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Chin. Phys. B  
  Chin. Phys. B--2006, Vol.15, No.11
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A new layered space--time detection algorithm for frequency selective fading multiple-input multiple-output channels based on particle filter

Du Zheng-Cong, Tang Bin, Liu Li-Xin
Chin. Phys., 2006, 15 (11): 2481-2488 doi: 10.1088/1009-1963/15/11/003
Full Text: [PDF 175 KB] (Downloads:515)
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In this paper, a new observation equation of non-Gaussian frequency selective fading Bell Labs layered space time (BLAST) architecture system is proposed, which is used for frequency selective fading channels and non-Gaussian noise in an application environment of BLAST system. With othogonal matrix triangularization (QR decomposition) of the channel matrix, the static observation equation of frequency selective fading BLAST system is transformed into a dynamic state space model, and then the particle filter is used for space--time layered detection. Making the full use of the finite alphabet of the digital modulation communication signal, the optimal proposal distribution can be chosen to produce particle and update the weight. Incorporated with current method of reducing error propagation, a new space--time layered detection algorithm is proposed. Simulation result shows the validity of the proposed algorithm.

The complexity nature of large-scale software systems

Yan Dong, Qi Guo-Ning, Gu Xin-Jian
Chin. Phys., 2006, 15 (11): 2489-2495 doi: 10.1088/1009-1963/15/11/004
Full Text: [PDF 185 KB] (Downloads:529)
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In software engineering, class diagrams are often used to describe the system's class structures in Unified Modelling Language (UML). A class diagram, as a graph, is a collection of static declarative model elements, such as classes, interfaces, and the relationships of their connections with each other. In this paper, class graphs are examined within several Java software systems provided by Sun and IBM, and some new features are found. For a large-scale Java software system, its in-degree distribution tends to an exponential distribution, while its out-degree and degree distributions reveal the power-law behaviour. And then a directed preferential-random model is established to describe the corresponding degree distribution features and evolve large-scale Java software systems.

Onthe Rosen-Edelstein model andthe theoretical foundation of nonholonomicmechanics

Li Guang-Cheng, Mei Feng-Xiang
Chin. Phys., 2006, 15 (11): 2496-2499 doi: 10.1088/1009-1963/15/11/005
Full Text: [PDF 97 KB] (Downloads:444)
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A new model in nonholonomic mechanics,the Rosen--Edelstein model, has been studied. We prove that the new model is a Lagrange problem in which the action integral $\int^{t_{1}}_{t_{0}}L\dd t$ can be made stationary.The theoretical basis of nonholonomic mechanics is investigated and discussed. Finally, we give the range of practical applications of theRosen--Edelstein model.

The pth-order periodic solutions for a family of N-coupled nonlinear SchrOdingerequations

Liu Guan-Ting
Chin. Phys., 2006, 15 (11): 2500-2505 doi: 10.1088/1009-1963/15/11/006
Full Text: [PDF 115 KB] (Downloads:484)
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By using the solutions of an auxiliary Lam\'e equation, a direct algebraic method is proposed to construct the exact solutions of $N$-coupled nonlinear Schr\"{o}dinger equations. The abundant higher-order exact periodic solutions of a family of $N$-coupled nonlinear Schr\"{o}dinger equations are explicitly obtained with the aid of symbolic computation and they include corresponding envelope solitary and shock wave solutions.

A scheme for transferring an unknown atomic entangledstate via cavity quantum electrodynamics

Wu Tao, Ye Liu, Ni Zhi-Xiang
Chin. Phys., 2006, 15 (11): 2506-2509 doi: 10.1088/1009-1963/15/11/007
Full Text: [PDF 97 KB] (Downloads:502)
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In this paper, we propose a scheme for transferring an unknown atomic entangled state via cavity quantum electrodynamics (QED). This scheme, which has a successful probability of 100 percent, does not require Bell-state measurement and performing any operations to reconstruct an initial state. Meanwhile, the scheme only involves atom--field interaction with a large detuning and does not require the transfer of quantum information between the atoms and cavity. Thus the scheme is insensitive to the cavity field states and cavity decay. This scheme can also be extended to transfer ring an entangled state of $n$-atom.

Entanglement and decoherence in a quantum dimer

Hou Xi-Wen, Hui Zi, Ding Rui-Min, Chen Xiao-Yang, Gao Yu
Chin. Phys., 2006, 15 (11): 2510-2513 doi: 10.1088/1009-1963/15/11/008
Full Text: [PDF 113 KB] (Downloads:622)
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The dynamical properties of quantum entanglement in an integrable quantum dimer are studied in terms of the reduced-density linear entropy with various coupling parameters and total boson numbers. The characteristic time of decoherence process in the early-time evolution of the linear entropy is obtained, indicating that the characteristic time and the corresponding entropy exhibit a maximum near the position of the corresponding classical separatrix energy.

Practical scheme for remote preparation of a photon-photon entangled state

Tan Jia, Fang Mao-Fa
Chin. Phys., 2006, 15 (11): 2514-2517 doi: 10.1088/1009-1963/15/11/009
Full Text: [PDF 97 KB] (Downloads:529)
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We present a scheme to remotely prepare a photon--photon entangled state via entanglement swapping in cavity QED. Using two successive processes of appropriate atom--cavity interaction and subsequent measurements, we obtain the entangled state with certain probability.

A scheme for conditional quantum phase gate viabimodal cavity and a Λ-type three-level atom

Cai Jian-Wu, Fang Mao-Fa, Liao Xiang-Ping, Zheng Xiao-Juan
Chin. Phys., 2006, 15 (11): 2518-2522 doi: 10.1088/1009-1963/15/11/010
Full Text: [PDF 186 KB] (Downloads:624)
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We propose a scheme to implement a two-qubit conditional quantum phase gatefor the intracavity field viaa single three-level $\Lambda$-type atom driven by two modes in a high-Q cavity. The quantum information is encoded on the Fock states of the bimodal cavity. The gate's averaged fidelity is expected to reach $99.8\%$.

Hawking radiation as tunnelling from arbitrarily dimensional Reissner--Nordstr?m de Sitter black hole

Jiang Qing-Quan, Yang Shu-Zheng, Wu Shuang-Qing
Chin. Phys., 2006, 15 (11): 2523-2528 doi: 10.1088/1009-1963/15/11/011
Full Text: [PDF 120 KB] (Downloads:643)
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This paper extends Parikh--Wilzcek's recent work, which treats the Hawking radiation as a semi-classical tunnelling process from the event horizon of four dimensional Schwarzshild and Reissner--Nordstr\"{o}m black holes, to that of arbitrarily dimensional Reissner--Nordstr\"{o}m de Sitter black hole. The result shows that the tunnelling rate is related to the change of Bekenstein--Hawking entropy and the factually radiant spectrum is no longer precisely thermal after taking the dynamical black hole background and energy conservation into account, but is consistent with the underlying unitary theory and then satisfies the first law of the black hole thermodynamics. Meanwhile, in Parikh--Wilzcek's framework, this paper points out that the information conservation is only suitable for the reversible process but in highly unstable evaporating black hole (irreversible process) the information loss is possible.

LMI-based output feedback fuzzy control of chaotic system with uncertainties

Tan Wen, Wang Yao-Nan, Duan Feng, Li Xiao-Hui
Chin. Phys., 2006, 15 (11): 2529-2534 doi: 10.1088/1009-1963/15/11/012
Full Text: [PDF 147 KB] (Downloads:498)
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This paper studies the robust fuzzy control for nonlinear chaotic system in the presence of parametric uncertainties. An uncertain Takagi--Sugeno (T--S) fuzzy model is employed for fuzzy modelling of an unknown chaotic system. A sufficient condition formulated in terms of linear matrix inequality (LMI) for the existence of fuzzy controller is obtained. Then the output feedback fuzzy-model-based regulator derived from the LMI solutions can guarantee the stability of the closed-loop overall fuzzy system. The T--S fuzzy model ofthe chaotic Chen system is developed as an example for illustration. The effectiveness of the proposed controller design methodology is finally demonstrated through computer simulations on the uncertain Chen chaotic system.

Existence of horseshoe maps in voltage-mode controlled buck converters

Dai Dong, Tse Chi-Kong, Ma Xi-Kui
Chin. Phys., 2006, 15 (11): 2535-2540 doi: 10.1088/1009-1963/15/11/013
Full Text: [PDF 169 KB] (Downloads:417)
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In this paper, chaos in a voltage-mode controlled buck converter is studied. The existence of chaos is proven theoretically in this system. The proof consists of showing that the dynamics of the system is semiconjugate to that of a one-sided shift map, which implies positive entropy of the system and hence chaotic behaviour. The essential tool is the horseshoe hypotheses proposed by Kennedy and Yorke, which will be reviewed prior to the discussion of the main finding.

Hybrid TS fuzzy modelling and simulation for chaotic Lorenz system

Li De-Quan
Chin. Phys., 2006, 15 (11): 2541-2548 doi: 10.1088/1009-1963/15/11/014
Full Text: [PDF 439 KB] (Downloads:574)
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The projection of the chaotic attractor observed from the Lorenz system in the $X$--$Z$ plane is like a butterfly, hence the classical Lorenz system is widely known as the butterfly attractor, and has served as a prototype model for studying chaotic behaviour since it was coined.In this work we take one step further to investigate some fundamental dynamic behaviours of a novel hybrid Takagi--Sugeno (TS) fuzzy Lorenz-type system, which is essentially derived from the delta-operator-based TS fuzzy modelling for complex nonlinear systems, and contains the original Lorenz system of continuous-time TS fuzzy form as a special case. By simply and appropriately tuning the additional parametric perturbations in the two-rule hybrid TS fuzzy Lorenz-type system, complex (two-wing) butterfly attractors observed from this system in the three dimensional (3D) $X$--$Y$--$Z$ space are created, which have not yet been reported in the literature, and the forming mechanism of the compound structures have been numerically investigated.

Controlling chaos using Takagi--Sugeno fuzzy model and adaptive adjustment

Zheng Yong-Ai
Chin. Phys., 2006, 15 (11): 2549-2552 doi: 10.1088/1009-1963/15/11/015
Full Text: [PDF 117 KB] (Downloads:618)
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In this paper, an approach to the control of continuous-time chaotic systems is proposed using the Takagi--Sugeno (TS) fuzzy model and adaptive adjustment. Sufficient conditions are derived to guarantee chaos control from Lyapunov stability theory. The proposed approach offers a systematic design procedure for stabilizing a large class of chaotic systems in the literature about chaos research. The simulation results on R\"{o}ssler's system verify the effectiveness of the proposed methods.

Synchronization and coherence resonance in chaotic neural networks

Wang Mao-Sheng, Hou Zhong-Huai, Xin Hou-Wen
Chin. Phys., 2006, 15 (11): 2553-2557 doi: 10.1088/1009-1963/15/11/016
Full Text: [PDF 170 KB] (Downloads:653)
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Synchronization and coherence of chaotic Morris--Lecar (ML) neural networks have been investigated by numerical methods. The synchronization of the neurons can be enhanced by increasing the number of the shortcuts, even though all neurons are chaotic when uncoupled. Moreover, the coherence of the neurons exhibits a non-monotonic dependence on the density of shortcuts. There is an optimal number of shortcuts at which the neurons' motion is most ordered, i.e. the order parameter (the characteristic correlation time) that is introduced to measure the coherence of the neurons has a maximum. These phenomena imply that stochastic shortcuts can tame spatiotemporal chaos. The effects of the coupling strength have also been studied. The value of the optimal number of shortcuts goes down as the coupling strength increases.

Influence of the probe--sample interaction on scanning near-field optical microscopic images in the far field

Li Zhi, Zhang Jia-Sen, Yang Jing, Gong Qi-Huang
Chin. Phys., 2006, 15 (11): 2558-2563 doi: 10.1088/1009-1963/15/11/017
Full Text: [PDF 193 KB] (Downloads:436)
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We have studied the influence of probe--sample interaction in a scanning near-field optical microscopy (SNOM) in the far field by using samples with a step structure. For a sample with a step height of $\sim \lambda $/4, the SNOM image contrast between the two sides of the step changes periodically at different scan heights. For a step height of $\sim \lambda $/2, the image contrast remains approximately the same. The probe--sample interaction determines the SNOM image contrast here. The influence of different refractive indices of the sample has been also analysed by using a simple theoretical model.

Optical properties of the direct-coupled Y-branch filtersby using photonic crystal slabs

Tian Jie, Ren Cheng, Feng Shuai, Liu Ya-Zhao, Tao Hai-Hua, Li Zhi-Yuan, Cheng Bing-Ying, Zhang Dao-Zhong, Jin Ai-Zi
Chin. Phys., 2006, 15 (11): 2471-2475 doi: 10.1088/1009-1963/15/11/001
Full Text: [PDF 1655 KB] (Downloads:862)
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We fabricated a new type of two-dimensional photonic crystal slab filter. The resonant cavities were directly put into the waveguide arms. The optical transmissions of the filters were measured and the results show that the optimized two-channel filters give good intensity distribution at the output ports of the waveguide. A minimum wavelength spacing of 5~nm of the filter outputs isrealized by accurately controlling the size of the resonant cavities.

Polar molecule dominated electrorheological effect

Lu Kun-Quan, Shen Rong, Wang Xue-Zhao, Sun Gang, Wen Wei-Jia, Liu Ji-Xing
Chin. Phys., 2006, 15 (11): 2476-2480 doi: 10.1088/1009-1963/15/11/002
Full Text: [PDF 274 KB] (Downloads:897)
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The yield stress of our newly developed electrorheological (ER) fluids consisting of dielectric nano-particles suspended in silicone oil reaches hundreds of kPa, which is orders of magnitude higher than that of conventional ones. We found that the polar molecules adsorbed on the particles play a decisive role in such new ER fluids. To explain this polar molecule dominated ER (PM-ER) effect a model is proposed based on the interaction of polar molecule-charge between the particles, where the local electric field is significantly enhanced and results in the polar molecules aligning in the direction of the electric field. The model can well explain the giant ER effect and a near-linear dependence of the yield stress on the electric field. The main effective factors for achieving high-performance PM-ER fluids are discussed. The PM-ER fluids with the yield stress higher than one MPa can be expected.

Features of the total disintegration events of heavyemulsion targets caused by 4.5A GeV/c16O

Zhang Dong-Hai, Liu Fang, He Chun-Le, Zhao Hui-Hua, Jia Hui-Ming, Li Xue-Qin, Li Zhen-Yu, Li Jun-Sheng
Chin. Phys., 2006, 15 (11): 2564-2570 doi: 10.1088/1009-1963/15/11/018
Full Text: [PDF 192 KB] (Downloads:533)
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Total disintegration events produced by 4.5\,A GeV/c $^{16}$O--AgBr interactions are analysed to investigate the characteristics of secondary charged particles produced in such collisions. The multiplicity distributions of grey, black, and relativistic charged particles can be well represented by Gaussian distribution. The average multiplicity of grey particles is found to increase with the mass of projectile increasing, while that of black particles is found to decrease with the mass of projectile increasing. This result is in good agreement with the prediction of fireball model. Finally, the linear dependence between grey and black particles is observed, but there is no distinct dependence between the production of relativistic charged particles and the target excitation.

Effects of spontaneously induced coherence on absorption of a ladder-type atom

Ma Hong-Mei, Gong Shang-Qing, Sun Zhen-Rong, Li Ru-Xin, Xu Zhi-Zhan
Chin. Phys., 2006, 15 (11): 2588-2592 doi: 10.1088/1009-1963/15/11/022
Full Text: [PDF 121 KB] (Downloads:492)
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This paper investigates the effects of spontaneously induced coherence on absorption properties in a nearly equispaced three-level ladder-type system driven by two coherent fields. It find that the absorption properties of this system with the probe field applied on the lower transition can be significantly modified if this coherence is optimized. In the case of small spontaneous decay rate in the upper excited state, it finds that such coherence does not destroy the electromagnetically induced transparency (EIT). Nevertheless, the absorption peak on both sides of zero detuning and the linewidth of absorption line become larger and narrower than those in the case corresponding to the effects of spontaneously induced coherence; while in the case of large decay rate, it finds that, instead of EIT with low resonant absorption, a sharp absorption peak at resonance appears. That is, electromagnetically induced absorption in the nearly equispaced ladder-type system can occur due to such coherent effects.

A scheme for implementing quantum clock synchronization algorithm in cavity QED

Wu Qin-Qin, Kuang Le-Man
Chin. Phys., 2006, 15 (11): 2593-2599 doi: 10.1088/1009-1963/15/11/023
Full Text: [PDF 147 KB] (Downloads:533)
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In this paper, we propose a scheme for implementing the quantum clock synchronization (QCS) algorithm in cavity quantum electrodynamic (QED) formalism. Our method is based on three-level ladder-type atoms interacting with classical and quantized cavity fields. Atom-qubit realizations of three-qubit and four-qubit QCS algorithms are explicitly presented.

The quantum features of the photon statistics in a semiconductor microcavity

Wei Wei
Chin. Phys., 2006, 15 (11): 2600-2605 doi: 10.1088/1009-1963/15/11/024
Full Text: [PDF 160 KB] (Downloads:474)
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The quantum features of the temporal photon statistics of an exciton--cavity coupled system in a quantum-well semiconductor microcavity are investigated analytically. Under the secular approximation, if the nonlinear interactions, i.e. the exciton--exciton coupling and the phase-space filling, are much weaker than the exciton--photon interaction, the evolution of the Fano factor shows that the distribution of the photon numbers exhibits the feature of collapses--revivals (CRs), and the relevant revival time may be adjusted by several factors such as the total particle number, the detuning, and the nonlinear coupling strengths, etc. Especially, the ideal maximum antibunching with the minimum value 0 of the Fano factor occurs periodically for such a situation, with the dissipation of exciton--polariton being ignored.

Passively mode-locked Nd:GdVO4 laser at 912nm

Zhang Chi, Wei Zhi-Yi, Zhang Ling, Zhang Chun-Yu, Zhang Zhi-Guo
Chin. Phys., 2006, 15 (11): 2606-2608 doi: 10.1088/1009-1963/15/11/025
Full Text: [PDF 105 KB] (Downloads:521)
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This paper demonstrates the passively mode-locked Nd:GdVO\xj{4} laser operating on the \sj{4}$F_{3/2}$--$^4I_{9/2}$ transition at 912\,nm by using a semiconductor saturable-absorber mirror for passive mode locking, stable continuous wave mode-locked 912\,nm laser was achieved with a repetition rate of 176\,MHz. At the incident pump power of 17.7\,W, 22.6\,mW average output power of stable mode-locked laser was obtained with a slope efficiency of 0.3\%.

Propagation properties of off-axis Hermite--cosh--Gaussian beam combinations through a first-order optical system

Tang Qian-Jin, Chen Da-Ming, Yu Yong-Ai, Hu Qi-Quan
Chin. Phys., 2006, 15 (11): 2609-2617 doi: 10.1088/1009-1963/15/11/026
Full Text: [PDF 1583 KB] (Downloads:531)
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Based on the Collins integral formula, the analytic expressions of propagation of the coherent and the incoherent off-axis Hermite--cosh--Gaussian (HChG) beam combinations with rectangular symmetry passing through a paraxial first-order optical system are derived, and corresponding numerical examples are given and analysed. The resulting beam quality is discussed in terms of power in the bucket (PIB). The study suggests that the resulting beam cannot keep the initial intensity shape during the propagation and the beam quality for coherent mode is not always better than that for incoherent mode. Reviewing the numerical simulations of Gaussian, Hermite--Gaussian (HG) and cosh--Gaussian (ChG) beam combinations indicates that the Hermite polynomial exerts a chief influence on the irradiance profile of composite beam and far field power concentration.

Nonlinear optical properties of [(CH3)4N]Au(dmit)2 using Z-scan technique

Sun Xiang-Bing, Ren Quan, Wang Xin-Qiang, Zhang Guang-Hui, Yang Hong-Liang, Feng Lin, Xu Dong, Liu Zhi-Bo
Chin. Phys., 2006, 15 (11): 2618-2622 doi: 10.1088/1009-1963/15/11/027
Full Text: [PDF 162 KB] (Downloads:583)
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The third-order optical nonlinearities of [(CH$_3$)$_4$N]Au(dmit)$_2$ (dmit = 4,5-dithiolate-1,3-dithiole-2-thione) at 532\,nm and 1064\,nm are investigated using the $Z$-scan technique with pulses of picoseconds duration. The $Z$-scan spectra reveal a strong nonlinear absorption (reverse saturable absorption) and a negative nonlinear refraction at 532\,nm. No nonlinear absorption is observed at 1064\,nm. The molecular second-order hyperpolarizability $\ga$ for the [(CH$_3$)$_4$N]Au(dmit)$_2$ molecule at 532\,nm is estimated to be as high as (2.1 $\pm$ 0.1) $\ti$ 10$^{-31}$\,esu, which is nearly three times larger than that at 1064\,nm. The mechanism responsible for the difference between the results is analysed. Nonlinear transmission measurements suggest that this material has potential applications in optical limiting.

Surface second harmonic generation of chiral molecules using three-coupled-oscillator model

Wang Xiao-Ou, Li Chun-Fei, Li Jun-Qing
Chin. Phys., 2006, 15 (11): 2623-2630 doi: 10.1088/1009-1963/15/11/028
Full Text: [PDF 186 KB] (Downloads:430)
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Based on the three-coupled-oscillator molecular model we proposed, the relation between the second-order susceptibilities of a chiral film and the molecular hyperpolarizabilities is given. The effect of microscopic parameters on the second-order susceptibilities is simulated numerically and the difference between the efficiencies of s-polarized second-harmonic fields induced by the left- and the right-handed circularly-polarized fundamental beams is discussed. The theoretical basis for studying second-order nonlinear optical properties of the chiral molecular media with a tripod-like structure is provided in this paper.

Effects of temperature on the stability of separatescreening bright--dark spatial soliton pair

Zhang Guang-Yong, Liu Jin-Song
Chin. Phys., 2006, 15 (11): 2631-2637 doi: 10.1088/1009-1963/15/11/029
Full Text: [PDF 222 KB] (Downloads:546)
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We investigate theoretically the temperature effects on the evolution and stability of a separate screening bright--dark soliton pair formed in a serial non-photovoltaic photorefractive crystal circuit. Our numerical results show that, for a stable bright--dark soliton pair originally formed in a crystal circuit at given temperatures, when one crystal temperature changes, the soliton supported by the other crystal will evolve into another stable soliton if the temperature change is quite small, whereas it will become unstable and experience larger cycles of compression or break up into beam filaments if the temperature difference is big enough. The dark soliton is more sensitive to the temperature change than the bright one.

Stability of dark soliton solutions of the quintic complex Ginzburg--Landau equation inthe case of normal dispersion

Tang Zheng-Hua, Yan Jia-Ren, Liu Ling-Hong
Chin. Phys., 2006, 15 (11): 2638-2643 doi: 10.1088/1009-1963/15/11/030
Full Text: [PDF 243 KB] (Downloads:463)
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Dark soliton solutions of the one-dimensional complex Ginzburg--Landau equation (CGLE) are analysed for the case of normal group-velocity dispersion. The CGLE can be transformed to the nonlinear Schr\"{o}dinger equation (NLSE) with perturbation terms under some practical conditions. The main properties of dark solitons are analysed by applying the direct perturbation theory of the NLSE. The results obtained may be helpful for the research on the optical soliton transmission system.

Velocity overshoot of start-up flow for a Maxwellfluid in a porous half-space

Tan Wen-Chang
Chin. Phys., 2006, 15 (11): 2644-2650 doi: 10.1088/1009-1963/15/11/031
Full Text: [PDF 139 KB] (Downloads:529)
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Stokes' first problem has been investigated for a Maxwell fluid in a porous half-space for gaining insight into the effect of viscoelasticity on the start-up flow in a porous medium. An exact solution was obtained by using the Fourier sine transform. It was found that at large values of the relaxation time the velocity overshoot occurs obviously and the system exhibits viscoelastic behaviours. On the other hand, for short relaxation time the velocity overshoot disappears and the system exhibits viscous behaviours. A critical value of the relaxation time was obtained for the emergence of the velocity overshoot. Furthermore, it was found that the velocity overshoot is caused by both the viscoelasticity of the Maxwell fluid and the Darcy resistance resulting from the structure of the micropore in the porous medium.

Partial wave scattering cross sectionsfor He--HBr collision

Yu Chun-Ri, Feng Er-Yin, Wang Rong-Kai, Yang Xiang-Dong
Chin. Phys., 2006, 15 (11): 2571-2577 doi: 10.1088/1009-1963/15/11/019
Full Text: [PDF 215 KB] (Downloads:495)
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A new anisotropic potential is fitted to {\it ab initio} data. The close-coupling approach is utilized to calculate state-to-state rotational excitation partial wave cross sections for elastic and inelastic collisions of He atom with HBr molecule based on the fitted potential. The calculation is performed separately at the incident energies: 75, 100 and 200~meV.The tendency of the elastic and inelastic rotational excitation partial wave cross sections varying with total angular quantum number $J$ is obtained.

Calculation of plasma characteristics of the sun

Muhammad Abbas Bari, Zhong Jia-Yong, Chen Min, Zhao Jing, Zhang Jie
Chin. Phys., 2006, 15 (11): 2578-2582 doi: 10.1088/1009-1963/15/11/020
Full Text: [PDF 147 KB] (Downloads:663)
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The ionization level and free electron density of most abundant elements (C, N, O, Mg, Al, Si, S, and Fe) in the sun are calculated from the centre of the sun to the surface of the photosphere. The model and computations are made under the assumption of local thermodynamic equilibrium (LTE). The Saha equation has been used to calculate the ionization level of elements and the electron density. Temperature values for calculations along the solar radius are taken from references.

The influence from high-n dielectronic satellites to Kɑ resonance line in helium-like aluminium

Fu Yan-Biao, Dong Chen-Zhong, Zhang Deng-Hong, FumihiroKoike, Takako Kato
Chin. Phys., 2006, 15 (11): 2583-2587 doi: 10.1088/1009-1963/15/11/021
Full Text: [PDF 327 KB] (Downloads:466)
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Based on the multi-configuration Dirac--Fock method, this paper has made theoretical calculations for the dielectronic recombination cross-sections and the high-$n$ dielectronic satellites to K$\alpha$ resonance line in helium-like aluminium ions. It is found that high-$n$ dielectronic satellites are seriously mixed with resonance line, which leads to a significant increase in both the apparent width and the intensity of K$\alpha$ resonance line. They also induce a positional shift of K$\alpha$ resonance line.

Mutual recombination in slow Si+ + H- collisions

Wang Jian-Guo, Liu Chun-Lei, R. K. Janev, Yan Jun, Shi Jian-Rong
Chin. Phys., 2006, 15 (11): 2651-2656 doi: 10.1088/1009-1963/15/11/032
Full Text: [PDF 163 KB] (Downloads:416)
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This paper studies the process of mutual neutralization of Si\sj{+} and H\sj{-} ions in slow collisions within the multi-channel Landau--Zener model. All important ionic-covalent couplings in this collision system are included in the collision dynamics. The cross sections for population of specific final states of product Si atom are calculated in the CM energy range 0.05\,eV/u--5\,keV/u. Both singlet and triplet states are considered. At collision energies below $\sim$10\,eV/u, the most populated singlet state is Si(3p4p, \sj{1}$S_0$), while for energies above $\sim$150\,eV/u it is the Si(3p, 4p, \sj{1}$P_1$) state. In the case of triplet states, the mixed 3p4p(\sj{3}$S_1$+\sj{3}$P_0$) states are the most populated in the entire collision energy range investigated. The total cross section exhibits a broad maximum around 200--300\,eV/u and for $E_{\rm CM}\leq$ 10\,eV/u it monotonically increases with decreasing the collision energy, reaching a value of $8\ti10^{-13}$\,cm\sj{2} at $E_{\rm CM}$ = 0.05\,eV/u. The ion-pair formation process in Si(3p\sj{2} \sj{3}$P_{\rm J}$)+H(1s) collisions has also been considered and its cross section in the considered energy range is very small (smaller than 10\sj{-20}\,cm\sj{2} in the energy region below 1\,keV/u).

Effect of magnetic field on the terahertz radiationdetection in high electron mobility transistors

Ma Ming-Rui, Chen Yu-Ling, Wang Chang
Chin. Phys., 2006, 15 (11): 2657-2660 doi: 10.1088/1009-1963/15/11/033
Full Text: [PDF 141 KB] (Downloads:536)
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In this paper, we make a theoretical investigation of the plasma-wave instability mechanism in a two-dimensional electron fluid in a high electron mobility transistor (HEMT) driven by the terahertz radiation in the presence of a perpendicular magnetic field. It is found that the resonant peaks of the gate-to-source/drain admittances and detection responsivity depend on the strength of the external magnetic field. Such phenomena can be used to produce a desired effect by adjusting the intensity of the magnetic field.

Study of the double rectangular waveguide grating slow-wave structure

Lu Zhi-Gang, Gong Yu-Bin, Wei Yan-Yu, Wang Wen-Xiang
Chin. Phys., 2006, 15 (11): 2661-2668 doi: 10.1088/1009-1963/15/11/034
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A slow-wave structure (SWS) with two opposite gratings inside a rectangular waveguide is presented and analysed. As an all-metal slow-wave circuit, this structure is especially suited for use in millimetre-wave travelling wave tubes (TWTs) due to its advantages of large size, high manufacturing precision and good heat dissipation. The first part of this paper concerns the wave properties of this structure in vacuum. The influence of the geometrical dimensions on dispersion characteristics and coupling impedance is investigated. The theoretical results show that this structure has a very strong dispersion and the coupling impedance for the fundamental wave is several tens of ohms, but the coupling impedance for --1 space harmonic wave is much lower than that for the fundamental wave, so the risk of backward wave oscillation is reduced. Besides these, the CST microwave studio is also used to simulate the dispersion property of the SWS. The simulation results from CST and the theoretical results agree well with each other, which supports the theory. In the second part, a small-signal analysis of a double rectangular waveguide grating TWT is presented. The typical small-signal gain per period is about 0.45 dB, and the 3-dB small-signal gain bandwidth is only 4\%.

Macroscopic cell experiments and three-dimensionalmodelling on electrode-shaping plasma display cell

Ouyang Ji-Ting, Cao Jing, He Feng
Chin. Phys., 2006, 15 (11): 2669-2675 doi: 10.1088/1009-1963/15/11/035
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A macroscopic cell and three-dimensional fluid model have been used to investigate the discharge characteristics in ac plasma display panel cells of electrode-shaping configurations. Four kinds of non-standard geometries (i.e. $D$-, ${\it\del}$-, $W$- and $U$-shape electrodes) have been considered. The characteristics of the discharge current, the operating voltage and the discharge efficiency of different configurations have been discussed. It is found that the discharge efficiency can be improved by about 10\%--30\% compared with the standard geometry, while the operating voltage increases slightly in the non-standard geometries. There is a trade-off between improving the discharge efficiency and lowering the sustaining voltage in design of plasma display cells by electrode shaping.

Molecular dynamics simulation on mechanicalproperty of carbon nanotube torsional deformation

Chen Ming-Jun, Liang Ying-Chun, Li Hong-Zhu, Li Dan
Chin. Phys., 2006, 15 (11): 2676-2681 doi: 10.1088/1009-1963/15/11/036
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In this paper torsional deformation of the carbon nanotubes is simulated by molecular dynamics method. The Brenner potential is used to set up thesimulation system. Simulation results show that the carbon nanotubes can bear larger torsional deformation, for the armchair type (10,10) single wall carbon nanotubes, with a yielding phenomenon taking place when the torsional angle is up to 63$^{\circ}$(1.1rad). The influence of carbon nanotube helicity in torsional deformation is very small. The shear modulus of single wall carbon nanotubes should be several hundred GPa, not 1\,GPa as others reports.

Two-dimensional numerical research on effects oftitanium target bombarded by TEMP II accelerator

Wu Di, Gong Ye, Liu Jin-Yuan, Wang Xiao-Gang, Liu Yue, Ma Teng-Cai
Chin. Phys., 2006, 15 (11): 2682-2687 doi: 10.1088/1009-1963/15/11/037
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Two-dimensional numerical research has been carried out on the ablation effects of titanium target irradiated by intense pulsed ion beam (IPIB) generated by TEMP II accelerator. Temporal and spatial evolution of the ablation process of the target during a pulse time has been simulated. We have come to the conclusion that the melting and evaporating process begin from the surface and the target is ablated layer by layer when the target is irradiated by the IPIB. Meanwhile, we also obtained the result that the average ablation velocity in target central region is about 10\,m/s, which is far less than the ejection velocity of the plume plasma formed by irradiation. Different effects have been compared to the different ratio of the ions and different energy density of IPIB while the target is irradiated by pulsed beams.

Study on the mixing of fluid in curved microchannelswith heterogeneous surface potentials

Lin Jian-Zhong, Zhang Kai, Li Hui-Jun
Chin. Phys., 2006, 15 (11): 2688-2696 doi: 10.1088/1009-1963/15/11/038
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In this paper the mixing of a sample in the curved microchannel with heterogeneous surface potentials is analysed numerically by using the control-volume-based finite difference method. The rigorous models for describing the wall potential and external potential are solved to get the distribution of wall potential and external potential, then momentum equation is solved to get the fully developed flow field. Finally the mass transport equation is solved to get the concentration field. The results show that the curved microchannel has an optimized capability of sample mixing and transport when the heterogeneous surface is located at the left conjunction between the curved part and straight part. The variation of heterogeneous surface potential $\psi_{\rm n}$has more influence on the capability of sample mixing than on that of sample transport. The ratio of the curved microchannel's radius to width has a comparable effect on the capability of sample mixing and transport. The conclusions above are helpful to the optimization of the design of microfluidic devices for the improvement of the efficiency of sample mixing.

Preparation and tribological properties of DLC/Ti filmby pulsed laser arc deposition

Zhang Zhen-Yu, Lu Xin-Chun, Luo Jian-Bin, Shao Tian-Min, Qing Tao, Zhang Chen-Hui
Chin. Phys., 2006, 15 (11): 2697-2705 doi: 10.1088/1009-1963/15/11/039
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This paper reports that DLC (diamond like carbon)/Ti and DLC films were prepared by using pulsed laser arc deposition. R-ray diffraction, Auger electron spectroscopy, Raman spectroscopy, atomic force microscopy, nanoindenter, spectroscopic ellipsometer, surface profiler and micro-tribometer were employed to study the structure and tribological properties of DLC/Ti and DLC films. The results show that DLC/Ti film, with $I(D)/I(G)$ 0.28 and corresponding to 76{\%} sp$^{3}$ content calculated by Raman spectroscopy, uniform chemical composition along depth direction, 98 at{\%} content of carbon, hardness 8.2 GPa and Young's modulus 110.5 GPa, compressive stress 6.579 GPa, thickness 46~nm, coefficient of friction 0.08, and critical load 95mN, exhibits excellent mechanical and tribological properties.

Growth studies of m-GaN layers on LiAlO2 by MOCVD

Zou Jun, Liu Cheng-Xiang, Zhou Sheng-Ming, Wang Jun, Zhou Jian-Hua, Huang Tao-Hua, Han Ping, Xie Zi-Li, Zhang Rong
Chin. Phys., 2006, 15 (11): 2706-2709 doi: 10.1088/1009-1963/15/11/040
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This paper reports that the $m$-plane GaN layer is grown on (200)-plane LiAlO$_{2}$ substrate by metal-organic chemical vapour deposition (MOCVD) method. Tetragonal-shaped crystallites appear at the smooth surface. Raman measurement illuminates the compressive stress in the layer which is released with increasing the layer's thickness. The high transmittance (80{\%}), sharp band edge and excitonic absorption peak show that the GaN layer has good optical quality. The donor acceptor pair emission peak located at $\sim$3.41\,eV with full-width at half maximum of 120\,meV and no yellow peaks in the photoluminescence spectra partially show that no Li incorporated into GaN layer from the LiAlO$_{2}$ substrate.

Induced growth of high quality ZnO thin filmsby crystallized amorphous ZnO

Wang Zhi-Jun, Song Li-Jun, Li Shou-Chun, Lu You-Ming, Tian Yun-Xia, Liu Jia-Yi, Wang Lian-Yuan
Chin. Phys., 2006, 15 (11): 2710-2712 doi: 10.1088/1009-1963/15/11/041
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This paper reports the induced growth of high quality ZnO thin film by crystallized amorphous ZnO. Firstly amorphous ZnO was prepared by solid-state pyrolytic reaction, then by taking crystallized amorphous ZnO as seeds (buffer layer), ZnO thin films have been grown in diethyene glycol solution of zinc acetate at 80\,\du. X-ray Diffraction curve indicates that the films were preferentially oriented [001] out-of-plane direction of the ZnO. Atomic force microscopy and scanning electron microscopy were used to evaluate the surface morphology of the ZnO thin film. Photoluminescence spectrum exhibits a strong ultraviolet emission while the visible emission is very weak. The results indicate that high quality ZnO thin film was obtained.

Optical emission spectroscopy study on depositionprocess of microcrystalline silicon

Wu Zhi-Meng, Lei Qing-Song, Geng Xin-Hua, Zhao Ying, Sun Jian, Xi Jian-Ping
Chin. Phys., 2006, 15 (11): 2713-2717 doi: 10.1088/1009-1963/15/11/042
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This paper reports that the optical emission spectroscopy (OES) is used to monitor the plasma during the deposition process of hydrogenated microcrystalline silicon films in a very high frequency plasma enhanced chemical vapour deposition system. The OES intensities (SiH\sj{*}, H$_\al^*$ and H$_\be^*$) are investigated by varying the deposition parameters. The result shows that the discharge power, silane concentrations and substrate temperature affect the OES intensities. When the discharge power at silane concentration of 4\% increases, the OES intensities increase first and then are constant, the intensities increase with the discharge power monotonously at silane concentration of 6\%. The SiH\sj{*} intensity increases with silane concentration, while the intensities of H$_\al^*$ and H$_\be^*$ increase first and then decrease. When the substrate temperature increases, the SiH\sj{*} intensity decreases and the intensities of H$_\al^*$ and H$_\be^*$ are constant. The correlation between the intensity ratio of $I_{\rm H_\al^*}$/$I_{{\rm SiH}^*}$ and the crystalline volume fraction ($X_{\rm c}$) of films is confirmed.

First-principles study on the effect of Hf content onmartensitic transformation temperatureof TiNiHf alloy

Tan Chang-Long, Cai Wei, TianXiao-Hua
Chin. Phys., 2006, 15 (11): 2718-2723 doi: 10.1088/1009-1963/15/11/043
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In this paper a first-principles study of the electronic structure and stability of B2 Ti$_{1 - x}$NiHf$_{x }\,(x=0.2, 0.4, 0.6)$ and B19$^\prime $ Ti$_{1 - x}$NiHf$_{x}(x=0$, 0.5) alloys is presented. The calculations are performed by the plane-wave pseudopotential method in the framework of the density functional theorywith the generalized gradient approximation. This paper calculates the lattice parameters, density of states, charge density, and heats of formation. The results show that the electronic structure and stability of B2 Ti$_{1 - x}$NiHf$_{x}$ change gradually with Hf content. However, Hf content has little effect on the electronic structure and stability of B19$^\prime $ Ti$_{1 - x}$NiHf$_{x}$. The mechanism of the effect of Hf content on martensitic transformation temperature of TiNiHf alloys is studied from the electronic structure.

The electric and magnetic properties of epitaxially grownA0.5-xLaxSr0.5MnO3 (A=Pr, Nd) thin film

Yang Shao-Bo, Zhong Jian-Ping, Yuan Jie, Zhu Shao-Jiang, Xu Bo, Cao Li-Xin, Qiu Xiang-Gang, Nie Liu-Ying, Xie Zhong, Zhao Li-Hua, Zhao Bai-Ru
Chin. Phys., 2006, 15 (11): 2724-2730 doi: 10.1088/1009-1963/15/11/044
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The epitaxial (single crystal-like) Pr$_{0.4}$La$_{0.1}$Sr$_{0.5}$MnO$_{3}$ (PLSMO) and Nd$_{0.35}$La$_{0.15}$Sr$_{0.5}$MnO$_{3}$ (NLSMO) thin films are prepared and characterized, and the electric and magnetic properties are examined. We find that both PLSMO and NLSMO have their own optimum deposition temperature ($T_{\rm o})$ in their growing into epitaxial thin films. When the deposition temperature is higher than $T_{\rm o}$, a $c$-axis oriented but polycrystalline thin film grows; when the deposition temperature is lower than $T_{\rm o}$, the thin film tends to be $a$-axis oriented and also polycrystalline. The most important point is that for the epitaxial PLSMO and NLSMO thin films the electronic phase transitions are closely consistent with the magnetic phase transitions, i.e. an antiferromagnetic phase corresponds to an insulating state, a ferromagnetic phase corresponds to a metallic state and a paramagnetic phase corresponds to a semiconducting state, while for the polycrystalline thin films the electronic phase transitions are always not consistent with the magnetic transitions.

Properties of the incandescent light emitted fromdouble-walled carbon nanotube filament

Wei Jin-Quan, Sun Jia-Lin, Wu De-Hai, Guo Ji-Hua, Luo Jian-Bin, Wang Kun-Lin
Chin. Phys., 2006, 15 (11): 2731-2734 doi: 10.1088/1009-1963/15/11/045
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We have studied the radiation of a double-walled carbon nanotube (DWNT) filament with a length of 4.5\,mm and a diameter of 10\,$\mu$m by applying an electric current through the filament. The DWNT filament starts emitting incandescent light at voltage $U=6$\,V. Emission spectra of the DWNT below temperature 1250\,K can well be fitted to those of the blackbody radiation. The intensity of the incandescent light shows an exponential dependence on the voltage applied on the DWNT filaments. The resistance of the DWNT filaments is very stable at high temperatures between 900 and 1250\,K during the emission of light in the experiments.

Self-consistent analysis of double-δ-doped InAlAs/InGaAs/InP HEMTs

Li Dong-Lin, Zeng Yi-Ping
Chin. Phys., 2006, 15 (11): 2735-2741 doi: 10.1088/1009-1963/15/11/046
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We have carried out a theoretical study of double-$\delta$-doped InAlAs/InGaAs/InP high electron mobility transistor (HEMT) by means of the finite differential method. The electronic states in the quantum well of the HEMT are calculated self-consistently. Instead of boundary conditions, initial conditions are used to solve the Poisson equation. The concentration of two-dimensional electron gas (2DEG) and its distribution in the HEMT have been obtained. By changing the doping density of upper and lower impurity layers we find that the 2DEG concentration confined in the channel is greatly affected by these two doping layers. But the electrons depleted by the Schottky contact are hardly affected by the lower impurity layer. It is only related to the doping density of upper impurity layer. This means that we can deal with the doping concentrations of the two impurity layers and optimize them separately. Considering the sheet concentration and the mobility of the electrons in the channel, the optimized doping densities are found to be $5\times 10^{12}$ and $3\times 10^{12}$~cm$^{ - 2}$ for the upper and lower impurity layers, respectively, in the double-$\delta$-doped InAlAs/InGaAs/InP HEMTs.

New aspects of HCI test for ultra-short channel n-MOSFET devices

Ma Xiao-Hua, Hao Yue, Wang Jian-Ping, Cao Yan-Rong, Chen Hai-Feng
Chin. Phys., 2006, 15 (11): 2742-2745 doi: 10.1088/1009-1963/15/11/047
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Hot carriers injection (HCI) tests for ultra-short channel n-MOSFET devices were studied. The experimental data of short channel devices (75--90\,nm), which does not fit formal degradation power law well, will bring severe error in lifetime prediction. This phenomenon usually happens under high drain voltage ($V_{\rm d}$) stress condition. A new model was presented to fit the degradation curve better. It was observed that the peak of the substrate current under low drain voltage stress cannot be found in ultra-short channel device. Devices with different channel lengths were studied under different $V_{\rm d}$ stresses in order to understand the relations between peak of substrate current ($I_{\rm sub}$) and channel length/stress voltage.

Experimental study of surface crystallization on integrated circuit chips

Zhang Xin, Liu Meng-Xin, Gao Yong, Wang Cai-Lin, Wang Zhi-Wei, Zhang Xian
Chin. Phys., 2006, 15 (11): 2746-2750 doi: 10.1088/1009-1963/15/11/048
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A surface crystallization phenomenon on bonding pads and wires of integrated circuit chip is reported in this paper. Through a lot of experiments, an unknown failure effect caused by mixed crystalline matter is revealed, whereas non-plasma fluorine contamination cannot cause the failure of bonding pads. By experiments combined with infrared spectroscopy analysis, the surface crystallization effect is studied. The conclusion of the study can provide the guidance for IC fabrication, modelling and analysis.

Silicon-on-nothing MOSFETs fabricated with hydrogenand helium co-implantation

Bu Wei-Hai, Huang Ru, Li Ming, Tian Yu, Wu Da-Ke, Chan Man-Sun, Wang Yang-Yuan
Chin. Phys., 2006, 15 (11): 2751-2755 doi: 10.1088/1009-1963/15/11/049
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In this paper, a method to fabricate Silicon-on-Nothing (SON) MOSFETs using H$^{ + }$ and He$^{ + }$ co-implantation is presented. The technique is compatible with conventional CMOS technology and its feasibility has been experimentally demonstrated. SON MOSFETs with 50nm gate length have been fabricated. Compared with the corresponding bulk MOSFETs, the SON MOSFETs show higher on current, reduced leakage current and lower subthreshold slope.

Temperature dependence of the luminescence properties of LaCl3:Ce crystal

Pei Yu, Chen Xiao-Feng, Qin Lai-Shun, Yao Dong-Min, Ren Guo-Hao
Chin. Phys., 2006, 15 (11): 2756-2760 doi: 10.1088/1009-1963/15/11/050
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The optical properties of LaCl3:Ce crystal are reported in this paper. Optical transmission spectrum, photoluminescence and time resolved photoluminescence spectra at different temperatures are investigated. It is found that optical transmittance is as high as 80{\%} between 320~nm and 600~nm, and no obvious absorption band is found in this region. Emission intensity and decay time of photoluminescence are quite stable with the change of the temperature between 80~K and 500~K. No thermal quenching is present up to 500~K, and decay time keeps at $17\pm 2$~ns. With the increase of the temperature, the whole emission bands and excitation bands present broadening and overlapping,$_{ }$leading to the strengthening of re-absorption of the Ce$^{3 + }$ emission, which makes the emission spectra have a red shift trend.

Photoluminescence of multiwalled carbon nanotubes excited at different wavelengths

Yuan Yan-Hong, Miao Run-Cai, Bai Jin-Tao, Hou Xun
Chin. Phys., 2006, 15 (11): 2761-2764 doi: 10.1088/1009-1963/15/11/051
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In this paper the multiwalled carbon nanotubes (MWNTs) were synthesized by a chemical vapour deposition and the SEM graph shows that the sample has good construction. The micro-Raman spectrum shows the characteristic line of the MWNTs and an additional line produced by the defects on the outer surface of MWNTs. The photoluminescence (PL) spectra observed experimentally are variable under different excitation wavelengths and the strong excitation wavelength dependence of luminescence indicates a distribution of emitters which include electron $\pi$ in excited states and the Van Hove singularities. The absorption spectra confirm the transition channels which are consistent with the PL emission.
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