Table of contents

20 October 1995, Volume 4 Issue 10 Previous issue    Next issue

ATOMIC AND MOLECULAR PHYSICS

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STUDY OF HOMOGENEOUS ADSORPTION KINETICS OF CRYSTAL VIOLET FU SHI-YOU (傅石友), GUO YU-FENG (郭余峰), WANG MING-JI (王明吉), ZHANG PENG-XIANG (张鹏翔) Acta Physica Sinica (Overseas Edition), 1995, 4 (10):  721-726.  DOI: 10.1088/1004-423X/4/10/001 Abstract ( 1167 )   PDF (152KB) ( 332 )   The adsorption kinetica of crystal violet (CV) on silver mirror and two different kinds of silver sols is studied. The adsorption of CV on silver is homogeneous. It is confirmed that the topography of the surface affects only adsorption rate constant, while it does not change heterogeneity parameter. The similar behavior of enhancement factor and adsorption rate constant of CV in the two silver sols is discussed. The adsorption energy of CV and the concentration of adsorbed sites on the surface are estimated by adsorption isotherm. It is found that the enhancement effect on the silver mirror is determined by the concentration of adsorbed sites on surface.

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MOTION OF CESIUM ATOMS IN THE ONE-DIMENSIONAL MAGNETO-OPTICAL TRAP LI YI-MIN (李义民), CHEN XU-ZONG (陈徐宗), WANG QING-JI (王庆吉), WANG YI-QIU (王义遒) Acta Physica Sinica (Overseas Edition), 1995, 4 (10):  727-737.  DOI: 10.1088/1004-423X/4/10/002 Abstract ( 1032 )   PDF (282KB) ( 305 )   We calculated the force to which Cs atoms are subject in the one-dimensional magneto-optical trap (1D-MOT), and the properties of this force are also discussed. Several methods to increase the number of Cs atoms in the 1D-MOT are presented on the basis of the analysis of the capture and escape of Cs atoms in the 1D-MOT.

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ELECTRONIC STRUCTURE STUDIES OF THE C60 FILM CONDENSED ON 2H-MoS2(0001) SURFACE LU HUA (陆华), CHEN TING (陈挺), SHEN DIAN-HONG (沈电洪), BAO CHANG-LIN (包昌林), ZHANG XIAO-JUN (张小军), ZHANG QING-ZHE (张青哲), CUI YU-DE (崔玉德), XIE KAN (谢侃), QIAN SHENG-FA (钱生法), WANG GANG (王刚), XIE SI-SHEN (解思深), LIN ZHANG-DA (林彰达) Acta Physica Sinica (Overseas Edition), 1995, 4 (10):  738-756.  DOI: 10.1088/1004-423X/4/10/003 Abstract ( 1278 )   PDF (566KB) ( 411 )   The electronic structure and vibrational spectrum of the C60 film condensed on a 2H- MoS2(0001) surface have been investigated by X-ray photoelectron spectroscopy (XPS), ul-traviolet photoelectron spectroscopy (UPS), Auger electron spectroscopy (AES) and infrared high-resolution electron-energy-loss spectroscopy (HREELS). AES analysis showed that at low energy side of the main transition, C60 contains a total of three peaks just like that of graphite. However, the energy position of the KLL main Auger transition of C60 looks like that of diamond, indicating that the hybridization of the carbon atoms in C60 is not strictly in sp2- bonded state but that the curvature of the molecular surface introduces some sp2pz- bonded character into the molecular orbitals. XPS showed that the C 1s binding energy in C60 was 285.0eV, and its main line was very symmetric and offered no indication of more than a single carbon species. In UPS measurement the valence band spectrum of C60 within 10eV below the Fermi level (EF) shows a very distinct five-band structure that character-izes the electronic structure of the C60 molecule. HREEL results showed that the spectrum obtained from the C60 film has very rich vibrational structure. At least, four distinct main loss peaks can be identified below 200 meV. The most intense loss was recorded at 66 meV, and relatively less intense losses were recorded at 95, 164 and 197meV at a primary energy of electron beam EP = 2.0eV. The other energy-loss peaks at 46, 136, 157 and 186meV in HREEL spectrum are rather weak. These results have been compared to infrared spectrum data of the crystalline solid C60 taken from recent literatures.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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STUDY OF THE MECHANISM OF GaAs(001) MOLECULAR-BEAM EPITAXY MAO HUI-BING (茅惠兵), LU WEI (陆卫), SHEN XUE-CHU (沈学础) Acta Physica Sinica (Overseas Edition), 1995, 4 (10):  757-765.  DOI: 10.1088/1004-423X/4/10/004 Abstract ( 985 )   PDF (238KB) ( 372 )   In this paper the nucleation and growth processes of GaAs(001) molecular-beam epitaxy were studied by Monte Carlo simulation, The density of islands and the density of isolated Ga adatoms were obtained for different growth temperatures, and the island size distribution at low coverage, as well as the correlation function between atoms and its relation with the temperature were studied in detail.

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

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TEMPERATURE-DEPENDENT ANISOTROPY IN La1.86Sr0.14CuO4 YUAN SONG-LIU (袁松柳) Acta Physica Sinica (Overseas Edition), 1995, 4 (10):  766-773.  DOI: 10.1088/1004-423X/4/10/005 Abstract ( 1039 )   PDF (236KB) ( 346 )   Based on the scaling rule: R(T, H, $\theta$) = R(T, h), where h = H(sin2$\theta$+cos2$\theta$/$\gamma$2)1/2 and $\theta$ is field angle with respect to the ab-plane, the scaling approach is performed to examine the c-axis resistances of single crystalline La1.86Sr0.14CuO4 as functions of field and its orientation at different temperatures. The anisotropy parameter $\gamma$ of the system is extracted from the scaling approach, but shows an unusual temperature-dependent behavior, which is not expected by conventional theory. A phenomenological explanation of this temperature dependence is presented.

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DETERMINATION OF THE OXYGEN CONTENT IN YBa2Cu3O7-y FILMS HAO JIAN-MIN (郝建民), WEN YE-LI (温业礼), YANG BING-CHUAN (杨秉川), WANG XIAO-PING (王小平), SHI DONG-QI (石东奇) Acta Physica Sinica (Overseas Edition), 1995, 4 (10):  774-777.  DOI: 10.1088/1004-423X/4/10/006 Abstract ( 1411 )   PDF (122KB) ( 332 )   A method for determination of the oxygen content (y) in YBa2Cu3O7-y films has been established, in which the lattice conetant difference (b-a) of the films was measured and used to fit the function of (b-a) vs y for the experimental data of bulk YBaaCuaO7-y given in the literature. It is suggested that the function of (b-a) vs y can indeed be used in the case of film. In this process the twin structure of the YBa2Cu3O7-y films was used.

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RAMAN SCATTERING OF $\alpha$-ET3(ReO4)2 CHARGE-TRANSFER SALT LIU DAO-ZHI (刘道志), W. HAYES Acta Physica Sinica (Overseas Edition), 1995, 4 (10):  778-782.  DOI: 10.1088/1004-423X/4/10/007 Abstract ( 956 )   PDF (138KB) ( 331 )   We describe the results of Haman studies on C=C stretch modes in $\alpha$-ET3(ReO4)2 charge-transfer salt with the incident laser beam polarised perpendicular and parallel to the large flat face of plate-like crystal. We have assigned central C=C stretch mode at 1454 cm-1 and ring C=C stretch mode at 1470cm-1. The change in ring C=C stretch vibration was observed at the metal-insulator transition of $\alpha$-ET3(ReO4)2 on warming due to the distortion of the ET molecules.

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INFLUENCE OF C+-IMPLANTATION DOSE ON BLUE EMISSION AND MICROSTRUCTURES OF Si-BASED POROUS $\beta$-SIC LIAO LIANG-SHENG (廖良生), BAO XI-MAO (鲍希茂), LI NING-SHENG (李宁生), YANG ZHI-FENG (杨志峰), MIN NAI-BEN (闵乃本) Acta Physica Sinica (Overseas Edition), 1995, 4 (10):  783-789.  DOI: 10.1088/1004-423X/4/10/008 Abstract ( 1168 )   PDF (277KB) ( 415 )   Crystal Si were implanted with different doses of C+ from 1011 to 1017 cm-2 at an energy of 50 keV. $\beta$-SiC precipitates were formed by thermal annealing at 1050 ℃ for 1 h and porous structures were prepared by electrochemical anodization. Under the excitation of ultraviolet, the samples, with C+ dose ≥1015 cm-2 have intense blue emission which is stronger than the photoluminescence (PL) intensity of reference porous silicon (PS), and increases as C+ dose increases; the samples with C+ dose ≤1014 cm-2 show similar PL spectra to those of PS. The blue peak intensity in PL spectra is correlated with the TO phonon absorption strength of $\beta$-SiC in infrared absorption spectra. The transmission electron microscopy study shows that the blue peak is also correlated with the microstructures. Because porous $\beta$-SiC is nanometer in size, it is suggested that the quantum confinement effect be responsible for the blue light emission.