Table of contents

20 May 1998, Volume 7 Issue 5 Previous issue    Next issue

NUCLEAR PHYSICS

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PSEUDORAPIDITY DISTRIBUTIONS OF RELATIVISTIC SINGLY CHARGED PARTICLES IN HIGH ENERGY NUCLEUS-NUCLEUS COLLISIONS LIU FU-HU (刘福虎) Acta Physica Sinica (Overseas Edition), 1998, 7 (5):  321-326.  DOI: 10.1088/1004-423X/7/5/001 Abstract ( 1197 )   PDF (193KB) ( 332 )   The pseudorapidity distributions of relativistic singly charged part icles produced in high energy nucleus-nucleus collisions are described by the thermalized cylinder picture. The calculated results are in agreement with the recent experimental data of gold induced interactions at the Brookhaven National Laboratory.

ATOMIC AND MOLECULAR PHYSICS

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CALCULATIONS OF STRETCHING VIBRATIONAL OVERTONES AND COMBINATIONS OF ARSINE BY NONLINEAR MODEL CHEN XIANG-RONG (陈向荣), GOU QING-QUAN (芶清泉), PANG XIAO-FENG (庞小峰) Acta Physica Sinica (Overseas Edition), 1998, 7 (5):  327-332.  DOI: 10.1088/1004-423X/7/5/002 Abstract ( 1213 )   PDF (158KB) ( 367 )   A three-parameter nonlinear model in nonlinear quantum theory, i.e., the quantized discrete self trapping equation, has been used to calculate the vibrational energy spectrum, including the overtones and combinations with many excited quanta, of AsH stretches of arsine, AsH3. The model calculations agree well with experiment and other calculations. It is shown that the dominant feature of the energy spectrum of AsH3 molecule is a pattern of local mode pairs, and that when n≥4, all the vibrational energies are almost localized on a single AsH bond.

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ANALYSIS OF F′0+u ION-PAIR STATE OF IODINE ZHANG LIAN-SHUI (张连水), LIU NING-NING (刘宁宁), LI XIAO-WEI (李晓苇), FU GUANG-SHENG (傅广生) Acta Physica Sinica (Overseas Edition), 1998, 7 (5):  333-339.  DOI: 10.1088/1004-423X/7/5/003 Abstract ( 1237 )   PDF (171KB) ( 359 )   The optical-optical double resonant multiphoton ionization (OODR-MPI) technique and the fluorescent excitation spectroscopy technique have been applied to the study of the F′0+u ion-pair state of iodine. This paper presents OODR-MPI spectrum and fluorescent excitation spectrum of I2 in the region of 54000-55300cm-1 by the three-photon resonant, two-photon ionization (1+2+2) and (1+(1+1)+2) processes.

CLASSICAL AREAS OF PHENOMENOLOGY

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HOW DOES AN IMPERFECT SYSTEM AFFECT THE MEASUREMENT OF SQUEEZING? ZHANG TIAN-CAI (张天才), ZHANG JUN-XIANG (张俊香), XIE CHANG-DE (谢常德), PENG KUN-CHI (彭堃墀) Acta Physica Sinica (Overseas Edition), 1998, 7 (5):  340-347.  DOI: 10.1088/1004-423X/7/5/004 Abstract ( 1063 )   PDF (186KB) ( 366 )   The effect of an imperfect system on the measurement of squeezing is studied. It is shown that the imperfectly efficient detectors and the unbalance of the beam-splitter will reduce the measured squeezing. The effects on quadrat ure phase squeezing and photon number squeezing are different from the usual balanced homodyne detection.

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

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THEORETICAL STUDY OF THE GROUND-STATE PROPERTY OF THE TWO-DIMENSIONAL HEISENBERG ANTIFERROMAGNET ON A TRIANGULAR LATTICE DONG ZHAN-HAI (董占海), FENG SHI-PING (冯世平) Acta Physica Sinica (Overseas Edition), 1998, 7 (5):  348-353.  DOI: 10.1088/1004-423X/7/5/005 Abstract ( 1517 )   PDF (171KB) ( 365 )   Within the Tyablikov's theoretical framework, the ground-state property of the two-dimensional antiferromagnetic Heisenberg model on a triangular lattice is studied. Our results show that the sublattice magnetization is M=0.241 and the ground-state energy per bond is Eg/ NZJ =-0.166, which are in agreement with the numerical simulations.

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MAGNETIC PROPERTIES OF Pr2Co17-x Mx ( M＝Ga,Si) COMPOUNDS ZHANG SHAO-YING (张绍英), SHEN BAO-GEN (沈保根), LI RUN-WEI (李润伟), LIANG BING (梁兵), ZHANG HONG-WEI (张宏伟), CHENG ZHAO-HUA (成昭华), WANG FANG-WEI (王芳卫), ZHAN WEN-SHAN (詹文山), ZHANG LI-GANG (张立刚) Acta Physica Sinica (Overseas Edition), 1998, 7 (5):  354-360.  DOI: 10.1088/1004-423X/7/5/006 Abstract ( 1215 )   PDF (200KB) ( 363 )   The influence of Ga or Si substitution for Co on the structural and magnetic properties of Pr2Co17 compounds is investigated. All samples studied here are single phase and have the rhombohedral Th2Zn17-type structure. The unit-cell volume is found to increase linearly by the substitution of Ga for Co,but reduce by the substitution of Si for Co in Pr2Co17 compounds. In Pr2Co17-x Mx, the Curie temperature decreases monoto nically with increasing at an approximate rate of 153K per Ga atom and 175K per Si atom. The saturation magnetic moment of Pr2Co17-x Mx ( M=Ga,Si) decreases with increasing x. The rates of the decrease are larger than that expected as a simple dilution. For Pr2Co17-xSix ,the spin reorientation transition is observed above room temperature. The spin-reorientation temperature Tsr first decreases with increasing Si content and then increases at higher x values (x>2). The spin reorientat ion behavior is interpreted by the competition between the Pr and Co sublattice anisotropies. The easy magnetization direction in Pr2Co17-xGax compounds is perpendicular to the c-axis, and no spin reorientation transition is observed.

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SPIN-DEPENDENT INTERFACIAL TUNNELING AND MAGNETO RESISTANCE IN THE FAMILY OF GRANULAR PEROVSKITE La1-xSrxMnO*3 ZHANG NING (张宁), DING WEI-PING (丁维平), TAN XI-LIN (谭锡林), XU YIN-LIN (徐寅林), XING DING-YU (邢定钰), DU YOU-WEI (都有为) Acta Physica Sinica (Overseas Edition), 1998, 7 (5):  361-367.  DOI: 10.1088/1004-423X/7/5/007 Abstract ( 1337 )   PDF (225KB) ( 371 )   The magnetic transport properties in granular perovskite system La1-xSrxMnO*3 have been investigated. The spin-dependent inter facial tunneling and the corresponding giant magnetoresistance (GMR) effect have been observed in the whole temperature range below the Curie point Tc for the samp les with concentration x from 0.05 to 0.45. Theoretical analysis shows that the interfacial tunneling originates from the difference in magnetism between surfaces and cores, and the tunnel-type GMR stems from the field-induced change of interfacial magnetic order.

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LINEAR AND NONLINEAR INTERSUBBAND OPTICAL PROPERTIES IN A STEP QUANTUM WELL WITH AN APPLIED ELECTRIC FIELD CHANG KAI (常凯), WU WEN-GANG (吴文刚), JIANG DE-SHENG (江德生), XIA JIAN-BAI (夏建白) Acta Physica Sinica (Overseas Edition), 1998, 7 (5):  368-378.  DOI: 10.1088/1004-423X/7/5/008 Abstract ( 1446 )   PDF (251KB) ( 348 )   Within the framework of the effective-mass envelope-function theory , the field-dependent intersubband optical properties of a Al0.4Ga0.6As/Al0.2Ga0.8As/GaAs step quantum well are investigated theoretic ally based on the periodic boundary condition. A very large Stark shift occurs when the lowest subband electron remains confined to the small well while the hig her subband electron confined to the big well. The optical nonlinearity in a step well due to resonant intersubband transition(ISBT) is analyzed using a density matrix approach. The second-harmonic generation coefficient $\chi$(2)2$\omega$ and nonlinear optical rectification $\chi$(2)0 have also been investigated theoretically. The results show that the ISBT in a step well can generate very large second order optical nonlinearities, $\chi$(2)0 and $\chi$(2)2$\omega$  can be tuned by the electric field over a wide range.

CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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A KINETIC MODEL FOR THE INITIAL GROWTH OF DIAMOND FILMS LIU QIU-XIANG (刘秋香), WANG JIN-BIN (王金斌), YANG GUO-WEI (杨国伟), YOU JIAN-QIANG (游建强) Acta Physica Sinica (Overseas Edition), 1998, 7 (5):  379-387.  DOI: 10.1088/1004-423X/7/5/009 Abstract ( 768 )   PDF (279KB) ( 312 )   Based on a surface reaction mechanism for diamond deposition from the gas phase, a kinetic model is developed to describe diamond nucleation sites and the initial stage of diamond growth in chemical vapor deposition. The timein dependent solutions to the rate equations, which describe the steady-state growth of diamond films, is obtained analytically for the case of small ratio of car bon flux to atomic hydrogen flux. The time-dependent solutions obtained by nume rical methods for large ratio of carbon to atomic hydrogen flux describe the nucleation and initial gorwth stage of diamond films. This model suggests some general predictions for diamond nucleation and growth and can be used to explain several important experimental phenomena observed by others.