Table of contents

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 (揭泉林), XU GONG-OU (徐躬耦) Acta Physica Sinica (Overseas Edition), 1995, 4 (9):  641-648.  DOI: 10.1088/1004-423X/4/9/001 Abstract ( 1253 )   PDF (192KB) ( 385 )   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 (段路明), GUO GUANG-CAN (郭光灿) Acta Physica Sinica (Overseas Edition), 1995, 4 (9):  649-662.  DOI: 10.1088/1004-423X/4/9/002 Abstract ( 1181 )   PDF (318KB) ( 394 )   The quantum nonlinear schr$\ddot{o}$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 (窦硕星), ZHANG JIA-SEN (张家森), YE PEI-XIAN (叶佩弦), HONG HAI-PING (洪海平), YE CHENG (叶成) Acta Physica Sinica (Overseas Edition), 1995, 4 (9):  663-669.  DOI: 10.1088/1004-423X/4/9/003 Abstract ( 1159 )   PDF (183KB) ( 323 )   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 $\lambda$ 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 (钱祖文) Acta Physica Sinica (Overseas Edition), 1995, 4 (9):  670-675.  DOI: 10.1088/1004-423X/4/9/004 Abstract ( 1182 )   PDF (141KB) ( 335 )   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 (张志友), SUN XIANG-DONG (孙向东), ZHANG PAN-LIN (张泮霖), CHENG ZHAO-HUA (成昭华), GOU CHENG (勾成), CHEN DONG-FENG (陈东风) Acta Physica Sinica (Overseas Edition), 1995, 4 (9):  676-681.  DOI: 10.1088/1004-423X/4/9/005 Abstract ( 1259 )   PDF (139KB) ( 323 )   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 (张家明), SHEN XUE-CHU (沈学础), XU YONG-CHEN (徐永晨), J. PELZL Acta Physica Sinica (Overseas Edition), 1995, 4 (9):  682-690.  DOI: 10.1088/1004-423X/4/9/006 Abstract ( 1246 )   PDF (297KB) ( 394 )   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 $\varGamma$4+. 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. 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 (谢建军), JIANG PING (蒋平), ZHANG KAI-MING (张开明) Acta Physica Sinica (Overseas Edition), 1995, 4 (9):  691-697.  DOI: 10.1088/1004-423X/4/9/007 Abstract ( 1163 )   PDF (193KB) ( 313 )   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($\nu$ = 0) and H2($\nu$ = 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 (陈俊芳), REN ZHAO-XING (任兆杏), DING ZHEN-FENG (丁振峰) Acta Physica Sinica (Overseas Edition), 1995, 4 (9):  698-704.  DOI: 10.1088/1004-423X/4/9/008 Abstract ( 1397 )   PDF (168KB) ( 387 )   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 (杨会生), ZHANG XIAO-WEI (张晓卫), XU YAO (徐瑶), ZHU WEN-KAI (朱文凯), WANG YIN-JUN (王荫君) Acta Physica Sinica (Overseas Edition), 1995, 4 (9):  705-711.  DOI: 10.1088/1004-423X/4/9/009 Abstract ( 1262 )   PDF (186KB) ( 453 )   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.