Table of Content

20 September 1995, Volume 4 Issue 9 Previous Issue    Next Issue

GENERAL

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SENSITIVITY TO PERTURBATION IN QUANTUM CHAOTIC SYSTEM JIE QUAN-LIN, XU GONG-OU 1995, 4 (9):  641-648.  doi: 10.1088/1004-423X/4/9/001 Abstract ( 0 )   PDF (192KB) ([an error occurred while processing this directive])   Numerical results show that, for quantum autonomous chaotic system, the evolution of initially coherent states are sensitive to perturbation. The overlap of a perturbed state with the unperturbed one decays exponentially, which is followed by fluctuation around N-1, N being the dimension of the Hilbert space. The matrix elements of the evolution operator in interaction picture tend to be a random distribution after sufficiently long time, where the interaction is the perturbation, even when the perturbation is very weak. The difference between a regular system and the chaotic one is shown clearly. In a regular system, the overlap shows strong revival. The distribution of the evolution matrix has only a few dominant terms.

CLASSICAL AREAS OF PHENOMENOLOGY

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CONSTRUCTION OF THE SOLITON STATES OF THE QUANTUM NONLINEAR SCHR?DINGER EQUATION DUAN LU-MING, GUO GUANG-CAN 1995, 4 (9):  649-662.  doi: 10.1088/1004-423X/4/9/002 Abstract ( 0 )   PDF (318KB) ([an error occurred while processing this directive])   The quantum nonlinear schr?dinger equation (QNSE) is exactly solved by Beth's ansatz method and we give a reasonable definition of the quantum soliton states. From the definition we construct the soliton states of the QNSE from its bound-state solutions. The dispersion effect of the quantum soliton is also exactly analysed.

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PHOTOCONDUCTIVITY STUDY OF A POTENTIAL PHOTOREFRACTIVE POLYMER DOU SHUO-XING, ZHANG JIA-SEN, YE PEI-XIAN, HONG HAI-PING, YE CHENG 1995, 4 (9):  663-669.  doi: 10.1088/1004-423X/4/9/003 Abstract ( 0 )   PDF (183KB) ([an error occurred while processing this directive])   Photoconductive properties of a polymer designed to be photorefractive are investigated. The polymer is composed of photoconducting PVK [poly(n-vinylcarbazole)], photosensitizing TNF (2, 4, 7-trinitro-9-fluorenone), and optically nonlinear DANS (4-N, N-dimethyl-4′-nitrostilbene). The electric-field dependence and λ dependence of its photoconductivity and photocarrier generation efficiency have been measured. And preliminary four-wave mixing experiments have been carried out.

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NONLINEAR ACOUSTICS IN HIGHER-ORDER APPROXIMATION QIAN ZU-WEN 1995, 4 (9):  670-675.  doi: 10.1088/1004-423X/4/9/004 Abstract ( 0 )   PDF (141KB) ([an error occurred while processing this directive])   Based on Lighthill's equation, the n-th order (n > 2) inhomogeneous wave equations are established by means of the perturbation method. The third-order nonlinear parameter C/A is defined as a new characteristic parameter in addition to the second-order one B/A, By using the Lagrange's parameter variation method, the third-order harmonic waves are obtained, in which the accumulation solution have a term proportional to the square of the distance, It is shown by analysis that all the solutions are valid only in the region where the accumulation terms are predominant.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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NEUTRON-POWDER-DIFFRACTION STUDY OF THE STRUCTURE AND MAGNETIC PROPERTIES OF Nd2Fe14Si3 ZHANG ZHI-YOU, SUN XIANG-DONG, ZHANG PAN-LIN, CHENG ZHAO-HUA, GOU CHENG, CHEN DONG-FENG 1995, 4 (9):  676-681.  doi: 10.1088/1004-423X/4/9/005 Abstract ( 0 )   PDF (139KB) ([an error occurred while processing this directive])   The crystal and magnetic structures of Nd2Fe14Si3 at room temperature were refined by Rietveld analysis of neutron-powder-diffraction data. It was found that silicon atoms occupy preferentially both 18h and 18f of Th2Zn17-type structure with occupancies 0.36 and 0.14, respectively, The Fe-Fe bond-lengths computed with the refined crystallographic parameters have optimum values, as compared with those of Nd2Fe17 compounds, which can explain well why the Curie temperature rises strongly when the unit cell volume reduces with the substitution of silicon for iron in Nd2Fe17.

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RAMAN STUDIES ON THE PHASE TRANSITIONS OF (NH4)2SnBr6 CRYSTALS ZHANG JIA-MING, SHEN XUE-CHU, XU YONG-CHEN 1995, 4 (9):  682-690.  doi: 10.1088/1004-423X/4/9/006 Abstract ( 0 )   PDF (297KB) ([an error occurred while processing this directive])   We report here the structural phase transitions of the crystal (NH4)2SnBr6 investigated by Raman scattering at temperatures ranging from 10K to room temperature. Two phase transitions occurring at 150 and ll0K are found. Based on the group theory, it is proposed that the crystal undergoes a second-order phase transition at 150 K, resulting from a ferro-distortion with symmetry Γ4+. The change of structure is confirmed to be O5h to C54h, which is assigned to the rotary of [SnBr6]2- ion groups around the axis of <001>. Furthermore the crystal undergoes an order-disorder phase transition at ll0K which is related with the reorientation of the ammonium ion group. It is noticed that the change of the vibrational modes at 77K does not show any phase transition.

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A THEORETICAL MODEL FOR H2 DISSOCIATIVE ADSORPTION ON Cu SURFACES XIE JIAN-JUN, JIANG PING, ZHANG KAI-MING 1995, 4 (9):  691-697.  doi: 10.1088/1004-423X/4/9/007 Abstract ( 0 )   PDF (193KB) ([an error occurred while processing this directive])   A theoretical model for describing H2 dissociative chemisorption on Cu surfaces is proposed. The sticking probability S is calculated as a function of vibrational state, average kinetic energy and incident angle of hydrogen molecular beam. Within the theoretical frame of this model, the different contributions to S from H2(v = 0) and H2(v = 1) can be clearly distinguished. The calculated results indicate that vibrational energy significantly promotes the chemisorption of H2 on Cu surfaces in the region of low translational energy. The equations derived can be used to analyze the experimental data for both pure and seeded molecular beams.

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STUDY ON THE OPTICAL PROPERTIES AND HYDROGEN CONTENT OF THE SILICON NITRIDE THIN FILM CHEN JUN-FANG, REN ZHAO-XING, DING ZHEN-FENG 1995, 4 (9):  698-704.  doi: 10.1088/1004-423X/4/9/008 Abstract ( 0 )   PDF (168KB) ([an error occurred while processing this directive])   The Si3N4 thin films have been manufactured by electron cyclotron resonance plasma enhanced chemical vapour deposition technology on the KBr and (111) monocrystal Si sub-strates, The infrared optical properties of the Si3N4 film have been studied by analysing its IR spectrum. The results show that the Si3N4 film can be used as an antireflexion and an-tireflectiug film of Si surface, The H content of Si3N4 thin film has been estimated from the infrared absorption area. It is obtained that the H content of the Si3N4 film deposited on the KBr substrate is lower than that deposited on Si substrate, and it derceases with increasing deposition temperature. The Raman spectra of the Si3N4 film deposited at 360℃ has also been measured.

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

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INVESTIGATION OF THE STRUCTURAL PHASE TRANSITION OF MnBi AND MnBiAl FILMS YANG HUI-SHENG, ZHANG XIAO-WEI, XU YAO, ZHU WEN-KAI, WANG YIN-JUN 1995, 4 (9):  705-711.  doi: 10.1088/1004-423X/4/9/009 Abstract ( 0 )   PDF (186KB) ([an error occurred while processing this directive])   Structural phase transition of MnBi and MnBiAl films has been investigated in the tem-perature range of 30-400℃. The transition from low-temperature phase to high-temperature phase occurs in both the films, but the phase transitions appear at different temperatures. According to the measurement of Kerr rotation as a function of thermal annealing and the phase transition process, it is shown that the transition is irreversible for MnBi film and reversible for MnBiAl film under our experimental condition. For this reason, we speculate that the aluminum added in MnBi makes the bonding force of Mn atoms with their neighbors stronger, which may be the cause for the difference of the phase transition between MnBi and MnBiAl films.