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1994年, 第3卷, 第7期　刊出日期：1994-07-20 上一期    下一期

THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

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WARD IDENTITIES IN PHASE SPACE AND THEIR APPLICATIONS 李子平 1994 (7):  481-492.  doi: 10.1088/1004-423X/3/7/001 摘要 ( 1120 )   PDF(290KB) ( 413 )   Starting from the phase space path integral, we have derived the Ward identities in canonical formalism for a system with regular and singular Lagrangian. This formulation differs from the traditional discussion based on path integral in configuration space. It is pointed out that the quantum canonical equations for systems with singular Lagrangians are different from the classical ones obtained from Dirac's conjecture, The preliminary applications of Ward identities in phase space to the Yang-Mills theory are given. Some relations among the proper vertices and propagators are deduced,the PCAC, AVV vertices and generalized PCAC expressions are also obtained. We have also pointed out that some authors in their early work had ignored the treatment of the constraints. 相关文章 | 计量指标

ATOMIC AND MOLECULAR PHYSICS

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RAMAN SPECTROSCOPIC STUDY OF Nd-DOPED LITHIUM TANTALATE 吴兴龙, 张明生, 陈强, 邹群, 耿兆华, 冯端 1994 (7):  493-500.  doi: 10.1088/1004-423X/3/7/002 摘要 ( 1500 )   PDF(217KB) ( 428 )   Raman spectra of Nd-doped LiTaO3 have been measured at right angle scattering geome-tries at room temperature. The spectra have drastically anomalous phenomena as compared with those of pure LiTaO3. We may attribute these anomalies to the enhanced photoinduced refractive index change and the change of LiTaO3 microstructure resulting from Nd doping. 相关文章 | 计量指标

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MEASUREMENTS OF 129Xe NUCLEAR MAGNETIC RESONANCE IN GASEOUS, LIQUID AND SOLID XENON 赵明信, 汪盛烈, 孙献平, 李丽云, 曾锡之 1994 (7):  501-505.  doi: 10.1088/1004-423X/3/7/003 摘要 ( 1190 )   PDF(121KB) ( 320 )   Natural xenon, contained in a ceil at a pressure of 6.5 atm, is frozen from 303 to 137 K on an WP-80SY NMR spectrometer. NMR signals of 129Xe atoms in gaseous, liquid and solid phases are measured at various temperatures, We found that the chemical shift of NMR signal of liquid 129Xe (expressed as ΔH) is directly proportional to the density of the sample with a coefficient of (4.73±0.05)×10-7; and the chemical shift of NMR signal of solid 129Xe (expressed as ΔH) is nearly proportional to the density of the sample with a coefficient of (5.00±0.08)×10-7. 相关文章 | 计量指标

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A STUDY ON REAL-TIME LOW-FREQUENCY SPATIAL FILTERING PROCESS OF AN OPTICAL IMAGE USING LiNbO3:Fe CRYSTAL 刘思敏, 陆猗, 陈海东, 刘军民, 许京军, 张光寅, 杨立森, 门丽秋, 孙骞 1994 (7):  506-511.  doi: 10.1088/1004-423X/3/7/004 摘要 ( 1143 )   PDF(203KB) ( 457 )   The optimum image processing result of low-frequency filtering was obtained when LiNbO3:Fe crystal as a spatial filter was placed at a certain position behind the spatial-frequency spectral plane of an optical Fourier transform system, which corresponds to the minimum transmittance ratio in Z-scan curve. The experimental results show that self-defocusing due to photorefractive negative-lens effect is the main factor responsible for the low- frequency filtering. 相关文章 | 计量指标

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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THE ANNEALING FEATURES OF Ta/Si MULTILAYER FILMS 卢江, 周贵恩, 张庶元, 贾云波, 李凡庆, 黄允兰, 谭舜, 石磊, 张裕恒 1994 (7):  512-518.  doi: 10.1088/1004-423X/3/7/005 摘要 ( 1121 )   PDF(213KB) ( 407 )   The Ta/Si multilayers on (100) Si substrate have been studied over the annealing temper-ature range from 500 to 900℃ by X-ray diffraction and cross-section transmission electron microscopy. The periodicity of the multilayers becomes worse with increasing annealing tem-perature and disappears at 750℃. At 600℃, two kinds of modulation wavelength coexist because the size of several TaSi2 grains is larger than the contracted original modulation wavelength. The films are contracted after annealing. The largest contraction, at least 40nm decreasing in thickness, occurs at 600℃. When the annealing temperature is lower than 600℃, h-TaSi2 grains grow randomly and the growth is not affected by the substrate. At temperatures higher than 750℃, h-TaSi2 grows preferentially in [001] direction parallel to [100] axis of Si substrate. The appearance of texture depends on whether the atomic diffusion is short range or long range at the corresponding annealing temperature. 相关文章 | 计量指标

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

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SYNTHESIS AND STRUCTURE OF CARBON NANOTUBES 解思深, 刘维, 张泽渤, 王刚, 钱生法, 傅春生, 李楠, 郑幼凤, 李超荣 1994 (7):  519-527.  doi: 10.1088/1004-423X/3/7/006 摘要 ( 1409 )   PDF(395KB) ( 463 )   The distribution, morphology and structure of carbon nanotubes and buckyonions produced from an arc discharge were investigated by means of scanning electron mi-croscopy and high-resolution transmission electron microscopy, The nanotubes and nanoonions were found to be located mainly near the porous region of the core in the deposited rods and the transition region between the growth ring-shaped graphite sheets. The tube bundles grew freely from carbon particles. Apart from the straight-line tubes, curved and bent tubes were also found. Studies on the structure of them showed that the carbon atomic sheets in the nanotubes displayed a stepped bending. Transverse sectional study predicted a helical structure of the carbon atomic sheets. In addition, the relationship between the number of pentagonal rings and cone angle at the tips of the tubes, as well as the mechanism of the formation of the steplike structure, were discussed. 相关文章 | 计量指标

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RESPONSE TIME OF PHOTOEMISSION OF ULTRAFINE PARTICLE THIN FILM 吴锦雷, 郭翎健, 吴全德 1994 (7):  528-538.  doi: 10.1088/1004-423X/3/7/007 摘要 ( 1194 )   PDF(268KB) ( 412 )   The response time of photoemissive materials is required for detecting ultrashort duration laser pulses. In this paper, the response time of photoemission in ultrafine particle thin film is studied, and the transit time spread (TTS) and response time of peak value (tM) are discussed. The photoelectron's response time will increase with increasing energy of photons. If the surface potential barrier of thin film declines, the photoemissive sensitivity or quantum yield will rise, however the response time will also increase, which means that response-time characteristic gets worse. As an example, the response time for Ag-O-Cs thin film is calculated for different cases when photoelectrons, excited in Ag ultrafine particles, travel through Cs2O semiconductor layer to the surface and escape into vacuum. The calculated response time is about 50 fs if this thin film is irradiated by infrared rays of wavelength 1.06μm. 相关文章 | 计量指标

8000 CROSSDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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INVESTIGATION OF THERMAL DENATURATION OF DNA MOLECULES BASED ON LANGEVIN EQUATION APPROACH 杨会杰, 卓益忠, 吴锡真 1994 (7):  539-549.  doi: 10.1088/1004-423X/3/7/008 摘要 ( 991 )   PDF(286KB) ( 305 )   In this paper, by using non-equilibrium transport theory, the thermal denaturation of DNA molecules is investigated as a preliminary step to clarify the dynamical process of DNA transcription, The distribution functions of the displacement of base pairs at different temperatures are calculated. A modified model is also proposed which can reproduce the essential features of the denaturation process, Calculations show that Langevin equation is an effective tool for describing the dynamical process of DNA molecules and it seems to be more advantageous over the Nosé method. 相关文章 | 计量指标