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Volume 24 Issue 12
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Original Articles
Conditional Lie Backlund Symmetries of Hamilton--Jacobi Equations
WANG Li-Zhen, GOU Ming, QU Chang-Zheng,
Chin. Phys. Lett. 2007, 24 (12): 3293-3296 .  
Abstract   PDF(pc) (138KB) ( 583 )
symmetry method, as a generalization of the conditional symmetry and Lie Backlund symmetry methods, is developed to study the Hamilton--Jacobi equations. It is shown that the equation ut=uxn+1+B(u)ux+C(u) admits a class of conditional Lie Backlund symmetry for certain functions B(u) and C(u). As a result, a complete description of structure of solutions to the resulting equations associated to the conditional Lie Backlund symmetry is performed.
Generation of Entangled Bloch States for Two Atomic Samples Trapped in Separated Cavities
ZHENG Shi-Biao
Chin. Phys. Lett. 2007, 24 (12): 3297-3299 .  
Abstract   PDF(pc) (115KB) ( 513 )
generation of entangled states for two atomic ensembles trapped in two distant cavities. In the scheme, each atomic sample is initially in a Bloch state and the cavity mode is initially in a coherent state with a small amplitude. The dispersive atom--cavity interaction leads to a photon-number dependent phase shift on the atomic system. The detection of a photon leaking from the cavities makes the two atomic samples collapse to an entangled Bloch state.
One-Dimensional Two-Component Bosons with Attractive Interaction
Chin. Phys. Lett. 2007, 24 (12): 3300-3303 .  
Abstract   PDF(pc) (130KB) ( 482 )
The Bethe-ansatz method is used to solve one-dimensional two-component
bosons with a δ-function potential considering the negative coupling constant part. With the string hypothesis of Minoru Takahashi, the features of the ground state and low-lying excited states of this model are discussed explicitly by analytical and numerical methods. Especially for a N=2 system, the two bosons being pairs is obvious, and the ground state which is independent of the coupling constant should be ferromagnetic.
Generation of Cluster States in Cavity QED
ZHOU Yan-Li, YANG Li-Jia, DAI Hong-Yi
Chin. Phys. Lett. 2007, 24 (12): 3304-3307 .  
Abstract   PDF(pc) (131KB) ( 460 )
We propose two schemes for the generation of cluster states in the context of cavity quantum electrodynamics (QED). In the first scheme, we prepare multi-cavity cluster states with information encoded in the coherent states. The second scheme is to generate multi-atom cluster states, where qubits
are represented by the states of cascade Rydberg atoms. Both the schemes are based on the atom--cavity interaction and the atomic spontaneous radiation can be efficiently reduced since the cavity frequency is largely detuned from the atomic transition frequency.
Mutual Information of Pauli Channels with Correlated Noise
HOU Li-Zhen, FANG Mao-Fa
Chin. Phys. Lett. 2007, 24 (12): 3308-3311 .  
Abstract   PDF(pc) (170KB) ( 566 )
A general formula for the mutual information of the Pauli channels with memory modelled by correlated noise is derived. It is shown that the mutual information depends on the channel shrinking factor, the input state parameter and the channel memory coefficient. The analyses based on the general formula reveal that the entanglement is always a useful resource to enhance the mutual information of some Pauli channels, such as the bit flip
channel and the bit-phase flip channel. Our analyses also show that the entanglement is not advantageous to the reliable transmission of classical information for some Pauli channels at any time, such as the phase flip channel and the phase damping channel.
Efficient Multiparty-to-Multiparty Quantum Secret Sharing via Continuous Variable Operations
HAN Lian-Fang, LIU Yi-Min, YUAN Hao, ZHANG Zhan-Jun
Chin. Phys. Lett. 2007, 24 (12): 3312-3315 .  
Abstract   PDF(pc) (569KB) ( 565 )
sharing scheme [Phys. Rev. A 71(2005)044301] proposed recently is extended to a multiparty-to-multiparty case. Furthermore, the continuous variable operations are employed in the extended scheme to replace the specific discrete unitary operations used in the original scheme. The complete randomicity of the continuous variable characterizing the unitary operations can ensure the security of secret sharing. Moreover, the present scheme is compared with the recent similar scheme [Phys. Rev. A 72(2005)012304]. It is found that the efficiency of the present scheme is n times of that of the previous one.
Experimental Realization of Arbitrary Accuracy Iterative Phase Estimation Algorithms on Ensemble Quantum Computers
LIU Xiu-Mei, , LUO Jun, , SUN Xian-Ping,
Chin. Phys. Lett. 2007, 24 (12): 3316-3319 .  
Abstract   PDF(pc) (163KB) ( 627 )
We report the first experimental demonstration of a nuclear magnetic resonance (NMR) realization of iterative phase estimation algorithms. Using feedback and iterations, we experimentally obtain the phase with 6 bits of precision on a two-qubit NMR quantum computer. Furthermore, we experimentally demonstrate the effect of gate noise on the iterative phase estimation algorithm. Our experimental results show that errors of measurements of the phase depend strongly on the precision of coupling gates. This experiment can be used as a benchmark for multi-qubit realizations of quantum information processing and precision measurements.
Boundary Quantum Entanglement of the XXZ Spin Chain with Boundary Impurities
ZHUO Wei, WANG Yu-Peng
Chin. Phys. Lett. 2007, 24 (12): 3320-3321 .  
Abstract   PDF(pc) (134KB) ( 643 )
The boundary quantum entanglement for the s=1/2 XXZ spin chain with boundary impurities is studied via the density matrix renormalization group (DMRG) method. It is shown that the entanglement entropy of the boundary bond (the impurity and the chain spin next to it) behaves differently in different phases. The relationship between the singular points of the boundary entropy and boundary quantum critical points is discussed.
Physics of a Kind of Normally Ordered Gaussian Operators in Quantum Optics
FAN Hong-Yi, Li Hong-Qi
Chin. Phys. Lett. 2007, 24 (12): 3322-3324 .  
Abstract   PDF(pc) (111KB) ( 676 )
Based on the technique of integration within an ordered product of operators we investigate a completeness relation of pure states (such as the coordinate eigenstate, the momentum eigenstate and the coherent state) into normally ordered Gaussian forms. The Weyl ordering invariance under similarity
transformations is employed to reveal physical meaning of a kind of normally ordered Gaussian operators, which have the similar forms to the bivariate normal distributions in statistics, i.e., the thermo mixed state density matrix.
Bianchi Type-III Cosmological Models with Gravitational Constant G and the Cosmological Constant ∧
J. P. Singh, R. K. Tiwari, Pratibha Shukla
Chin. Phys. Lett. 2007, 24 (12): 3325-3327 .  
Abstract   PDF(pc) (111KB) ( 732 )
Einstein field equations with variable gravitational and cosmological constants are considered in the presence of perfect fluid for the Bianchi type-III universe by assuming conservation law for the energy-momentum tensor. Exact solutions of the field equations are obtained by using the scalar of expansion proportional to the shear scalar θ∝σ, which leads to a relation between metric potential B= Cn, where n is a constant. The corresponding physical interpretation of the cosmological solutions are also discussed.
Electromagnetic Response of High-Frequency Gravitational Waves by Coupling Open Resonant Cavity
LI Fang-Yu, CHEN Ying, WANG Ping
Chin. Phys. Lett. 2007, 24 (12): 3328-3331 .  
Abstract   PDF(pc) (148KB) ( 582 )
We present a new detecting scheme of high-frequency gravitational waves (HFGWs) in the GHz band, the scheme consists of a high-quality-factor open microwave cavity, a static magnetic field passing through the cavity and an
electromagnetic (EM) normal mode stored in the cavity. It is found that under the resonant condition first- and second-order perturbation EM effects have almost the same detecting sensitivity to the HFGWs in the GHz band (h~10-26,ν~5GHz), but the former contains more information from the HFGWs. We also provide a very brief review for possible improving way of the sensitivity.
This scheme would be highly complementary to other schemes of detecting the HFGWs.
Note on Invariance of One-Dimensional Lattice-Boltzmann Equation
RAN Zheng
Chin. Phys. Lett. 2007, 24 (12): 3332-3335 .  
Abstract   PDF(pc) (112KB) ( 536 )
Invariance of the one-dimensional lattice Boltzmann model is proposed together with its rigorous theoretical background. It is demonstrated that the symmetry inherent in Navier--Stokes equations is not really recovered in the one-dimensional lattice Boltzmann equation (LBE), especially for shock calculation. Symmetry breaking may be the inherent cause for the non-physical oscillations in the vicinity of the shock for LBE calculation.
Tunnelling Radiation of Charged and Magnetized Massive Particles from BTZ Black Holes
HE Tang-Mei, ZHANG Jing-Yi
Chin. Phys. Lett. 2007, 24 (12): 3336-3339 .  
Abstract   PDF(pc) (126KB) ( 367 )
We investigate the tunnelling radiation of charged and magnetized massive particles from a Banados--Teitelboim--Zanelli (BTZ) black hole by extending the Parikh--Wilczek tunnelling framework. In order to calculate the emission rate, we reconstruct the electromagnetic field tensor and the Lagrangian of the field corresponding to the source with electric and magnetic charges, and treat the charges as an equivalent electric charge for simplicity in the later calculation. The result supports Parikh-Wilczek's conclusion, that is, the Hawking thermal radiation actually deviates from perfect thermality and agrees with an underlying unitary theory.
Particle Transport with Asymmetric Unbiased Forces and Entropic Barrier
XIE Hui-Zhang, AI Bao-Quan, LIU Xue-Mei, CHENG Xiao-Bo, LIU Liang-Gang, LI Zhi-Bing
Chin. Phys. Lett. 2007, 24 (12): 3340-3343 .  
Abstract   PDF(pc) (186KB) ( 572 )
Transport of a Brownian particle moving along the axis of a three-dimensional (3D) symmetric and periodic tube is investigated in the presence of asymmetric unbiased forces. It is found that in the presence of entropic barrier, the asymmetry of the unbiased forces is a way of inducing a net particle current. The particle current is a peaked function of temperature,
which indicates that the thermal noise may facilitate the transport even in the presence of entropic barrier. There exists an optimized radius at the bottleneck at which the particle current takes its maximum value. The current can be influenced by the slope of tube walls and there exists an optimized slope for which the particle current takes its maximum value.
Dynamics Analysis and Transition Mechanism of Bursting Calcium Oscillations in Non-Excitable Cells
ZHANG Feng, LU Qi-Shao, DUAN Li-Xia
Chin. Phys. Lett. 2007, 24 (12): 3344-3346 .  
Abstract   PDF(pc) (167KB) ( 685 )
A one-pool model with Ca2+-activated inositol-trisphosphate-concentration degradation is considered. For complex bursting Ca2+ oscillation, point--cycle bursting of subHopf--subHopf type is found to be in the intermediate state from quasi-periodic bursting to point--point bursting of subHopf--subHopf type. The fast--slow burster analysis is used to study the transition mechanisms among simple periodic oscillation, quasi-periodic bursting, point--point and point--cycle burstings. The dynamics analysis of different oscillations provides better insight into the generation and transition mechanisms of
complex intra- and inter-cellular Ca2+ signalling.
Existence and Stability of Two-Dimensional Compact-Like Discrete Breathers in Discrete Two-Dimensional Monatomic Square Lattices
XU Quan, TIAN Qiang
Chin. Phys. Lett. 2007, 24 (12): 3347-3350 .  
Abstract   PDF(pc) (994KB) ( 382 )
Two-dimensional compact-like discrete breathers in discrete two-dimensional monatomic square lattices are investigated by discussing a generalized discrete two-dimensional monatomic model. It is proven that the two-dimensional compact-like discrete breathers exist not only in two-dimensional soft ψ4 potentials but also in hard two-dimensional ψ4 potentials and pure two-dimensional K4 lattices. The measurements of the two-dimensional compact-like discrete breather cores in soft and hard two-dimensional ψ4 potential are determined by coupling parameter K4, while those in pure two-dimensional K4 lattices have no coupling with parameter K4. The stabilities of
the two-dimensional compact-like discrete breathers correlate closely to the coupling parameter K4 and the boundary condition of lattices.
Multi-site Compact-Like Discrete Breather in Discrete One-Dimensional Monatomic Chains
XU Quan, TIAN Qiang
Chin. Phys. Lett. 2007, 24 (12): 3351-3355 .  
Abstract   PDF(pc) (869KB) ( 307 )
Multi-site compact-like discrete breathers in discrete one-dimensional monatomic chains are investigated by discussing a generalized discrete one-dimensional monatomic model. We obtain that the two-site compact-like discrete breathers with codes σ ={ 0,... ,0,1,1,0,... ,0} and codes σ={0,... , 0,1,-1,0,... ,0} can exist in discrete one-dimensional monatomic chain with quartic on-site and inter-site potentials. However, the former can only exist in hard quartic on-site potential and cannot exist in soft quartic on-site potential, whereas the latter is just reversed. All of the two-site Compact-like discrete breathers with codes σ.={0,....,0,1,1,0,.... ,0} and σ ={0,... , 0,1,-1,0, .... ,0} cannot exist in a pure K4 chain.
Phase Transition of a Distance-Dependent Ising Model on the Barabasi--Albert Network
DAI Jun, HE Da-Ren
Chin. Phys. Lett. 2007, 24 (12): 3355-3357 .  
Abstract   PDF(pc) (266KB) ( 523 )
We report our investigation on the behaviour of distance-dependent Ising models, which are located on the BA model network. The interaction strength between two nodes (the spins) is considered to obey an exponential decay dependence on the geometrical distance. The Monte Carlo simulation shows a phase transition from ferromagnetism to paramagnetism, and the critical
temperature approaches a constant temperature as the interaction decaying exponent increases.
Observation of Diffusion Process of a Water Droplet Immersed in Protein Solution in Microgravity
DUAN Li, SUN Zhi-Wei, KANG Qi, CUI Hai-Liang, LIN Hai, HU Liang, XU Sheng-Hua, LI Gen-Pei
Chin. Phys. Lett. 2007, 24 (12): 3358-3361 .  
Abstract   PDF(pc) (1175KB) ( 423 )
Pure liquid--liquid diffusion driven by concentration gradients is hard to study in a normal gravity environment since convection and sedimentation also contribute to the mass transfer process. We employ a Mach--Zehnder interferometer to monitor the mass transfer process of a water droplet in EAFP protein solution under microgravity condition provided by the Satellite Shi Jian No 8. A series of the evolution charts of mass distribution during the diffusion process of the liquid droplet are presented and the relevant diffusion coefficient is determined.
Optimized Optomechanical Micro-Cantilever Array for Uncooled Infrared Imaging
DONG Feng-Liang, ZHANG Qing-Chuan, CHEN Da-Peng, MIAO Zheng-Yu, XIONG Zhi-Ming, GUO Zhe-Ying, LI Chao-Bo, JIAO Bin-Bin, WU Xiao-Ping
Chin. Phys. Lett. 2007, 24 (12): 3362-3364 .  
Abstract   PDF(pc) (1640KB) ( 612 )
We present a new substrate-free bimaterial cantilever array made of SiNx and Au for an uncooled micro-optomechanical infrared imaging device. Each cantilever element has an optimized deformation magnification structure. A
160×160 array with a 120μm×120μm pitch is fabricated and an optical readout is used to collectively measure deflections of all microcantilevers in the array. Thermal images of room-temperature objects with higher spatial resolution have been obtained and the noise-equivalent temperature difference of the fabricated focal plane arrays is given statistically and is measured to be about 270mK.
Design, Fabrication and Measurement of Ni/Ti Multilayer Used for Neutron Monochromator
ZHANG Zhong, WANG Zhan-Shan, ZHU Jing-Tao, WU Yong-Rong, MU Bao-Zhong, WANG Feng-Li, QIN Shu-Ji, CHEN Ling-Yan
Chin. Phys. Lett. 2007, 24 (12): 3365-3357 .  
Abstract   PDF(pc) (245KB) ( 635 )
Ni/Ti multilayers, which can be used for neutron monochromators, are designed, fabricated and measured. Firstly, their reflectivities are simulated based on the Nevot--Croce model. Reflectivities of two Ni/Ti multilayer mirrors
with periods d=10.3nm (M1) and d=7.8nm (M2) are calculated. In the calculation, the reflectivity of the Ni/Ti multilayer is taken as a function of the grazing angle with different roughness factors δ=1.0nm and delta=1.5nm. Secondly, these two multilayers are fabricated by the direct current magnetron sputtering technology. Thirdly their structures are characterized by
small-angle x-ray diffraction. The roughness factors are fitted to be 0.68nm and 1.16nm for M1 and M2, respectively. Finally their reflective performances are measured on the V14 neutron beam line at the Berlin Neutron Scattering Centre (BENSC), Germany. The experimental data show that the grazing angle of the reflected neutron intensity peak increases, but the reflected neutron intensity decreases, with the decreasing periods of the multilayers.
Investigation of a Tabletop Confocal Micro X-Ray Fluorescence Setup
LIN Xiao-Yan, WANG Zhi-Hong, CHU Xue-Lian, SUN Tian-Xi, DING Xun-Liang
Chin. Phys. Lett. 2007, 24 (12): 3368-3370 .  
Abstract   PDF(pc) (1700KB) ( 613 )
A new tabletop confocal micro x-ray fluorescence setup with an MCBM 50-0.6B x-ray tube is assembled. The confocal micro x-ray fluorescence setup includes two lenses, a polycapillary full lens in the excitation channel and a polycapillary half lens in the detection channel. A Ni--Cr wire in diameter 25μm is used to investigate the FWHM of three-dimensional confocal volume. A basso-relievo capital letter of a 1-jiao RMB coin of 2005 version is studied with this confocal micro x-ray fluorescence setup.
Equivalence of Different Descriptions for η Particle in Simplest Little Higgs Model
LU Ran, WANG Qing
Chin. Phys. Lett. 2007, 24 (12): 3371-3373 .  
Abstract   PDF(pc) (119KB) ( 420 )
In the SU(3) simplest little Higgs model, a characteristic particle is the light pseudoscalar boson η, it can leads to interesting signals in the LHC/ILC and has been studied in the literature with different parameterizations. We
show that these different descriptions for η particle are equivalent up to some SU(3) rotations as long as we suitably redefine the pseudo-Goldstone boson fields. We evaluate the necessary SU(3) rotations and build up explicit expressions for redefined fields.
Flat Currents and Solutions of Sigma Model on Supercoset Targets with Z2m Grading
KE San-Min, SHI Kang-Jie, WANG Chun, WU Sheng
Chin. Phys. Lett. 2007, 24 (12): 3374-3377 .  
Abstract   PDF(pc) (264KB) ( 631 )
We find one parameter flat currents of the sigma model on supercoset targets with Z2m grading given by Young satisfaction equations of motion and the Virasoro constraint. This means that one can generate a series of classical solutions from the original one. For these new solutions one can also construct flat currents and conserved charges, which form the same set with the original one.
Doubly Heavy Baryon Production at Polarized Photon Collider
YANG Zhong-Juan, YAO Tao
Chin. Phys. Lett. 2007, 24 (12): 3378-3380 .  
Abstract   PDF(pc) (169KB) ( 492 )
We study the inclusive production of doubly heavy baryon Ξcc at polarized photon collider. Our results show that proper choice of the initial beam polarizations may increase the production rate of Ξcc approximately 10%.
Kaonic Nuclear Cluster K- pp in Quark Delocalization Colour Screening Model
DENG Cheng-Rong, PING Jia-Lun,
Chin. Phys. Lett. 2007, 24 (12): 3381-3383 .  
Abstract   PDF(pc) (259KB) ( 419 )
The quark-delocalization colour-screening model is employed to study the kaonic nuclear cluster K-pp system. The calculation shows that there is a strong effective attraction between kaon and protons. The bound state can be formed and the binding energy is estimated to be about 80MeV, and the space configuration is a symmetrical linear triatomic molecule with radius 1.15fm. The results also show that the quark delocalization is responsible for
the strong attraction in the system and the colour screening adds a little attraction in this case.
Angular Dispersion and Deflection Function for Heavy Ion Elastic Scattering
BAI Zhen, WANG Qi, HAN Jian-Long, XIAO Zhi-Gang, XU Hu-Shan, SUN Zhi-Yu, HU Zheng-Guo, ZHANG Xue-Ying, WANG Hong-Wei, MAO Rui-Shi, YUAN Xiao-Hua, XU Zhi-Guo, ZHANG Hong-Bin, XU Hua-Gen, QIHui-Rong, WANG Yue, JIA Fei, WU Li-Jie, DING Xian-Li, GAO Qi, GAO Hui, LI Song-Lin, LI Jun-Qing, ZHANG Ya-Peng, XIAO Guo-Qing, JIN Gen-Ming, REN Zhong-Zhou, ZHOU Shan-Gui, XU Wang, Fan Gong-Tao, ZHANG Shuang-Quan, PANG Dan-Yang, SERGEY Yu-Kun,
Chin. Phys. Lett. 2007, 24 (12): 3384-3387 .  
Abstract   PDF(pc) (231KB) ( 476 )
The differential cross sections for elastic scattering products of 17F on 208Pb have been measured. The angular dispersion plots of ln(dσ/dθ) versus θ2 are obtained from the angular distribution of the elastic scattering differential cross sections. Systematical analysis on the angular dispersion for the available experimental data indicates that there is an angular dispersion turning angle at forward angular range within the grazing angle. This turning
angle can be clarified as nuclear rainbow in classical deflection function. The exotic behaviour of the nuclear rainbow angle offers a new probe to investigate the halo and skin phenomena.
Phenomenological Scaling of Rapidity Dependence for Anisotropic Flows in 25MeV/nucleon Ca+Ca by Quantum Molecular Dynamics Model
YAN Ting-Zhi, MA Yu-Gang, CAI Xiang-Zhou, FANG De-Qing, LUGuang-Cheng, SHEN Wen-Qing, TIAN Wen-Dong, WANG Hong-Wei, WANG Kun
Chin. Phys. Lett. 2007, 24 (12): 3388-3391 .  
Abstract   PDF(pc) (213KB) ( 747 )
Anisotropic flows (v1, v2, v3 and v4) of light fragments up to the mass number 4 as a function of rapidity are studied for 25MeV/nucleon 40Ca + 40Ca at large
impact parameters by a quantum molecular dynamics model. A phenomenological scaling behaviour of rapidity dependent flow parameters vn (n = 1, 2, 3 and 4) is found as a function of mass number plus a constant term, which may arise from the interplay of collective and random motions. In addition, v4v22 keeps to be almost independent of rapidity and remains a
rough constant of 1/2 for all light fragments.
Hyperspherical Calculations on Electron Affinity and Geometry for Li- and Na-
HAN Hui-Li, ZHANG Xian-Zhou, SHI Ting-Yun
Chin. Phys. Lett. 2007, 24 (12): 3392-3395 .  
Abstract   PDF(pc) (164KB) ( 518 )
Using a model potential to describe the interaction between the core and the valence electron, we perform hyperspherical calculations for electron affinity and geometry of the weakly bound Li- and Na- systems. In our calculation, channel functions are expanded in terms of B-splines. Using the special properties of B-splines, we make the knot distributions more precisely, characterizing the behaviour of channel functions. This improves the convergence greatly. Our results are in good agreement with the other theoretical and experimental values.
Coherent Scattering of Light by Bose--Einstein Condensation in a Tight Confinement
QU Qiu-Zhi, ZHOU Shu-Yu, LONG Quan, XU Zhen, LIU Liang, WANG Yu-Zhu
Chin. Phys. Lett. 2007, 24 (12): 3396-3399 .  
Abstract   PDF(pc) (1515KB) ( 565 )
We have observed strong scattering of probe light by dilute Bose--Einstein condensate (BEC) 87Rb gas in a tight magnetic trap. The scattering light forms fringes at the image plane. It is found that we can infer the real size of the
condensation and the number of the atoms by modelling the imaging system. We present a quantitative calculation of light scattering by the condensed atoms. The calculation shows that the experimental results agree well with the prediction of the generalized diffraction theory, and thus we can directly observe the phase transition of BEC in a tight trap.
Photoassociation Reactions H+D+ and H++D in Ultrashort Pulse Laser Fields
NIU Ying-Yu, WANG Rong, LIU Li, CONG Shu-Lin
Chin. Phys. Lett. 2007, 24 (12): 3400-3403 .  
Abstract   PDF(pc) (264KB) ( 610 )
The photoassociation reactions H+D+ and H++D induced by the one- and two-colour laser pulses are theoretically studied. The reactions occur through two channels: (i) H(1S)+D+ →HD+, and (ii) H++D(1S)→HD+. The reaction probability through channel (ii) is higher than through channel (i). The populations of the products H++D and HD+ and the ratio of H++D to HD+
can be controlled by laser pulses. The two-colour laser pulses can more
efficiently lower the dissociation probability and therefore enhance the
yield ratio of the product HD+.
Effects of Configuration Interaction on Dielectronic Recombination of Cu-Like Gold Ion through 3d+ e →4l'l'' Capture Process
MENG Fan-Chang, CHEN Chong-Yang, WANG Yan-Shen, ZOU Ya-Ming,
Chin. Phys. Lett. 2007, 24 (12): 3404-3407 .  
Abstract   PDF(pc) (203KB) ( 460 )
Effects of configuration interaction on dielectronic recombination of Cu-like gold ions through the 3d+e → 4l'4l'' capture process are studied in the models of isolated configurations approximation, configuration mixing within 3d94s4l'4l'', and configuration mixing within 3d94l4l'4l'' (l≥0), employing a relativistic distorted-wave approximation. Nonresonant raditive stabilizing transitions and decays to autoionizing levels followed by radiative cascades, as well as resonant stabilizing transitions from the resonant levels, are taken into account. The additional mixing with 3d94l4l'4l'' (0<l≤ l'≤l''3) shifts slightly the peaks of cross section towards low energy. The rate coefficient at low temperature is dramatically changed. The rate coefficient at temperature above 100eV is enhanced by a factor between 26% and 13%.
Optical Potential Calculation for Positron Collision with Helium
CHENG Yong-Jun, ZHOU Ya-Jun
Chin. Phys. Lett. 2007, 24 (12): 3408-3411 .  
Abstract   PDF(pc) (184KB) ( 458 )
The positron--helium system is studied with the momentum-space coupled-channel optical method. The positronium formation cross sections from the positronium formation threshold to 400eV and total cross sections from 17 to 3000eV are calculated. Ionization continuum and positronium formation channels are included via a complex equivalent-local optical potential in the
present calculations. The results are compared with the available experimental and theoretical data.
Formation of Small Bottle Light Beams
RAO Lian-Zhou, PU Ji-Xiong
Chin. Phys. Lett. 2007, 24 (12): 3412-3415 .  
Abstract   PDF(pc) (2115KB) ( 727 )
A method for obtaining small bottle light beams, e.g. 0.92λ×0.4λ, in a high numerical-aperture lens system is proposed and numerically demonstrated. This can be achieved by changing the radius of each zone of the binary element and polarization rotation angle of the cylindrically polarized vectorial vortex beam. It is found that the transversal and axial sizes of this bottle beam are equal to about 0.92λ and 0.4λ, respectively. In addition, the connection between angular momentum and topological Pancharatnam charge is also shown.
Photoinduced Birefringence and Broadband All-Optical Photonic Switch in a Bacteriorhodopsin/Polymer Composite Film
WEI Lai, TENG Xue-Lei, LU Ming, ZHAO You-Yuan, MA De-Wang, DING Jian-Dong
Chin. Phys. Lett. 2007, 24 (12): 3416-3419 .  
Abstract   PDF(pc) (1036KB) ( 639 )
Photoinduced birefringence with large optical nonlinearity in a bacteriorhodopsin/polymer composite film is observed. A high refractive index change of 8.5×10-5 photoinduced by 476nm pumping beam is reached at the low intensity of 6.5mW/cm2. Based on it, a broadband all-optical photonic
switch is realized with an optical controlling switch system. Because of controlling beam's selectivity in switching, the transporting beams of different wavelengths with different intensities and shapes can be modulated by adjusting the wavelength and intensity of the controlling beam.
Interactions of Three Dual-Dressing Effects of Four-Wave Mixing in a Five-Level Atomic System
LI Pei-Zhe, NIE Zhi-Qiang, ZHANG Yan-Peng, JIANG-Tong, DU Yi-Gang, GAN Chen-Li, SONG Jian-Ping, LU Ke-Qing
Chin. Phys. Lett. 2007, 24 (12): 3420-3423 .  
Abstract   PDF(pc) (260KB) ( 617 )
We study the four-wave mixing (FWM) in an opening five-level system with two dressing fields. There are three kinds of doubly dressing mechanisms (parallel cascade, sequential cascade, and nested cascade) in the system for doubly dressed four-wave mixing. These mechanisms reflect different correlations between two dressing fields and different effects of two dressing fields to the FWM. Investigation of these mechanisms is helpful to understand the generated high-order nonlinear optical signal dressed by multi-fields.
Monolithically Integrated Transceiver with Novel Y-Branch by Bundle Integrated Waveguide for Fibre Optic Gyroscope
WANG Lu, LIAO Zai-Yi, CHENG Yuan-Bing, ZHAO Ling-Juan, PAN Jiao-Qing, ZHOU Fan, WANG Wei
Chin. Phys. Lett. 2007, 24 (12): 3424-3427 .  
Abstract   PDF(pc) (751KB) ( 634 )
A novel Y-branch based monolithic transceiver with a superluminescent diode and a waveguide photodiode (Y-SDL-PD) is designed and fabricated by the method of bundle integrated waveguide (BIG) as the scheme for monolithic integration and angled Y-branch as the passive bi-directional waveguide. The simulations of BIG and Y-branches show low losses and improved far-field patterns, based on the beam propagation method (BPM). The amplified spontaneous emission of the device is up to 10mW at 120mA with no threshold and saturation. Spectral characteristics of about 30nm width and less than 1dB modulation are achieved using the built-in anti-lasing ability of
Y-branch. The beam divergence angles in horizontal and vertical directions are optimized to as small as 12°× 8°, resulting in good fibre coupling.
High-Power Operation of Uncoated Strain-Compensated Quantum Cascade Lasers at 4.8μm
LI Lu, SHAO Ye, LIU Jun-Qi, LIU Feng-Qi, WANG Zhan-Guo
Chin. Phys. Lett. 2007, 24 (12): 3428-3430 .  
Abstract   PDF(pc) (195KB) ( 584 )
High-power operation of uncoated 22-μm-wide quantum cascade lasers (QCLs) emitting at λ≈4.8μm is reported. The emitting region of the QCL structure consists of a 30-period strain-compensated In0.68Ga0.32As/In0.37Al0.63As superlattice. For a 4-mm-long laser in pulsed mode, a peak output power is achieved in excess of 2240mW per facet at 81K with a threshold current density of 0.64kA/cm2. The effects of varying the cavity lengths from 1 to 4mm on the performances of the QCLs are analysed
in detail and the low waveguide loss of only about 1.4cm-1 is extracted.
Zero-Chirp Return-to-Zero Pulses Generation with Two Single-Driver z-Cut Mach--Zehnder Modulators
QIN Xi, CAO Ji-Hong, ZHANG Feng, WANG Mu-Guang, ZHANG Jian-Yong, JIAN Shui-Sheng,
Chin. Phys. Lett. 2007, 24 (12): 3431-3434 .  
Abstract   PDF(pc) (222KB) ( 689 )
A novel method is proposed to suppress the frequency chirp of single-driver z-cut Mach--Zehnder modulators. Theoretical analysis shows that by multiplying the output pulses of a half clock frequency driving single-driver z-cut modulator with the one delayed odd multiple bit duration, the frequency chirp can be removed entirely, and return-to-zero (RZ) pulses with duty cycles of about 25% and 56% are obtained. An experimental scheme is proposed to validate the proposed method. The experimental results show that perfect 40GHz zero-chirp RZ pulses can be obtained by using this scheme.
Coherent and Incoherent Interactions between Discrete-Soliton Trains in Two-Dimensional Light-Induced Photonic Lattices
XIAO Fa-Jun, ZHANG Peng, LIU Sheng, ZHAO Jian-Lin
Chin. Phys. Lett. 2007, 24 (12): 3435-3438 .  
Abstract   PDF(pc) (1298KB) ( 451 )
The coherent and incoherent interactions between discrete-soliton trains are numerically investigated in light-induced two-dimensional photonic lattices. The solutions of discrete-soliton trains for diamond and square lattices are obtained by Petviashvili iteration method. It is found that for both the kinds of lattices, two in-phase (out-of-phase) discrete-soliton trains attract (repel) each other, and the intermediates are always accompanied with energy transfer. While the interaction forces between two incoherent discrete-soliton trains are always attractive.
Scattering-Enhanced Femtosecond Optical Parametric Generation
YUAN Peng, QIAN Lie-Jia, LUO Hang, ZHU He-Yuan
Chin. Phys. Lett. 2007, 24 (12): 3439-3442 .  
Abstract   PDF(pc) (494KB) ( 431 )
Scattering-enhanced femtosecond optical parametric generation (OPG) has
been observed and studied in detail, which may decrease the pump threshold of OPGs dramatically and may make OPGs reliable. The experimental demonstration in a LiNbO3 crystal shows that strong enough OPG can be obtained at pump intensity of only about 30GW/cm2 which is well below the crystal damage threshold. Either a synchronized pulsed laser or a cw laser has been used as the scattering source, of which the wavelength, spectral shape and irradiating angle are not strictly required.
Intensity-Dependent Optical Nonlinear Absorption and Refraction of Gold Nanorods
GONG Hong-Mei, ZHOU Zhang-Kai, XIAO Si, SONG Hao, SU Xiong-Rui, LI Min, WANG Qu-Quan,
Chin. Phys. Lett. 2007, 24 (12): 3443-3446 .  
Abstract   PDF(pc) (770KB) ( 658 )
Au nanorods dispersed in aqueous solution were prepared with the electrochemical method. The absorption spectrum shows two absorption
peaks corresponding to the perpendicular and transverse surface plasma
resonance absorption of the nanorods. The third-order optical nonlinear
properties are investigated by Z-scans. The signs of the nonlinear absorption coefficient and refractive index are reversed as the intensity of incident laser increases, which is due to the shape change of the gold nanoparticles melted by the intense laser pulses.
Negative Refraction in One-Dimensional Photonic Crystals with Tilted Interface
YU Xiao-Tong, WEI Ze-Yong, LI Hong-Qiang, ZHANG Ye-Wen, CHEN Hong
Chin. Phys. Lett. 2007, 24 (12): 3447-3449 .  
Abstract   PDF(pc) (929KB) ( 544 )
We investigate the wave propagation through the tilted interface of one-dimensional photonic crystals. Negative refraction can be realized by excitation of the Bloch states in the extended Brillouin zone with suppressed reflection. Equi-frequency surface analysis shows that the positive refraction, negative refraction or birefringence in this configuration can be achieved under a proper incident angle, which is confirmed by finite-difference time-domain simulations. The results may be useful in applications in the new devices based on one-dimensional photonic or optical waveguide arrays.
Semiconductor-Optical-Amplifier-Based Inverted and Non-Inverted Wavelength Conversion at 40Gb/s Using a Detuning Optical Bandpass Filter
DONG Jian-Ji, ZHANG Xin-Liang, HUANG De-Xiu
Chin. Phys. Lett. 2007, 24 (12): 3450-3453 .  
Abstract   PDF(pc) (805KB) ( 892 )
We experimentally demonstrate 40Gb/s semiconductor-optical-amplifier-based tunable wavelength conversion (WC) using a detuning optical bandpass filter. Both inverted and non-inverted WCs are obtained by shifting the filter central
wavelength with respect to the probe wavelength. When the filter is red shifted by 0.4nm or blue shifted by 0.3nm, the WC is non-inverted. However, when the filter is blue shifted by 0.1nm, the WC is inverted. It is experimentally demonstrated that the WC has a tunable range covering the C-band.
Numerical Simulation of Shear-Horizontal-Wave-Induced Electromagnetic Field in Borehole Surrounded by Porous Formation
CUI Zhi-Wen, WANG Ke-Xie, SUN Jian-Guo, ZHU Zheng-Ya, YAO Gui-Jin, HU Heng-Shan
Chin. Phys. Lett. 2007, 24 (12): 3454-3457 .  
Abstract   PDF(pc) (164KB) ( 576 )
Seismoelectric field excited by purely torsional loading applied directly to the borehole wall is considered. A brief formulation and some computed waveforms show the advantage of using shear-horizontal (SH) transverse-electric (TE) seismoelectric waves logging to measure shear velocity in a
fluid-saturated porous formation. By assuming that the acoustic field is not influenced by its induced electromagnetic field due to seismoelectric effect, the coupling governing equations for electromagnetic field are reduced to Maxwell equations with a propagation current source. It is shown that this simplification is valid and the borehole seismoelectric conversion efficient is
mainly dependent on the electrokinetic coupling coefficient. The receivers to detect the conversion electromagnetic field and to obtain shear velocity can be set in the borehole fluid in the SH-TE seismoelectric wave log.
An Effective Method on Two-Dimensional Lattice Boltzmann Simulations with Moving Boundaries
LI Hua-Bing, ZHANG Chao-Ying, LU Xiao-Yang, FANG Hai-Ping
Chin. Phys. Lett. 2007, 24 (12): 3458-3461 .  
Abstract   PDF(pc) (236KB) ( 1132 )

We propose a lattice Boltzmann scheme for two-dimensional complex boundaries moving in fluid flow. The hydrodynamic forces exerting on the moving boundaries are calculated based on a stress-integration method proposed before, but the extrapolation procedure is avoided, and the
stability of this model is improved. The accuracy and robustness are demonstrated by numerical simulations of a circular particle settling in a two-dimensional vertical channel. The numerical convergence is studied by varying the time-step and the dimensionless particle sizes.

Abnormal Cutoff Thickness of Long-Range Surface Plasmon Polariton Modes Guided by Thin Metal Films
LIU Fang, RAO Yi, HUANG Yi-Dong, ZHANG Wei, PENG Jiang-De
Chin. Phys. Lett. 2007, 24 (12): 3462-3465 .  
Abstract   PDF(pc) (335KB) ( 542 )
Long-range surface plasmon polariton (LRSPP) modes guided by a thin metal film surrounded by semi-infinite dielectrics with different refractive indices are studied. Our calculation results show that the cutoff thickness of the metal film does not monotonically increase with refractive index difference △n between the substrate and superstrate. Just because of this abnormal behaviour of cutoff thickness, the existence of LRSPP illustrates complicated situations in asymmetric configurations. For a certain metal film thickness, LRSPP may exist in one, two or three refractive index difference △n regions.
Femtosecond Laser-Induced Breakdown Spectroscopy for Detection of Trace Elements in Sophora Leaves
Myriam Bossu, HAO Zuo-Qiang, Matthieu Baudelet, YU Jin, ZHANG Zhe, ZHANG Jie,
Chin. Phys. Lett. 2007, 24 (12): 3466-3468 .  
Abstract   PDF(pc) (146KB) ( 944 )
Sophora leaves from several areas in Beijing are analysed by femtosecond laser-induced breakdown spectroscopy (femto-LIBS). Although the used spectral detection system is not time-resolved, the spectral lines of trace mineral elements are detected and analysed. It is proven that the femto-LIBS can be an efficient method to detect mineral trace elements contained in tree leaves which is a biomonitor for atmospheric pollution assessment or botanic studies. An interesting case of correlation between trace elements detected in tree leaves and the pollution of the concerned area is presented, for the first time to our knowledge.
(Ti,Al)N Film on Normalized T8 Carbon Tool Steel Prepared by Pulsed High Energy Density Plasma Technique
LIU Yuan-Fu, DENG Fu-Ping, HAN Jian-Min, XU Xiang-Yang, YANG Si-Ze, LIU Xiu-Bo
Chin. Phys. Lett. 2007, 24 (12): 3469-3472 .  
Abstract   PDF(pc) (1295KB) ( 596 )
Under optimized operating parameters, a hard and wear resistant (Ti,Al)N film is prepared on a normalized T8 carbon tool steel substrate by using pulsed high energy density plasma technique. Microstructure and composition of the film are analysed by x-ray diffraction, x-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning electron microscopy. Hardness profile and
tribological properties of the film are tested with nano-indenter and ring-on-ring wear tester, respectively. The tested results show that the microstructure of the film is dense and uniform and is mainly composed of (Ti,Al)N and AlN hard phases. A wide transition interface exists between the film and the normalized T8 carbon tool steel substrate. Thickness of the film is about 1000nm and mean hardness value of the film is about 26GPa. Under dry sliding wear test conditions, relative wear resistance of the (Ti,Al)N film is
approximately 9 times higher than that of the hardened T8 carbon tool steel reference sample. Meanwhile, the (Ti,Al)N film has low and stable friction coefficient compared with the hardened T8 carbon tool steel reference sample.
Structural and Magnetic Properties of Codoped ZnO based Diluted Magnetic Semiconductors
LI Bin-Bin, SHEN Hong-Lie, ZHANG Rong, XIU Xiang-Qiang, XIE Zhi
Chin. Phys. Lett. 2007, 24 (12): 3473-3476 .  
Abstract   PDF(pc) (236KB) ( 663 )

Zn1-xCoxO (x=0.01, 0.02, 0.05, 0.10 and 0.20) diluted magnetic semiconductors are prepared by the sol-gel method. The structural and magnetic properties of the samples are studied using x-ray diffraction (XRD), extended x-ray absorption fine structure (EXAFS) and superconducting quantum interference device (SQUID). The XRD patterns does not show any
signal of precipitates that are different from wurtzite type ZnO when Co content is lower than x=0.10. An EXAFS technique for the Co K-edge has been employed to probe the local structures around Co atoms doped in ZnO powders by fluorescence mode. The simulation results for the first shell EXAFS signals indicate that Zn sites can be substituted by Co atoms when Co content is lower than x=0.05. The SQUID results show that the samples (x<0.05) exhibit clear hysteresis loops at 300K, and magnetization versus temperature from 5K to 350K at H=100,Oe for the sample x=0.02 shows
that the samples have ferromagnetism above room temperature. A double-exchange mechanism is proposed to explain the ferromagnetic properties of the samples.

Structural and Optical Properties of Zinc Nitride Films Prepared by Pulsed Filtered Cathodic Vacuum Arc Deposition
Chin. Phys. Lett. 2007, 24 (12): 3477-3480 .  
Abstract   PDF(pc) (310KB) ( 2599 )
Polycrystalline zinc nitride films are deposited on Corning 7059 glass substrates by pulsed filtered cathodic vacuum arc deposition (PFCVAD). The crystallographic structure is studied by means of x-ray diffraction. These
measurements show that all the films are crystallized in the cubic structure, in a preferred orientation along the (332) and (631) directions. Weak XRD signal shows small crystallites distributed in an amorphous tissue. A small improvement of crystallinity is observed with annealing. Optical parameters such as absorption, energy band gap, Urbach tail, extinction coefficients have been determined. The Urbach tail energy is decreased with annealing at 500°C for one hour. Energy band gap values are found to be increased by
Strain Field in GaAs/GaN Wafer-Bonding Interface and Its Microstructure
WU Di, GUO Xia, GU Xiao-Ling, LI Yi-Bo, SHEN Guang-Di
Chin. Phys. Lett. 2007, 24 (12): 3481-3484 .  
Abstract   PDF(pc) (2123KB) ( 379 )
The strain fields in a wafer-bonded GaAs/GaN structure are measured by electron backscatter diffraction (EBSD). Image quality (IQ) of EBSD Kikuchi patterns and rotation angles of crystal lattices as strain sensitive parameters are employed to characterize the distortion and the rotation of crystal lattices in the GaAs--interface--GaN structure, as well as to display the strain fields. The results indicate that the influence region of the strains in the wafer-bonded GaAs/GaN structure is mainly located in GaAs side because the strength of GaAs is weaker than that of GaN. The cross-sectional image of transmission electron microscopy (TEM) further reveals the distortion and the rotation of crystal lattices induced by strains systematically.
Phase Transition Induced by Small Molecules in Confined Copolymer Films
Chin. Phys. Lett. 2007, 24 (12): 3485-3588 .  
Abstract   PDF(pc) (202KB) ( 463 )
We investigate the phase transition induced by small molecules in confined copolymer films by using density functional theory. It is found that the addition of small molecules can effectively promote the phase separation of copolymers. In a symmetric diblock copolymer film, the affinity and concentration of small molecules play an important role in the structure
transitions. The disordered--lamellar transitions, lamellar--lamellar transitions and the re-entrant transitions of the same structures are observed. Our results have potential applications in the fabrication of new functional materials.
Dynamics Simulation on Charge Transfer Relaxation between Myoglobin and Water
CHENG Wei, ZHANG Feng-Shou, ZHANG Bo-Yang, ZHOU Hong-Yu
Chin. Phys. Lett. 2007, 24 (12): 3489-3491 .  
Abstract   PDF(pc) (144KB) ( 368 )
Dynamical processes of myoglobin after photon-excited charge transfer between Fe ion and surrounding water anion are simulated by a molecular dynamics model. The roles of Coulomb interaction effect and water effect in the relaxation process are discussed. It is found that the relaxations before and after charge transfer are similar. Strong Coulomb interactions and less
water mobility decrease Coulomb energy fluctuations. An extra transferred charge of Fe ion has impact on water packing with a distance up to 0.86nm.
Optoelectronic Characteristics and Field Emission Properties of Indium-Doped Tin Oxide Nanowire Arrays
XUE Xin-Yu, SHI Song-Lin, LIN Zhi-Xian, ZHENG Ke-Lu, ZHANG Yong-Ai, GUO Tai-Liang, WANG Tai-Hong
Chin. Phys. Lett. 2007, 24 (12): 3492-3494 .  
Abstract   PDF(pc) (964KB) ( 547 )
Optoelectronic characteristics of individual indium-doped tin oxide (In--SnO2) nanowires are investigated by performing transport measurement with UV illumination on/off circles. The current rapidly increases from 0.15 to 55nA
under UV illumination, which is ascribed to the increase of carrier concentration and the decrease of surface depletion. Efficient and stable field emission is obtained from In--SnO2 nanowire arrays. The current density is up to 17mA/cm2 at 3.4V/μm, and the fluctuations are less than 1%. The emission behaviour is perfectly in agreement with the Fowler--Nordheim theory. Our results imply that In--SnO2 nanowires are promising candidates for UV
detectors and field emission displays.
Disc-Capped ZnO Nanocombs
LI Xin, XU Chun-Xiang, ZHU Guang-Ping, YANG Yi, LIU Jin-Ping, SUN Xiao-Wei, CUI Yi-Ping
Chin. Phys. Lett. 2007, 24 (12): 3495-3498 .  
Abstract   PDF(pc) (2516KB) ( 469 )
Nanocombs with a disc cap structure of ZnO have been synthesized on Si substrates by using pure Zinc powders as the source materials based on a vapour-phase transport process. The morphology and the microstructure are investigated by a scanning electron microscopy and x-ray diffraction. Based on the transmission electron microscopy and selected area electron diffraction analysis, the growth directions of three representative parts, nanoribbon stem, nanorod branch and nanodisc cap of the nanocomb are revealed. The
growth mechanism of the disc-capped nanocombs is discussed based on
the self-catalyzed vapour-liquid-solid process.
Raman Spectroscopy and Magnetic Properties of Mn-Doped ZnO Bulk Single Crystal
HE Qing-Bo, XU Jia-Yue, LI Xin-Hua, A. Kamzin, L. Kamzina
Chin. Phys. Lett. 2007, 24 (12): 3499-3501 .  
Abstract   PDF(pc) (266KB) ( 594 )
Mn doped ZnO bulk single crystals are grown by the modified Bridgman method. The as-grown crystals are red in colour. The additional Raman mode observed at 524cm-1 is attributed to the Mn ions incorporating into ZnO crystal. The crystal exhibited paramagnetic under lower applied field below 2280Oe. Then diamagnetism is observed in the crystal when the magnetic field rises up and becomes dominant under applied field above 5270Oe. The
magnetic susceptibility dependence on the temperature follows a Curie law indicating a typical paramagnetic characteristic under an applied field of 2kOe. No ferromagnetic ordering is observed in the as-grown Mn-doped ZnO crystal.
Vacancy Aggregation in Diamond Films grown in CH4+H2 Atmosphere by MPCVD
LIU Yan-Yan, ZHANG Qing-Yu, Elizabeth BAUER-GROSSE
Chin. Phys. Lett. 2007, 24 (12): 3502-3505 .  
Abstract   PDF(pc) (2647KB) ( 452 )
Transmission electron microscopy is applied to study the diamond film grown in a CH4 and H2 gaseous mixture by microwave plasma assisted chemical vapour deposition. Defects in the nanometre scale, dislocation loops, are
first observed in diamond films. The dislocation loops are found to be of co-existence with planar defects and are next to the planar defects for {111} faceting grains. A possible mechanism is suggested to interpret the co-existence of dislocation loops with planar defects.
Codoping of Potassium and Bromine in Carbon Nanotubes: A Density Functional Theory Study
XIAO Yang, YAN Xiao-Hong, DING Jian-Wen
Chin. Phys. Lett. 2007, 24 (12): 3506-3508 .  
Abstract   PDF(pc) (295KB) ( 464 )
We investigate the co-doping of potassium and bromine in single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) based on density functional theory. In the co-doped (6,0) SWCNTs, the
4s electron of potassium is transferred to nanotube and Br, leading to the n-type feature of SWCNTs. When potassium is intercalated into inner tube and bromine is put on outer tube, the positive and negative charges reside on the outer and inner tubes of the (7,0)@(16,0) DWCNT, respectively. It is expected that DWCNTs would be an ideal candidate for p--n junction and diode applications.
Photoinduced Reconstruction of Electronic Structure in Half-Metal CrO2
WU Xue-Wei, NIU Dong-Lin, LIU Xiao-Jun
Chin. Phys. Lett. 2007, 24 (12): 3509-3512 .  
Abstract   PDF(pc) (227KB) ( 658 )
We investigate the photoinduced effects on the electronic structure for half-metallic ferromagnet CrO2 (Tc~390K), in which the conducting electrons are totally polarized, by using the LSDA+U method. A significant change is found for the band structure and the density of states (DOS) for CrO2 under
photo-excitation, especially for the Cr 3dt2g band: disappearance of the spin-split band, suggesting collapse of the half-metallic state. We ascribe the change of electronic structure under photo-excitation to the wider one-electron band W via the strong hybridization of the down-spin Cr 3d and O 2p
states. Furthermore we discuss the magnetic properties under photo-excitation.
Electrical Characteristics of Copper Phthalocyanine Thin-Film Transistors with Polyamide-6/Polytetrafluoroethylene Gate Insulator
YU Shun-Yang, XU Shi-Ai, MA Dong-Ge
Chin. Phys. Lett. 2007, 24 (12): 3513-3515 .  
Abstract   PDF(pc) (194KB) ( 440 )
Polyamide-6(PA 6)/polytetrafluoroethylene is studied as a potential gate dielectric for flexible organic thin film transistors. The same method used for the formation of organic semiconductor and gate dielectric films greatly simplifies the fabrication process of devices. The fabricated transistors show good electrical characteristics. Ambipolar behaviour is observed even when the device is operated in air.
Kink Structures of Spin-Polarized Electrons due to Electron--Magnon Scattering in Ferromagnetic State
MA Lei
Chin. Phys. Lett. 2007, 24 (12): 3516-3519 .  
Abstract   PDF(pc) (234KB) ( 546 )
We propose a model composed of spin-polarized itinerant electrons and bosonic spin-wave excitations, and study renormalization of the spin-polarized itinerant electron bands due to electron--magnon scattering. Spin-polarized kink structures are predicted in the normal state quasiparticle dynamics of ferromagnetic superconductor as UGe2. It is suggested that
the angle-resolved photoemission experiment may be helpful in this respect.
Quasi-Hexagonal Ordered Arrays of FePt Nanoparticles Prepared by a Micellar Method
QU Sheng, ZHANG Xing-Wang, YIN Zhi-Gang, YOU Jing-Bi, CHEN Nuo-Fu
Chin. Phys. Lett. 2007, 24 (12): 3520-3523 .  
Abstract   PDF(pc) (2596KB) ( 558 )
Hexagonally ordered arrays of magnetic FePt nanoparticles on Si substrates are prepared by a self assembly of diblock copolymer PS-b-P2VP in toluene, a dip coating process and finally plasma treatment. The as-treated FePt nanoparticles are covered by an oxide layer that can be removed by a 40Ar+ sputtering. The effects of the sequence of adding salts on the composition distribution are revealed by x-ray photoelectron spectroscopy measurements. No particle agglomeration is observed after 600°C annealing for the present
ordered array of FePt nanoparticles, which exhibits advantages in patterning FePt nanoparticles by a micellar method. Moreover, magnetic properties of the annealed FePt nanoparticles at room temperature are investigated by a vibrating sample magnetometer.
ESR Spectrometer as a Possible Tool for Rapid Analysis of Cane Sugar Purity
Kheamrutai Thamaphat, Pichet Limsuwan, Siwaporn Meejoo
Chin. Phys. Lett. 2007, 24 (12): 3524-3527 .  
Abstract   PDF(pc) (156KB) ( 1517 )
A method for quantitative/qualitative determination of cane sugar purity by ESR is devised. Refined sugar, plantation white sugar, soft brown sugar and raw sugar are used as samples in this work. The sucrose radical is produced by pulverization of sugar and it increases as the particle size decreases. Based on pulverization-induced sucrose radical, ESR study demonstrates the effects of sugar purity on characteristic of ESR spectrum. The relationship between the sucrose contents and peak area under the ESR spectrum is manifested. It is found that the peak area or sucrose radical concentration increases linearly with the increase of sucrose content. Using the linear
regression method, the sucrose amount can be revealed. This approach is a promising fast and accurate method for sugar purity analysis.
Influences of Pressure and Substrate Temperature on Epitaxial Growth of γ-Mg2SiO4 Thin Films on Si Substrates
KANG Lin, GAO Ju, XU Hua-Rong, ZHAO Shao-Qi, CHEN Hong, WU Pei-Heng
Chin. Phys. Lett. 2007, 24 (12): 3528-3531 .  
Abstract   PDF(pc) (775KB) ( 505 )

An epitaxial γ-Mg2SiO4 thin film can be a good buffer between the Si ubstrate and some oxide thin films. For high temperature superconducting multilayer structures, hopefully it can be taken as an insulating layer to
replace the widely used MgO film. To explore such possibilities, we carry out systematic studies on the influences of pressure and substrate temperature on the epitaxy of γ-Mg2SiO4 thin films grown on Si (100) substrates using rf magnetron sputtering with an Mg target of purity of 99.95 percent. With the
substrate temperature kept at 500°C and the pressure changing from 10Pa to 15Pa, in the XRD spectra the γ-Mg2SiO4 (400) peak grows drastically while the MgO (200) peak is suppressed. Keeping the pressure at 15Pa and
increasing the temperature from 500°C to 570°C further can improve the film epitaxy, while working at 780°C and 11Pa seems to give very good
results. X-ray photoelectronic spectroscopy and Ф scan are used to characterize the stoichiometry, crystallinity, and in-plane growth of the samples.

Structure Characterization of HSQ Films for Low Dielectrics Using D5 as Sacrificial Porous Materials
YIN Gui-Qin, NING Zhao-Yuan, YUAN Qiang-Hua
Chin. Phys. Lett. 2007, 24 (12): 3532-3534 .  
Abstract   PDF(pc) (156KB) ( 789 )
Low-density materials, commercially available hydrogensilsesquioxane (HSQ) offer a low dielectric constant. HSQ films can be obtained by spin on deposition (SOD). In this work, low-dielectric-constant HSQ films are prepared by using D5 (decamethylcyclopentasiloxane) as sacrificial porous materials. The dielectric constant of silica films significantly changes from 3.0 to 2.4. We report the structural aspects of the films in relation to their composition after annealed at 300°C, 400°C, and 500°C for 1.5h in nitrogen ambient and annealed at 400°C for 1.5h in vacuum. Si--OH appears after annealed at
400°C for 1.5h in vacuum. The results indicate that the proper condition is in nitrogen ambient. Intensity of the Si--H peak increases with the increasing temperature. Fourier transform infrared spectroscopy is used to identify the network structure and cage structure of Si--O--Si bonds and other possible bonds. Dielectric constant k is significantly lowered by annealing at 350°C for 1.5h in nitrogen ambient. The I--V and C--V measurements are used to determine the dielectric constant, the electric resistivity and the breakdown electric field.
Phase Transition and High Piezoactivity of Sb Doped (Na0.53K0.435Li0.035)Nb0.94Ta0.06O3 Lead-Free Ceramics
QI Peng, WANG Jin-Feng, MING Bao-Quan, WANG Chun-Ming, LIANG Xing-Hua
Chin. Phys. Lett. 2007, 24 (12): 3535-3538 .  
Abstract   PDF(pc) (214KB) ( 618 )
Lead-free piezoelectric ceramics with the composition of (Na0.53K0.435Li0.035)Nb0.94-xSbxTa0.06O3 (NKLNST) are synthesized by a conventional solid-state sintering process. An MPB-like region between orthorhombic and pseudocubic phases is found in this system. The density, piezoelectric and dielectric properties are enhanced greatly in this region. A composition (Na0.53K0.435Li0.035) (Nb0.86Sb0.08Ta0.06)O3 is found to have excellent
electrical properties: d33=320pC/N, kp=49% and kt=43%, as well as relatively low loss, tan δ=4.2%, and high relative density higher than 96%, which indicate that this ceramics is a promising lead-free piezoceramics replacing for lead zirconate titanate.
Subwavelength Imaging in a One-Dimensional Metal-Dielectric Structure
LI Ming-Yu, GU Pei-Fu, ZHANG Jin-Long, LI Yi-Yu, LIU Xu
Chin. Phys. Lett. 2007, 24 (12): 3539-3542 .  
Abstract   PDF(pc) (260KB) ( 593 )
We analyse the dispersion relation of a one-dimensional (1D) metal-dielectric (MD) structure for H-polarized light (i.e. the magnetic field is parallel to the interfaces of the layers) and use the transfer matrix method to simulate the subwavelength image effect through the 1D-MD structure. The structure operates in the self-collimation regime, and does not involve negative refraction or amplification of evanescent waves. The Fabry--Perot resonance effect is studied in order to obtain optimum parameters for maximum transmission. A resolution of λ/10 for a single point source is achieved when the thickness of the 1D-MD is about 300nm. Taking into account the actual
values of the dielectric constants of the metal (silver) and the dielectric (HfO2) layers, we find that a silver/HfO2 stack, with suitable parameters, has a resolution of λ/5 at visible wavelengths.
Optimization of Metamorphic InGaAs Quantum Wells on GaAs Grown by Molecular Beam Epitaxy
WU Bing-Peng, WU Dong-Hai, NI Hai-Qiao, HUANG She-Song, ZHAN Feng, XIONG Yong-Hua, XU Ying-Qiang, NIU Zhi-Chuan
Chin. Phys. Lett. 2007, 24 (12): 3543-3546 .  
Abstract   PDF(pc) (1089KB) ( 690 )

We investigate the molecular beam epitaxy growth of metamorphic InxGa1-xAs materials (x up to 0.5) on GaAs substrates systematically. Optimization of structure design and growth parameters is aimed at obtaining smooth surface and high optical quality. The optimized structures have an average surface roughness of 0.9--1.8nm. It is also proven by PL measurements that the optical properties of high indium content (55%) InGaAs quantum wells are improved apparently by defect reduction technique and by introducing Sb as a surfactant. These provide us new ways for growing device quality metamorphic structures on GaAs substrates with long-wavelength emissions.

Polymer White-Light-Emitting Diodes with High Work Function Cathode Based on a Novel Phosphorescent Chelating Copolymer
XIONG Yan, ZHANG Yong, ZHOU Jian-Lin, PENG Jun-Biao, HUANG Wen-Bo, CAO Yong
Chin. Phys. Lett. 2007, 24 (12): 3547-3550 .  
Abstract   PDF(pc) (211KB) ( 633 )
Polymer white-light-emitting diodes are fabricated based on the blend of poly[9,9-di-(2-% ethylhexyl)-fluorenyl-2,7-diyl]-end capped with polysilsesquioxane (PFO) and a chelating copolymer of poly[(9,9-bis(3'-(N,N-dimethylamino) propyl)-2,7-fluorene-alt-2,7-(9,9-dioctylfluorene))-co- [2,7-(9,9-dioctlyfluorene)-alt-5,5-bis(2-(4-methyl-1-naphtha-lene) pyridine-C2,N)
iridium (III) acethylacetonate]] (PFN-NaIr). The device with the sole aluminium cathode is able to produce a comparably white electroluminescence efficiency of 1.31cd/A to that of the device using low work function cathodes (such as Ba, Ca, etc.). The CIE coordinates of the white light emission consisting of red, green and blue three components are nearly at (0.34, 0.35). The mechanism of the white light emission from the device with the Al cathode is investigated, which is related to the efficient injection of electrons through the interface of PFN-NaIr/Al.
Formation of Mixture of A and C Centres in Diamond Synthesized with Fe90Ni10-C-High-Content Additive NaN3 by HPHT
LIANG Zhong-Zhu, JIA Xiao-Peng, LIANG Jing-Qiu
Chin. Phys. Lett. 2007, 24 (12): 3551-3554 .  
Abstract   PDF(pc) (294KB) ( 528 )
Very rich nitrogen concentration with the dominant C centres and some A centres are found in diamonds grown from a Fe90Ni10-C-high-content NaN3 additive system. The concentrations of C centres rapidly increase with increasing content of NaN3 additive, while the concentrations of A centres increase slowly. The total nitrogen concentration tends to increase rapidly
with increasing content of NaN3 additive when the content of NaN3 is below 0.7wt%. However, the total concentration of nitrogen in the diamonds increases slowly when the content of NaN3 is further increased up to 1.0wt%, and the total nitrogen average concentration are calculated to be around 2230ppm for most of the analysed synthetic diamonds. Furthermore, the nitrogen impurities in different crystal sectors of the diamonds are inhomogeneously distributed. The nitrogen impurities in the diamonds in [111] zones are incorporated more easily than that in [100].
Effect of Crucibles on Qualities of Self-Seeded Aluminium Nitride Crystals Grown by Sublimation
HAN Qi-Feng, DUAN Cheng-Hong, QIU Kai, JI Chang-Jian, LI Xin-Hua, ZHONG Fei, YIN Zhi-Jun, CAO Xian-Cun, ZHOU Xiu-Ju, WANG Yu-Qi
Chin. Phys. Lett. 2007, 24 (12): 3555-3558 .  
Abstract   PDF(pc) (3463KB) ( 558 )
Self-seeded aluminium nitride (AlN) crystals are grown in tungsten and hot pressed boron nitride (HPBN) crucibles with different shapes by a sublimation method. The qualities of the AlN crystals are characterized by high-resolution
transmission electronic microscopy (HRTEM), scanning electron microscopy (SEM) and Micro-Raman spectroscopy. The results indicate that the better quality crystals can be collected in conical tungsten crucible.
Effect of Annealing Temperature on Electrical Properties of Ferroelectric Bi3.25La0.75Ti3O12 Capacitors
YAN Zheng, ZHANG Wei-Tao, WANG Yi, ZHANG Xin, LI Li, ZHAO Qing-Xun, DU Jun, LIU Bao-Ting
Chin. Phys. Lett. 2007, 24 (12): 3559-3562 .  
Abstract   PDF(pc) (156KB) ( 601 )
Lanthanum-modified bismuth titanate (Bi3.25La0.75Ti3O12, BLT) thin films are
fabricated on platinized Si wafers by the sol-gel method, and the effect of annealing temperatures ranging from 650°C to 800°C on the electrical properties of Pt/BLT/Pt capacitors are investigated. It is found that polarization and leakage current of BLT capacitors strongly depend on the annealing temperature although all the capacitors demonstrate very similar characteristics, except the value of polarization, in pulse-width dependence, retention, and fatigue. Remanent polarization increases with the increase of annealing temperature, and annealing temperature of 700°C can yield the
largest remanent polarization, and then polarization decreases with increasing annealing temperature. For the 700°C annealed Pt/BLT/Pt capacitor, the remanent polarization 2Pr and the coercive field 2Ec, at an electric field of 226kV/cm, are 23.8μC/cm2 and 130kV/cm, respectively. Dielectric breakdown voltages of BLT films annealed at 750°C and 800°C are much lower than those annealed at 650°C and 700°C. At 100kV/cm, the leakage currents of BLT films prepared at 650°C and 700°C are only
1.5×10-6A/cm2 and 8.9×10-7A/cm2, espectively. Moreover, all the Pt/BLT/Pt capacitors exhibit excellent retention properties after a cumulative time of 1× m 104s and do not show any significant fatigue up to 1×1010 switching cycles
at frequency of 1MHz.
An Improved CE/SE Scheme and Its Application to Detonation Propagation
WANG Gang, ZHANG De-Liang, LIU Kai-Xin
Chin. Phys. Lett. 2007, 24 (12): 3563-3566 .  
Abstract   PDF(pc) (910KB) ( 531 )
An improved two-dimensional space-time conservation element and solution element (CE/SE) method with second-order accuracy is proposed, examined and extended to simulate the detonation propagations using detailed chemical reaction models. The numerical results of planar and cellular detonation are compared with corresponding results by the Chapman--Jouguet theory and experiments, and prove that the method is a new reliable way for numerical simulations of detonation propagation.
Effects of Different Dispersion Methods on the Microscopical Morphologyof TiO2 Film
LAN Xiao-Hua, YANG Shu-Qin, ZOU Yu, WANG Zhi-An, HUANG Ning-Kang
Chin. Phys. Lett. 2007, 24 (12): 3567-3569 .  
Abstract   PDF(pc) (1505KB) ( 1395 )
Nanocrystalline porous TiO2 films were prepared on conducting glass supports (ITO) by processed commercial TiO2 nanometre powder (P25). Three methods of physical dispersing for TiO2 powder, i.e. grinding, magnetic stirring, sonicleaning, were used to disperse TiO2 nanometre powder. Surface morphologies of TiO2 films were observed by optic-microscope and SEM. It is
found that the surface morphologies of TiO2 films are determined not only by the dispersing methods but also by the percentage of TiO2 powder in the dispersing system. Different film morphologies can be obtained under the same preparation condition but with different dispersing methods. A lot of cracks exist on the film surface for which the TiO2 slurry is dispersed by grinding. Magnetic stirring leads to some white points and micro-holes on the
film surface. Only a few of micro-holes can be observed on the film surface, in which the TiO2 slurry is dispersed by sonicleaning. Different surface morphologies can also be found with different thicknesses of TiO2 films. Different film thicknesses are due to different percentages of TiO2 powder in the slurry. The related mechanism leading to different features of the surface morphologies for the TiO2 films is discussed.
Transport Properties of Binary Clusters
WAN Hai-Qing, ZHOU Yan-Hong, XU Ying
Chin. Phys. Lett. 2007, 24 (12): 3570-3573 .  
Abstract   PDF(pc) (455KB) ( 413 )
We present first-principles studies on the transport properties of small silicon and aluminium clusters: Al2, Si2, Al4 and AlSi sandwiched between two Al (100) electrodes. The variation of the equilibrium conductance as a function of contact distance for these two-probe systems is probed. Our results show that the transport properties are dependent on both the specific nanostructure and the separation distance between the central molecule and the electrodes. For equilibrium transport properties, the clusters with the similar structure show similar transmission spectra at large distances, the small difference can be explained by the electron filling. For current-voltage
characteristics, all the clusters show the metallic behaviour at lower bias, however very different non-linear behaviour can be observed at higher bias. For AlSi and Al2, when the distance between the central cluster and the electrodes is 3.5AA, large negative differential resistance (NDR) can be found in the bias range 0.8V~1.4\,V.
High-Speed and Large-Scale Electromagnetically Actuated Resonant MEMS Optical Scanner
MU Can-Jun, ZHANG Fei-Ling, WU Ya-Ming
Chin. Phys. Lett. 2007, 24 (12): 3574-3577 .  
Abstract   PDF(pc) (1061KB) ( 1039 )
A high speed electromagnetically actuated resonant micro-electromechanical systems (MEMS) optical scanner with large mirror area of 6×4mm2 has been
developed. The MEMS optical scanner chip is fabricated using bulk silicon micromachining process and electroplating technique, and can generate the maximum optical deflection angle of ±6.8°circ at the 2.95kHz resonant frequency with a quality factor of 197 in air under the low power consumption of 50mW, when it is immersed in a constant 510.2mT magnetic field parallel to the coil plane. In addition, the surface roughness of less than 20nm for scanning mirror has been measured and the optical reflectivity of mirror at
wavelength of 1550nm is high up to 85%. The results show that the device can satisfy the demands of mm-sized scanning systems in optical communications.
Active Control of Cellular Orientation through In-Situ Stress in the Substrate
WU Heng-An, WANG Xiu-Xi, YAN Shun-Ping
Chin. Phys. Lett. 2007, 24 (12): 3578-3581 .  
Abstract   PDF(pc) (158KB) ( 370 )
We investigate the orientation of cells on substrates to find possible methods for controlling the cellular orientation. The force dipole model is employed in our modelling and simulation. The elastic interaction between cells as well as the elastic interaction between the cell and in-situ stress field in the substrate are found to be the two main physical mechanisms to control the cellular orientation. The former interaction dominates the cellular orientation when the in-situ stress is small, while the later dominates when the in-situ stress is large enough. Two cells tend to align perpendicularly on a free substrate, but the cellular orientation varies with the increasing in-situ stress. Two cells tend
to align in parallel when the normal stress is large enough. Their direction is perpendicular to the extension stress direction or parallel to the compression stress direction. When the positive in-situ shear stress is large enough, the two cells tend to align at -45°. Based on this theoretical simulation, it is believed that the cellular orientation on substrates can be controlled by the
in-situ stresses.
Modelling Human Cortical Network in Real Brain Space
ZHAO Qing-Bai, FENG Hong-Bo, TANG Yi-Yuan,
Chin. Phys. Lett. 2007, 24 (12): 3582-3585 .  
Abstract   PDF(pc) (179KB) ( 479 )
Highly specific structural organization is of great significance in the topology of cortical networks. We introduce a human cortical network model, taking the specific cortical structure into account, in which nodes are brain sites placed in the actual positions of cerebral cortex and the establishment of edges depends on the spatial path length rather than the linear distance. The resulting network exhibits the essential features of cortical connectivity, properties of small-world networks and multiple clusters structure. Additionally, assortative mixing is also found in this model. All of these findings may be attributed to the specific cortical architecture.
Formation of Vegetation Patterns and Hysteresis Phenomena in Arid and Semiarid Zones
HUA Da-Yin, WANG Lie-Yan
Chin. Phys. Lett. 2007, 24 (12): 3586-3589 .  
Abstract   PDF(pc) (3417KB) ( 626 )
Considering the spatial effect of the complicated interactions between plant and resource (soil water) and the stochastic character of the complicated ecological processes in an ecosystem, we introduce a lattice gas model to investigate the vegetation pattern formation in the arid and the semiarid ecosystems with Monte Carlo simulations. With consistency of some previous
mean-field models, the model reproduces a wide range of patterns observed in the arid and the semiarid regions. The sequences of vegetation states are also investigated with scanning three parameters, i.e., the precipitation and the plant growth rate, and then the parameter ranges are identified where a hysteresis loop appears and two different stable states coexist. The simulation results denote that the complex structures occur only when the
precipitation parameter decreases. Moreover, based on the model, it is found that an increase of the competition of the plant for the resource along the slope direction results in the regular stripes parallel to the hill's contours. The model provides an interesting mechanism to understand the formation of the other regular vegetation stripe in a limited resource condition.
Chaos Behaviour of Molecular Orbit
LIU Shu-Tang, SUN Fu-Yan, SHEN Shu-Lan
Chin. Phys. Lett. 2007, 24 (12): 3590-3592 .  
Abstract   PDF(pc) (147KB) ( 431 )
Based on Hückel's molecular orbit theory, the chaos and bifurcation behaviour of a molecular orbit modelled by a nonlinear dynamic system is studied. The relationship between molecular orbit and its energy level in the nonlinear dynamic system is obtained.
81 articles