and correlation lengths in xy plane and in z direction, have been calculated as functions of parameters $\lambda$ and $\lambda'$.

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RECOMBINATION DYNAMICS IN ASYMMETRIC COUPLED QUANTUM WELL STRUCTURES MAO HUI-BING (茅惠兵), SHEN XUE-CHU (沈学础), XU ZHONG-YING (徐仲英) Acta Physica Sinica (Overseas Edition), 1997, 6 (3):  223-230.  DOI: 10.1088/1004-423X/6/3/008 Abstract ( 1089 )   PDF (205KB) ( 531 )   The time-resolved photoluminescence (PL) investigations of asymmetric coupled quantum well structures have been carried out in this paper. The experimental results show that for a wider interbarrier thickness the PL in the AlGaAs well will decay almost as a single exponential function, and for a thin interbarrier thickness the PL decay in the AlGaAs well is not a single exponential: the decay rate decreases gradually. These results indicate that when the tunneling becomes the main decay process in the AlGaAs well, the "effective mass filtering" phenomenon will be displayed in the PL decay process, which decreases the tunneling rate. At low temperature, the PL decay time increases with the increase of temperature. With further increase of temperature, the PL decay time decreases because of the increase of the tunneling rate and nonradiative recombination coefficient.