Table of contents

20 October 2006, Volume 15 Issue 10 Previous issue    Next issue

GENERAL

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Three-order pseudo-Hamilton canonical equations Ma Shan-Jun(马善钧), Huang Pei-Tian(黄沛天), Yan Rong(颜蓉), and Zhao Hong-Xia(赵红霞) Chinese Physics, 2006, 15 (10):  2193-2196.  DOI: 10.1088/1009-1963/15/10/001 Abstract ( 1569 )   PDF (92KB) ( 713 )   Based on the three-order Lagrangian equations, Hamilton's function of acceleration $H^\ast$  and generalized acceleration momentum $P_\alpha ^\ast$ are defined, and pseudo-Hamilton canonical equations corresponding to three-order Lagrangian equations are obtained. The equations are similar to Hamilton's canonical equations of analytical mechanics in form.

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New non-Noether conserved quantities of mechanical system in phase space Yan Xiang-Hong (闫向宏), Fang Jian-Hui (方建会) Chinese Physics, 2006, 15 (10):  2197-2201.  DOI: 10.1088/1009-1963/15/10/002 Abstract ( 1659 )   PDF (92KB) ( 640 )   This paper focuses on studying non-Noether conserved quantities of Lie symmetry and of form invariance for a mechanical system in phase space under the general infinitesimal transformation of groups. We obtain a new non-Noether conserved quantity of Lie symmetry of the system, and Hojman and Mei's results are of special cases of our conclusion. We find a condition under which the form invariance of the system will lead to a Lie symmetry, and, further, obtain a new non-Noether conserved quantity of form invariance of the system. An example is given finally to illustrate these results.

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Construction of doubly-periodic solutions to nonlinear partial differential equations using improved Jacobi elliptic function expansion method and symbolic computation Zhao Xue-Qin(赵雪芹), Zhi Hong-Yan(智红燕), and Zhang Hong-Qing(张鸿庆) Chinese Physics, 2006, 15 (10):  2202-2209.  DOI: 10.1088/1009-1963/15/10/003 Abstract ( 1876 )   PDF (133KB) ( 849 )   Some doubly-periodic solutions of the Zakharov--Kuznetsov equation are presented. Our approach is to introduce an auxiliary ordinary differential equation and use its Jacobi elliptic function solutions to construct doubly-periodic solutions of the Zakharov--Kuznetsov equation, which has been derived by Gottwald as a two-dimensional model for nonlinear Rossby waves. When the modulus $k \rightarrow 1$, these solutions reduce to the solitary wave solutions of the equation.

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New exact solutions to some difference differential equations Wang Zhen (王振) and Zhang Hong-Qing(张鸿庆) Chinese Physics, 2006, 15 (10):  2210-2215.  DOI: 10.1088/1009-1963/15/10/004 Abstract ( 1591 )   PDF (109KB) ( 890 )   In this paper, we use our method to solve the extended Lotka--Volterra equation and discrete KdV equation. With the help of Maple, we obtain a number of exact solutions to the two equations including soliton solutions presented by hyperbolic functions of sinh and cosh, periodic solutions presented by trigonometric functions of sin and cos, and rational solutions. This method can be used to solve some other nonlinear difference--differential equations.

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Dynamics of solitons in Bose-Einstein condensate with time-dependent atomic scattering length Li Hua-Mei(李画眉) Chinese Physics, 2006, 15 (10):  2216-2222.  DOI: 10.1088/1009-1963/15/10/005 Abstract ( 1822 )   PDF (1578KB) ( 755 )   The evolution of solitons in Bose--Einstein condensates (BECs) with time-dependent atomic scattering length in an expulsive parabolic potential is studied. Based on the extended hyperbolic function method, we successfully obtain the bright and dark soliton solutions. In addition, some new soliton solutions in this model are found. The results in this paper include some in the literature (Phys. Rev. Lett. 94 (2005) 050402 and  Chin. Phys. Lett. 22 (2005) 1855).

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On the generator of Lorentz boost Wang Zhi-Yong(王智勇) and Xiong Cai-Dong(熊彩东) Chinese Physics, 2006, 15 (10):  2223-2227.  DOI: 10.1088/1009-1963/15/10/006 Abstract ( 1724 )   PDF (108KB) ( 648 )   Traditionally, the theory related to the spatial angular momentum has been studied completely, while the investigation in the generator of Lorentz boost is inadequate. This paper shows that the generator of Lorentz boost has a nontrivial physical significance: it endows a charged system with an electric moment, and has an important significance for the electrical manipulations of electron spin in spintronics. An alternative treatment and interpretation for the traditional Darwin term and spin--orbit coupling are given.

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High-dimension multiparty quantum secret sharing scheme with Einstein-Podolsky-Rosen pairs Chen Pan(陈攀), Deng Fu-Guo(邓富国), and Long Gui-Lu (龙桂鲁) Chinese Physics, 2006, 15 (10):  2228-2235.  DOI: 10.1088/1009-1963/15/10/007 Abstract ( 1724 )   PDF (142KB) ( 753 )   In this paper a high-dimension multiparty quantum secret sharing scheme is proposed by using Einstein--Podolsky--Rosen pairs and local unitary operators. This scheme has the advantage of not only having higher capacity, but also saving storage space. The security analysis is also given.

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Heisenberg algebra for noncommutative Landau problem Li Kang(李康), Cao Xiao-Hua(曹小华), and Wang Dong-Yan(汪东燕) Chinese Physics, 2006, 15 (10):  2236-2239.  DOI: 10.1088/1009-1963/15/10/008 Abstract ( 1686 )   PDF (92KB) ( 675 )   The Landau problem on non-commutative quantum mechanics is studied, where the Heisenberg algebra and the Landau energy levels as well as the non-commutative angular momentum are constructed in detail in non-commutative space and non-commutative phase space respectively.

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Probabilistic teleportation of a non-symmetric three-particle state Chen Xiu-Bo (陈秀波), Wen Qiao-Yan (温巧燕), Zhu Fu-Chen (朱甫臣) Chinese Physics, 2006, 15 (10):  2240-2245.  DOI: 10.1088/1009-1963/15/10/009 Abstract ( 1578 )   PDF (122KB) ( 559 )   This paper proposes a scheme for teleporting a kind of essential three-particle non-symmetric entangled state, which is much more valuable than a GHZ and W state for some applications in quantum information processing. In comparison with previous proposal of teleportation, the resources of entangled states as quantum channel and the number of classical messages required by our scheme can be cut down. Moreover, it is shown that there exists a class of transformations which ensure the success of this scheme, because the two-particle transformation performed by the receiver in the course of teleportation may be a generic two-particle operation instead of a control-NOT (CNOT) operation. In addition, all kinds of transformations performed by sender and receiver are given in detail.

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A new optical scheme for teleportation of entangled coherent state Liao Jie-Qiao(廖洁桥) and Kuang Le-Man(匡乐满) Chinese Physics, 2006, 15 (10):  2246-2251.  DOI: 10.1088/1009-1963/15/10/010 Abstract ( 1519 )   PDF (270KB) ( 627 )   We propose a nearly perfect optical scheme for the quantum teleportation of entangled coherent states using optical devices such as nonlinear Kerr media, beam splitters, phase shifters, and photon detectors. Different from those previous schemes, our scheme needs only ``yes' or `no' measurements of the photon number of the related modes, i.e. nonzero- and zero-photon measurements, while in previous schemes one has to exactly identify the even or odd parity character of the photon numbers detected by detectors.

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Secret sharing of quantum information via entanglement swapping Zhang Ying-Qiao(张英俏), Jin Xing-Ri(金星日), and Zhang Shou(张寿) Chinese Physics, 2006, 15 (10):  2252-2255.  DOI: 10.1088/1009-1963/15/10/011 Abstract ( 1555 )   PDF (109KB) ( 681 )   Based on entanglement swapping, a scheme for the secret sharing of an arbitrary two-particle entangled state is proposed. If the controllers do not co-operate with the eavesdropper, the eavesdropper's successful probability decreases with the number of the controllers increasing. In addition, only the Bell-state measurements are required to realize the secret sharing scheme.

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Hawking radiation of a uniformly accelerating black hole Ren Jun (任军), Cao Jiang-Ling (曹江陵), and Zhao Zheng (赵峥) Chinese Physics, 2006, 15 (10):  2256-2259.  DOI: 10.1088/1009-1963/15/10/012 Abstract ( 1674 )   PDF (97KB) ( 536 )   In this paper, we study the Hawking radiation via tunnelling from a uniformly accelerating black hole. Although the Bekenstein--Hawking entropy is proportional also to the area of the event horizon, the radius of it, $r_{\rm H}$, is a function of $\theta$, which leads to the difficulties in the calculation of the emission rate. In order to overcome the mathematical difficulties, we propose a new technique to calculate the emission rate and the result obtained is reasonable.

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Experimental observation of partial amplitude death in coupled chaotic oscillators Liu Wei-Qing (刘维清), Yang Jun-Zhong (杨俊忠), Xiao Jing-Hua (肖井华) Chinese Physics, 2006, 15 (10):  2260-2265.  DOI: 10.1088/1009-1963/15/10/013 Abstract ( 1386 )   PDF (180KB) ( 653 )   The dynamics of coupled Lorenz circuits is investigated experimentally. The partial amplitude death reported in Phys. Rev.E 72, 057201 (2005) is verified by physical experiments with electronic circuits. With the increase of coupling constant, the coupled circuits undergo the transition from the breakdown of both the reflection symmetry and the translational symmetry to the partial amplitude death. Its stability is also confirmed by analysing the effects of noise.

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Passive control of chaotic system with multiple strange attractors Song Yun-Zhong(宋运忠), Zhao Guang-Zhou(赵光宙), and Qi Dong-Lian(齐冬莲) Chinese Physics, 2006, 15 (10):  2266-2270.  DOI: 10.1088/1009-1963/15/10/014 Abstract ( 1554 )   PDF (152KB) ( 771 )   In this paper we present a new simple controller for a chaotic system, that is, the Newton--Leipnik equation with two strange attractors: the upper attractor (UA) and the lower attractor (LA). The controller design is based on the passive technique. The final structure of this controller for original stabilization has a simple nonlinear feedback form. Using a passive method, we prove the stability of a closed-loop system. Based on the controller derived from the passive principle, we investigate three different kinds of chaotic control of the system, separately: the original control forcing the chaotic motion to settle down to the origin from an arbitrary position of the phase space; the chaotic intra-attractor control for stabilizing the equilibrium points only belonging to the upper chaotic attractor or the lower chaotic one, and the inter-attractor control for compelling the chaotic oscillation from one basin to another one. Both theoretical analysis and simulation results verify the validity of the suggested method.

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Time-resolved measurement of atomic emission enhancement by fs--ns dual-pulsed laser-induced breakdown spectroscopy Yan Li-Xin(颜立新), Zhang Yong-Sheng(张永生), Zheng Guo-Xin(郑国鑫), Liu Jing-Ru(刘晶儒), Cheng Jian-Ping(程建平), and Lü Min(吕敏) Chinese Physics, 2006, 15 (10):  2271-2274.  DOI: 10.1088/1009-1963/15/10/015 Abstract ( 1439 )   PDF (163KB) ( 635 )   Time-resolved measurement of atomic emission enhancement is performed by using a 500-fs KrF laser pulse incident upon a high density supersonic O2 gas jet, synchronized with an orthogonal ns frequency-doubled Nd:YAG laser pulse. The ultra-short pulse serves as an igniter of the gas jet, and the subsequent ns-laser pulse significantly enhances the atomic emission. Analysis shows that the contributions to the enhancement effect are made mainly by the bremsstrahlung radiation and cascade ionization.

ATOMIC AND MOLECULAR PHYSICS

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Laser controlled quantum motion of two Paul trapped ions Cai Li-Hua (蔡丽华), Hai Wen-Hua (海文华), Lu Geng-Biao (鲁耿彪) Chinese Physics, 2006, 15 (10):  2275-2287.  DOI: 10.1088/1009-1963/15/10/016 Abstract ( 1313 )   PDF (807KB) ( 546 )   We investigate the quantum motion of two ions stored in a Paul trap and interacting with a time-periodic laser field. In the pseudopotential approximation and large detuning condition, we find that the relative motion is independent of the laser field, but the exact centre-of-mass motion is closely related to the laser field. By adjusting the laser intensity and frequency, we can well control the quantum motion of the centre-of-mass. We illustrate some physical properties described by the centre-of-mass states, such as the squeezed coherent property, the widths and heights of the wavepackets of probability density, the classical-quantum correspondence, the resonance ladders of expectation energy and the transition probabilities between time-dependent quantum levels.

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The second dissociation threshold bound levels of hydrogen molecule Zhang Yan-Peng(张彦鹏), Song Jian-Ping(宋建平), Gan Chen-Li(甘琛利), Yan Xiang-An(严祥安), Nie Zhi-Qiang(聂志强), Jiang Tong(姜彤), Li Ling(李岭), Du Kai(杜凯), Zhang Xiang-Chen(张相臣), Lu Ke-Qing(卢克清), and E.E. Eyler Chinese Physics, 2006, 15 (10):  2288-2296.  DOI: 10.1088/1009-1963/15/10/017 Abstract ( 1525 )   PDF (215KB) ( 566 )   The near-threshold highly bound states of all three stable isotopic variants of molecular hydrogen have been studied. Numerous perturbations and unexpected transitions are observed as far as 1cm-1 just below the second dissociation threshold. This complex structure may arise from a combination of nonadiabatic coupling between B, B', C electronic states, perturbations due to fine and hyperfine interactions, and strong shape resonances. The perturbed near-threshold states and vibrational continuum exhibit finegrained structure, differing greatly between isotopes because of varying nonadiabatic coupling.

CLASSICAL AREAS OF PHENOMENOLOGY

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Low-parasitic ESD protection strategy for RF ICs in 0.35μm CMOS process Wang Yuan(王源), Jia Song(贾嵩), Chen Zhong-Jian(陈中建), and Ji Li-Jiu(吉利久) Chinese Physics, 2006, 15 (10):  2297-2305.  DOI: 10.1088/1009-1963/15/10/018 Abstract ( 1705 )   PDF (488KB) ( 729 )   A systemic and comprehensive ESD-induced parasitic model is presented in this paper, which is used to analyse the parasitic influences of electrostatic discharge (ESD) protection circuits on the performance of radio frequency applications. A novel low-parasitic ESD protection structure is made in a 0.35\mum 1P3M silicide CMOS process. The measured results show that this novel structure has a low parasitic capacitance about 310fF and a low leakage current about 12.2nA with a suitable ESD robustness target about 5kV human body model.

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Soliton-like pulse timing jitter in dispersion-managed systems Li Qi-Liang(李齐良), Li Qing-Shan(李庆山), and Lin Li-Bin(林理彬) Chinese Physics, 2006, 15 (10):  2306-2314.  DOI: 10.1088/1009-1963/15/10/019 Abstract ( 1364 )   PDF (182KB) ( 571 )   In this paper, the timing jitter in dispersion-managed soliton-like systems with the Gaussian pulse is studied by using two methods. Firstly, the derivation of the dynamic equations for the evolution of soliton-like parameters and the timing jitter expressions for the dispersion-managed soliton-like systems are carried out by the perturbed variational method. By analysing and simulating these timing jitter expressions, one can find that the timing jitter is induced by the amplified spontaneous emission noise and the frequency shift, etc. Nonlinear gain can suppress the timing jitter. The chirp sign and the filters action have also effects on the total timing jitter. Secondly, the timing jitter is calculated and analysed by using the moment method. The results of the two methods prove to be consistent with each other.

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Generation of four-atom cluster states in thermal cavity and implementing remote controlled not gate Yang Rong-Can(杨榕灿), Li Hong-Cai(李洪才), Chen Mei-Xiang(陈美香), and Lin Xiu(林秀) Chinese Physics, 2006, 15 (10):  2315-2319.  DOI: 10.1088/1009-1963/15/10/020 Abstract ( 1448 )   PDF (121KB) ( 678 )   We propose an experimentally feasible scheme for preparing a four-atom cluster state in a thermal cavity. In the scheme, the cavity field is only virtually excited and the photon-number-dependent part in the effective Hamiltonian is cancelled so that the system is insensitive to the cavity decay and the thermal field. At the same time, the scheme can be generalized to prepare n-atom cluster states with the success probability 100%. In addition, using the four-atom cluster state, we also propose a simpler scheme for implementing a remote--controlled not gate (CNOT) without the Bell states measurement.

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Implementing the Deutsch--Jozsa algorithm by using Schrödinger cat states in cavity QED Yang Rong-Can(杨榕灿), Li Hong-Cai(李洪才), Lin Xiu(林秀), and Chen Mei-Xiang(陈美香) Chinese Physics, 2006, 15 (10):  2320-2323.  DOI: 10.1088/1009-1963/15/10/021 Abstract ( 1408 )   PDF (107KB) ( 477 )   We propose a scheme to implement the Deutsch--Jozsa algorithm by using Schr?dinger cat states in cavity quantum electron-dynamics (QED). The scheme is based on the Raman interaction of a degenerate three-level $\Lambda$ -type atom with a coherent state in a cavity. By using Schr?dinger cat states, the atomic spontaneous emission can be minimized and the Hadamard transformation in our scheme is not needed.

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The statistical fluctuation of a single-mode laser system driven by coloured pump noise with signal modulation and the quantum noise with cross-correlation between its real and imaginary parts Xu Dai-Hai (徐大海), Cheng Qing-Hua (程庆华), Cao Li (曹力), Wu Da-Jin (吴大进) Chinese Physics, 2006, 15 (10):  2324-2331.  DOI: 10.1088/1009-1963/15/10/022 Abstract ( 1509 )   PDF (718KB) ( 483 )   Using the linear approximation method, this paper studies the statistical property of a single-mode laser driven by both coloured pump noise with signal modulation and the quantum noise with cross-correlation between its real and imaginary parts, and calculates the steady-state mean normalized intensity fluctuation and intensity correlation time. It analyses the influences of the modulation signal, the net gain coefficient, the noise and its correlation form on the statistical fluctuation of the laser system respectively. It is found that the coloured pump noise modulated by the signal has a great suppressing action on the statistical fluctuation of the laser system; the pump noise self-correlation time and the specific frequency of modulation signal have the result that the statistical fluctuation tends to zero. Furthermore, the `colour' correlation of pump noise has much influences on the statistical fluctuation of the laser system. Increasing the intensity of pump noise will augment the statistical fluctuation of the laser system, but the intensity of quantum noise and the coefficient of cross-correlation between its real and imaginary parts have less influence on the statistical fluctuation of the laser system. Therefore, from the conclusions of this paper the statistical property can be known and a theoretical basis for steady operation and output of the laser system can be provided.

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Electron acceleration by two crossed Bessel--Gaussian beams in vacuum Zhao Zhi-Guo(赵志国) and Lü Bai-Da(吕百达) Chinese Physics, 2006, 15 (10):  2332-2337.  DOI: 10.1088/1009-1963/15/10/023 Abstract ( 1349 )   PDF (144KB) ( 497 )   The direct acceleration of electrons by using two linearly polarized crossed Bessel--Gaussian (BG) beams with equal frequency and amplitude in vacuum is proposed and studied. It is shown that two linearly polarized BG beams of the same order (0 or 1) with a $\pi$-rad phase difference have a resultant non-zero longitudinal electric field on the z-axis and can be used, in principle, to accelerate electrons.

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Carrier--envelope phase effects for a dipolar molecule interacting with ultrashort laser pulse Zhao Ke(赵珂), Li Hong-Yu(李洪玉), Liu Ji-Cai(刘纪彩), and Wang Chuan-Kui(王传奎) Chinese Physics, 2006, 15 (10):  2338-2342.  DOI: 10.1088/1009-1963/15/10/024 Abstract ( 1497 )   PDF (217KB) ( 515 )   In this paper the phase-dependent features of ultrashort laser pulse resonant propagation in a two-level dipolar molecule are demonstrated by solving full Maxwell--Bloch equations. The electronic properties of dipolar molecule 4-trans-[p-(N, N-Di-n-butylamino)-p -stilbenylvinyl] pyridine (DBASVP) molecule, one-dimensional asymmetric organic molecule, is calculated by density functional theory at ab initio level. The numerical results show that the carrier propagation and the spectrum evolution of the pulse are sensitive to its initial phase and the phase sensitivity is more obvious for larger area pulse. The phase-dependent feature is more evident in dipolar molecule because the permanent dipole moment makes the nonlinear effects stronger.

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The damage of the optical components induced by the stimulated Brillouin scattering Ge Zi-Ming(葛自明), Lü Zhi-Wei(吕志伟), Cai Jun-Wei(蔡君伟), Ao Shu-Yan(敖淑艳), and Luo You-Hua(罗有华) Chinese Physics, 2006, 15 (10):  2343-2346.  DOI: 10.1088/1009-1963/15/10/025 Abstract ( 1446 )   PDF (149KB) ( 528 )   A theory of excitation of ultrasonic waves in the stimulated Brillouin scattering (SBS) process is presented in this paper. By using several reasonable approximations, a numerical calculation of the transient longitudinal SBS shows that large amplitude of acoustic waves can be built up by the nanosecond pulse of high-power laser, which may result in the damage of optical glasses. The maximal density change and the maximal acoustic wave intensity in optical glasses of 5 cm in thickness are calculated by using different parameters of the high-energy laser, such as the intensity, the pulse width, and the wave length. The damage threshold of the optical glasses is about 80 GW/cm2 when using a 1064 nm laser. The dynamic mechanism of SBS is the electrostriction effect of the components coupling with the high-power laser.

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The effect of intermolecular interactions on photoluminescence of a porphyrin side-chain polymer Wang Hui (王惠), Zhang Wei (张伟), Yu Han-Cheng (余汉城), Huang Jin-Wang (黄锦汪), Lin Wei-Zhu (林位株), Ji Liang-Nian (计亮年) Chinese Physics, 2006, 15 (10):  2347-2351.  DOI: 10.1088/1009-1963/15/10/026 Abstract ( 1348 )   PDF (150KB) ( 578 )   Photoluminescence properties and exciton decay dynamics in a porphyrin side-chain polymer, poly[porphyrin acrylate- acrylonitrile (abbreviated p[(por)A-AN]), have been investigated by femtosecond time-resolved photoluminescence spectroscopy. All the luminescences of p[(por)A-AN] films are due to the emissive decay of the photoexcited singlet excitons in the porphyrins. The luminescence efficiencies and lifetimes are increased for samples from pure films to dilute blend films. However, they are increased as the intrachain concentration of the porphyrin sidechain groups is decreased. The intrachain rotation motions of porphyrin sidechain groups result in the initial ultrafast luminescence decays, which are much faster than those due to the interchain interactions. All the samples show no significant red-shift and broadening of the transient luminescence spectra. The interchain and intrachain nonradiative exciton relaxation processes may play an important role in the luminescence dynamics in the p[(por)A-AN] films. The possible origin of different intrachain and interchain dynamic behaviours in p[(por)A-AN] films is discussed.

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An analysis of the incompressible viscous flows problem by meshless method Xiong Yuan-Bo(熊渊博) and Wang Hao(王浩) Chinese Physics, 2006, 15 (10):  2352-2356.  DOI: 10.1088/1009-1963/15/10/027 Abstract ( 1364 )   PDF (215KB) ( 624 )   Generally the incompressible viscous flow problem is described by the Navier--Stokes equation. Based on the weighted residual method the discrete formulation of element-free Galerkin is inferred in this paper. By the step-by-step computation in the field of time, and adopting the least-square estimation of the-same-order shift, this paper has calculated both velocity and pressure from the decoupling independent equations. Each time fraction Newton--Raphson iterative method is applied for the velocity and pressure. Finally, this paper puts the method into practice of the shear-drive cavity flow, verifying the validity, high accuracy and stability.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Modulation of ionization on laser frequency in ultra-short pulse intense laser--gas-target Hu Qiang-Lin(胡强林) and Liu Shi-Bing(刘世炳) Chinese Physics, 2006, 15 (10):  2357-2362.  DOI: 10.1088/1009-1963/15/10/028 Abstract ( 1349 )   PDF (143KB) ( 502 )   Based on the dispersion relation of intense laser pulse propagating in gradually ionized plasma, this paper discusses the frequency modulation induced by ionization of an ultra-short intense laser pulse interacting with a gas target. The relationship between the frequency modulation and the ionization rate, the plasmas frequency variation, and the polarization of atoms (ions) is analysed. The numerical results indicate that, at high frequency, the polarization of atoms (ions) plays a more important role than plasma frequency variation in modulating the laser frequency, and the laser frequency variation is different at different positions of the laser pulse.

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Effects of atomic number Z on the energy distribution of hot electrons generated by femtosecond laser interaction with metallic targets Cai Da-Feng(蔡达锋), Gu Yu-Qiu(谷渝秋), Zheng Zhi-Jian(郑志坚), Zhou Wei-Min(周维民), Jiao Chun-Ye(焦春晔), Chen Hao(陈豪), Wen Tian-Shu(温天舒), and Chunyu Shu-Tai(淳于书泰) Chinese Physics, 2006, 15 (10):  2363-2367.  DOI: 10.1088/1009-1963/15/10/029 Abstract ( 1731 )   PDF (456KB) ( 462 )   The effects of atomic number Z on the energy distribution of hot electrons generated by the interaction of 60fs, 130mJ, 800nm, and $7\times10^{17}$W/cm2 laser pulses with metallic targets have been studied experimentally. The results show that the number and the effective temperature of hot electrons increase with the atomic number Z of metallic targets, and the temperature of hot electrons are in the range of 190--230keV, which is consistent with a scaling law of hot electrons temperature.

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Observation of hydrogen pellet ablation material flow by tomography Dong Jia-Fu(董贾福), Wang Shi-Qing(王世庆), and Li Wen-Zhong(郦文忠) Chinese Physics, 2006, 15 (10):  2368-2373.  DOI: 10.1088/1009-1963/15/10/030 Abstract ( 1569 )   PDF (645KB) ( 452 )   An H$\alpha$ emission measurement array with 25 detection channels has been built on HL-1M tokamak. Reconstruction maps of H$\alpha$ emission distribution in plasma cross-section have been obtained by using tomography, with a hydrogen pellet injected into the plasma. The dimension, the shape and the rotation characteristic of the cross-section of the pellet ablation material flow tube have been observed. These results have been analysed and explained tentatively by using the `tail' model and the linear expansion model.

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Spatial distribution of SiCln (n=0--2) in SiCl4 plasma measured by mass spectroscopy Wang Zhao-Kui(王照奎), Lin Kui-Xun(林揆训), Lou Yan-Hui(娄艳辉), Lin Xuan-Ying(林璇英), and Zhu Zu-Song(祝祖送) Chinese Physics, 2006, 15 (10):  2374-2377.  DOI: 10.1088/1009-1963/15/10/031 Abstract ( 1322 )   PDF (134KB) ( 562 )   For a better understanding of the deposition mechanism of thin films in SiCl4 source gas, we have measured the spatial distributions of SiCln (n=0--2) radicals in SiCl4 radio frequency glow discharge plasma utilizing a mass spectrometer equipped with a movable gas sampling apparatus. The experimental results demonstrate that the relative densities of SiCln (n=0--2) radicals have peak values at the position of 10mm above the powered electrode along the axial direction; the relative densities of the Si and SiCln (n=1, 2) radicals have peak values at the positions of 27mm and 7mm away from the axis along the radial direction, respectively. Generally speaking, in the whole SiCl4 plasma bulk region, the relative density of Si is one order of magnitude higher than that of SiCl, and the relative density of SiCl is several times higher than that of SiCl2/sub>. This reveals that Si and SiCl may be the primary growth precursors in forming thin films.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Deformation measurements of three types of Portevin--Le Chatelier bands Xiang Guo-Fu (项国富), Zhang Qing-Chuan (张青川), Liu Hao-Wen (刘颢文), Jiang Hui-Feng (江慧丰), Wu Xiao-Ping (伍小平) Chinese Physics, 2006, 15 (10):  2378-2384.  DOI: 10.1088/1009-1963/15/10/032 Abstract ( 1483 )   PDF (877KB) ( 650 )   In this paper a technique based on high-speed digital photography and the digital speckle correlation (DSC) method is used for the quantitative measurement of the displacement and strain fields of various Portevin--Le Chatelier (PLC) bands (types A, B, and C). The experimental results clearly show the nucleation process of a type-B band and the propagation of a type-A band. The results also reveal that there exists an elastic shrinkage deformation outside a PLC band during a large avalanche-like deformation inside the PLC band.

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The optical properties of MgxZn1-xO thin films Zhang Xi-Jian(张锡健), Ma Hong-Lei(马洪磊), Li Yu-Xiang(李玉香), Wang Qing-Pu(王卿璞), Ma Jin(马瑾), Zong Fu-Jian(宗福建), and Xiao Hong-Di(肖洪地) Chinese Physics, 2006, 15 (10):  2385-2388.  DOI: 10.1088/1009-1963/15/10/033 Abstract ( 1467 )   PDF (131KB) ( 488 )   MgxZn1-xO thin films have been prepared on silicon substrates by radio frequency magnetron sputtering at 60℃. The thin films have hexagonal wurtzite single-phase structure and a preferred orientation with the c-axis perpendicular to the substrates. The refractive indices of MgxZn1-xO films are studied at room temperature by spectroscopic ellipsometry over the wavelength range of 400--760 nm at the incident angle of 70°. Both absorption coefficients and optical band gaps of MgxZn1-xO films are determined by the transmittance spectra. While Mg content is increasing, the absorption edges of MgxZn1-xO films shift to higher energies and band gaps linearly increase from 3.24.eV at x=0 to 3.90 eV at x=0.30. These results provide important information for the design and modelling of ZnO/ MgxZn1-xO heterostructure optoelectronic devices.

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

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Local field distribution and configuration of CO molecules adsorbed on the nanostructure platinum surface Huang Xiao-Jing (黄晓菁), He Su-Zhen (何素贞), Wu Chen-Xu (吴晨旭) Chinese Physics, 2006, 15 (10):  2389-2396.  DOI: 10.1088/1009-1963/15/10/034 Abstract ( 1407 )   PDF (764KB) ( 513 )   This paper shows that the local electric field distribution near the nanostructure metallic surface is obtained by solving the Laplace equation, and furthermore, the configuration of CO molecules adsorbed on a Pt nanoparticle surface is obtained by using Monte Carlo simulation. It is found that the uneven local electric field distribution induced by the nanostructure surface can influence the configuration of carbon monoxide (CO) molecules by a force, which drags the adsorbates to the poles of the nanoparticles. This result, together with our results obtained before, may explain the experimental results that the nanostructure metallic surface can lead to abnormal phenomena such as anti-absorption infrared effects.

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Emitter of hetero-junction solar cells created using pulsed rapid thermal annealing Xu Ying(许颖), Diao Hong-Wei(刁宏伟), Hao Hui-Ying(郝会颖), Zeng Xiang-Bo(曾湘波), and Liao Xian-Bo(廖显伯) Chinese Physics, 2006, 15 (10):  2397-2401.  DOI: 10.1088/1009-1963/15/10/035 Abstract ( 1357 )   PDF (428KB) ( 548 )   In this paper, we use a pulsed rapid thermal processing (RTP) approach to create an emitter layer of hetero-junction solar cell. The process parameters and crystallization behaviour are studied. The structural, optical and electric properties of the crystallized films are also investigated. Both the depth of PN junction and the conductivity of the emitter layer increase with the number of RTP pulses increasing. Simulation results show that efficiencies of such solar cells can exceed 15% with a lower interface recombination rate, but the highest efficiency is 11.65% in our experiments.

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GaN-based heterostructures: electric--static equilibrium and boundary conditions Zhang Jin-Feng(张金风) and Hao Yue(郝跃) Chinese Physics, 2006, 15 (10):  2402-2406.  DOI: 10.1088/1009-1963/15/10/036 Abstract ( 1534 )   PDF (115KB) ( 736 )   In the GaN-based heterostructures, this paper reports that the strong electric fields induced by polarization effects at the structure boundaries complicate the electric--static equilibrium and the boundary conditions. The basic requirements of electric--static equilibrium for the heterostructure systems are discussed first, and it is deduced that in the application of the coupled Schr?dinger--Poisson model to the heterostructures of electric--static equilibrium state, zero external electric field guarantees the overall electric neutrality, and there is no need to introduce the charge balance equation. Then the relation between the screening of the polar charges in GaN-based heterostructures and the possible boundary conditions of the Poisson equation is analysed, it is shown that the various boundary conditions are equivalent to each other, and the surface charge, which can be used in studying the screening of the polar charges, can be precisely solved even if only the conduction band energy is correctly known at the surface. Finally, through the calculations on an AlGaN/GaN heterostructure with typical structure parameters by the coupled Schr?dinger--Poisson model under the various boundary conditions, the correctness of the above analyses are validated.

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The photoluminescence of ZnSe bulk single crystals excited by femtosecond pulse Li Huan-Yong(李焕勇), Jie Wan-Qi (介万奇), Zhang Shi-An(张诗按), Sun Zhen-Rong(孙真荣), and Xu Ke-Wei(徐可为) Chinese Physics, 2006, 15 (10):  2407-2414.  DOI: 10.1088/1009-1963/15/10/037 Abstract ( 1496 )   PDF (200KB) ( 651 )   This paper reports on the photoluminescence spectra of ZnSe single crystal with trace chlorine excited by the femtosecond laser pulse. Three emission bands, including second-harmonic-generation, two-photon-excited peak and a broad band at 500--700nm, were detected. The thermal strain induced by femtosecond pulse strongly influences the photoluminescence of ZnSe crystal. The corresponding strain $\varepsilon$ in ZnSe crystal is estimated to be about $8.8\times10^{-3}$ at room temperature. The zinc-vacancy, as the main point defect induced by femtosecond pulse, is successfully used to interpret the broad emission at 500--700nm. The research shows that self-activated luminescence possesses the recombination mechanism of donor--vacancy pair, and it is also influenced by a few selenium defects and the temperature. The rapid decrease in photoluminescence intensity of two-photon-excited fluorescence and second-harmonic generation emission at lower temperature is attributed to the fact that more point defects result in the thermal activation of the two-photo-absorption energy converting to the stronger recombination emission of chlorine--zinc vacancy in 500--700nm. The experimental results indicate that the femtosecond exciting photoluminescence shows a completely different emission mechanism to that of He--Cd exciting luminescence in ZnSe single crystal. The femtosecond laser exhibits a higher sensitive to the impurity in crystal materials, which can be recommended as an efficient way to estimate the trace impurity in high quality crystals.

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Nonideal effects in quantum field-effect directional coupler Xie Yue-E(谢月娥), Yan Xiao-Hong(颜晓红), and Chen Yuan-Ping(陈元平) Chinese Physics, 2006, 15 (10):  2415-2421.  DOI: 10.1088/1009-1963/15/10/038 Abstract ( 1458 )   PDF (289KB) ( 460 )   The nonideal effects in a quantum field-effect directional coupler where two quantum wires are coupled through a finite potential barrier are studied by adopting the lattice Green function method. The results show that the electron energy distribution, asymmetric geometry and finite temperature all have obvious influence on the electron transfer of the coupler. Only for the electrons with energies in a certain region, can the complete periodic transfer between two quantum wires take place. The conductance of these electrons as a function of the barrier length and potential height exhibits a fine periodic or quasi-periodic pattern. For the electrons with energies beyond the region, however, the complete periodic transfer does not hold any more since many irregular oscillations are superimposed on the conductance profile. In addition, the finite temperature and asymmetric geometry both can reduce the electron transfer efficiency.

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A bistable, self-latching inverter by the monolithic integration of resonant tunnelling diode and high electron mobility transistor Ma Long(马龙), Huang Ying-Long(黄应龙), Zhang Yang(张杨), Yang Fu-Hua(杨富华), and Wang Liang-Chen(王良臣) Chinese Physics, 2006, 15 (10):  2422-2426.  DOI: 10.1088/1009-1963/15/10/039 Abstract ( 1814 )   PDF (408KB) ( 531 )   This paper reports that the structures of AlGaAs/InGaAs high electron mobility transistor (HEMT) and AlAs/GaAs resonant tunnelling diode (RTD) are epitaxially grown by molecular beam epitaxy (MBE) in turn on a GaAs substrate. An Al0.24Ga0.76As chair barrier layer, which is grown adjacent to the top AlAs barrier, helps to reduce the valley current of RTD. The peak-to-valley current ratio of fabricated RTD is 4.8 and the transconductance for the 1-μm gate HEMT is 125mS/mm. A static inverter which consists of two RTDs and a HEMT is designed and fabricated. Unlike a conventional CMOS inverter, the novel inverter exhibits self-latching property.

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Resistivity and critical temperature of (La1-xPrx)0.7Ca0.3MnO3 Liu Zi-Xin(刘自信) and Bai Chun-Xu(白春旭) Chinese Physics, 2006, 15 (10):  2427-2430.  DOI: 10.1088/1009-1963/15/10/040 Abstract ( 1514 )   PDF (108KB) ( 564 )   An empirical formula of the critical temperature that is concentration dependent for polycrystalline (La1-xPrx)0.7Ca0.3MnO3 is presented in this paper. With this formula, the temperature dependence of resistance is simulated for various values of x by using the random resistor network model and the Monte Carlo method. The hysteresis effect in $\rho$ -- T curves is reasonably explained. The simulation results are in good agreement with the relevant experimental measurements.

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Evaluation of negative bias temperature instability in ultra-thin gate oxide pMOSFETs using a new on-line PDO method Ji Zhi-Gang (纪志罡), Xu Ming-Zhen (许铭真), Tan Chang-Hua (谭长华) Chinese Physics, 2006, 15 (10):  2431-2438.  DOI: 10.1088/1009-1963/15/10/041 Abstract ( 1526 )   PDF (275KB) ( 591 )   A new on-line methodology is used to characterize the negative bias temperature instability (NBTI) without inherent recovery. Saturation drain voltage shift and mobility shift are extracted by ID-VD characterizations, which were measured before stress, and after every certain stress phase, using the proportional differential operator (PDO) method. The new on-line methodology avoids the mobility linearity assumption as compared with the previous on-the-fly method. It is found that both reaction--diffusion and charge-injection processes are important in NBTI effect under either DC or AC stress. A similar activation energy, 0.15 eV, occurred in both DC and AC NBTI processes. Also degradation rate factor is independent of temperature below 90℃ and sharply increases above it. The frequency dependence of NBTI degradation shows that NBTI degradation is independent of frequencies. The carrier tunnelling and reaction--diffusion mechanisms exist simultaneously in NBTI degradation of sub-micron pMOSFETs, and the carrier tunnelling dominates the earlier NBTI stage and the reaction--diffusion mechanism follows when the generation rate of traps caused by carrier tunnelling reaches its maximum.

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Study on the thermo-optic properties of DR1/PMMA composite Li Xiang(李翔), Cao Zhuang-Qi(曹庄琪), Shen Qi-Shun(沈启舜), and Yang Yan-Fang(杨艳芳) Chinese Physics, 2006, 15 (10):  2439-2444.  DOI: 10.1088/1009-1963/15/10/042 Abstract ( 1448 )   PDF (161KB) ( 695 )   This paper reports that the thermo-optic coefficient (dn/dT) as well as thermal expansion coefficients ($\beta$) of DR1/PMMA polymer film are measured for both TE (transversal electric) and TM (transversal magnetic) polarizations by using an attenuated total reflection configuration at the wavelengths of 832nm. The thermo-optic coefficients of DR1/PMMA are negative and as high as the order of 10-4/℃. The influences of dopant concentration, poling process and photobleaching process on the thermo-optic properties of DR1/PMMA are also investigated.

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Structure and visible photoluminescence of Sm3+, Dy3+ and Tm3+ doped c-axis oriented AlN films Liu Fu-Sheng(刘福生), Liu Quan-Lin(刘泉林), Liang Jing-Kui(梁敬魁), Luo Jun(骆军), Su Jun(苏俊), Zhang Yi(张毅), Sun Bao-Juan(孙宝娟), and Rao Guang-Hui(饶光辉) Chinese Physics, 2006, 15 (10):  2445-2449.  DOI: 10.1088/1009-1963/15/10/043 Abstract ( 1517 )   PDF (201KB) ( 775 )   Visible photoluminescence (PL) has been observed from rare earth (Tm, Sm and Dy)-doped AlN films grown by radio-frequency magnetron reactive sputtering. X-ray diffraction indicates that the films are c-axis-oriented hexagonal wurtzite type structure with an average crystal size of about 80--110nm. Room-temperature PL spectra indicate that the blue emission is due to the transition of 1D2 to 3F4 and 1G2 to 3H6 intra 4f electron of Tm3+, the yellow emissions of AlN:Sm are due to 4G5/2 to the 6HJ (J = 5/2, 7/2, 9/2, 11/2) and the reddish emissions of AlN:Dy correspond to the 4F9/2 to 6HJ (J = 15/2, 13/2, 11/2 and 9/2) and 6F11/2 transitions.

CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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The spike timing precision of FitzHugh--Nagumo neuron network coupled by gap junctions Zhang Su-Hua(张素花), Zhan Yong(展永), Yu Hui(于慧), An Hai-Long(安海龙), and Zhao Tong-Jun(赵同军) Chinese Physics, 2006, 15 (10):  2450-2457.  DOI: 10.1088/1009-1963/15/10/044 Abstract ( 1185 )   PDF (263KB) ( 407 )   It has been proved recently that the spike timing can play an important role in information transmission, so in this paper we develop a network with N-unit FitzHugh--Nagumo neurons coupled by gap junctions and discuss the dependence of the spike timing precision on synaptic coupling strength, the noise intensity and the size of the neuron ensemble. The calculated results show that the spike timing precision decreases as the noise intensity increases; and the ensemble spike timing precision increases with coupling strength increasing. The electric synapse coupling has a more important effect on the spike timing precision than the chemical synapse coupling.

GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS

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Effect of change in large and fast solar wind dynamic pressure on geosynchronous magnetic field Borodkova N L, Liu Jing-Bo(刘静波), Huang Zhao-Hui(黄朝晖), Zastenker G N, Wang Chi(王赤), and Eiges P E Chinese Physics, 2006, 15 (10):  2458-2464.  DOI: 10.1088/1009-1963/15/10/045 Abstract ( 1325 )   PDF (194KB) ( 593 )   We present a comparison of changes in large and sharp solar wind dynamic pressure, observed by several spacecraft, with fast disturbances in the magnetospheric magnetic field, measured by the geosynchronous satellites. More than 260 changes in solar wind pressure during the period 1996--2003 are selected for this study. Large statistics show that an increase (a decrease) in dynamic pressure always results in an increase (a decrease) in the magnitude of geosynchronous magnetic field. The amplitude of response to the geomagnetic field strongly depends on the location of observer relative to the noon meridian, the value of pressure before disturbance, and the change in amplitude of pressure.

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Dynamics of quintessential inflation Zhai Xiang-Hua(翟向华) and Zhao Yi-Bin(赵一斌) Chinese Physics, 2006, 15 (10):  2465-2469.  DOI: 10.1088/1009-1963/15/10/046 Abstract ( 1574 )   PDF (168KB) ( 487 )   In this paper, we study a realistic model of quintessential inflation with radiation and matter. By the analysis of the dynamical system and numerical work about the evolution of the equation of state and cosmic density parameter, we show that this model is a good match for the current astronomical observation. The conclusion we obtain is in favour of the model where the modular part of the complex field plays the role of the inflaton whereas the argument part is the quintessence field. Numerical calculation shows that a heteroclinic orbit (solution of the dynamical system) is interpolated between early-time de Sitter phase (an unstable critical point) and a late-time de Sitter attractor.