Table of contents

20 December 1998, Volume 7 Issue 12 Previous issue    Next issue

ATOMIC AND MOLECULAR PHYSICS

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EXPERIMENTAL STUDY ON LASER COOLING OF CESIUM ATOMS BY OPTICAL MOLASSES HOU JI-DONG (候继东), YANG YI-MIN (李义民), YANG DONG-HAI (杨东海), WANG YI-QIU (王义遒) Acta Physica Sinica (Overseas Edition), 1998, 7 (12):  881-885.  DOI: 10.1088/1004-423X/7/12/001 Abstract ( 1208 )   PDF (165KB) ( 536 )   We have studied the relationship between the temperature of Cs cold atoms and the parameters of the cooling laser. The atoms are first cooled and captured by a magnetooptical trap and then further coaled by optical molasses. The temperature of atoms la measured by a time-of-flight method. For relatively large laser intensity and small detuning, the temperature depends linearly on the intensity-to-detuning ratio, and nonlinear relationship has alao been found in other case.

CLASSICAL AREAS OF PHENOMENOLOGY

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DYNAMIC QUANTUM NOISE REDUCTION IN A CASCADE LASER WITH AND WITHOUT INVERSION HU XIANG-MING (胡响明), PENG JIN-SHENG (彭金生) Acta Physica Sinica (Overseas Edition), 1998, 7 (12):  886-897.  DOI: 10.1088/1004-423X/7/12/002 Abstract ( 1173 )   PDF (300KB) ( 391 )   In this paper we investigate the effect of two incoherent steps on the statistical properties of cascade lasers without and with inversion. It is demonstrated that the noise in the intensity difference may be reduced 50% below the shot noise. A simple physical explanation of the mechanism for squeezing is given.

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MODE-COMPETITION EFFECTS OF A TWO-MODE LASER WITH MULTIPLICATIVE COLORED NOISE WITH SATURATION EFFECTS CHEN LI-MEI (陈黎梅), CAO LI (曹力), QIU JUN-LIN (丘军林) Acta Physica Sinica (Overseas Edition), 1998, 7 (12):  898-904.  DOI: 10.1088/1004-423X/7/12/003 Abstract ( 1151 )   PDF (175KB) ( 370 )   The effect of multiplicative colored noise on mode-competition of the two-mode laser with saturation effects is studied, By means of linear stability analysis, and by considering $\tau$ as a small parameter, some significant conclusions have been obtained. In strong coupling, the effect of multiplicative colored noise on mode-competition is stronger than that of multiplicative white noise, and it is enhanced with the increase of noise strength. In weak coupling, the effect of multiplicative colored noise on mode-competition is weaker than that of multiplicative white noise, and it is decreased with the increase of coupling constants.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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SIZE AND GRAIN-DISTRIBUTION EFFECTS IN ELECTRONIC PROPERTIES OF TWO-DIMENSIONAL NANOCRYSTALLINE RECTANGLE SYSTEMS YAN XIAO-HONG (颜晓红), YANG QI-BIN (杨奇斌), DUAN ZHU-PING (段祝平), ZHANG LI-DE (张立德) Acta Physica Sinica (Overseas Edition), 1998, 7 (12):  905-911.  DOI: 10.1088/1004-423X/7/12/004 Abstract ( 1174 )   PDF (201KB) ( 379 )   According to the structural characters of real nanostructured systems, a model for two-dimensional nanostructured systems has been proposed. By developing a renormalization-group Green's function scheme, local electronic density of states at a type of crystallire sites is presented on the pure hopping model. It is found that the changes of all the grain-distribution rules, the average atomic number and the atomic interaction are connected with the spectral structures of nanostructured systems. However, bule shifts of the spectra of nanostruetured systems seem to be modulated mainly by the changes of the bond-parameters which are correlated with the lattice distortions of the nano-sized grains.

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

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SIMS STUDY OF OXYGEN SPIRAL DIFFUSION C-TEXTURED Yba2Cu3O7-$\delta$/SrTiO3 EPITAXIAL THIN FILM CAI ZHEN (蔡震), JIN XUE-JUN (金学军) Acta Physica Sinica (Overseas Edition), 1998, 7 (12):  912-918.  DOI: 10.1088/1004-423X/7/12/005 Abstract ( 1168 )   PDF (182KB) ( 393 )   Secondary ion mass spectroscopy was used to study the chemical diffusivity of O18 in c-textured YBa2Cu3O7-$\delta$/SrTiO3 epitaxial thin film. By fitting experimental data to the one- dimensional diffusion curve, the apparent diffusivity along the c-axis was obtained to be equal to l.02×1014cm2/sec when the temperature was 350℃. A computer analysis method was put forward to calculate the "spiral diffusion" process, and the diffusivity anisotopy of films with different mosaic size obtained. For a film of 7000×7000?2 mosaic size, Dab was found to be ～3.55×10-5×exp((-1.03 ev)/kT) cm2/sec. The calculated results reveal that the variation of the results of Dc is not the result of diffusivity anisotropy but of the difference in mosaic size.

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AGNETORESISTANCE, SPECIAL HEAT AND AC MAGNETIC SUSCEPTIBILITY IN La1-xCaxMnO3 SYSTEM ZHOU YA-QIN (周雅琴), LIAN GUI-JUN (连贵君), ZHANG YIN (张寅), XIONG GUANG-CHENG (熊光成), WANG KE-QIN (王克勤), RUAN KE-QING (阮可青), CAO LIE-ZHAO (曹烈兆), YE HONG-JUAN (叶红娟) Acta Physica Sinica (Overseas Edition), 1998, 7 (12):  919-924.  DOI: 10.1088/1004-423X/7/12/006 Abstract ( 1160 )   PDF (181KB) ( 438 )   We have measured the resistivity, special heat and AC magnetic suceptibility versus temperature in La1-xCaxMnO3(LCMO) bulk samples with x=0.3, 0.4, 0.5, 0.6. In the LCMO (x=0.3 and 0.4) samples a transition from d$\rho$/dT<0 to d$\rho$/dT>0 was observed, accompanied by a peak in specific heat. In AC magnetic suceptibility measurement, a ferromagnetic and an antiferromagnetic transitions were observed in LCMO (x=0.5) sample.

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STABILITY OF SECOND KIND OF DUMBBELL DOMAINS SUBJECTED TO AN IN-PLANE FIELD AT DIFFERENT BIAS FIELDS WANG YUAN-FEI (王远飞), HAN BAO-SHAN (韩宝善), TANG GUI-DE (唐贵德), WANG HONG-XIN (王洪信), SUN HUI-YUAN (孙会元), NIE XIANG-FU (聂向富) Acta Physica Sinica (Overseas Edition), 1998, 7 (12):  925-929.  DOI: 10.1088/1004-423X/7/12/007 Abstract ( 1187 )   PDF (199KB) ( 453 )   The softening process of the second kind of dumbbell domalns(liDs) in garnet bubble films subjected to an in-plane field Hip at different static bias field Hb was studied experimentally. It was found that when Hb is larger, the remaining percentage of IID, RIID, drops sharply at a certain Hip, and with the increase of Hb the drop occurs at lower Hip and becomes more intensive. We have confirmed that this is related to the "spontaneous-shrink" 0f IIDs, which plays an important role for the breakdown oF vertical Bloeh line chains of lids subjected to joint fields Hip and Hb .

CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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PROPERITES OF HYDROGENATED AMORPHOUS SILICON CARBIDE FILMS IRRADIATED BY EXCIMER PULSE LASER WANG LI (王立), MA TIAN-FU (马天夫), HUANG XIN-FAN (黄信凡), XU JUN (徐俊), LI QI-LIANG (李启亮), WU ZHUANG-CHUN (吴状春), CHEN KUN-JI (陈坤基) Acta Physica Sinica (Overseas Edition), 1998, 7 (12):  930-935.  DOI: 10.1088/1004-423X/7/12/008 Abstract ( 1044 )   PDF (174KB) ( 327 )   A series of hydrogenated amorphous silicon carbide film (a-SiC:H) were prepared by rf plasma-enhanced chemical vapor deposition method. The optical band gap(Eoptg) of the films can be extended to 2.6eV. The as-deposited alma were then irradiated by a KrF excimer laser. During the irradiation process, hydrogen escaped out of the films, and the structure of the films was changed from an amorphous phase to mixed phases of nanocrystallites of silicon and amorphous silicon carbide. The room-temperature dark conductivity of the laser irradiated films is 6-7 orders of magnitude larger than that of the as-deposited films, which was attributed to the modification of the conductivity mechanism resulting from the structural change.