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Volume 21 Issue 8
Online Date:
Original Articles
 Select Quantum Information Measurements for Garfinkle--Horne Dilaton Black Holes GE Xian-Hui, SHEN You-Gen, Chin. Phys. Lett. 2004, 21 (8): 1413-1416 .   Abstract   PDF(pc) (275KB) ( 531 ) The quantum non-cloning theorem is discussed for Garfinkle--Horne dilaton black holes. It is found that if the black hole complementarity principle is correct, then it will be questioned whether the quantum non-cloning theorem is well established inside the inner horizon. It is also found that another complementarity principle may be needed inside the inner horizon of the Garfinkle--Horne dilaton black hole.
 Select Preparation of the W State of Atoms in a Single Cavity or N Distant Cavities by Photon Interference LU Hong, CHEN Li-Bing, CHEN Wei-Cheng, ZHOU Zheng-Wei Chin. Phys. Lett. 2004, 21 (8): 1417-1420 .   Abstract   PDF(pc) (320KB) ( 477 ) We suggest two schemes to generate the W state of N Λ-type three-level atoms. In the schemes, identical N three-level atoms are trapped in a cavity or N distant cavities. The success or failure of the generation of the W state can be determined by detecting the polarization of photon leaking out of the cavity. The result demonstrates that the W state is free from both the cavity loss and the spontaneous emission due to the fact that the two ground states (left and right) of the three-level atoms are stable states (or metastable states).
 Select Does the Quantum Player Always Win the Classical One? ZHAO Hai-Jun, FANG Xi-Ming Chin. Phys. Lett. 2004, 21 (8): 1421-1424 .   Abstract   PDF(pc) (371KB) ( 420 ) We study quantum games in which the players have different strategic spaces. We find that the player who can use a quantum strategic space does not always possess more payoffs than the player who is restricted to apply only classical strategies. We find the condition of the classical player getting more payoffs than the quantum player. We also find that the game exhibits intriguing structures.
 Select Soliton Solutions of Bose--Einstein Condensate in Linear Magnetic Field and Time-Dependent Laser Field LI Hua-Mei, WU Feng-Min Chin. Phys. Lett. 2004, 21 (8): 1425-1428 .   Abstract   PDF(pc) (296KB) ( 475 ) With the help of symbolic computation, the tanh method is extended to find some new exact solutions of nonlinear Gross--Pitaevskii equation with weak bias magnetic and time-dependent laser fields. As a result, the bright and dark soliton solutions are obtained. In addition, some new soliton solutions in this model are found
 Select A New Type of Cascading Synchronization for Halo-Chaos and Its Potential for Communication Applications FANG Jin-Qing, YU Xing-Huo Chin. Phys. Lett. 2004, 21 (8): 1429-1432 .   Abstract   PDF(pc) (501KB) ( 519 ) Study of beam halo-chaos has become a key issue of concern for many future important applications. Control of halo-chaos has been researched intensively. This is the first time that the synchronization of beam halo-chaos has been realized in this field so far. Two nonlinear feedback control methods are proposed for the cascading synchronizing halo-chaos in coupled lattices of a periodic focusing channel. The simulation results show that the methods are effective. The realization of the synchronization of beam halo-chaos is significant not only for halo-chaos control itself but also for halo-chaos-based secure communication which may become an innovative technique.
 Select Dynamics of Coupled Quantum--Classical Oscillators He Wei-Zhong, XU Liu-Su, ZOU Feng-Wu Chin. Phys. Lett. 2004, 21 (8): 1433-1436 .   Abstract   PDF(pc) (507KB) ( 472 ) The dynamics of systems consisting of coupled quantum--classical oscillators is numerically investigated. It is shown that, under certain conditions, the quantum oscillator exhibits chaos. When the mass of the classical oscillator increases, the chaos will be suppressed; if the energy of the system and/or the coupling strength between the two oscillators increases, chaotic behaviour of the system appears. This result will be helpful to understand the probability of the emergence of quantum chaos and may be applied to explain the spectra of complex atoms qualitatively.
 Select Transition to Antispirals in the Complex Ginzburg--Landau Equation WANG Hong-Li, OU-YANG Qi Chin. Phys. Lett. 2004, 21 (8): 1437-1440 .   Abstract   PDF(pc) (340KB) ( 496 ) We report a continuous transition from outwardly rotating spiral waves to antispirals in the complex Ginzburg--Landau equation. Numerical simulations demonstrate that the normal spiral to antispiral transition is fulfilled through a rest spiral wave with zero propagation speed. The propagation direction of spiral waves and the power law behaviour close to the transition boundary are examined.
 Select Communication Scheme via Cascade Chaotic Systems HUA Chang-Chun, GUAN Xin-Ping Chin. Phys. Lett. 2004, 21 (8): 1441-1444 .   Abstract   PDF(pc) (474KB) ( 449 ) A new chaotic communication scheme is constructed. Different from the existing literature, cascade chaotic systems are employed. Two cascade modes are considered. First, we investigate the input to state cascade mode; cascade systems between different kinds of chaotic systems are considered. Then the parameter cascade case of chaotic system is studied. Under the different cases, the corresponding receivers are designed, which can succeed in recovering the former emitted signal. Simulations are performed to verify the validity of the proposed main results.
 Select A Chaotic Communication Scheme Based on Generalized Synchronization and Hash Functions XU Jiang-Feng, MIN Le-Quan, CHEN Guan-Rong Chin. Phys. Lett. 2004, 21 (8): 1445-1448 .   Abstract   PDF(pc) (468KB) ( 664 ) A new chaotic communication scheme based on generalized chaotic synchronization (GCS) and hash function transpositions is presented. The communication scheme has nonsymmetric secrete keys and its ability is similar to traditional digital signatures, i.e.a receiver can convince himself whether or not the sender's message contents have been modified. As a direct application of the scheme, a GCS system is designed by using Chen's chaotic circuit and is studied in some detail. The numerical simulation shows that this Chen GCS system has high security and is fast and reliable for secure Internet communications.
 Select New Variable Separated Solutions and Ghoston Structure for the (2+1)-Dimensional Sine-Gordon System ZHANG Jie-Fang, LAI Xian-Jing Chin. Phys. Lett. 2004, 21 (8): 1449-1452 .   Abstract   PDF(pc) (572KB) ( 467 ) The Bäcklund transformation and variable separation approach are developed for sine-Gordon systems. Three new types of variable separated solutions with some arbitrary functions have been obtained. A new kind of ghoston structure, which is invisible at most of time and can only be detected when it meets with a foldon, is found. This new structure shows a novel interesting and mysterious phenomenon.
 Select Soliton Solution of SU(3) Gauge Fields WANG Dian-Fu, SONG He-Shan, AN Ying Chin. Phys. Lett. 2004, 21 (8): 1453-1454 .   Abstract   PDF(pc) (181KB) ( 485 ) Starting from a simplified model involving the interactions between colour quark fields, colour-SU(3) gauge fields, and colour scalar fields, it is shown, to the lowest-order approximation in ħ, that the vacuum expectation value of the gauge fields is equivalent, mathematically, to the vacuum expectation value of the scalar fields. Based on this relationship, a soliton solution of the gauge fields is given by solving the Euler equation of the scalar fields.
 Select Dibaryon Mass and Width Calculation with Tensor Interaction PANG Hou-Rong, PING Jia-Lun, CHEN Ling-Zhi, WANG Fan Chin. Phys. Lett. 2004, 21 (8): 1455-1458 .   Abstract   PDF(pc) (333KB) ( 370 ) The effect of tensor interaction due to gluon and Goldstone boson exchange on the dibaryon mass and decay width has been studied in the framework of the quark delocalization and colour screening model. The effective S-D wave transition interactions induced by gluon and Goldstone boson exchanges decrease quickly with the increasing channel strangeness, and there is no six-quark state in the light flavour world, which can become a bound one by the help of these tensor interactions, except for the deuteron. The K and η meson exchange effect has been shown to be negligible after a short-range truncation in this model approach. The partial D-wave decay widths, from the NΩ state to the ΛΞ final states of spins 0 and 1, are 20.7keV and 63.1keV respectively. This is a very narrow dibaryon resonance, that might be detected in the relativistic heavy ion reaction by the existing RHIC detectors through the reconstruction of the ΛΞ vertex mass and by the future COMPAS detector at CERN and the FAIR project in Germany.
 Select In-Medium Nucleon Electromagnetic Form Factors in Vector Meson Dominance Model CHEN Wen-Fang, LU Ding-Hui Chin. Phys. Lett. 2004, 21 (8): 1459-1462 .   Abstract   PDF(pc) (525KB) ( 351 ) We study medium modifications of the nucleon electromagnetic form factors in the vector meson dominance model. The in-medium vector meson masses are taken from a chiral SU(3) model. We find that the electric and magnetic form factors of the bound nucleon deviate considerably from those of the free nucleon. Our results are comparable to the results from the quark meson coupling model approach and are consistent with present experimental limits.
 Select On the Neutron Electric Dipole Moment Z. Bentalha, O. Lazrec Chin. Phys. Lett. 2004, 21 (8): 1463-1466 .   Abstract   PDF(pc) (263KB) ( 373 ) Within the Kobayashi--Maskawa mechanism of electroweak interaction and using the recent measured mass of the top quark, we estimate the neutron electric dipole moment (NEDM) via the diquark electroweak interaction. The resulting moment is about 10-30 ecm. The actual upper bound on the NEDM is 6.3× 10-26 ecm and it can reach the value 5×10-28 ecm predicted by experiments in recent years.
 Select A Comparison of Different Measures for Dynamical Event Mean Transverse Momentum Fluctuation LIU Lian-Shou, FU Jing-Hua Chin. Phys. Lett. 2004, 21 (8): 1467-1470 .   Abstract   PDF(pc) (350KB) ( 364 ) Various measures for the dynamical event mean transverse momentum fluctuation are compared with the real dynamical fluctuation using a Monte Carlo model. The variance calculated from the G-moments can reproduce the dynamical variance well, while those obtained by subtraction procedures are approximate measures for not very low multiplicity. Фpt, proposed by Gazdzicki M and Mrowczynski S [Z.Phys.C 54(1992)127], can also serve as an approximate measure after being divided by the square root of mean multiplicity.
 Select Quark Virtuality and QCD Vacuum Condensates ZHOU Li-Juan, MA Wei-Xing, Chin. Phys. Lett. 2004, 21 (8): 1471-1474 .   Abstract   PDF(pc) (212KB) ( 627 ) Based on the Dyson--Schwinger equations (DSEs) in the `rainbow' approximation, we investigate the quark virtuality in the vacuum state and quantum-chromodynamics (QCD) vacuum condensates. In particular, we calculate the local quark vacuum condensate and quark-gluon mixed condensates, and then the virtuality of quark. The calculated quark virtualities are λ 2u,d = 0.7GeV2 for u,d quarks, and λ 2s = 1.6GeV2 for s quark. Our theoretical predictions are consistent with empirical values used in QCD sum rules, and also fit to lattice QCD predictions.
 Select Influence of Traxiality on the Signature Inversion in Odd--Odd Nuclei ZHENG Ren-Rong, ZHU Shun-Quan, LUO Xiang-Dong, Janos Timar, Andree Gizon, Jean Gizon, D.Sohler, B.M.Nyako, L.Zolnai, E.S.Paul Chin. Phys. Lett. 2004, 21 (8): 1475-1478 .   Abstract   PDF(pc) (453KB) ( 374 ) The nature of signature inversion in the πg9/2vh11/2 bands of odd--odd98,102Rh nuclei is studied. Calculations are performed by using a triaxial rotor plus two-quasiparticle model and are compared with the experimentally observed signature inversions. The calculations reproduce well the observations and suggest that, in these bands, the signature inversion can be interpreted mainly as a competition between the Coriolis and the proton--neutron residual interactions in low K space. The triaxiality applied in the Hamiltonian enlarges the amplitudes of high spin signature zigzags at small triaxial deformation and might push the signature inversion point to higher spin at large triaxial deformation.
 Select Occurrence of Superdeformation in Even-Even Isotopes of Zn WANG Ting-Tai, JIANG Wei-Zhou, ZHU Zhi-Yuan, ZHAO Yao-Lin, ZHANG Wei, CHEN Jin-Gen Chin. Phys. Lett. 2004, 21 (8): 1479-1482 .   Abstract   PDF(pc) (436KB) ( 411 ) Occurrence of superdeformed (SD) shape from the relationship between the collective rotation and the pairing correlations is investigated in the relativistic mean field theory framework. It is found that pairing correlation plays an important role in the occurrence of SD shape. It is also shown that the SD band of 66Zn is more difficult to be observed than that of60 Zn experimentally.
 Select Influence of Different Y-Y Interactions on the Stability of Strange Hadronic Matter SONG Hong-Qiu, , SU Ru-Keng, QIAN Wei-Liang Chin. Phys. Lett. 2004, 21 (8): 1483-1486 .   Abstract   PDF(pc) (363KB) ( 328 ) An effective model is used to study the equation of state (EOS) of strange hadronic matter with nucleons,Λ-hyperons and Ξ-hyperons. In the calculation, a newest weak hyperon--hyperon (Y--Y) interaction deduced from the recent observation [Phys. Rev. Lett. 87(2001)212502-1] of a 6ΛΛHe double hypernucleus is adopted.The calculated results are compared to those calculated with the strong Y-Y interaction used in previous studies.
 Select Energy Loss of Fast Quarks in Nuclear Drell-Yan Dimuon Production DUAN Chun-Gui, , CUI Shu-Wen, SHEN Peng-Nian, LI Guang-Lie, Chin. Phys. Lett. 2004, 21 (8): 1487-1490 .   Abstract   PDF(pc) (368KB) ( 421 ) The energy loss effect in nuclear matter, which is another nuclear effect apart from the nuclear effects on the parton distribution as in the deep inelastic scattering process, can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process.By means of the quark energy loss parametrization given in literature and the nuclear parton distribution extracted only with lepton-nucleus deep inelastic scattering experimental data, measured Drell-Yan production cross sections are analysed for 800-GeV protons incident on a variety of nuclear targets from FNAL E866. The average energy loss of quarks are given by fitting the Fe/Be and W/Be Drell-Yan cross section ratios versus the incident parton momentum fraction.
 Select Effects of Target Deformation on the Synthesis of Superheavy Nucleus 283112 LIU Zu-Hua, BAO Jing-Dong, Chin. Phys. Lett. 2004, 21 (8): 1491-1494 .   Abstract   PDF(pc) (321KB) ( 426 ) We investigate the effects of target deformation on the synthesis of superheavy nucleus 283112 in the framework of the extra-push model. Our results show that the cross sections of the 3n evaporation residue in the 48Ca+238U reaction for the case of β2 = 0.275 are several times larger than those of β2 = 0. Meanwhile, the peak position of ER excitation function in the case of the deformed target is shifted to lower energy as compared to that of the spherical target.
 Select Effect of Coulomb Interaction on the Isospin Fractionation Process GUO Wen-Jun, LIU Jian-Ye, , XING Yong-Zhong, Chin. Phys. Lett. 2004, 21 (8): 1495-1497 .   Abstract   PDF(pc) (367KB) ( 689 ) We studied the effect of Coulomb interaction on the isospin fractionation in the intermediate energy heavy ion collisions by using the isospin-dependent quantum molecular dynamics model. The calculated results show that Coulomb interaction induces the reduction of the isospin fractionation process with the evolutions of neutron-proton ratio and mass of system. Because Coulomb interaction is repulsive for the proton, more binding protons become free, which produces the neutron-poor gas phase and neutron-rich liquid phase, compared to the neutron-proton ratio of the system. The isospin fractionation degree is weakened by the Coulomb term. In contrast, the symmetry potential is repulsive for neutrons and attractive for protons in the neutron-rich system, and then the binding neutrons more than the protons become free, which produces a neutron-rich gas phase and neutron-poor liquid phase, so that the isospin fractionation degree is increased. The competition between the effects from the Coulomb interaction and the symmetry potential induces the reduction of the isospin fractionation degree for all the system masses. The properties for the sensitive dependence of isospin fractionation degree on the symmetry potential and weak dependence on the nucleon- nucleon cross section are preserved for all the neutron-rich systems.
 Select Influence of Multiple Scattering on Two-Pion Correlation Measurements TANG Gui-Xin, ZHANG Wei-Ning, LIU Yi-Ming, HUO Lei, ZHANG Jing-Bo Chin. Phys. Lett. 2004, 21 (8): 1498-1500 .   Abstract   PDF(pc) (350KB) ( 480 ) Using the relativistic quantum molecular dynamics model, we study the influence of multiple scattering on the result of two-pion correlation measurements. The scales of pion spatial distribution are larger at thermal freeze-out than at chemical freeze-out. By varying the value of the parameter of cross section from 0 to 90 mb, we find that the sizes of pion source measured by two-particle correlation functions are almost independent of the parameter of cross section. However, λ parameters are sensitive to the parameter of cross section.
 Select Production of Hyperpolarized 129Xe Gas Without Nitrogen by Optical Pumping at 133Cs D2 Line in Flow System ZHOU Xin, SUN Xian-Ping, LUO Jun, ZENG Xi-Zhi, LIU Mai-Li, ZHAN Ming-Sheng Chin. Phys. Lett. 2004, 21 (8): 1501-1503 .   Abstract   PDF(pc) (308KB) ( 657 ) We report production of hyperpolarized 129Xe gas via spin-exchange with optically pumped Cs atoms at the D2 line, achieved at low magnetic field in a flow system and in the absence of nitrogen gas. The nuclear spin polarization of hyperpolarized 129Xe gas is enhanced by a factor of 10000 compared to that without optical pumping under the same condition, which corresponds to polarization of about 2.66%. Due to the high spin polarization, the radiation damping of hyperpolarized 129Xe gas has also been observed in the flow system.
 Select Controllable Double-Well Magneto-Optical Trap for Neutral Atoms YUN Min, YIN Jian-Ping Chin. Phys. Lett. 2004, 21 (8): 1504-1507 .   Abstract   PDF(pc) (367KB) ( 394 ) We propose a novel controllable double-well magneto-optical trap (MOT) by using a square current-carrying wire and a bias magnetic field. The spatial distributions of the magnetic fields and their gradients are calculated, and the results show that the proposed trap has double magnetic wells with two centres of zero magnetic field and can be continuously evolved as a single-well trap by reducing the current in the wire or increasing the bias field, which can be used to realize a controllable double-well MOT, even to prepare one- and two-dimensional arrays of magneto-optical lattices on the surface of an atom chip. We also estimate the number (～107) and temperature ( ～260μ K) of trapped cold atoms in our MOT.
 Select Algebraic Hamiltonian for Vibrational Spectra of Stibine HOU Xi-Wen Chin. Phys. Lett. 2004, 21 (8): 1508-1511 .   Abstract   PDF(pc) (198KB) ( 671 ) An algebraic Hamiltonian, which in a limit can be reduced to an extended local mode model by Law and Duncan, is proposed to describe both stretching and bending vibrational energy levels of polyatomic molecules, where Fermi resonances between the stretches and the bends are considered. The Hamiltonian is used to study the vibrational spectra of stibine (SbH3). A comparison with the extended local mode model is made. Results of fitting the experimental data show that the algebraic Hamiltonian reproduces the observed values better than the extended local mode model.
 Select Single-Electron Detachment Cross Sections for Transition-Element Negative Ions Ti-,Cr-, Cu- in Collision with N2 HUANG Yong-Yi, ZHANG Xue-Mei, WU Shi-Min, LI Guang-Wu, LU Fu-Quan Chin. Phys. Lett. 2004, 21 (8): 1512-1514 .   Abstract   PDF(pc) (319KB) ( 577 ) Single-electron detachment (SED) cross sections for Cr- and Ti- in collision with N2 have been obtained in the energy region of 10-30keV, for the first time to our knowledge. In the present energy range, the magnitude of the Cr-+N2 and Fe-+N2 SED cross sections is larger than that of Cu-+N2. It is also found that the cross sections for Cr- and Ti- in collisions with N2 exhibit different dependences on anion impact velocity from that of Cu-
 Select Improvement of Three-Dimensional Resolution in Optical Data Storage by Combination of Two Annular Binary Phase Filters ZHAO Xiao-Feng, LI Cheng-Fang, RUAN Hao Chin. Phys. Lett. 2004, 21 (8): 1515-1517 .   Abstract   PDF(pc) (290KB) ( 1059 ) We present an improved confocal readout system to achieve three-dimensional superresolution. This improved system is based on a combination of two different annular binary phase filters, the one designed for increasing the transverse superresolution and the other for achieving axial superresolution. By adjusting the pupil parameters, each pupil can be well designed. The simulation results show that with this improved system, the area of the central lobe of the three-dimensional point spread function of the read optics is greatly reduced. Moreover, the side-lobes are extinguished.
 Select Quantum Interference Between Decay Channels of a Three-Level Atom Placed Between Two Parallel Plates ZHOU Lu, GAN Zhong-Wei, LI Gao-Xiang Chin. Phys. Lett. 2004, 21 (8): 1518-1521 .   Abstract   PDF(pc) (292KB) ( 535 ) We investigate the generation of quantum interference induced by spontaneous emission from two transitions of a V-type three-level atom embedded between two parallel plates (one or both the plates have infinite permeability, i.e.μ→∞). The result shows that, due to the anisotropy of vacuum, quantum interference still exists although the two dipole matrix elements of the atom are orthogonal to each other. When the atom is located very close to one of the plates, the quantum interference effect is particularly prominent. The strength of quantum interference displays oscillating behaviour with the position of the atom. With the increase of the distance between the plates, the oscillation becomes dense.
 Select Resonantly Enhanced Continuous-Wave Four-Wave Mixing in a Five-Level Cold Atomic Medium LI Jia-Hua, LUO Jin-Ming, YANG Wen-Xing, PENG Ju-Cun Chin. Phys. Lett. 2004, 21 (8): 1522-1524 .   Abstract   PDF(pc) (295KB) ( 396 ) Using Schrödinger-Maxwell formalism, we propose and analyse a cw four-wave mixing (FWM) scheme for the generation of coherent light in a five-level double-Λ atomic system based on electromagnetically induced transparency. We derive the corresponding explicit analytical expressions for the generated FWM field. The influence of hyperfine sublevel on the amplitude of the generated FWM field is predicted in detail. We also give a brief discussion on the experimental realization of the proposed scheme.
 Select Implementing Entanglement Swapping with Trapped Atoms via Cavity Decay LIN Xiu-Min, YU Bo, ZHOU Zheng-Wei, XUE Peng, GUO Guang-Can Chin. Phys. Lett. 2004, 21 (8): 1525-1528 .   Abstract   PDF(pc) (258KB) ( 808 ) With trapped atoms, we propose an experimental scheme to implement entanglement swapping based on adiabatic passage and the detection of cavity decay. This scheme is inherently robust to diverse sources of noise, such as atomic spontaneous emission, or detector inefficiency. The advantages make it realizable with the current experimental technology.
 Select An Experimental Study of Ultrashort Pulsed Ytterbium-Doped Fibre Laser and Amplifier YANG Ling-Zhen, XIONG Hong-Jun, CHEN Guo-Fu, WANG Yi-Shan, ZHAO Wei, CHENG Zhao Chin. Phys. Lett. 2004, 21 (8): 1529-1531 .   Abstract   PDF(pc) (347KB) ( 389 ) We report the generation of ultrashort pulses in ytterbium-doped fibre oscillator emitting around 1.05μm at a repetition rate of 17.6MHz. A diode laser with single silica fibre at 976nm pumps the ytterbium fibre laser, the all-fibre picosecond pulsed oscillator has excellent stability and compact size, and freedom from misalignment. After amplifying, pulse energy of 3.4nJ and an average power of 60mW are obtained. The compression is obtained with a grating pair out of the cavity. The compressor produces 307fs with the peak power 5.47kW. A practical fibre-based source with good performance is thus demonstrated.
 Select Continuous-Wave Green Laser of 9.9W by Intracavity Frequency Doubling in Laser-Diode Single-End-Pumped Nd:YVO4/LBO BAI Yang, LI Long, CHEN Hao-Wei, YANG Zhi, BAI Jin-Tao Chin. Phys. Lett. 2004, 21 (8): 1532-1534 .   Abstract   PDF(pc) (327KB) ( 729 ) A maximum of 9.9W cw TEM00 output at 532nm laser has been obtained by intracavity frequency doubling with LBO in laser-diode single-end-pumped Nd:YVO4. The Nd:YVO4/LBO green laser has a simple three-mirror V-fold cavity structure. The optical-optical conversion efficiency was 34.8%. Based on the equation of thermal conduction, a general solution for the laser-crystal interior temperature distribution is obtained by the semi-analytical thermal analysis method. Using the software system, the cavity parameters have been optimized according to the stability condition and the astigmatic compensation principle. The astigmatism in the cavity has been effectively controlled and the resonator was insensitive to the thermal lens in the Nd:YVO4 crystal.
 Select Orientation-Enhanced Photorefractive Effect in PVK-PBA:DR1:TNF Polymer LI Lu-Ying, ZHAO You-Yuan, LI Fu-Ming, YANG Jian, CHEN Guo-Rong, WANG Chang-Chun Chin. Phys. Lett. 2004, 21 (8): 1535-1538 .   Abstract   PDF(pc) (392KB) ( 500 ) We developed a novel photorefractive (PR) polymer PVK-PBA:DR1:TNF, and its film sample was prepared with outstanding performance by using the method of combination of vacuum saturated vapour resolving with vacuum hot-pressing. The sample exhibits distinctive PR properties with the two-beam coupling coefficient up to 140cm-1 and four-wave mixing (FWM) diffraction efficiency above 1.5% in the absence of applied external electric field. The designed experiments, including measurements of the second-order nonlinear coefficient and birefringence as well as the relationship between the diffraction efficiencies of the FWM and the external bias field, were performed to understand the underlying mechanism, because this phenomenon cannot be explained by the conventional PR theories. It is presented that because of its high orientational mobility and large dipole moment, the polymer produces the photovoltaic effect under the irradiation of laser to induce a space-charge field so as to engender the PR effect under zero or low external fields. A model based on the assumption was established and the simulation agrees well with the experimental results.
 Select Large Bandwidth Optical Limiting by Kerr Medium Doped One-Dimensional Coupled Cavity Optical Waveguides DING Wei-Qiang, CHEN Li-Xue, LIU Shu-Tian Chin. Phys. Lett. 2004, 21 (8): 1539-1541 .   Abstract   PDF(pc) (457KB) ( 779 ) We present a new method to realize large bandwidth optical limiting using Kerr nonlinearity doped one-dimensional coupled cavity optical waveguides (CCOWs). When the incident intensity is weak, the structure is a perfect CCOW that supports a high transmission band. When the intensity is increased, the Kerr effects change the refractive index of the Kerr cavity which results in a large decrease of transmission coefficients in the whole band. We numerically analyse the limiter using the nonlinear transfer matrix method and nonlinear finite difference in time domain method. Optical limiting effects are observed in the whole transmission band, and optimization methods are also discussed.
 Select Nonreciprocal Coupling in Asymmetric Dual-Core Photonic Crystal Fibres ZHANG Lin, YANG Chang-Xi Chin. Phys. Lett. 2004, 21 (8): 1542-1544 .   Abstract   PDF(pc) (365KB) ( 542 ) The photonic crystal fibre with asymmetric dual cores is shown to attain strongly nonreciprocal coupling of the lightwave propagating along the fibre, for the first time to our knowledge. It is found that the coupling properties can be quite different when the incident position is changed. This kind of fibre could have potential for unidirectional coupler applications in fibre-optic local and metropolitan area networks. We also examine the polarization and wavelength dependence of the coupling nonreciprocity in the asymmetric dual-core photonic crystal fibres.
 Select Calculation of Guided Modes and Leaky Modes in Photonic Crystal Slabs YE Wei-Min, YUAN Xiao-Dong, JI Jia-Rong, ZENG Chun Chin. Phys. Lett. 2004, 21 (8): 1545-1548 .   Abstract   PDF(pc) (311KB) ( 679 ) The scattering matrix S describing photonic crystal slabs is formulated. A new method is introduced to solve the eigenfrequency ω for a given Bloch wave vector K from the equation det S-1 ( ω ,K)=0. Using this method, we can obtain not only guided modes but also leaky modes in photonic crystal slabs with a higher-frequency resolution than that of the FDTD method.
 Select Multi-Mode Coupling in Long-Period Fibre Gratings LIU Zi-Xi, YANG Chang-Xi Chin. Phys. Lett. 2004, 21 (8): 1549-1552 .   Abstract   PDF(pc) (405KB) ( 479 ) We report multi-mode coupling in long-period fibre gratings (LPFGs). The analytical solution to three-mode coupling equations is presented for the first time. A 3×3 transmission matrix is attained and can be used to calculate the transmission spectra of nonuniform gratings in a way much faster than direct numerical integration. It is shown that when the resonant wavelengths of cladding modes are far from each other, two-mode coupling model can still be used. Otherwise we can only choose a multi-mode coupling model. Theoretically fitting of the result from the multi-mode coupling equations agrees well with the experimental one for mechanically-induced LPFGs.
 Select Formation of Optical Waveguide and Annealing Behaviour of LiNbO3 Implanted by 3.0-MeV Nickel Ions ZHANG Ting-Ting, LU Fei, LI Shi-Ling, WANG Xue-Lin, SHEN Ding-Yu, MA Hong-Ji Chin. Phys. Lett. 2004, 21 (8): 1553-1555 .   Abstract   PDF(pc) (406KB) ( 401 ) The optically polished LiNbO3 crystal was implanted with 3.0MeV nickel ions to a dose of 8×1014 ions/cm2. The implanted sample was orderly annealed at different temperatures for different times in air ambient. The waveguide properties before and after annealing were investigated. Dark modes were observed by the prism coupling technique. The reconstructed refractive index profiles were obtained with the reflectivity calculation method. With the fibre probe technique, the attenuation of the Ni-implanted barrier-confined waveguide was measured for the first time. The waveguide loss was reduced from 1.65dB/cm to 1.19dB/cm when annealing was at 300°C for 30min. With the annealing temperature increasing to 370°C , only fewer broad dark modes were found. It is indicated that the lattice damage by implantation began to resume under this annealing condition. After annealing at 380°C for 60min, all the dark modes disappeared.
 Select Fabrication of an 8× 8 Multimode Interference Optical Coupler on a BK7 Glass Substrate by Ion-Exchange LI Xia, LI Xi-Hua, JIANG Xiao-Qing, WANG Ming-Hua Chin. Phys. Lett. 2004, 21 (8): 1556-1557 .   Abstract   PDF(pc) (281KB) ( 478 ) Based on the principle of the graded-index multimode interference (MMI), an 8×8 MMI optical coupler is designed and fabricated by using K+- Na+ ion-exchange technique on a BK7 glass substrate. The performance of the device is tested. The output of optical coupler has a high uniformity of approximately 0.72dB.
 Select Light-Induced Array of Three-Dimensional Waveguides in Lithium Niobate by Employing Two-Beam Interference Field ZHANG Peng, YANG De-Xing, ZHAO Jian-Lin, SU Kun, ZHOU Jian-Bo, LI Bi-Li, YANG Dong-Sheng Chin. Phys. Lett. 2004, 21 (8): 1558-1561 .   Abstract   PDF(pc) (356KB) ( 582 ) We propose a novel approach to fabricate an array of three-dimensional waveguides in lithium niobate by employing illuminations of a pair of mutually coherent or incoherent two-beam interference patterns. Adjusting periods of the patterns and the angle between the grating vectors of the two patterns, we find that arrays of square, rectangular or parallelogrammic waveguides can be created. An array of rectangular waveguides is demonstrated in an iron doped lithium niobate by the double exposures of two-beam interference patterns with different orientations. The measured index distribution and the guiding test results show that the waveguide array is successfully fabricated.
 Select Dispersion Analysis of Wave Propagation in Cubic--Tetrahedral Assembly by Doublet Mechanics JIN Yan-Fang, ZHANG Jue, FANG Jing, Mauro Ferrari Chin. Phys. Lett. 2004, 21 (8): 1562-1565 .   Abstract   PDF(pc) (479KB) ( 761 ) Based on elongation and shear microstrains between the doublet particles, we present the dynamic scaling equations of plane wave propagation in a cubic-tetrahedral assembly (lattice type H4) in accordance with the formalism of doublet mechanics (DM). The relations between the micro-moduli of DM constitutions and the macro-parameters of the Cosserat continuum model are obtained by a mapping process and a non-scale approximation of the DM model. With multi-scale characteristics, the frequency dispersion curves from DM reflect the effect of granule inhomogeneity and the anisotropic nature of the micro-structure on the wave propagation in the H4 medium.
 Select Pattern Formation in Dynamic Phase Transitions Shao-Qiang, WANG Ping Chin. Phys. Lett. 2004, 21 (8): 1566-1568 .   Abstract   PDF(pc) (280KB) ( 476 ) Instability is the main challenge in simulating dynamic phase transitions. For a van der Waals fluid, we introduce low order dissipative mechanisms with discrete Bhatnagar-Gross-Krook (BGK) models, including a relaxation model. In one and higher space dimensions, numerical results demonstrate the complexities of dynamics. While eventually a good separation of phases is reached, interesting wave patterns are observed at an earlier stage.
 Select A Geometry Model for Tortuosity of Flow Path in Porous Media YU Bo-Ming, LI Jian-Hua Chin. Phys. Lett. 2004, 21 (8): 1569-1571 .   Abstract   PDF(pc) (288KB) ( 1159 ) A simple geometry model for tortuosity of flow path in porous media is proposed based on the assumption that some particles in a porous medium are unrestrictedly overlapped and the others are not. The proposed model is expressed as a function of porosity and there is no empirical constant in this model. The model predictions are compared with those from available correlations obtained numerically and experimentally, both of which are in agreement with each other. The present model can also give the tortuosity with a good approximation near the percolation threshold. The validity of the present tortuosity model is thus verified.
 Select Electronegative Plasma Sheath Structure in a Magnetic Field ZOU Xiu, LIU Jin-Yuan, WANG Zheng-Xiong, GONG Ye, LIU Yue, WANG Xiao-Gang Chin. Phys. Lett. 2004, 21 (8): 1572-1574 .   Abstract   PDF(pc) (447KB) ( 514 ) The structure of an electronegative plasma sheath in an oblique magnetic field is investigated with a fluid model. We assume the system consists of hot electrons and negative ions as well as cold positive ions. Densities of particles and distributions of the spacious potential in various states of magnetic field are studied. The result shows that the existence of magnetic field and negative ions has great effects on the plasma sheath structures. In addition, the effects of negative ion density and temperature on the structure of the electronegative plasma sheath are discussed.
 Select Magnetic Field Gradient and Curvature-Driven Drift Modes in Toroidal Plasmas WANG Ai-Ke, H. Sanuki, DONG Jia-Qi, F. Zonca, K. Itoh Chin. Phys. Lett. 2004, 21 (8): 1575-1577 .   Abstract   PDF(pc) (351KB) ( 323 ) A new kind of instability driven by the magnetic field gradient and curvature (MFGC) in toroidal plasmas is presented. It is found that the MFGC drift modes possess finite growth rates even if the plasma pressure gradient vanishes. In addition, the effects of plasma pressure gradient and safety factor on the MFGC modes have been analysed numerically.
 Select Edge Electrostatic Fluctuation Characteristics in the Sino-United Spherical Tokamak WANG Wen-Hao, HE Ye-Xi, GAO Zhe, ZENG Li, ZHANG Guo-Ping, XIE Li-Feng, FENG Chun-Hua, XIAO Qiong, LI Xiao-Yan Chin. Phys. Lett. 2004, 21 (8): 1578-1581 .   Abstract   PDF(pc) (441KB) ( 433 ) Edge plasma parameters, including electron temperature Te, density ne, plasma potential Фp , radial electric field Er and the corresponding fluctuations in the Sino-United Spherical Tokamak, have been systematically measured with Langmuir probe arrays. Wavenumber spectrum analyses show that edge fluctuations have a radial propagation character of the drift wave turbulence, with a characteristic radial phase velocity vphr ～ 0.7 km.s-1 in the scrape-off layer and vsuB>phr ～ 0.9-1.4km.s-1 in the plasma edge.
 Select Stochastic Ripple Diffusion of Energetic Particles in Reversed Magnetic Shear Tokamak GAO Qing-Di, LONG Yong-Xing Chin. Phys. Lett. 2004, 21 (8): 1582-1585 .   Abstract   PDF(pc) (415KB) ( 474 ) The stochastic ripple diffusion is investigated in a realistic reversed magnetic shear discharge. Rippled field produces variations in the velocity of trapped particles leading to excursion of the tip position for successive banana bounces. When the excursion is large enough, the trapped energetic particles are lost rapidly via stochastic banana diffusion. The ripple diffusion of fast ions produced during the neutral beam injection is calculated by assuming that the trapped ions are lost if their turning points are in regions where the ripple exceeds a threshold for the stochastic ripple loss. As the safety factor is of higher value inside the reversed magnetic shear plasma, the ripple loss in a modelled reversed magnetic shear discharge of HL-2A is much stronger than that in a non-RS discharge.
 Select Multiple-Scattering Approaches to Near-Edge X-Ray Absorption Fine Structure of N2O/Cu(100) WU Tai-Quan, TANG Jing-Chang, SHEN Shao-Lai, CAO Song, LI Hai-Yang Chin. Phys. Lett. 2004, 21 (8): 1586-1589 .   Abstract   PDF(pc) (435KB) ( 475 ) The nitrogen 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of the N2O adsorbed on the Cu(100) surface have been studied by multiple-scattering cluster (MSC) and self-consistent field DV-Xαmethods. It is shown that the N2O molecule is adsorbed on the hollow site with the adsorption height h = 3.0±0.1A. The MSC calculation confirmed by a DV-Xα analysis has revealed the physical cause of the weak feature in the NEXAFS spectra mentioned above, which originates from the $1s$ core electrons of the centre and terminal nitrogen atoms transiting into the unoccupied σ* orbital of the N2O molecule.
 Select Ternary Eutectic Growth in a Highly Undercooled Liquid Alloy RUAN Ying, WANG Nan, CAO Chong-De, WEI Bing-Bo Chin. Phys. Lett. 2004, 21 (8): 1590-1592 .   Abstract   PDF(pc) (426KB) ( 573 ) The crystal nucleation and growth mechanism during the formation of Ag42.4Cu21.6Sb36 ternary eutectic are investigated under substantial undercooling conditions. The x-ray diffraction analysis shows that the solidified eutectic phases are not involved (Ag) within a wide undercooling range of 6-114K. This indicates that under high undercooling condition, the phase constitution of Ag-Cu-Sb eutectic is different from that in the equilibrium phase diagram. With the increase of undercooling, the crystalline morphology of Ag42.4Cux21.6Sb36 alloy transforms from the mixed structure of primary θ(Cu2Sb), two pseudobinary eutectics and (ε+θ+Sb) ternary eutectic into a unique (ε+θ+Sb) ternary eutectic. The calculated results indicate that θ(Cu2Sb) is the leading nucleating phase among the three eutectic phases. In addition, the growth morphology of primary ε(Ag3Sb) compound in Ag60Cu6Sb34 alloy exhibits the characteristics of solid solution and its orthorhombic dendrite grows along the <111> directions.
 Select Serrated Plastic Flow in a Zr-based Bulk Metallic Glass During Nanoindentation DAI Lan-Hong, LIU Long-Fei, YAN Min, WEI Bing-Chen, ECKERT Jürgen Chin. Phys. Lett. 2004, 21 (8): 1593-1595 .   Abstract   PDF(pc) (349KB) ( 557 ) We investigate plastic deformation of Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass using depth sensing nanoindentation. Numerous serrations in the load-displacement curves during indentation, shear bands and pile-ups around the indent were observed. The results revealed that the serrated plastic flow behaviour in this alloy depends strongly on the indentation strain rate.
 Select Local Lattice Distortion Around V2-Pb in PbWO4 and the Origin of the 420nm Luminescence Band LIU Ting-Yu, ZHANG Qi-Ren, ZHUANG Song-Lin Chin. Phys. Lett. 2004, 21 (8): 1596-1599 .   Abstract   PDF(pc) (440KB) ( 558 ) The lattice structures around one lead vacancy V2-Pb in PbWO4 are studied within the framework of the full-relativistic density functional theory. Using the conjugate gradient method, we optimize the geometry of the ions around V2-Pb by moving the ions within the sub-cell until specified tolerance is satisfied. We obtain the geometric positions of ions around V2-Pb after optimization. The calculated results indicate that there would be local lattice distortion caused by the existence of V2-Pb. The electronic structures of both the optimized and pre-optimized PWO containing V2-Pb have been calculated. The density of states of the distorted PWO indicates that the energy gap between the 2p state of O2- and the 5d state of W6+ is 3.90eV, which shows that the distorted W-O tetrahedron may be the 420nm luminescence centre.
 Select Silicon-on-Insulating Multi-Layers for Total-Dose Irradiation Hardness ZHANG En-Xia, YI Wan-Bing, LIU Xiang-Hua, CHEN Meng, LIU Zhong-Li, Wang Xi Chin. Phys. Lett. 2004, 21 (8): 1600-1603 .   Abstract   PDF(pc) (382KB) ( 570 ) Silicon-on-insulating multi-layer (SOIM) materials were fabricated by co-implantation of oxygen and nitrogen ions with different energies and doses. The multilayer microstructure was investigated by cross-sectional transmission electron microscopy. P-channel metal--oxide--semiconductor (PMOS) transistors and metal--semiconductor--insulator--semiconductor (MSIS) capacitors were produced by these materials. After the irradiated total dose reaches 3×105 rad (Si), the threshold voltage of the SOIM-based PMOS transistor only shifts 0.07V, while thin silicon-on-insulating buried-oxide SIMOX-based PMOS transistors have a shift of 1.2V, where SIMOX represents the separated by implanted oxygen. The difference of capacitance of the SOIM-based MSIS capacitors before and after irradiation is less than that of the thin-box SIMOX-based MSIS capacitor. The results suggest that the SOIM materials have a more remarkable irradiation tolerance of total dose effect, compared to the thin-buried-oxide SIMOX materials.
 Select Structures of Adatom Clusters on Ag(111) Surface by Genetic Algorithm SUN Zhi-Hua, LIU Qing-Wei, LI Yu-Fen, ZHUANG Jun Chin. Phys. Lett. 2004, 21 (8): 1604-1607 .   Abstract   PDF(pc) (411KB) ( 395 ) We study the structures of Ag adatom clusters supported on the metal Ag(111) surface using the genetic algorithm (GA). The atomic interactions are modelled by the surface-embedded-atom method. The lowest-energy structures of adatom clusters with sizes n=3-20 are obtained, in which n=7, 10, 12, 14, 16, 19 are the magic numbers. Furthermore, we give a series of structures with energies close to the lowest energy (the lower-energy isomers), and the structure features are studied in detail. Except for some magic clusters and small clusters, every configuration of adatom clusters generally has two distinct adsorption ways, so the isomers always appear in pairs.
 Select Room-Temperature Growth of Al Films on Si(111)-7×7 Surface LIU Hong, ZHANG Yan-Feng, WANG De-Yong, JIA Jin-Feng, XUE Qi-Kun Chin. Phys. Lett. 2004, 21 (8): 1608-1611 .   Abstract   PDF(pc) (368KB) ( 464 ) Reflection high energy electron diffraction and scanning tunnelling microscopy (STM) are used to investigate the structure and morphology of Al films deposited on Si(111)-7×7 surface at room temperature. The films are polycrystalline, made up of (100) and (111) oriented islands, which primarily result from the interface elastic effect and free surface energies of the Al (100) and (111) surfaces.
 Select Electronic Structures and Magnetic Properties of CoN, NiN and CuN WANG Hong-Bo, XUE De-Sheng Chin. Phys. Lett. 2004, 21 (8): 1612-1615 .   Abstract   PDF(pc) (495KB) ( 455 ) Electronic structures and magnetic properties of CoN, NiN and CuN in zinc-blende, rocksalt, nickel arsenide, wurtzite and caesium chloride structures have been calculated by employing a first-principle full-potential linearized muffin-tin orbital method with the generalized gradient approximation. The results reveal that the zinc-blende structure is the ground state for the three mononitrides. The Stoner criterion indicates that the rocksalt and caesium chloride structures of CoN may have magnetic ordering, but the magnetic ordered phases are not stable. Compared with the result calculated with the local density approximation, the equilibrium lattice constant of CoN with the generalized gradient approximation is in better agreement with the experimental results.
 Select Electric Effect of Impurity in Square Quantum Wires LI Kui-Hua, ZHANG Ying-Tao, LI You-Cheng, Chin. Phys. Lett. 2004, 21 (8): 1616-1619 .   Abstract   PDF(pc) (455KB) ( 516 ) In the presence of an electric field perpendicular to the axes of the wire, the binding energy of shallow donor impurity in finite square quantum well wires is calculated. For different impurity positions and aspect ratios of the wires, we investigate the Stark shift of the $1s$-like state energy of the impurity by expanding the wavefunction into a two-dimensional Fourier series and by using the variational scheme. It is found that the electric field breaks down the degeneracy of the states for impurities symmetrically positioned within the structure and leads to red-shift or blue-shift of the impurity Stark energy, respectively. Furthermore, the scaling rule of the binding energy will not be valid for the square quantum well wire under the applied electric field.
 Select Exciton States in Wurtzite InGaN Coupled Quantum Dots XIA Cong-Xin, SHI Jun-Jie, WEI Shu-Yi Chin. Phys. Lett. 2004, 21 (8): 1620-1623 .   Abstract   PDF(pc) (319KB) ( 576 ) Based on the effective-mass approximation, exciton states confined in wurtzite InxGa1-xN/GaN strained coupled quantum dots (QDs) are investigated, in which the strong built-in electric field effects due to the piezoelectricity and spontaneous polarization are considered. We find that the barrier thickness between the two QDs has a considerable influence on the exciton states and the interband optical transitions. If the barrier thickness is increased, the exciton binding energy is decreased, the emission wavelength is increased, and the electron--hole recombination rate is obviously reduced. Our theoretical results are in qualitative agreement with the experimental measurements.
 Select Effects of Rapid Cycle Annealing Temperature on TbFe Magnetostrictive Films JIANG Hong-Chuan, ZHANG Jin-Ping, ZHANG Wan-Li, PENG Bin, ZHANG Wen-Xu, YANG Shi-Qing, ZHANG Huai-Wu Chin. Phys. Lett. 2004, 21 (8): 1624-1627 .   Abstract   PDF(pc) (504KB) ( 433 ) The effects of annealing temperature on TbFe films prepared by dc magnetron sputtering were discussed. X-ray diffraction patterns indicate that these polycrystalline films consisting mainly of α-Fe and TbFe2 lave phase with grain sizes less than 25nm can be obtained by a rapid cycle annealing process. Grain sizes can be controlled by varying annealing temperatures. Film hysteresis loop studies show that annealing treatment can improve TbFe film in-plane soft magnetic performances. Magnetic domain structures explored by a magnetic force microscopy show that in the as-deposited films, maze domain structures exist, hence it possesses perpendicular anisotropy and larger anisotropic constant Ku. No domains are observed when annealing temperature is lower than 400°C. However, maze domain structures appear again when annealing temperature is higher than 400°C. Two maxima of magnetostrictive coefficients are obtained at annealing temperatures of 300°C and 500°C in the presence of a 40kA.m-1 external magnetic field.
 Select Spin-Flip Behaviour Observed in (Pt/Co)5/Ru/(Co/Pt)5 Films ZHANG Ai-Guo, WANG Yin-Jun, HAN Xiu-Feng, ZHAN Wen-Shan Chin. Phys. Lett. 2004, 21 (8): 1628-1631 .   Abstract   PDF(pc) (549KB) ( 582 ) (Pt/Co)5/Ru/(Co/Pt)5 films with different Ru thicknesses were prepared by magnetron sputtering. Oscillatory behaviour of effective perpendicular anisotropy and remanence in the (Pt/Co)5/Ru/(Co/Pt)5 films as a function of the thickness of Ru has been first observed, from which we can obtain the conclusion that the synthetic spin in the (Pt/Co)5/Ru/(Co/Pt)5 films rotates from the vertical direction to the in-plane one periodically with the change of the thickness of the spacer layer of Ru. The oscillatory period is about two atomic layers of Ru and different from the long and short oscillatory periods of the interlayer antiferromagnetic coupling in Co/Ru/Co, Co/Cu/Co, and Fe/Cr/Fe, etc.
 Select Electronic and Magnetic Properties of 3d Transition-Metal-Doped III-V Magnetic Semiconductor ZENG Yong-Zhi, HUANG Mei-Chun Chin. Phys. Lett. 2004, 21 (8): 1632-1635 .   Abstract   PDF(pc) (496KB) ( 702 ) A systematic study based on an ab initio calculation within a local spin density approximation is applied to material design of GaAs- and GaP-base doped by 3d transition metals. It is found that the ferromagnetic (FM) state is ready to achieve by V-, Cr- and Mn-doped GaP and GaAs. (Ga, Cr)P and (Ga, Cr)As are the most promising candidates for high Curie temperature (above room temperature). In order to increase the Curie temperature, the Mg co-doped method is applied to (Ga, Mn)P and (Ga, Mn)As. By the co-doping, the energy difference between the antiferromagnetic state and the FM state is enlarged, and the partial density of states of 3d-Mn at Fermi energy EF is increased, which increases the Curie temperature of the diluted magnetic semiconductors. By this co-doping, the anti-bonding state of 3d-Mn is pushed up to a higher region, hence the 3d electrons are more delocalized and itinerated. This makes double exchange dominant, and (Ga, Mn)P and (Ga, Mn)As more stable.
 Select Femtosecond Time-Resolved Absorption of Oxyhaemoglobin Photolysis in Living Erythrocytes CEN Yan, MA Jiong, ZHU Rong-Yi, LU Jun-Jun, QIAN Shi-Xiong, CHEN Ji-Yao, Chin. Phys. Lett. 2004, 21 (8): 1636-1639 .   Abstract   PDF(pc) (416KB) ( 838 ) By using the pump--probe technique, the femtosecond (fs) time-resolved absorption dynamics of oxyhaemoglobin (oxy Hb) in living erythrocytes was studied for the first time to our knowledge. The changing course of erythrocyte absorption at 400nm was found to be composed of three exponential decay components with the time constants of 200±28fs, 3.60±0.14ps and 215±21ps respectively, which are consistent with those of oxy Hb water solution measured in the same way, indicating that the fast process (less than 1ns) of photo-induced response in erythrocytes was as the same as that in oxy Hb aqueous solution. These three decay components were assigned to the transitions from excited states of unligated haemoglobin (HbI*, HbII*) and fast geminate recombination of O2 and Hb, respectively.
 Select A Thermally Activated Exciton--Exciton Collision Process in ZnO Microrods ZHAO Dong-Xu, LIU Yi-Chun, SHEN De-Zhen, LU You-Ming, ZHANG Ji-Ying, FAN Xi-Wu Chin. Phys. Lett. 2004, 21 (8): 1640-1643 .   Abstract   PDF(pc) (535KB) ( 436 ) Room-temperature P-band emission induced by an exciton--exciton collision process was observed in ZnO micro-rods. Both temperature- and excitation-intensity-dependent photoluminescence (PL) measurements were conducted. The excitation-intensity-dependent measurement illustrated that the P-band emission could occur at far lower excitation intensity than that reported in the literature. Higher-order transitions were also observed at the excitation intensity of 7.1kW/cm2 or above. The temperature-dependent PL showed that the P-band emission process was thermally activated. It is suggested that both the density and activity of free excitons played important roles in the exciton--exciton collision process.
 Select Optical Field Measurement of Nano-Apertures with a Scanning Near-Field Optical Microscope XU Tie-Jun, XU Ji-Ying, WANG Jia, TIAN Qian Chin. Phys. Lett. 2004, 21 (8): 1644-1647 .   Abstract   PDF(pc) (450KB) ( 429 ) We investigate optical near-field distributions of the unconventional C-apertures and the conventional square apertures in preliminary experiment with an aperture scanning near-field optical microscope. These nano-apertures are fabricated in Au film on a glass substrate with focused ion beam technology. The experimental results indicate the uptrend of output light intensity that a C-aperture enables the intensity maximum to increase at least 10 times more than a square aperture with same unit length. The measured near-field light spot sizes of C-aperture and square aperture with 200-nm unit length are 439nm×500nm and 245nm×216nm, respectively.
 Select Dependence of Growing High-Quality Gem Diamonds on Growth Rates by Temperature Gradient Method ZANG Chuan-Yi, JIA Xiao-Peng, REN Guo-Zhong, WANG Xian-Cheng Chin. Phys. Lett. 2004, 21 (8): 1648-1650 .   Abstract   PDF(pc) (492KB) ( 416 ) Using the temperature gradient method under high pressure and high temperature, we investigate the dependence of growing high-quality gem diamond crystals on the growth rates. It is found that the lower the growth rate of gem diamond crystals, the larger the temperature range of growing high-quality gem diamond crystals, and the easier the control of temperature. In particular, when growing gem diamonds under a very-low growth rate, the temperature range of growing high-quality gem diamonds can extend from a low-temperature pure {100} growth region to {100}+{111} growth regions, and finally to a high-temperature only-{111}-growth region. When growing gem diamonds under a high growth rate, some metal inclusions in the growing diamonds always exist near the seeds, no matter whether the growth temperature is high or low. This result is not in agreement with the result of Sumitomo Electric Corporation in Japan.
 Select Grain Crush and Its Evolution in Granular Material: a Two-Dimensional Distinct Element Model Approach WANG Bao-Shan, SHI Xing-Jue, CHEN Yong, GE Hong-Kui, WONG Teng-Fong Chin. Phys. Lett. 2004, 21 (8): 1651-1654 .   Abstract   PDF(pc) (499KB) ( 582 ) A crush criterion and a simplified post-crush process for spherical grains are introduced into the traditional distinct element model (DEM). The crush criterion is based on Hertzian contact, and it indicates a negative relation between critical force Fcr and radius R via Fcr∝R-3/2. Effects of grain crush on deformation pattern and statistical features of crush evolution for samples under uniaxial strain load are intensively investigated. Influences of maximum crush times and particle size distribution (PSD) are also discussed. It is found that: (1) Grain crush will blur the localization of deformation. (2) Crush is prone to occur in larger grains, due to force concentration and lower critical force Fcr for larger grains. (3) Grain crush only temporarily reduces contact force, which results in the most rapid increase of the number of grains with maximum crush time.
 Select Magnetic Microstructure of Sintered Nd-Fe-B Magnets Made from Casting Strips FANG Yi-Kun, ZHU Ming-Gang, GUO Yong-Quan, LI Wei, HAN Bao-Shan Chin. Phys. Lett. 2004, 21 (8): 1655-1658 .   Abstract   PDF(pc) (432KB) ( 525 ) The magnetic microstructures of two Dy-Al substituted sintered Nd-Fe-B magnets with the different nominal compositions of Nd12.2Dy0.6Fe80.4Al0.7B6(at.%) (composition-A, C-A) and Nd13.7Dy0.6Fe78.8Al0.7B6.2(at.%) (composition-B, C-B) prepared by strip casting technique have been revealed by using a magnetic force microscope. The magnetic properties of sintered C-B magnets are worse than that of C-A sintered magnets. In particular, the value of density products (BH)max for sintered C-A magnets is about 32% higher than that of C-B magnets, which is reflected by their quite different magnetic microstructures. We believe that for the C-B samples, the inappropriate composition and thus the redundant Nd2Fe17(B) phase of the casting strips make its final magnetic microstructures worse than the C-A, and then deteriorates the performance of the C-B magnets.
 Select Membrane Tether Formation on a Cell Surface with Reservoir JIANG Yu-Qiang, GUO Hong-Lian, LIU Chun-Xiang, LI Zhao-Lin, CHENG Bing-Ying, ZHANG Dao-Zhong, JIA Suo-Tang Chin. Phys. Lett. 2004, 21 (8): 1659-1662 .   Abstract   PDF(pc) (305KB) ( 533 ) We propose a mathematical model to analyse the membrane tether formation process on a cell surface with reservoir. Based on the experimental results, the membrane reservoir density of breast cancer cell was obtained, ρ = 8.02. The membrane surface viscosity between membrane and environment η is 0.021(pN.s/μm3), and the static force F0 = 5.71pN.
 Select Photoinduced Polaron-Splitting in Polymer TANG Fei, XU Xiao-Hua, SUN Xin, Chin. Phys. Lett. 2004, 21 (8): 1663-1665 .   Abstract   PDF(pc) (337KB) ( 324 ) We simulate a relaxation process of a polaron in polymer after photo excitation, and a new state is realized by means of proper excitation. The original lattice configuration of the polaron splits into two symmetrical peaks, and consequently a double-well potential is formed, where the wavefunctions of electron localized in these two wells are entangled. Thus, this process provides a method to generate the Schrödinger cat state. According to the dynamical process of the lattice configuration, the relaxation time of splitting is about 150fs.
 Select Noise-Induced Bursting and Coherence Resonance in Minimal Cytosolic Ca2+ Oscillation Model JIA Ya, YANG Li-Jian, WU Dan, LIU Quan, ZHAN Xuan Chin. Phys. Lett. 2004, 21 (8): 1666-1669 .   Abstract   PDF(pc) (583KB) ( 511 ) A stochastic calcium oscillation model based on the minimal calcium oscillation model is investigated by numerical computation. When the extracellular stimulation is sub-threshold and random, the oscillations of cytosolic calcium show complex behaviour: a bursting-like phenomenon induced by noise, that is, the phase of glomerate spikes are separated by phase of quiescence (but fluctuations in the baseline values of calcium with small amplitude during the silent phase), in a pattern that occurs at irregular intervals. By using the histogram of interspike intervals of calcium concentration spikes, it is found that the noise-induced coherence resonance phenomenon occurs at the cellular level.
 Select Higher-Dimensional Cosmological Models with Density-Parameter-Dependent Cosmological Constant HUANG Xiu-Ju, WANG Yong-Jiu Chin. Phys. Lett. 2004, 21 (8): 1670-1672 .   Abstract   PDF(pc) (176KB) ( 399 ) We discuss the evolution of the scale factor in a higher-dimensional cosmological model in which the cosmological constant is given by the scalar arisen by the contraction of the stress-energy tensor.
 Select Dynamics of the Globular Cluster NGC 6656 with WFPC2 CHEN Ding, CHEN Li, WANG Jia-Ji Chin. Phys. Lett. 2004, 21 (8): 1673-1676 .   Abstract   PDF(pc) (350KB) ( 569 ) We have used the Hubble Space Telescope observations to measure proper motion of the globular cluster NGC 6656 (M22) with respect to the background bulge stars and its internal velocity dispersion profile. Based on the proper motion of the cluster, its space velocity (II,,W) = (184±3,209±14, 132±15)kms-1 and galactic orbit are also obtained. The central velocity dispersion in radial and tangential components of the internal motion of cluster stars is 16.99kms-1. We derive the mass-to-light ratio M/Lv～3.3±0.2, which is relatively higher than the previous results.
 Select Star Formation in Molecular Cloud Associated with IRAS QIN Sheng-Li, WU Yue-Fang, WANG Jun-Jie, ZHAO Gang, SHI Jian-Rong, MARTIN Miller Chin. Phys. Lett. 2004, 21 (8): 1677-1680 .   Abstract   PDF(pc) (542KB) ( 752 ) The first mapping observations in 12CO J=2-1 and 12CO J=1-0 lines were made towards molecular cloud associated with IRAS 07028-1100. The results show a mono-polar outflow (primarily blueshifted component) near IRAS 07028-1100, which suggests that star formation is occurring in this region. On the basis of the MSX (Midcourse Space Experiment) band-A image, molecular cloud core contours, NVSS data and IRAS data, we identify IRAS 07028-1100 as an embedded young intermediate-mass star. According to the 2MASS data, we suggest a sequential star formation in the infrared cluster associated with IRAS 07028-1100.
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