中国物理B

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DIFFUSIVE AGGREGATION ON ION IMPLANTED THIN FILMS

王坚, 吴杏芳, 方正知

1992 (2): 81-85. doi: 10.1088/1004-423X/1/2/001

摘要 ( 1231 )

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Diffusive aggregation on-ion implanted thin films is studied. It is revealed that aggregation is realized mainly by atoms or clusters in the film matrix. The implanting ions play the role of triggering them into motion and supplying the kinetic energy for their diffusion. The aggregation process is characterized by finite density of aggregating particles, random triggering, and limited diffusion distance. The aggregate observed shows scaling or fractal property.

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THE BEAM TEMPERATURE AND ENERGY BROADENING OF A CHARGED-PARTICLE BEAM IN AN AXIALLY SYMMETRIC MAGNETIC FIELD

田人和, MANFRED FINK

1992 (2): 86-93. doi: 10.1088/1004-423X/1/2/002

摘要 ( 1268 )

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The beam temperature and energy broadening of a charged-particle beam in an axially symmetric mag-netic field are investigated in consideration of the space charge effect. The result shows that this kind of energy broadening consists of three parts: the thermal motion broadening, the space charge broadening, and the magnetic-field broadening. For the nonscalloping beam (including the space charge equilibrium flow and Brillouin flow) held by the equilibrium between the magnetic-field convergence and the space charge diver-gence, the energy broadening ΔE is directly proportional to the square of the equilibrium magnetic induction intensity B_e and the beam radius R, and inversely proportional to the mass of beam particles. For the im-mersed flow (magnetic shield coefficient M = 1), the magnetic field does not result in an energy broadening, and the energy broadening caused by space charge is dominant. The beam temperature is defined by the mean square deviation of the velocity of beam particles. The beam temperature in the θ direction is much higher, whereas the beam temperature in the meridian direction is much lower than the temperature of the thermal cathode.

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A FULL QUANTUM THEORY OF THE THREE-MODE INTERACTIONS INSIDE AN OPO CAVITY

张天才, 谢常德, 彭堃墀

1992 (2): 94-103. doi: 10.1088/1004-423X/1/2/003

摘要 ( 1499 )

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A full quantum treatment about the process of parametric down-conversion with frequency degenerate but polarization pon-degenerate in an optical parametric oscillator (OPO) cavity is presented. Using the linearized Langevin equations and spectral matrix, we calculated the squeezing spectra of the coupled mode in the output field. The squeezing as a function of driving field and detection frequency is obtained. The resuits obtained, which are compared with those found semiclassically by Reynaud et al., indicate that it is possible to generate a two-mode coherent squeezed state with large amplitude. The quantum correlation between the signal and the idler modes is also discussed. It is shown that there is an inseparable relationship between the two-mode squeezing and the intermode quantum correlation.

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INTERFACE STRESS, TENSION AND FREE ENERGY DENSITY OF CONDENSED MATTER

梁忠诚

1992 (2): 104-112. doi: 10.1088/1004-423X/1/2/004

摘要 ( 1127 )

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A model of geometrical interface with inherent elastic stress is developed. The general formulas for interface stress, tension and free energy density of condensed matter as well as their relations are derived. The constitutive relationship of the interface is also discussed. The results so obtained all agree with the current theories, and some new conclusions are drawn.

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ON THE LOCALIZATION OF ELECTRONIC STATES IN ONE-DIMENSIONAL QUASILATTICES

邓文基, 刘有延, 黄秀清

1992 (2): 113-122. doi: 10.1088/1004-423X/1/2/005

摘要 ( 1196 )

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For the localization of electronic states of one-dimensional quasilattices, two kinds of methods extensively used (KKT renormalization-group method and numerical simulation methods) have given contradictory, results. In this paper, an approach based on the transfer matrix method is adopted to deal with this problem in general. We confirm that the above two methods describe the ideal infinite quasilattices in different asymptotical ways. so different results are obtained. We also study analytically the localization of the zero-energy electronic states of the one-dimensional quasilattices, and provide some new results different from that of the previous work.

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THERMALLY ACTIVATED FLUX MOTION IN HIGH-T_c SUPERCONDUCTORS

范宏昌, 张贻瞳, 金新, 童红武, 姚希贤

1992 (2): 123-129. doi: 10.1088/1004-423X/1/2/006

摘要 ( 1151 )

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Using the modified Anderson-Kim theory of flux creep and the Bean model, we derive an analytical ex-pression for magnetic relaxation of high-T_c superconductors, which is applicable in the whole flux creep region. The high driving force limit of the expression gives the usual logarithmic decay law and its low driving force limit takes the exponential form. Theoretical analysis is in agreement with the existing experimental results.

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RAMAN SCATTERING INTENSITIES OF FOLDED LONGITUDINAL ACOUSTIC PHONONS IN Ge_xSi_1-x/Si SUPERLATTICES

金鹰, 张树霖, 秦国刚, 樊永良, 周国良, 俞鸣人

1992 (2): 130-137. doi: 10.1088/1004-423X/1/2/007

摘要 ( 1336 )

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In terms of photoelastic mechanism we have investigated the Raman scattering intensities of the folded longitudinal acoustic (FLA) phonons in Ge_xSi_1-x/ Si superlattices (SLs), taking into account the differences between the acoustic and photoelastic parameters of the two constituents in the SLs. The relative intensities calculated for the FLA phonons are in excellent agreement with the experimental results at the frequencies up to about 50 cm^-1. The broadening of the linewidth arising from the so called strong acoustic attenuation, which was reported previously located around the frequency 15 cm^-1 in Ge_xSi_1-x/Si SLs(x≈0.5), has not been observed in this work.

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MASS ATTENUATION COEFFICIENTS FOR ELEMENTS MEASURED WITH CHARACTERISTIC X-RAYS FROM TARGETS EXCITED BY ENERGETIC PROTON

王大椿, 丁训良, 杨华, 罗平安

1992 (2): 138-148. doi: 10.1088/1004-423X/1/2/008

摘要 ( 1102 )

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The characteristic X-rays from elemental or compound targets excited by energetic proton are quasi-monochromatic X-ray sources. The advantages of high line/ background ratio, controllable intensity as well as many available energies, make them suitable for applications in many important fields. The total mass attenuation cross sections of yttrium have been systematically measured by using this kind of X-ray source. The accuracy of experimental data has been improved to ±1%, which is much better than that of earlier results. The contributions of the coherent and incoherent scattering crees sections have been calcu-lated in accordance with the present experimental condition. And the total photoelectric cross sections have been obtained by subtracting the scattering cross section from the measured total cross sections. The com-parisons of our experimental results with the available data of earlier investigations as well as with the theo-retical calculations have been presented and discussed.

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