Table of contents

13 May 2002, Volume 11 Issue 5 Previous issue    Next issue

GENERAL

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Topological quantization of disclination points in three-dimensional liquid crystals Yang Guo-Hong (杨国宏), Zhang Hui (张慧), Duan Yi-Shi (段一士) Chinese Physics, 2002, 11 (5):  415-418.  DOI: 10.1088/1009-1963/11/5/301 Abstract ( 1242 )   PDF (210KB) ( 445 )   Using the $\phi$-mapping method and topological current theory, we study the inner structure of disclination points in three-dimensional liquid crystals. By introducing the strength density and the topological current of many disclination points, it is pointed out that the disclination points are determined by the singularities of the general director field and they are topologically quantized by the Hopf indices and Brouwer degrees.

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Monte Carlo simulation of the behaviour of electrons during electron-assisted chemical vapour deposition of diamond Dong Li-Fang (董丽芳), Chen Jun-Ying (陈俊英), Dong Guo-Yi (董国义), Shang Yong (尚勇) Chinese Physics, 2002, 11 (5):  419-424.  DOI: 10.1088/1009-1963/11/5/302 Abstract ( 1355 )   PDF (241KB) ( 604 )   The behaviour of electrons during electron-assisted chemical vapour deposition of diamond is investigated using Monte Carlo simulation. The electron energy distribution and velocity distribution are obtained over a wide range of reduced field E/N (the ratio of the electric field to gas molecule density) from 100 to 2000 in units of 1Td = 10-17Vcm2. Their effects on the diamond growth are also discussed. The main results obtained are as follows. (1) The velocity profile is asymmetric for the component parallel to the field. The velocity distribution has a peak shift in the field direction. Most electrons possess non-zero velocity parallel to the substrate. (2) The number of atomic H is a function of E/N. (3) High-quality diamond can be obtained under the condition of E/N from 50 to 800Td due to sufficient atomic H and electron bombardment.

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Bäcklund transformation and multiple soliton solutions for the (3+1)-dimensional Jimbo-Miwa equation Zhang Jie-Fang (张解放), Wu Feng-Min (吴锋民) Chinese Physics, 2002, 11 (5):  425-428.  DOI: 10.1088/1009-1963/11/5/303 Abstract ( 1491 )   PDF (191KB) ( 808 )   We study an approach to constructing multiple soliton solutions of the (3+1)-dimensional nonlinear evolution equation. We take the (3+1)-dimensional Jimbo－Miwa (JM) equation as an example. Using the extended homogeneous balance method, one can find a B?cklund transformation to decompose the (3+1)-dimensional JM equation into a linear partial differential equation and two bilinear partial differential equations. Starting from these linear and bilinear partial differential equations, some multiple soliton solutions for the (3+1)-dimensional JM equation are obtained by introducing a class of formal solutions.

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Theory of symmetry for a rotational relativistic Birkhoff system Luo Shao-Kai (罗绍凯), Chen Xiang-Wei (陈向炜), Guo Yong-Xin (郭永新) Chinese Physics, 2002, 11 (5):  429-436.  DOI: 10.1088/1009-1963/11/5/304 Abstract ( 1196 )   PDF (255KB) ( 635 )   The theory of symmetry for a rotational relativistic Birkhoff system is studied. In terms of the invariance of the rotational relativistic Pfaff－Birkhoff－D'Alembert principle under infinitesimal transformations, the Noether symmetries and conserved quantities of a rotational relativistic Birkhoff system are given. In terms of the invariance of rotational relativistic Birkhoff equations under infinitesimal transformations, the Lie symmetries and conserved quantities of the rotational relativistic Birkhoff system are given.

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Construction of the solution of variational equations for constrained Birkhoffian systems Zhang Yi (张毅) Chinese Physics, 2002, 11 (5):  437-440.  DOI: 10.1088/1009-1963/11/5/305 Abstract ( 1111 )   PDF (203KB) ( 583 )   In this paper we present the variational equations of constrained Birkhoffian systems and study their solution. It is proven that, under some conditions, a particular solution of variational equations can be obtained by using a first integral. At the end of the paper, an example is given to illustrate the application of the results.

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Chaos in the second-order autonomous Birkhoff system with a heteroclinic circle Chen Xiang-Wei (陈向炜) Chinese Physics, 2002, 11 (5):  441-444.  DOI: 10.1088/1009-1963/11/5/306 Abstract ( 1189 )   PDF (199KB) ( 694 )   Chaotic behaviour in a second-order autonomous Birkhoff system with a heteroclinic circle under weakly periodic perturbation is studied using the Melnikov method. The equations of heteroclinic orbits and the criteria for chaos are given. One example is also presented to illustrate the application of the results.

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Noether's theorem of a rotational relativistic variable mass system Fang Jian-Hui (方建会), Zhao Song-Qing (赵嵩卿) Chinese Physics, 2002, 11 (5):  445-449.  DOI: 10.1088/1009-1963/11/5/307 Abstract ( 1177 )   PDF (205KB) ( 550 )   Noether's theory of a rotational relativistic variable mass system is studied. Firstly, Jourdain's principle of the rotational relativistic variable mass system is given. Secondly, on the basis of the invariance of the Jourdain's principle under the infinitesimal transformations of groups, Noether's theorem and its inverse theorem of the rotational relativistic variable mass system are presented. Finally, an example is given to illustrate the application of the result.

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Average mutual information of the random block-message ensembles for many-letters Hao San-Ru (郝三如), Hou Bo-Yu (侯伯宇) Chinese Physics, 2002, 11 (5):  450-455.  DOI: 10.1088/1009-1963/11/5/308 Abstract ( 1149 )   PDF (256KB) ( 404 )   By making use of the theoretical framework presented by Bostroem (K. J. Bostroem, LANL quant-ph/0009052), we generalize the standard quantum information theory of block messages with fixed block length to the variable one. We show that the states belonging to a sufficiently large Hilbert space are the highly distinguishable states. We also consider the collection states (product states of more than one qubit state) and seek a "pretty good measurement"(PGM) with measurement vectors to improve the mutual information. The average mutual information over random block-message ensembles with variable block length n is discussed in detail.

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New approach to the normal mode method in underwater acoustics Wang Ning (王宁), Liu Jin-Zhong (刘进忠) Chinese Physics, 2002, 11 (5):  456-460.  DOI: 10.1088/1009-1963/11/5/309 Abstract ( 1147 )   PDF (217KB) ( 527 )   A new approach to the numerical solution of normal mode problems in underwater acoustics is presented, in which the corresponding normal mode problem is transformed to the problem of solving a dynamic system. Three applications are considered: (1) the broad band normal mode problem; (2) the range-dependent problem with perturbation proportional to the range parameter; and (3) the evolution of the normal mode with environmental parameters. A numerical simulation for a broad band problem is performed, and the calculated eigenvalues have good agreement with those obtained by the standard normal mode code KRAKAN.

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A special form of electrodynamical response to a gravitational wave: outgoing and imploding photon fluxes Li Fang-Yu (李芳昱), Su Xun (苏荀), Long Bing-Wei (龙炳蔚), Tang Meng-Xi (唐孟希) Chinese Physics, 2002, 11 (5):  461-466.  DOI: 10.1088/1009-1963/11/5/310 Abstract ( 1129 )   PDF (267KB) ( 446 )   We have investigated the interaction of an electromagnetic (EM) wave with a standing gravitational wave (GW) in an external static magnetic field, and obtained concrete forms of first-order perturbative EM energy fluxes. Unlike the propagating properties of the "left-circular" and "right-circular" waves of the tangential perturbative energy fluxes around the symmetrical axis, the radial perturbative energy fluxes are expressed as the outgoing and imploding waves to the symmetrical axis. We also examine several physical examples and show that this effect can produce very small but nonvanishing radial perturbative photon fluxes. This may be useful for EM detection of the high-frequency relic GWs of the GHz region in quintessential inflationary models.

ATOMIC AND MOLECULAR PHYSICS

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An effective potential method for the calculation of hydrogen molecule ion energy in a strong magnetic field Jiao Zhi-Yong (焦志勇), Li Yu-Cheng (李毓成) Chinese Physics, 2002, 11 (5):  467-471.  DOI: 10.1088/1009-1963/11/5/311 Abstract ( 1240 )   PDF (211KB) ( 484 )   Using the adiabatic approximation and adiabatic variational approximation with an effective potential, the total energies and the equilibrium internuclear separations of H2+ ion in states $\sigma_g$, $\pi_u$, $\delta_g$, $\phi_u$, $\gamma_g$, $\eta_u$ in strong magnetic fields have been calculated. Our results reproduced those obtained by Vincke and Baye (Vincke M and Baye D 1985 J. Phys. B: At. Mol. Phys. 18 167), which are considered the most reliable. We found a basic function with better convergence than the Landau functions.

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Arrays of microscopic magnetic traps for cold atoms and their applications in atom optics Yin Jian-Ping (印建平), Gao Wei-Jian (高伟建), Hu Jian-Jun (胡建军) Chinese Physics, 2002, 11 (5):  472-480.  DOI: 10.1088/1009-1963/11/5/312 Abstract ( 1074 )   PDF (375KB) ( 838 )   A single microscopic magnetic trap for neutral atoms using planar current-carrying wires was proposed and studied theoretically by Weinstein et al. In this paper, we propose three structures of composite current-carrying wires to provide 1D, 2D and 3D arrays of microscopic magnetic traps for cold alkali atoms. The spatial distributions of magnetic fields generated by these structures are calculated and the field gradient and curvature in each single microtrap are analysed. Our study shows that arrays of microscopic magnetic traps can be used to provide 1D, 2D or 3D atomic magnetic lattices, and even to realize 1D, 2D and 3D arrays of magneto-optical traps, and so on.

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Investigation of the A2Σ- state of CuO by laser-induced fluorescence Jin Jin (金瑾), Ran Qin (冉琴), Zhang Xiao-Peng (张霄鹏), Chen Yang (陈旸), Chen Cong-Xiang (陈从香) Chinese Physics, 2002, 11 (5):  481-485.  DOI: 10.1088/1009-1963/11/5/313 Abstract ( 1294 )   PDF (222KB) ( 460 )   The laser-induced fluorescence excitation spectrum of the A2Σ－X2Π3/2 transition of CuO in the 540－620nm region has been studied, where the CuO molecule was produced by using the technique of dc discharge reaction under a supersonic condition. We have recorded and rotationally analysed the 0－0, 1－0, 2－0 and 3－0 bands. The rotational constants of the upper state A2Σ- were determined and vibrational constants improved. In addition, the lifetime measurement for the A2Σ- state was carried out under the collision-free condition, and the lifetimes obtained are 469±2, 456±2, 488±3 and 490±4ns for v'=0, v'=1, v'=2 and v'=3 levels, respectively.

CLASSICAL AREAS OF PHENOMENOLOGY

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k-quantum nonlinear Jaynes－Cummings model in two trapped ions Zeng Hao-Sheng (曾浩生), Kuang Le-Man (匡乐满), Gao Ke-Lin (高克林) Chinese Physics, 2002, 11 (5):  486-491.  DOI: 10.1088/1009-1963/11/5/314 Abstract ( 1236 )   PDF (262KB) ( 501 )   We have obtained a k-quantum nonlinear Jaynes－Cummings model for two trapped ions interacting with laser beams resonant to the kth red side-band of the centre-of-mass mode, far from the Lamb－Dicke regime. The exact analytic solution shows the existence of quantum collapses and revivals of the occupation of two atoms.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Structural properties of polycrystalline silicon films formed by pulsed rapid thermal processing Wang Yong-Qian (王永谦), Liao Xian-Bo (廖显伯), Diao Hong-Wei (刁宏伟), Zhang Shi-Bin (张世斌), Xu Yan-Yue (徐艳月), Chen Chang-Yong (陈长勇), Chen Wei-De (陈维德), Kong Guang-Lin (孔光临) Chinese Physics, 2002, 11 (5):  492-495.  DOI: 10.1088/1009-1963/11/5/315 Abstract ( 1230 )   PDF (246KB) ( 525 )   A novel pulsed rapid thermal processing (PRTP) method has been used for realizing solid-phase crystallization of amorphous silicon films prepared by plasma-enhanced chemical vapour deposition. The microstructure and surface morphology of the crystallized films were investigated using x-ray diffraction and atomic force microscopy. The results indicate that PRTP is a suitable post-crystallization technique for fabricating large-area polycrystalline silicon films with good structural quality, such as large grain size, small lattice microstrain and smooth surface morphology on low-cost glass substrates.

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Morphologies and microstructures of carbon nanotubes prepared by self-sustained arc discharging Tang Dong-Sheng (唐东升), Zhou Wei-Ya (周维亚), Ci Li-Jie (慈立杰), Yan Xiao-Qin (闫小琴), Yuan Hua-Jun (袁华军), Zhou Zhen-Ping (周振平), Liang Ying-Xin (梁迎新), Liu Dong-Fang (刘东方), Liu Wei (刘维) Chinese Physics, 2002, 11 (5):  496-501.  DOI: 10.1088/1009-1963/11/5/316 Abstract ( 1156 )   PDF (274KB) ( 571 )   We have investigated the morphology and microstructure of carbon nanotubes and nanoparticles in cathode deposits prepared by self-sustained arc discharge. Scanning electron microscopy images indicate that there are two regions exhibiting different morphologies on the top surface of the cathode deposits. In the central region, there is a triangular pattern of spots with a diameter up to 100μm, which consists of carbon nanotubes and nanoparticles. In the fringe region, carbon nanotubes and nanoparticles are distributed randomly. In addition, carbon nanotubes in the central region have a larger inner diameter, compared with those in the fringe region. The outer diameter distribution of tubes in the central region is narrower than that of tubes in the fringe region, while the former has a smaller peak value than the latter. For the nanoparticles, they exhibit a different behaviour from the tubes existing in the same region. The difference between the microstructure of tubes or particles in the two regions is attributed to the different temperatures and temperature gradients during their formation.

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Photoluminescence of amorphous carbon films fabricated by layer-by-layer hydrogen plasma chemical annealing method Xu Jun (徐骏), Huang Xiao-Hui (黄晓辉), Li Wei (李伟), Wang Li (王立), Chen Kun-Ji (陈坤基) Chinese Physics, 2002, 11 (5):  502-505.  DOI: 10.1088/1009-1963/11/5/317 Abstract ( 1195 )   PDF (195KB) ( 647 )   A method in which nanometre-thick film deposition was alternated with hydrogen plasma annealing (layer-by-layer method) was applied to fabricate hydrogenated amorphous carbon films in a conventional plasma-enhanced chemical vapour deposition system. It was found that the hydrogen plasma treatment could decrease the hydrogen concentration in the films and change the sp2/sp3 ratio to some extent by chemical etching. Blue photoluminescence was observed at room temperature, as a result of the reduction of sp2 clusters in the films.

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

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A switch in the electron transfer from heme a to binuclear centre of cytochrome c oxidase Wang Ao-Jin (王敖金), Xu Jian-Xing (徐建兴) Chinese Physics, 2002, 11 (5):  506-508.  DOI: 10.1088/1009-1963/11/5/318 Abstract ( 1092 )   PDF (183KB) ( 428 )   New experimental evidence that a switch controls the reduction of the heme a3－CuB binuclear centre has been observed in the N2-dried thin film of purified cytochrome oxidase. When immersing the enzyme film into the acid phosphate buffer with extremely low concentration of dithionite, a spectrum was given to show a reduction of heme a with no electrons resting on CuA. By increasing dithionite, electrons could be accumulated gradually on CuA, but the binuclear centre still remains in the oxidized state. When the accumulation of electrons on CuA and/or heme a exceeded a threshold, a turnover of reduction of the binuclear centre and oxidation of heme a occurred abruptly. This switch-like action is pH-dependent.