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Volume 23 Issue 4
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Original Articles
Semiclassical Analysis of Quarter Stadium Billiards
XU Xue-You, GAO Song, GUO Wen-Hao, ZHANG Yan-Hui, LIN Sheng-Lu
Chin. Phys. Lett. 2006, 23 (4): 765-767 .  
Abstract   PDF(pc) (219KB) ( 609 )
An expansion method for stationary states is applied to obtain the eigenfunctions and the eigenenergies of the quarter stadium billiard, and its nearest energy-level spacing distribution is obtained. The histogram is consistent with the standard Wigner distribution, which indicates that the stadium billiard system is chaotic. Particular attention is paid to pursuing the quantum manifestations of such classical chaos. The correspondences between the Fourier transformation of quantum spectra and classical orbits are investigated by using the closed-orbit theory. The analytical and numerical results are in agreement with the required resolution, which corroborates that the semiclassical method provides a physically meaningful image to understand such chaotic systems.
Preparation and Decoherence of Two-Atom Entangled States in a Dissipative Cavity
XIANG Shao-Hua, SONG Ke-Hui
Chin. Phys. Lett. 2006, 23 (4): 768-771 .  
Abstract   PDF(pc) (245KB) ( 695 )
We present a scheme for generating four pairs of two-atom Einstein--Podolsky--Rosen (EPR) states using the simultaneous interaction of the two atoms with a single-mode cavity field under a large detuning condition. The influence of cavity dissipation on the prepared EPR states is investigated by means of the superoperator method and the state fidelity. It is shown that some kinds of the prepared EPR states are robust against cavity dissipation and the intensity of the field, and maintain their entanglement invariance, and the others are fragile and completely destroyed by the action of cavity dissipation and the intensity of the field in the long-time limit. Decoherence time of the fragile entangled states is extremely small for a typical cavity-QED experimental data.

Entanglement Distillation for Mixed States Using Particle Statistics
HUANG Xiao-Li, CHENG Li-Hong, YI Xue-Xi
Chin. Phys. Lett. 2006, 23 (4): 772-774 .  
Abstract   PDF(pc) (218KB) ( 499 )
We extend the idea of entanglement concentration protocol for pure states (Phys. Rev. Lett. 88, 187903) to the case of entanglement distillation for mixed states. The scheme works only with particle statistics and local operations, without the need of any other interactions. We show that the maximally entangled state can be distilled out when the initial state is pure, otherwise the entanglement distilled depends on the off-diagonal element of density matrix of the initial state. Because of the requirement for density matrix, the entanglement distilled is always less than one, and this result is the same for both fermionic and bosonic particles. The distillation efficiency is a product of the diagonal elements of the initial state, it takes the maximum 50%, the same as that in the case for pure states.
Nonorthogonal Decoy-State Quantum Key Distribution
LI Jing-Bo, FANG Xi-Ming
Chin. Phys. Lett. 2006, 23 (4): 775-778 .  
Abstract   PDF(pc) (242KB) ( 622 )
In practical quantum key distribution (QKD), weak coherent states as the photon source have a limit in the secure key rate and transmission distance because of the existence of multi-photon pulses and heavy loss in transmission line. The decoy-state method and the nonorthogonal encoding protocol are two important methods to combat these effects. Here, we combine both the methods and propose an efficient method that can substantially improve the performance of QKD. We find a 78-km increase over the prior record using the decoy-state method and a 123-km increase over the result of the SARG04 protocol in transmission distance.
White Noise in Quantum Random Walk Search Algorithm
MA Lei, DU Jiang-Feng, LI Yun, LI Hui, KWEK L. C., OH C.H.
Chin. Phys. Lett. 2006, 23 (4): 779-782 .  
Abstract   PDF(pc) (245KB) ( 504 )
The quantum random walk is a possible approach to construct new quantum search algorithms. It has been shown by Shenvi et al. [Phys. Rev. A 67(2003)52307] that a kind of algorithm can perform an oracle search on a database of N items with O(√N) calling to the oracle, yielding a speedup similar to other quantum search algorithms. We study the effect of white or Gaussian noise on this algorithm. The algorithm loses efficiency when noise is added. We also show that noise on the target state plays a more important role than that on other states. Finally we compare the effects of similar types of noise in the quantum random walk search algorithm and Grover's search algorithm.

Rediscussion of the Stability Problem of the Schwarzschild Black Hole
Tian Gui-Hua
Chin. Phys. Lett. 2006, 23 (4): 783-785 .  
Abstract   PDF(pc) (181KB) ( 571 )
We use the Kruskal time coordinate T to define the initial time. By this way, the stability study naturally becomes the one connected with the two regions, i.e. the white-hole-connected region and the black-hole-connected region. The union of the two regions covers the Schwarzschild space-time (r≥2m). We also obtain the very reasonable conclusion: the white-hole-connected region is unstable and the black-hole-connected region is stable. If we take the instability with caution and seriousness, it is not unreasonable to regard that the Schwarzschild black hole might be unstable to some extent.
Non-Local Coupling and Partial Synchronization in Chaotic Systems
AO Bin, MA Xiao-Juan, LI Yun-Yun, ZHENG Zhi-Gang
Chin. Phys. Lett. 2006, 23 (4): 786-789 .  
Abstract   PDF(pc) (283KB) ( 955 )
Partial synchronization (PaS) on regular networks with a few non-local couplings are studied. The criterion that PaS can emerge in any given network and some relevant phenomena about Lyapunov exponents are found. Theoretical and numerical analysis show that the non-local coupling is the key mechanism of the emergence of PaS.
Transition to Antiphase Synchronization
QIAN Xiao-Lan, LIU Wei-Qing, YANG Jun-Zhong
Chin. Phys. Lett. 2006, 23 (4): 790-973 .  
Abstract   PDF(pc) (400KB) ( 634 )
We study the anti-phase synchronization (APS) in a system of two coupled chaotic oscillators. The necessary condition and the stability analysis for the APS are given theoretically. The APS state in specific systems such as Chua circuits and Lorenz oscillators are numerically studied. The different types of transitions to APS in both the systems are found.
A New Method to Measure the Divergence of X-Ray Beams from Capillaries
LIN Xiao-Yan, LI Yu-De, CHI Ji-Hong, LIU An-Dong, TAN Guo-Tai
Chin. Phys. Lett. 2006, 23 (4): 794-796 .  
Abstract   PDF(pc) (207KB) ( 477 )
A new method to measure the divergence of x-ray beams propagated out from several capillaries is introduced. This new method is based on Bragg's law and is proven efficiently by the experimental measurement with collimators and straight polycapillaries.

New Spinor Field Realizations of the Non-Critical W3 String
ZHANG Li-Jie, LIU Yu-Xiao, REN Ji-Rong
Chin. Phys. Lett. 2006, 23 (4): 797-799 .  
Abstract   PDF(pc) (207KB) ( 485 )
We investigate the new spinor field realizations of the W3 algebra, making use of the fact that the W3 algebra can be linearized by the addition of a spin-1 current. We then use these new realizations to build the nilpotent Becchi--Rouet--Stora--Tyutin charges of the spinor non-critical W3 string.
Photon Production in a Chemically Equilibrating Quark--Gluon Plasma at Finite Baryon Density: Complete Leading Order Results
LONG Jia-Li, HE Ze-Jun, , MA Yu-Gang,
Chin. Phys. Lett. 2006, 23 (4): 800-803 .  
Abstract   PDF(pc) (241KB) ( 530 )
We investigate hard photon production of the near-collinear bremsstrahlung and a new process called the inelastic pair annihilation, fully including the LPM effect, in a chemically equilibrating quark-gluon plasma at finite baryon density, and find that the effect of the system evolution on the photon production and large contribution of the bremsstrahlung make the total photon yield of the two processes as a strongly increasing function of the initial quark chemical potential.
Neutron Skin Thickness of Nuclei and Effective Nucleon--Nucleon Interactions
LIU Min, WANG Ning, LI Zhu-Xia, , WU Xi-Zhen,
Chin. Phys. Lett. 2006, 23 (4): 804-807 .  
Abstract   PDF(pc) (282KB) ( 471 )
The Skyrme energy density functional is applied to study the ground state properties of a series of finite nuclei. The charge rms radii, neutron rms radii, and the neutron skin thickness for some nuclei are calculated and compared with the experimental data. The constraint on the effective interactions, especially, the density dependence of the isospin-dependent part of Skyrme interactions is extracted by the data of neutron skin thicknesses of 208Pb and isotopes of Sn.
New Levels in 118Pd Observed in the β Decay of Very Neutron-Rich 118Rh Isotope
WANG You-Bao, P.Dendooven, J.Huikari, A.Jokinen, V. S.Kolhinen, G.Lhersonneau, A.Nieminen, S.Nummela, H.Penttila, K.Perajarvi, S.Rinta-Antila, J.Szerypo, J.C.Wang, J.Ä, ystö,
Chin. Phys. Lett. 2006, 23 (4): 808-811 .  
Abstract   PDF(pc) (240KB) ( 532 )
We investigate the β decay of very neutron-rich 118Rh isotope using on-line mass-separated sources which are produced by applying 25MeV proton induced symmetric fission of natural uranium at the IGISOL facility. The β--γ and γ--γ coincidence spectroscopy is employed to establish the level scheme of daughter nucleus 118Pd. Five low-lying new levels are identified for the first time with tentative spin and parity assignments based on the even-mass Pd systematics.
Half-Lives of Spherical Proton Emitters
JIANG Jian-Guo, REN Zhong-Zhou,
Chin. Phys. Lett. 2006, 23 (4): 812-814 .  
Abstract   PDF(pc) (232KB) ( 525 )
The distorted-wave Born approximation (DWBA) method is used to calculate the half-lives of spherical proton emitters. The calculated results are in agreement with the experimental data. The sensitivity of the half-lives to the depth of central potential V0 is investigated by using the DWBA method. The half-lives of spherical proton emitters are insensitive to the detail of their nuclear potential.
Evidence of Strong Pion Fluctuation in Jet-Like Events in 32--AgBr Interactions
Dipak Ghosh, Argha Deb, Prabir Kumar Haldar, Sima Guptaroy
Chin. Phys. Lett. 2006, 23 (4): 815-818 .  
Abstract   PDF(pc) (247KB) ( 626 )
We presents the analysis of ring-like and jet-like events in terms of Scaled Factorial Moments (SFMs) in one-dimensional space up to the sixth order of moments for 32--AgBr interactions at 200AGeV energy. The study reveals a power law growth of SFMs with decreasing bin width of the azimuthal distribution in the 32S--AgBr data at 200AGeV in both the cases. It is seen that strong intermittent pattern is revealed only in jet-like events.
Computation of Bond Dissociation Energies for Removal of Nitrogen Dioxide Groups in Certain Aliphatic Nitro Compounds
SHAO Ju-Xiang, CHENG Xin-Lu, YANG Xiang-Dong, XIANG Shi-Kai
Chin. Phys. Lett. 2006, 23 (4): 819-821 .  
Abstract   PDF(pc) (208KB) ( 767 )
Bond dissociation energies for removal of nitrogen dioxide groups in 10 aliphatic nitro compounds, including nitromethane, nitroethylene, nitroethane, dinitromethane, 1-nitropropane, 2-nitropropane, 1-nitrobutane, 2-methyl-2-nitropropane, nitropentane, and nitrohexane, are calculated using the highly accurate complete basis set (CBS-Q) and the three hybrid density functional theory (DFT) methods B3LYP, B3PW91 and B3P86 with 6-31G** basis set. By comparing the computed bond dissociation energies and experimental results, we find that the B3LYP/6-31G** and B3PW91/6-31G** methods are incapable of predicting the satisfactory bond dissociation energy (BDE). However, B3P86/6-31G** and CBS-Q computations are capable of giving the calculated BDEs, which are in extraordinary agreement with the experimental data. Nevertheless, since CBS-Q computational demands increase rapidly with the number of containing atoms in molecules, larger molecules soon become prohibitively expensive. Therefore, we suggest to take the B3P86/6-31G** method as a reliable method of computing the BDEs for removal of the NO2 groups in the aliphatic nitro compounds.
A Novel Gravito-Optical Surface Trap for Neutral Atoms
XIE Chun-Xia, WANG Zhengling, YIN Jian-Ping
Chin. Phys. Lett. 2006, 23 (4): 822-825 .  
Abstract   PDF(pc) (263KB) ( 471 )
We propose a novel gravito-optical surface trap (GOST) for neutral atoms based on one-dimensional intensity gradient cooling. The surface optical trap is composed of a blue-detuned reduced semi-Gaussian laser beam (SGB), a far-blue-detuned dark hollow beam and the gravity field. The SGB is produced by the diffraction of a collimated Gaussian laser beam passing through the straight edge of a semi-infinite opaque plate and then is reduced by an imaging lens. We calculate the intensity distribution of the reduced SGB, and study the dynamic process of the SGB intensity-gradient induced Sisyphus cooling for 87Rb atoms by using Monte Carlo simulations. Our study shows that the proposed GOST can be used not only to trap cold atoms loaded from a standard magneto-optical trap, but also to cool the trapped atoms to an equilibrium temperature of 3.47μK from ~120μK, even to realize an all-optical two-dimensional Bose--Einstein condensation by using optical-potential evaporative cooling.
Observation of Tri-photon K-Shell X-Rays
CHENG Yao, XIA Bing, LI Jin,
Chin. Phys. Lett. 2006, 23 (4): 826-827 .  
Abstract   PDF(pc) (185KB) ( 749 )
We report the observation of coincidence of three K-shell x-rays generated from the long-lived rhodium isomer excited by bremsstrahlung irradiation. Our previous report revealed that the E3 Mössbauer transition has anisotropic emission due to anisotropic gravitational acceleration [Chin. Phys. Lett. 22 (2005) 2530]. Now, from broader energy-resolved spectra, we further discover abnormal coincidences and abnormal sum energies of the three K-shell x-rays. The coincidence cannot be explained by currently understood photon statistics, since the measured tri-photon count and the pile-up estimate differ by three orders of magnitude.
Thermal Rate Constants of the N(4S)+O2(X3Σg-) → NO(X2II) +O(3P) Reaction on the 2A’ Potential Energy Surface
HE Jian-Feng, CHEN Feng, LI Jing
Chin. Phys. Lett. 2006, 23 (4): 828-831 .  
Abstract   PDF(pc) (233KB) ( 774 )
A quasiclassical trajectory study with the sixth-order explicit symplectic algorithm for the N(4S)+O2(X3Σg-) → NO(X2II) +O(3P) reaction has been reported by employing a new ground potential energy surface. We have discussed the influence of the relative translational energy, the vibrational and rotational levels of O2 molecules on the total reaction cross section. Thermal rate constants at temperatures 300, 600, and 1000K determined in this work for the reaction are 4.4×107, 1.8×1010, and 3.1 1011cm3mol-1s-1, respectively. It is found that they are in better agreement with the experimental data than previous theoretical values.
Dyadic Green Function for an Electromagnetic Medium Inspired by General Relativity
Akhlesh Lakhtakia, Tom G. Mackay
Chin. Phys. Lett. 2006, 23 (4): 832-833 .  
Abstract   PDF(pc) (176KB) ( 805 )
The dyadic Green function for a homogeneous electromagnetic medium inspired by the spatiotemporally nonhomogeneous constitutive equations of gravitationally affected vacuum is derived.
Coupled Optical Solitons for Pulse Propagation in Multi-Level Media
HUANG Guo-Xiang, Jacob Szeftel
Chin. Phys. Lett. 2006, 23 (4): 834-837 .  
Abstract   PDF(pc) (208KB) ( 496 )
We investigate the shape-preserving propagation of N optical pulses in an (N+1)-level medium. We solve Maxwell-Schrödinger equations exactly and provide several types of explicit coupled soliton solutions, which are temporally amplitude- and group-velocity-matched multi-mode slow-optical pulses of the system.
Extremely Increasing the Operating Frequency Range of Mode-Locked Hybrid Soliton Pulse Source
Nuran Dogru
Chin. Phys. Lett. 2006, 23 (4): 838-841 .  
Abstract   PDF(pc) (234KB) ( 833 )
Numerical simulations show that proper fundamental mode-locking repetition range of hybrid soliton pulse source where transform-limited pulses are obtained is extremely increased with the use of linearly chirped tanh apodized fibre Bragg grating. Near transform-limited pulses are generated over a frequency range of 1.6GHz (1.9--3.4GHz) around a system operating frequency of 2.5GHz.
S-Band Gain-Flattened Double-Pass Discrete Fibre Raman Amplifiers Using Mechanically Induced Long-Period Fibre Gratings
LI Yong-Nan, LU Fu-Yun, FAN Yu, WANG Xin-Wei, WEI Dai
Chin. Phys. Lett. 2006, 23 (4): 842-844 .  
Abstract   PDF(pc) (325KB) ( 909 )
We experimentally demonstrate an S-band double-pass (DP) discrete fibre Raman amplifier (FRA) gain-flattened by using a mechanically induced long-period fibre grating (LPFG). Due to a photo-elastic effect in the fibre and its peak loss, the wavelength and depth of the mechanically induced LPFG are continuously regulated by varying the pressures, the angle of the fibre on the graphite rods which are used to produce the periodical pressures along the fibre, the number and the diameter of the graphite rods. Using this gain flattening filter, the gain profile of the DP-FRA is flattened to within ±0.8dB in the wavelength range from 1485nm to 1525nm.
Broadband Frequency Down-Conversion Using Coupled Cavity Structures in One-Dimensional Photonic Crystals
LI Wen-Hui, CHEN Li-Xue, TANG Dong-Hua, DING Wei-Qiang, LIU Shu-Tian
Chin. Phys. Lett. 2006, 23 (4): 845-848 .  
Abstract   PDF(pc) (303KB) ( 878 )
The frequency down-conversion of one-dimensional photonic crystals with the coupled cavity structure is investigated by the nonlinear finite-difference time-domain method. The efficient frequency conversion is obtained by utilizing the advantages of the broad eigenfrequency band, the strong localization and the Bloch phase matching of the coupled cavity structure. More importantly, the signal frequency could be tuned continuously within the whole band of the coupled cavity structure (with a bandwidth to central frequency ratio of 5.4%), and the gains are homogeneous in the band.
High-Power Continuous-Wave Diode-End-Pumped Intracavity Frequency Doubled Nd:YVO4 Laser at 671nm with a Compact Three-Element Cavity
ZHOU Rui, DING Xin, WEN Wu-Qi, CAI Zhi-Qiang, WANG Peng, YAO Jian-Quan
Chin. Phys. Lett. 2006, 23 (4): 849-851 .  
Abstract   PDF(pc) (227KB) ( 939 )
We report a high-power high-efficient continuous-wave (cw) diode-end-pumped Nd:YVO4 1342-nm laser with a short plane-parallel cavity and an efficient cw intracavity frequency-doubled red laser at 671nm with a compact three-element cavity. At incident pump power of 20.6W, a maximum output power of 7W at 1342nm is obtained with a slope efficiency of 37.3%. By inserting a type-I critical phase-matched LBO crystal as intracavity frequency-doubler, a cw red output as much as 2.85-W is achieved with an incident pump power of 16.9W, inducing an optical-to-optical conversion efficiency of 16.9%. To the best of our knowledge, this is the highest output of diode-pumped solid-state Nd:YVO4 red laser. During half an hour, the red output is very stable, and the instability of output power is less than 1%.
Structural and Luminescence Properties of Transparent Nanocrystalline ZrO2:Er3+ Films
ZHANG Qin-Yuan, YANG Gang-Feng, JIANG Zhong-Hong, W. X. Que
Chin. Phys. Lett. 2006, 23 (4): 852-855 .  
Abstract   PDF(pc) (515KB) ( 612 )
The structural and luminescence properties of nanocrystalline ZrO2:Er3+ films are reported. Transparent nano-ZrO2 crystalline films doped with Er3+ have been prepared using a wet chemistry process. An intense room-temperature emission at 1527nm with a full width at half-maximum of 46nm has been observed, which is assigned to the 4I13/24I15/2 intra-4fn electric transition of Er3+. Correlations between the luminescence properties and structures of the nanocrystalline ZrO2:Er3+ films have been investigated. Infrared-to-visible upconversion occurs simultaneously upon excitation of a commercially available 980-nm laser diode and the involved mechanisms have also been explained. The results indicate that the nanocrystalline ZrO2:Er3+ films might be suggested as promising materials for achieving broadband Er3+-doped waveguide amplifiers and upconversion waveguide lasers.
Image Restoration Phase-Filtering Lateral Superresolution Confocal Microscopy
ZHAO Wei-Qian, QIU Li-Rong, CHEN Shan-Shan, FENG Zheng-De
Chin. Phys. Lett. 2006, 23 (4): 856-859 .  
Abstract   PDF(pc) (350KB) ( 926 )
Image restoration phase-filtering lateral superresolution confocal microscopy, a new approach, is proposed to achieve lateral superresolution using a confocal microscope. This approach uses a lateral superresolution pupil filter to preliminarily improve its lateral resolution and uses a single-image superresolution restoration technique based on a maximum likelihood estimate to further improve its lateral resolution. The new approach has the advantages of a low cost and the remarkable superresolution effect without excessive system complexity. Experiments indicate that the proposed approach can improve the lateral resolution of a confocal microscope from 0.3μm to less than 0.1μm when λ=632.8nm and NA=0.85.
Investigation on the Fabrication of Photonic Crystal Fibre
LOU Shu-Qin, FANG Hong, GUO Tie-Ying, JIAN Shui-Sheng
Chin. Phys. Lett. 2006, 23 (4): 860-863 .  
Abstract   PDF(pc) (518KB) ( 587 )
Effects of draw parameters, such as drawing temperature and feed speed, on the capillaries and the geometry of the final photonic crystal fibre (PCF) are investigated. Inert gas pressurization is introduced in the preform during the fibre drawing process to finely control the geometry of the PCF so that good uniform in transversal and longitudinal of the final PCF can be realized. Due to the introduction of a special method, the drawing temperature is increased over 1900°C and the strength of the PCF is enhanced.
Dynamic Polarization-Mode-Dispersion Compensation for 160Gbit/s OTDM Systems
LI Tang-Jun, WANG Mu-Guang, CAI Li-Bo, ZHAO Jing, JIAN Shui-Sheng
Chin. Phys. Lett. 2006, 23 (4): 864-867 .  
Abstract   PDF(pc) (367KB) ( 674 )
We report on 160Gbit/s RZ (return-to-zero) code transmission experiments including a dynamic polarization mode dispersion (PMD) compensation. The 2.5-ps first-order and 15-ps2 second-order PMD are compensated for. The PMD compensation time is within 24ms. The experimental results show that a significant improvement of system performance can be achieved by auto-correlative curves.
Mach--Zehnder Interferometers with Asymmetric Modulation Arms in Applications of High Speed Silicon-on-Insulator Based Optical Switches
SUN Fei, YU Jin-Zhong
Chin. Phys. Lett. 2006, 23 (4): 868-870 .  
Abstract   PDF(pc) (242KB) ( 565 )
Modulation arms with different widths are introduced to Mach--Zehnder interferometers (MZIs) to obtain improved performance. Theoretical analysis and numerical simulation have shown that when the widths of the two arms are properly designed to achieve an inherent mπ/2 (m is an odd integer) optical phase difference between the arms, the asymmetric MZI presents higher modulation speed. Furthermore, the carrier-absorption induced divergence of insertion losses in silicon-on-insulator (SOI) based MZI optical switches can be obviously improved.
Acoustic Localization in Weakly Compressible Elastic Media Permeated with Air Bubbles
LIANG Bin, ZHU Zhe-Min, CHENG Jian-Chun
Chin. Phys. Lett. 2006, 23 (4): 871-874 .  
Abstract   PDF(pc) (276KB) ( 559 )
The propagation of longitudinal acoustic waves in weakly compressible elastic media permeated with air bubbles is investigated on the basis of the radial pulsation equation of a single bubble. The multiple scattering of waves in such media is rigorously described by using a self-consistent approach. Theoretical results show that there exists strong acoustic localization in a range of frequency slightly above the bubble resonance frequency, even for a very small volume fraction of bubbles. Further study reveals that the localization is in fact attributed to collection behaviour of bubbles, allowing for an efficient cancellation of propagating waves. This is essentially consistent with the known conclusions recently drawn for bubbly liquid by Kou et al. [2003 Appl. Phys. Lett. 83 4247]
Theoretical and Experimental Investigation of Ultrasonic Focusing with Annular Phased Array
ZHANG Bi-Xing, WANG Cheng-Hao, LAI Pu-Xiang
Chin. Phys. Lett. 2006, 23 (4): 875-878 .  
Abstract   PDF(pc) (444KB) ( 517 )
The focused acoustic field generated by an annular array transducer and its reflection field on a solid--liquid interface are investigated theoretically and experimentally. Theoretically, the concise analytic expressions about the radiation and reflection acoustic fields of the annular phased array are obtained by the ray approach method (saddle-point method). In experiment, an annular transducer with 8 equal-area elements is designed and fabricated, and a series of experiments about the radiation acoustic field and its reflection on the liquid-solid interface are carried out. The experimental characteristics of the transducer are in good agreement with the numerical ones. It shows the correctness of the theoretical result and the feasibility of dynamic focusing of the experiment system. With the maximum amplitude and its emergence time of the reflection wave, we can acquire the information and the imaging of the reflection interface by the annular phased array dynamic focusing.
Vapour Recoil Effect on a Vapour--Liquid System with a Deformable Interface
LIU Rong, LIU Qiu-Sheng
Chin. Phys. Lett. 2006, 23 (4): 879-882 .  
Abstract   PDF(pc) (228KB) ( 541 )
A new two-sided model of vapour--liquid layer system with a deformable interface is proposed. In this model, the vapour recoil effect on the Marangoni--Bénard instability of a thin evaporating liquid layer can be examined only when the interface deflexion is considered. The instability of a liquid layer undergoing steady evaporation induced by the coupling of vapour recoil effect and the Marangoni effect is analysed using a linear stability theory. We modify and develop the Chebyshev--Tau method to solve the instability problem of a deformable interface system by introducing a new equation at interface boundary. New instability behaviour of the system has been found and the self-amplification mechanism between the evaporation flux and the interface deflexion is discussed.
Lagrangian and Eulerian Statistics from Direct Numerical Simulations of Turbulent Channel Flow
LUO Jian-Ping, Tatsuo Ushijima, Osami Kitoh
Chin. Phys. Lett. 2006, 23 (4): 883-886 .  
Abstract   PDF(pc) (256KB) ( 686 )
Lagrangian and Eulerian statistics are obtained from the direct numerical simulation of a turbulent channel flow. The Reynolds number is obtained to be Reτ=100 (based on friction velocity and channel half-height). The Lagrangian time microscales are compared to their Eulerian equivalents. It is found that the Lagrangian time microscales equal the Eulerian time microscales at the wall, but they are consistently larger than the Eulerian away from the wall. The Eulerian time scales are also found to be scaled by the propagation velocity rather than the mean velocity. The ratio of the Lagrangian to the Eulerian time microscales is found to be nearly constant away from the wall (y+>40).
Variable Coefficient KdV Equation and the Analytical Diagnoses of a Dipole Blocking Life Cycle
TANG Xiao-Yan, HUANG Fei, , LOU Sen-Yue,
Chin. Phys. Lett. 2006, 23 (4): 887-890 .  
Abstract   PDF(pc) (1035KB) ( 675 )
A variable coefficient Korteweg de Vries (VCKdV) system is derived by considering the time-dependent basic flow and boundary conditions from the well-known Euler equation with an earth rotation term. The analytical solution obtained from the VCKdV equation can be successfully used to explain fruitful phenomena in fluid and other physical fields, for instance, the atmospheric blocking phenomena. In particular, a diploe blocking case happened during 9 April 1973 to 18 April 1973 read out from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data is well described by the analytical solution.
A New Criterion for Disruption Prediction on HL-2A
YANG Qing-Wei, ZHOU Hang-Yu, FENG Bei-Bin, LIU Yi, PAN Yu-Dong, LI Wei, DUAN Xu-Ru, CHEN Wei, CUI Zheng-Ying, JI Xiao-Quan, DING Xuan-Tong, HL-A team
Chin. Phys. Lett. 2006, 23 (4): 891-894 .  
Abstract   PDF(pc) (293KB) ( 500 )
A new criterion has been proposed to predict the major disruptions caused by tearing mode instabilities. According to the HL-2A experimental results, the statistical analyses are employed to investigate the relationships between MHD activities and the plasma disruptions. Two kinds of the tearing mode activities can finally cause the disruption on HL-2A operations. By introducing a new parameter, i.e. an integral of poloidal magnetic field over time, as the criterion of disruption precursor, almost all of the disruptions can be predicted.
Stability of Rayleigh--Taylor Vortices in Dusty Plasma
MA Jun, CHEN Yin-Hua, GAN Bao-Xia, WANG Fei-Hu, WANG Dong
Chin. Phys. Lett. 2006, 23 (4): 895-898 .  
Abstract   PDF(pc) (282KB) ( 481 )
The evolution of Rayleigh--Taylor mode in dusty plasma with vortex-flow is investigated. Based on fluid theory and Bayly’s method, we derive the coupling equations describing the Rayleigh--Taylor mode in the core of vortex, and research the evolution characteristics of the perturbation amplitude with time numerically. It is shown that the eccentric of vortex and the content of dust have considerable effects on the amplitude evolutions.
Pulse-Width Increase of Reflex Triode Vircator Using the Carbon Fibre Cathode
LIU Lie, LI Li-Min, ZHANG Xiao-Ping, WEN Jian-Chun, WAN Hong
Chin. Phys. Lett. 2006, 23 (4): 899-902 .  
Abstract   PDF(pc) (561KB) ( 602 )
We present the investigation on the reflex triode virtual cathode oscillator in which performances of carbon-fibre and stainless-steel cathodes are compared with each other. The experimental results and analyses show that surface tracking induces the electron emission of the carbon fibre cathode. There are electron emission phenomena observed not only from the top of the carbon fibre but also from its side surface. Compared with the case of the stainless steel cathode, the plasma expansion velocity for the carbon fibre cathode is slower, and using the carbon fibre cathode can widen the pulse width of output microwave. The output microwave pulse width reaches an increase of about 20%. This mechanism is different from the conventional explosive emission of metal cathodes.

Room-Temperature Inductively Coupled Plasma Etching of InP Using Cl2N2 and Cl2/CH4/H2
LEE Chee-Wei, CHIN Mee-Koy
Chin. Phys. Lett. 2006, 23 (4): 903-906 .  
Abstract   PDF(pc) (638KB) ( 1826 )
We optimize the room-temperature etching of InP using Cl2N2 and Cl2/CH4/H2 inductively coupled plasma reactive ions. A design of experiment is used in the optimization. The results, in terms of etch rate, surface roughness and etched profile, are presented. These Cl2-based recipes do not require substrate heating and thus can be more cost effectively and widely applied. The Cl2/CH4/H2 process is able to give a higher etch rate (about 850nm/min) and cleaner surface with less polymer formation compared to the conventional CH4/H2 process. The Cl2/N2 process produces even higher etch rate (as high as 2μm/min), but rougher surface with slight sidewall undercut. The Cl2/N2 process also has no polymer formation due to the absence of methane gas. Both the processes give very good selectivity to the silicon dioxide (SiO2) etch mask. The selectivity of InP to the oxide mask (up to 55:1) for the Cl2/N2 process is one of the highest reported so far. The etched structures possess reasonably good sidewall verticality and surface quality comparable to that obtained under elevated temperature condition (>200°C).
Analysis of Local Structures around Ni Atoms Doped in ZnO-Based Diluted Magnetic Semiconductors by Fluorescence EXAFS
LI Bin-Bin, XIU Xiang-Qian, ZHANG Rong, TAO Zhi-Kuo, CHEN Lin, XIE Zi-Li, ZHENG You-Dou, HE Bo/sup>
Chin. Phys. Lett. 2006, 23 (4): 907-910 .  
Abstract   PDF(pc) (260KB) ( 705 )
Zn1-xNixO (x=0.001, 0.01, 0.02, 0.05 and 0.20) powders are prepared by sol-gel method. An extended x-ray absorption fine structure technique (EXAFS) for the Ni K-edge is employed to probe the local structures around Ni atoms doped in ZnO powders by fluorescence mode. The near edge EXAFS of the samples does not change in the range of Ni concentration from x=0.001 to 0.05, which is consistent with the results of x-ray diffraction of the samples. The simulation results for the first shell EXAFS signals indicated that Ni atoms are substituted in Zn sites.
Compressibility of Lattice Parameters of Several Layered Compounds
LI Feng-Ying, JIN Chang-Qing, CHEN Liang-Chen, ZHOU Bo, SHI Li-Chi, LIU Jing, LI Xiao-Dong, LI Yan-Chun, YU Ri-Cheng
Chin. Phys. Lett. 2006, 23 (4): 911-914 .  
Abstract   PDF(pc) (224KB) ( 666 )
The lattice parameters of AlB2, MgB2 and TiB2 under pressures are determined with a high-energy synchrotron source in a diamond anvil cell. The experimental results indicate that these three compounds have different mechanical behaviour under pressures, TiB2 is the hardest and MgB2 is the softest among the three materials. The phenomena are explained in terms of bonding strength in the crystal. Our results may be helpful for understating the decrease of the superconducting transition temperature of MgB2 under pressures.
Molecular Dynamics Study of Icosahedral Clusters in Ni--Zr Amorphous Alloys
YANG Quan-Wen, ZHANG Tao
Chin. Phys. Lett. 2006, 23 (4): 915-918 .  
Abstract   PDF(pc) (836KB) ( 543 )
Formation of icosahedral clusters in rapidly solidified binary amorphous NixZr100-x (x=15, 33.3, 50, 66.7, 85) is studied by using molecular dynamics simulation methods. A large number of icosahedral clusters with 13 atoms (Ih13) were observed in NixZr100-x alloys, and most of them, even those in Zr-rich alloys, are found to be Ni-centred. Studies on the structures of Ni33.3Zr66.7 obtained at different cooling rates demonstrate that most of iscosahedral clusters enhanced by decreasing cooling rates are also Ni-centred. The essentials of Ni atoms preferring to be the core of icosahedral clusters are illustrated with the criterion of energy minimization and the equilibrium interatomic distances between different atoms.
Implant Depth Influence on InGaAsP/InP Double Quantum Well Intermixing Induced by Phosphorus Ion Implantation
ZHAO Jie, CHEN Jie, WANG Yong-Chen, HAN De-Jun
Chin. Phys. Lett. 2006, 23 (4): 919-921 .  
Abstract   PDF(pc) (236KB) ( 584 )
We investigate quantum well intermixing of a double-quantum-well structure caused by phosphorus ion implantation by means of photoluminescence (PL). The ion implantation is performed at the energy of 120keV with the dose ranging from 1×1011 to 1×1014/cm2. The rapid thermal annealing is performed at the temperature of 700°C for 30s under pure nitrogen protection. The PL measurement shows that the band gap blueshift is influenced by the depth of ion implantation. The blueshift of the upper well which is closer to the implanted vacancies is enhanced with the ion dose faster than that from a lower well under the lower dose implantation (<5×1011/cm2). When the ion dose is over 1012/cm2, the band gap blueshift from both the wells increases with the ion dose and finally the two peaks combine together as one peak, indicating that the ion implantation results in a total intermixing of both the quantum wells.
Optical Waveguide Formed in Yb:KLu(WO4)2 Crystal by 6.0MeV O+ Implantation
JIANG Yi, WANG Ke-Ming, WANG Xue-Lin, JIA Chuan-Lei, ZHANG Jian-Xiu, WANG Ji-Yang, MA Hong-Ji, NIE Rui, SHEN Ding-Yu
Chin. Phys. Lett. 2006, 23 (4): 922-924 .  
Abstract   PDF(pc) (246KB) ( 537 )
A planar optical waveguide is formed in monoclinic double rare-earth-tungstate laser crystal Yb:KLu(WO4)2 by 6.0MeV oxygen ion implantation with a dose of 2 1015ions/cm2 at room temperature. Subsequently, annealing at 300°C for an hour in air is performed on the sample to decrease colour centres to improve the thermal stability of the waveguide. The refractive index profiles of the waveguide are reconstructed by an effective refractive index method. Dark modes of the waveguide are observed at wavelengths of 633nm and 1539nm. TRIM'98 is used to simulate the damage profile caused by the implantation process. It is found that the refractive index change may be mainly due to the damage induced by the nuclear energy loss.
Ab Initio Calculations of Elastic Constants of Li2O under Pressure
LI Xiao-Feng, CHEN Xiang-Rong, JI Guang-Fu, MENG Chuan-Min
Chin. Phys. Lett. 2006, 23 (4): 925-927 .  
Abstract   PDF(pc) (228KB) ( 1812 )
We investigate the equilibrium lattice constant, bulk modulus, elastic constants and Debye temperature of Li2O under pressure by using ab initio unrestricted Hartree--Fock (HF) linear combination of atomic orbital (LCAO) periodic approach. The obtained results at zero pressure are well consistent with the available experimental data and other theoretical results. It is found that the elastic constants C11, C12 and C44 and bulk modulus B increase monotonously as pressure increases. Also, the anisotropy will weaken and the Debye temperature will rise with pressure increasing.

Improved Performance of Organic Light-Emitting Diodes with MgF2 as the Anode Buffer Layer
XIE Jing, ZHANG De-Qiang, WANG Li-Duo, DUAN Lian, QIAO Juan, QIU Yong
Chin. Phys. Lett. 2006, 23 (4): 928-931 .  
Abstract   PDF(pc) (689KB) ( 1541 )
Organic light-emitting diodes (OLEDs) based on N,N’-bis(1-naphthyl)-N,N’-diphenyl-1,1’-biphenyl-4,4’-diamine (NPB) and tris (8-hydroxyquinoline) aluminium (Alq3) are improved by using a thin MgF2 buffer layer sandwiched between the indium tin oxide (ITO) anode and hole transporting layer (HTL) of NPB. The current-voltage curves of the OLEDs with MgF2 buffers shift to lower voltages, which can be explained by the tunnelling effect. Under 10V bias, the current density and brightness for the optimized OLED with a 1.0-nm MgF2 are 196A/m2 and 517cd/m2, respectively, while for the OLED without anode buffer layer are only 109A/m2 and 156cd/m2. The atomic force microscopy shows that the rms roughness of NPB on ITO/MgF2 is only 1/3 of NPB on bare ITO. The improved morphology of the HTL would lead to more robust OLEDs. The OLED with a 1.0-nm MgF2 layer has a long lifetime of more than five times of the MgF2-free reference device due to the combined electrical and morphological effects of the MgF2 layer.
Effect of Anti-Diffusion Oxide Layer on Enhanced Thermal Stability of Magnetic Tunnel Junctions
ZHANG Zong-Zhi, ZHAO Hui, Cardoso S., Freitas P. P.
Chin. Phys. Lett. 2006, 23 (4): 932-935 .  
Abstract   PDF(pc) (270KB) ( 588 )
Magnetic tunnel junctions (MTJs) with one proper oxidized FeOx layer placed between the Al oxide barrier and the top CoFe pinned layer show large tunnelling-magnetoresistance (TMR) signals as high as 39% after anneal at 380°C. The increased TMR signal may originate from the as-deposited Fe/FeOx (non-magnetic) layers changing to Fe+magnetic FeOy layer (some Fe3O4 and mostly other kind of magnetic Fe oxide) after high temperature anneal. The maximum TMR value (TMRmax) and the corresponding temperature Ts where the TMRmax occurs upon annealing are closely associated with the oxidation time of the AlOx and FeOx layers, too long oxidation for the Fe layers is detrimental for the TMR value. In addition to the enhanced AlOx barrier quality upon anneal, the improved thermal stability is also attributed to the Mn diffusion retardation by the presence of the FeOx layer which acts as an antidiffusion layer. For MTJs without the interposed FeOx layer, the TMR signal reduction at 300°C originates from the MnIr/CoFe partially decoupling and CoFe/AlOx interface polarization loss due to the significant Mn diffusion.
Experimental Studies on Thermal and Electrical Properties of Platinum Nanofilms
ZHANG Xing, ZHANG Qing-Guang, CAO Bing-Yang, FUJII Motoo, TAKAHASHI Koji, IKUTA Tatsuya
Chin. Phys. Lett. 2006, 23 (4): 936-938 .  
Abstract   PDF(pc) (464KB) ( 1982 )
We experimentally studied the in-plane thermal and electrical properties of a suspended platinum nanofilm in thickness of 15nm. The measured results show that the in-plane thermal conductivity, the electrical conductivity and the resistance-temperature coefficient of the studied nanofilm are much less than those of the bulk material, while the Lorenz number is greater than the bulk value. Comparing with the results reported previously for the platinum nanofilm in thickness of 28nm, we further find that the in-plane thermal conductivity, the electrical conductivity and the resistance-temperature coefficient decrease with the decreasing thickness of the nanofilm, while the Lorenz number increases with the decreasing thickness of the nanofilm. These results indicate that strong size effects exist on the in-plane thermal and electrical properties of platinum nanofilms.
Characterization of Undoped and Cu-Doped ZnO Thin Films Deposited on Glass Substrates by Spray Pyrolysis
Metin Bedir, Mustafa Ö, ztas, A. Necmeddin Yazici, E. Vural Kafadar
Chin. Phys. Lett. 2006, 23 (4): 939-942 .  
Abstract   PDF(pc) (257KB) ( 4686 )
Undoped and copper doped zinc oxide (ZnO) thin films have been prepared on glass substrates by spray pyrolysis technique. The films were doped with copper using the direct method by addition of a copper salt (CuCl2) in the spray solution of ZnO. Variation of structural, electrical, optical and thermoluminescence (TL) properties with doping concentrations is investigated in detail.

Quasiparticle Band Structure of BaS
LU Tie-Yu, CHEN De-Yan, HUANG Mei-Chun
Chin. Phys. Lett. 2006, 23 (4): 943-945 .  
Abstract   PDF(pc) (207KB) ( 428 )
We calculate the band structure of BaS using the local density approximation and the GW approximation (GWA), i.e. in combination of the Green function G and the screened Coulomb interaction W. The Ba 4d states are treated as valence states. We find that BaS is a direct band-gap semiconductor. The result shows that the GWA band gap (Eg-GW=3.921eV) agrees excellently with the experimental result (Eg-EXPT=3.88eV or 3.9eV).
Non-Achievability of Metal--Insulator Transition in Two-Dimensional Systems
A. John Peter
Chin. Phys. Lett. 2006, 23 (4): 946-949 .  
Abstract   PDF(pc) (219KB) ( 466 )
We present a simple demonstration of the nonfeasibility of metal-insulator transition in an exactly two-dimensional (2D) system. The Hartree--Fock potential in the 3D system is suitably modified and presented for the 2D case. The many body effects are included in the screening function, and binding energies of a donor are obtained as a function of impurity concentration so as to find out the possible way leading metal-insulator transition in the 2D system. While solving for the binding energy for a shallow donor in an isolated well of a GaAs/Ga1-x Als As superlattice system within the effective mass approximation, it leads to unphysical results for higher concentrations. It shows that the phase transition, the bound electron entering into the conduction band whereby min= 0, is not possible beyond this concentration. The results suggest that a phase transition is impossible in 2D systems, supporting the scaling theory of localization. The results are compared with the existing data available and discussed in the light of existing literature.
Hole Transport Properties of MEH-PPV at Different Excitation Wavelengths
SHI Quan-Min, HOU Yan-Bing, LU Jing, JIN Hui, LI Yun-Bai
Chin. Phys. Lett. 2006, 23 (4): 950-952 .  
Abstract   PDF(pc) (248KB) ( 1413 )
Using the time-of-flight photocurrent measurements, we investigate the hole transport properties of polymer 2-methoxy, 5-(2’-ethyl-hexyloxy)-1, 4-phenylene vinylene (MEH-PPV). The change of hole transport properties from non-dispersive transport to a dispersive type is presented, with the increasing excitation wavelength near the MEH-PPV absorption edge. At room temperature, the effective mobility of MEH-PPV depends on the applied electric field as commonly seen in some organic materials.
Hopping Conductivity in a Single-Walled Carbon Nanotube Network
FANG Jing-Hai, LIU Li-Wei, KONG Wen-Jie, CAI Jian-Zhen, LU Li
Chin. Phys. Lett. 2006, 23 (4): 953-955 .  
Abstract   PDF(pc) (386KB) ( 659 )
We investigate the resistance and magnetoresistance (MR) of an entangled single-walled carbon nanotube (SWNT) network. The temperature dependence of conductance is fitted by formula G(T)=G0exp[-(T0/T)1/2] with T0=15.8K at a wide temperature range from 4K to 300K. The MR defined by [R(T,H)-R(T,0)]/R(T,0) as a function of temperature and magnetic field perpendicular to the tube axis is negative at low temperatures. The MR amplitude increases as the temperature decreases at relative high temperature, but becomes decrease when temperature below 4K. The results are explained in terms of the coherent hopping of carriers in the presence of a Coulomb gap at low temperature.
Strained and Piezoelectric Characteristics of Nitride Quantum Dots
LU Yan-Wu, CAI Lin, LIANG Shuang
Chin. Phys. Lett. 2006, 23 (4): 956-959 .  
Abstract   PDF(pc) (1035KB) ( 591 )
The deformation potential and piezoelectric field in nitride GaN/AlN quantum dots (QDs) are investigated in the framework of effective mass approximation (EMA) and finite element method (FEM). The strained fields and piezoelectric characteristics are studied by using FEM for GaN/AlN QDs (GaN embedded in AlN) in the shape of truncated hexagonal pyramids. We presented the calculated results of the electronic states, wave functions, QD strain field distribution and piezoelectric effects in the QDs. Effects of spontaneous and piezoelectric polarization are taken into account in the calculation. The theoretical results are dependent on QD shapes and sizes. Some of them make the GaN/AlN QDs interesting candidates in optoelectronic applications.
Effect of Bias Step on the I-V Curve in Double-Barrier AlGaAs/GaAs/AlGaAs Resonant-Tunnelling Devices
DAI Zhen-Hong, NI Jun
Chin. Phys. Lett. 2006, 23 (4): 960-963 .  
Abstract   PDF(pc) (319KB) ( 714 )
We investigate the non-equilibrium electron transport properties of double-barrier AlGaAs/GaAs/AlGaAs resonant-tunnelling devices in nonlinear bias using the time-dependent simulation technique. It is found that the bias step of the external bias voltage applied on the device has an important effect on the final current-voltage (I-V) curves. The results show that different bias step applied on the device can change the bistability, hysteresis and current plateau structure of the I-V curve. The current plateau occurs only in the case of small bias step. As the bias step increases, this plateau structure disappears.

Mechanical Properties of (Bi,Pb)-2223 Multifilament Tapes with Ag-Alloy Sheath
LIANG Ting, QU Ti-Ming, LI Pei, HAN Zheng-He
Chin. Phys. Lett. 2006, 23 (4): 964-966 .  
Abstract   PDF(pc) (754KB) ( 529 )
Ag-Mg-V alloy is prepared and investigated to develop a new sheath alloy used for BSCCO tapes. Bi-2223 Ag/AgMgV and Bi-2223 AgMgV/AgMgV tapes are studied with the help of stress-strain measurement, optical microstructure and critical current Ic. The value of Ic at 77K and at magnetic field B=0 is obtained to be 90A/cm2 for the samples of Bi-2223 Ag/AgMgV tapes, which is higher than that of Bi-2223 AgMgV/AgMgV tapes (72A/cm2). The resistance of AgMgV alloy, up to 0.37μΩ.cm at 77K, is higher than that of pure Ag (0.28μ after annealed at 840°C for 40h, which is studied for reducing the ac loss. The values of the fracture strength and the maximum strain are 86MPa and 0.50% for Bi-2223 Ag/AgMgV tapes and 108MPa and 0.33% for Bi-2223 AgMgV/AgMgV tapes, respectively.

Order Parameter of a Nanometre-Scale S-Wave Superconducting Grain in Quantum Tunnelling Process: Frequency Space Analysis
R. Afzali, A. T. Rezakhani,
Chin. Phys. Lett. 2006, 23 (4): 967-970 .  
Abstract   PDF(pc) (231KB) ( 603 )
A nano-scale $s$-wave superconducting grain, coupled to a normal metallic contact through a tunnelling junction, is placed in an external magnetic field. We suppose that effect of this quantum tunnelling on the Fourier transform of the order parameter is in the form of a small additive correction to the BCS order parameter. At the first order approximation in terms of this correction term and by using an instanton method, the related Green functions (in frequency space) are obtained. By establishing a self-consistent configuration an analytic formula for the order parameter is also found. We also show that a departure from superconductivity can be captured by this formula. This change of state is indeed a manifestation of a quantum transition induced by quantum fluctuations. In this sense, this is an advantage of our simple method which, like other more elaborate methods, can detect a quantum transition in the state of the grain.

Numerical Simulation of Leakage Effect for Quantum NOT Operation on Three-Josephson-Junction Flux Qubit
WU Tao, LIU Jian-She, LI Zheng
Chin. Phys. Lett. 2006, 23 (4): 971-974 .  
Abstract   PDF(pc) (457KB) ( 604 )
Superconducting flux qubits with three Josephson junctions are promising candidates for the building blocks of a quantum computer. We have applied the imaginary time evolution method to study the model of this qubit accurately by calculating its wavefunctions and eigenenergies. Because such qubits are manipulated with magnetic flux microwave pulses, they might be irradiated into non-computational states, which is called the leakage effect. By the evolution of the density matrix of the qubit under either hard-shaped π-pulse or Gaussian-shaped π-pulse to carry out quantum NOT operation, it has been demonstrated that the leakage effect for a flux qubit is very small even for hard-shaped microwave pulses while Gaussian-shaped pulses may
suppress the leakage effect to a negligible level.
Magnetic Pair-Breaking in Y1-xHoxNi2B2C ( x=0, 0.25, 0.5, 0.75) Single Crystals
ZHAO Song-Rui, SHEN Jing-Qin, XU Zhu-An, Takeya H, Hirata K
Chin. Phys. Lett. 2006, 23 (4): 975-977 .  
Abstract   PDF(pc) (259KB) ( 707 )
Temperature-dependent resistivity and magnetic susceptibility were studied for quaternary borocarbide intermetallic compounds Y1-xHoxNi2B2C (x=0, 0.25, 0.5, 0.75), which show coexistence of superconductivity with magnetism. In a normal state, the compounds exhibit conventional metallic behaviour. The Debye temperature θD is derived by fitting the temperature dependence of resistivity to the Bloch--Gruneisen expression, i.e. θD scales with M-0.5 (M is the averaged atomic mass on the Y3+ site), which means that the acoustic mode of the lattice vibrating spectrum is influenced by the Y3+ site atoms. Fitting the temperature-dependent magnetic susceptibility above TN to the Curie--Weiss law, effective magnetic moment μeff is deduced, and then de Gennes factor dG is calculated. It is found that as Ho content increases, μeff as well as dG increases and TC decreases. Moreover, the decrease of TC scales with dG, i.e., Δ TC ∝ -nI2 N(εF)dG, which is consistent with the prediction of the Abrikosov--Gor'kov theory. We suggest that the depression of TC could be mainly ascribed to the magnetic pair-breaking effect of magnetic Ho3+ ions. The change of Debye temperature with Ho content may not have significant impact on TC.
Perpendicular Exchange Coupling in TbFeCo/FePt Bilayer Films
ZHA Chao-Lin, ZHANG Yi-Song, MA Bin, ZHANG Zong-Zhi, JIN Qing-Yuan, GAN Fu-Xi, LIU Yao-Wen, GAO Tie-Ren
Chin. Phys. Lett. 2006, 23 (4): 978-981 .  
Abstract   PDF(pc) (242KB) ( 663 )
We investigate the structure and exchange coupling in TbFeCo/FePt bilayer films. It is found that FePt has the L10 structure and the easy axis of the FePt film is perpendicular to the film plane. Results of the vibrating sample magnetometer and the magneto-optical Kerr effect measurements show a strong perpendicular exchange coupling between the ferrimagnetic TbFeCo layer and the hard ferromagnetic FePt layer. The magnetization direction of each layer and the process of magnetization reversal are discussed in detail. The switching field dependence on the exchange coupling has been modelled by micromagnetic simulation and the interlayer coupling constant is about -0.9erg/cm2 according to this simulation.
Photoelectric Characteristic of La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3 p--n eterojunctions
HUANG Yan-Hong, JIN Kui-Juan, ZHAO Kun, Lü Hui-Bin, HE Meng, CHEN Zheng-Hao, ZHOU Yue-Liang, YANG Guo-Zhen , MA Xiu-Liang
Chin. Phys. Lett. 2006, 23 (4): 982-985 .  
Abstract   PDF(pc) (414KB) ( 496 )
Good rectifying current--voltage characteristics and nanosecond photoelectric effects are observed in the p--n heterojunctions of La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3 fabricated by laser molecular beam epitaxy. The rise time is about 26ns and the full width at half maximum is about 125ns for the open-circuit photovoltaic pulses when the La0.9Sr0.1MnO3/ film in the heterojunction is irradiated by a laser operated at wavelength 308nm with pulse duration of about 25ns. A qualitative explanation is presented, based on an analysis of the photoelectric effect of p--n heterojunction.
Frequency Dependence of Resonance Field of One-Dimensional Heisenberg Antiferromagnet KCuF3
SHI Qing-Fan, Lü Zhen, MA Mu-Yan, MA Chao, LI Liang-Sheng
Chin. Phys. Lett. 2006, 23 (4): 986-989 .  
Abstract   PDF(pc) (247KB) ( 494 )
The frequency dependence of the in-plane angular change of the antiferromagnetic resonance (AFMR) field of KCuF3 is systematically measured at frequencies ranging from 3.8 to 10.6GHz at 4.2K. The effect of inequivalent g-tensors is found to gradually diminish with decreasing the frequency, and completely vanish when the frequency is decreased to the lower-frequency branch of C-band, while the effect of the effective anisotropy field is significantly enhanced with decreasing the frequency. The calculated AFMR field Hres based on the eight-sublattice model proposed by Yamada and Kato [J. Phys. Soc. Jpn. 63(1994)289] is in good agreement with the experimental data.
Analysis of Electrical Properties of Post-Annealed Polycrystalline CaCu3Ti4O12 Films by Impedance Spectroscopy
FANG Liang, SHEN Ming-Rong, LI Zhen-Ya, CAO Wen-Wu
Chin. Phys. Lett. 2006, 23 (4): 990-993 .  
Abstract   PDF(pc) (234KB) ( 587 )
Impedance spectroscopy is performed to establish the electrical property and microstructure relations of the as-deposited and post-annealed polycrystalline CaCu3Ti4O12 (CCTO) films. Our results show that the resistance and capacitance of the grains and grain boundaries could be tuned by changing the annealing atmosphere and temperature. The simple resistor--capacitor equivalent circuit and the modified constant phase element (CPE) circuit are used to describe the impedance spectroscopy, and excellent agreement between the calculated and measured curves is obtained in the CPE circuit. Based on the experimental results, it is suggested that the origin of the semiconductivity of the grains in CCTO polycrystalline films originates from their oxygen-loss, while the grain boundaries are close to oxygen- stoichiometry.
Negative Refraction and Imaging in a Triangular-Lattice Metallic Photonic-Crystal Slab
FENG Shuai, SUN Mei, REN Cheng, REN Kun, FENG Zhi-Fang, LI Zhi-Yuan, CHENG Bing-Ying, ZHANG Dao-Zhong
Chin. Phys. Lett. 2006, 23 (4): 994-997 .  
Abstract   PDF(pc) (576KB) ( 583 )
Imaging properties of a two-dimensional photonic crystal (PC) slab consisting of a triangular lattice of metallic cylinders immersed in a dielectric background are investigated by the finite-difference time-domain technique. With the calculated field patterns of a point source placed in the vicinity of the PC slab and the corresponding equifrequency-surface contours, we find that a high-quality image can form in the opposite side of the slab in the lowest TM-polarized photonic band, and this near-field image is formed mainly by the self-collimation effect.
Anisotropy in Thermo-Optic Coefficient of Different Polymer Systems by Attenuated Total Reflection Configuration
LI Xiang, CAO Zhuang-Qi, SHEN Qi-Shun, MENG Qing-Hua, HUANG De-Ying, GUO Kun-Peng, QIU Ling, SHEN Yu-Quan
Chin. Phys. Lett. 2006, 23 (4): 998-1001 .  
Abstract   PDF(pc) (258KB) ( 892 )
Thermo-optic coefficient dn/dT as well as volume expansion coefficients β of different polymer systems are measured for both TE and TM polarizations in an attenuated total reflection (ATR) configuration. Experimental results indicate that cross-linked polymer systems exhibit the thermal expansion coefficients smaller than those of the original side-chain systems. Moreover, the anisotropies in thermo-optic coefficients of the polymer systems with small birefringence exhibit linear relationship with the anisotropies in volume expansion coefficients, but the polymer systems with larger birefringence exhibit more complicated relationship.
Nonlinear Shift of the Raman A1 Mode in Ga-Incorporated CuInSe2 Thin Films
XU Chuan-Ming, SUN Yun, LI Feng-Yan, ZHANG Li, XUE Yu-Ming, HE Qing, LIU Hong-Tu
Chin. Phys. Lett. 2006, 23 (4): 1002-1004 .  
Abstract   PDF(pc) (217KB) ( 799 )
Composition dependence of quaternary CuIn1-xGaxSe2 films on Ga content has been systematically investigated by Raman scattering. The dominant A1 mode shifts from 174cm-1 for CuInSe2 to 185cm-1 for CuGaSe2 in an approximately polynomial curve other than a linear curve, indicating existence of asymmetric distribution of Ga and In on a microscopic scale in films. With Ga content x>0.3, the significantly broadening and intensity decrease of A1 modes suggest the degradation of crystalline quality of chalcopyrite phase. Additionally, the quenching of additional Raman band at 183cm-1 for the Ga-rich films reveals that CuAu-ordered phase can coexist in nominal chalcopyrite CuInSe2 films but not in CuGaSe2, due to Ga inhibition effect.
Influence of Growth Parameters of Frequency-Radio Plasma Nitrogen Source on Extending Emission Wavelengths from 1.31μm to 1.55μm GaInNAs/GaAs Quantum Wells Grown by Molecular-Beam Epitaxy
WU Dong-Hai, NIU Zhi-Chuan, ZHANG Shi-Yong, NI Hai-Qiao, HE Zhen-Hong, ZHAO Huan, PENG Hong-Ling, YANG Xiao-Hong, HAN Qin, WU Rong-Han
Chin. Phys. Lett. 2006, 23 (4): 1005-1008 .  
Abstract   PDF(pc) (508KB) ( 507 )
High (42.5%) indium content GaInNAs/GaAs quantum wells with room temperature emission wavelength from 1.3μm to 1.5μm range were successfully grown by Radio Frequency Plasma Nitrogen source assisted Molecular Beam Epitaxy. The growth parameters of plasma power and N2 flow rate were optimized systematically to improve the material quality. Photoluminescence and transmission electron microscopy measurements showed that the optical and crystal quality of the 1.54μm GaInNAs/GaAs QWs was kept as comparable as that in 1.31μm.
Neural Approach for Calculating Permeability of Porous Medium
ZHANG Ji-Cheng, LIU Li, SONG Kao-Ping
Chin. Phys. Lett. 2006, 23 (4): 1009-1011 .  
Abstract   PDF(pc) (203KB) ( 515 )
Permeability is one of the most important properties of porous media. It is considerably difficult to calculate reservoir permeability precisely by using single well-logging response and simple formula because reservoir is of serious heterogeneity, and well-logging response curves are badly affected by many complicated factors underground. We propose a neural network method to calculate permeability of porous media. By improving the algorithm of the back-propagation neural network, convergence speed is enhanced and better results can be achieved. A four-layer back-propagation network is constructed to effectively calculate permeability from well log data. Spontaneous potential, resistivity of deep lateral log, resistivity of micro-gradient log, resistivity of micro-normal log, Interval transit time of acoustic log and resistivity of shallow lateral log are selected as the inputs, and permeability is selected as the output. There are 35 and 40 units used in the two hidden layers, respectively. During the training course, the correlation coefficient between the calculated permeability and the standard pattern is as high as 0.9937, the average absolute error between them is 0.046μm2 and the average relative error is only 1.93%. For practical applications, the average relative error between the calculated permeability and actual permeability is also as low as about 10.0%.
Pure RGB Emissions Based on a White OLED Combined with Optical Colour Filters
WU Xiao-Ming, HUA Yu-Lin, WANG Zhao-Qi, YIN Shou-Gen, ZHENG Jia-Jin, DENG Jia-Chun, M. C. Petty
Chin. Phys. Lett. 2006, 23 (4): 1012-1014 .  
Abstract   PDF(pc) (287KB) ( 744 )
We report on a white organic light emitting device (OLED) with a single light emitting layer consisting of a greenish-white emitting host bis-(2-(2-hydroxyphenyl) benzothiazole)zinc (Zn(BTZ)2) and an orange-red dopant 5,6,11,12-tetraphenylnaphthacene (rubrene). The Commission Internationale De L'Eclairage (CIE) coordinates, external quantum efficiency, and brightness of the white OLED are (0.341, 0.334), 0.63% and 4000Cd/m2 at the bias of 20V, respectively. Pure red-green-blue (RGB) emissions have been successfully achieved from the white OLED combined well with several built-in optical colour filters (CFs). The CIE coordinates of the white mixture calculated in theory are very close to the coordinates of the white mixture which recorded with spectrophotometer in practice.
High-Efficiency Saturated Red Bilayer Light-Emitting Diodes: Comparative Studies with Devices from Blend of the Same Light-Emitting Polymers
ZHANG Yong, HOU Qiong, MO Yue-Qi, PENG Jun-Biaov, CAO Yong
Chin. Phys. Lett. 2006, 23 (4): 1015-1018 .  
Abstract   PDF(pc) (270KB) ( 646 )
High-efficient saturated red light-emitting diodes are realized based on a bilayer of phenyl-substituted poly [p-phenylene vinylene] derivative (P-PPV) and {copolymer (PFO-DBT15) of 9,9-dioctylfluorene (DOF) and 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DBT)}. External electroluminescent (EL) quantum efficiency of PFO-DBT15 is increased from 1.6% for a single-layer device to 4.7% for the bilayer device by insertion of a P-PPV layer between PEDOT (polyethylene dioxythiophene-polystyrene sulfonic acid) and PFO-DBT15 at the current density of 35mA/cm2. The luminescence efficiency reaches 0.83cd/A, and the Commission Internationale de I'Eclairage coordinates (CIE) become nearly x=0.700 and y=0.300. In comparison with the devices from PFO-DBT15 and P-PPV blend films, the P-PPV/PFO-DBT15 bilayer device shows higher EL quantum efficiency and better stability under high current density. The improved device performance can be attributed to the charge-confinement effect at the interface of the P-PPV/PFO-DBT15 bilayer structure.
Effect of Physical Parameters on Shape Instability of Sonoluminescing Bubbles
LU Tao, AN Yu
Chin. Phys. Lett. 2006, 23 (4): 1019-1022 .  
Abstract   PDF(pc) (248KB) ( 511 )
Considering the vapour effects, we calculate the shape instability of single-bubble sonoluminescence (SBSL) in the phase diagram of the amplitude of driving pressure versus ambient radius, i.e. the pa-R0 diagram. The numerical calculation shows that the results calculated by the present model are reliable, even some parameters, such as the binary diffusion constant and the thermal conductivity of the mixture of argon and water vapour inside the bubble, are roughly evaluated. It is found by numerical calculation that the shape stable area of a single argon bubble in those viscous liquids with low vapour pressure, such as oil of vitriol, glycerol and 1,2-propanediol, can be extended to a wider region. Combining with the calculation of the maximum temperature inside the bubble, we may predict that these areas are probably the stable region of SBSL.
Structural, Morphology and Optical Properties of Epitaxial ZnO Films Grown on Al2O3 by MOCVD
ZHOU Sheng-Qiang, WU Ming-Fang, YAO Shu-De, WANG Li, JIANG Feng-Yi
Chin. Phys. Lett. 2006, 23 (4): 1023-1025 .  
Abstract   PDF(pc) (723KB) ( 627 )
Epitaxial ZnO films are grown on Al2O3 (0001) by the MOCVD method. These films are high quality wurtzite crystals with (0001) orientation. Big hexagonal crystallites (diameter from several decades to 100μm) are found on the surface. Inside these crystallites, a stronger luminescence is observed compared with the plain area. Transmission electronic microscopy reveals that the film is thicker inside the hexagonal crystallites than the plain area, and some crystallites are not connected with each other and are slightly rotated with respect to their neighbours.
Study on Synthesis and Gas Sensitivity of SnO2 Nanobelts
YING Peng-Zhan, NI Zi-Feng, XIU Wei-Jie, JIA Liang-Ju, LUO Yong
Chin. Phys. Lett. 2006, 23 (4): 1026-1028 .  
Abstract   PDF(pc) (800KB) ( 581 )
Tin dioxide (SnO2) nanobelts have been successfully synthesized in bulk quantity by the CVD process based on the thermal evaporation of tin powders. The x-ray diffraction analysis indicates that the nanobelts are the tetragonal rutile structure of SnO2. Scanning electron microscopy and transmission electron microscopy observations reveal that the nanobelts are uniform. The selected-area electron diffraction analysis demonstrates that the nanobelts are single crystals. The energy dispersive x-ray analysis of the nanobelt shows that the nanobelts are composed of Sn and O. Gas-sensing components have been manufactured with prepared SnO2 nanobelts. Their performance indicates that SnO2 nanobelts have high sensitivity and selectivity to liquefied petroleum gas with fairly good response-recovery characteristic and stability at 220 °C.
Preparation of a Single Layer of Luminescent Nanocrystalline Si Structures by Laser Irradiation Method
CEN Zhan-Hong, XU Jun, LIU Yan-Song, HAN Pei-Gao, LI Wei, HUANG Xin-Fan, CHEN Kun-Ji
Chin. Phys. Lett. 2006, 23 (4): 1029-1031 .  
Abstract   PDF(pc) (511KB) ( 806 )
KrF excimer laser annealing on ultrathin hydrogenated amorphous Si films with various initial Si thicknesses is carried out to obtain a single layer of nanocrystalline Si structures. It is found that Si nanograins can be obtained with the area density as high as 1011cm-2 under the irradiation with suitable laser fluence. Raman and planar transmission electron microscopy are used to characterize the formation process of Si nanocrystals from amorphous phase. Moreover, a strong photoluminescence is observed at room temperature from well-relaxed nanocrystalline Si structures.
Applications of Oblique-Incidence Reflectivity Difference Method in Primary Study of Protein Biomolecules
ZHANG Hong-Yan, LIANG Ru-Qiang, JIN Kui-Juan, Lü Hui-Bin, ZHU Xiang-Dong, ZHOU Yue-Liang, RUAN Kang-Cheng, YANG Guo-Zhen
Chin. Phys. Lett. 2006, 23 (4): 1032-1033 .  
Abstract   PDF(pc) (225KB) ( 663 )
Oblique-incidence reflectivity difference (OI-RD) analysis is applied to detect the immunoglobulin-G and cytochrome biomolecules on standard glass substrates without fluorescence labelling. The OI-RD intensities not only depend on the protein structure, but also vary with the protein concentration. The results indicate that this method should have potential applications in detection of biochemical processes.
Monte Carlo Study of CO--NO Catalytic Surface Reaction Including CO--CO Repulsion
Waqar Ahmad, Musa Kaleem Baloach
Chin. Phys. Lett. 2006, 23 (4): 1034-1037 .  
Abstract   PDF(pc) (258KB) ( 650 )
The CO--NO reaction on a catalytic surface is studied by using Langmuir--Hinshelwood thermal mechanism with Monte Carlo computer simulation. In this model, a novel concept of CO--CO repulsion is introduced, which has experimental evidence due to the formation of dipoles when these molecules are chemisorbed on the surface. The system is investigated by applying two approaches of NO dissociation. In the first case, NO always decomposes into N and O before adsorption on the surface. In the second case, NO adsorbs on the surface molecularly and then dissociates into N and O if a vacancy is present in its adjacent neighbourhood. The steady state reactive window (i.e. the continuous production of CO2 and N2) is obtained only with the diffusion of N-atoms on the surface, which extends with CO--CO repulsion in the first case. However, in the second case, reactive window is obtained with CO--CO repulsion alone. The reactive window width in this case is reasonably large. The first-order phase transition is eliminated in both the cases with CO--CO repulsion.
A Monte Carlo Study of Influences on Depletion Force from Another Large Sphere in Colloidal Suspensions
XIAO Chang-Ming, GUO Ji-Yuan, HU Ping
Chin. Phys. Lett. 2006, 23 (4): 1038-1041 .  
Abstract   PDF(pc) (254KB) ( 675 )
According to the acceptance ratio method, the influences on the depletion interactions between a large sphere and a plate from another closely placed large sphere are studied by Monte Carlo simulation. The numerical results show that both the depletion potential and depletion force are affected by the presence of the closely placed large sphere; the closer the large sphere are placed to them, the larger the influence will be. Furthermore, the influences on the depletion interactions from another large sphere are more sensitive to the angle than to the distance.
Comparison of Properties of Pt/PZT/Pt and Ru/PZT/Pt Ferroelectric Capacitors
JIA Ze, REN Tian-Ling, LIU Tian-Zhi, HU Hong, ZHANG Zhi-Gang, XIE Dan, LIU Li-Tian
Chin. Phys. Lett. 2006, 23 (4): 1042-1045 .  
Abstract   PDF(pc) (315KB) ( 1209 )
Pb(Zr0.4Ti0.6)O3 film prepared by sol-gel spin coating on a Pt/Ti/SiO2/Si substrate is applied to ferroelectric capacitors with Pt or Ru as the top electrode. For the Pt/PZT/Pt and Ru/PZT/Pt ferroelectric capacitors, although with the same ferroelectric film, different top electrode materials incur different properties of PZT capacitors, such as fatigue, leakage, remanent and saturated polarization, except the similar crystal orientations of the PZT film. After 1010 switch cycles, the remanent polarizations of the Ru/PZT/Pt and Pt/PZT/Pt capacitors decrease to 70% and 84%, respectively. The leakage current density of the latter increases obviously at positive bias after 108 switch cycles, compared with the former. Different materials for the top electrode bring different conditions at the PZT/top electrode interface. The influence of oxygen-vacancy concentration at the PZT/electrode interface and the influence of oxides of the electrode material at the PZT/electrode interface to charge injection can explain the difference of properties of the PZT capacitors with Pt or Ru as the top electrodes.
Synchronizability of Highly Clustered Scale-Free Networks
WU Xiang, WANG Bing-Hong, ZHOU Tao, WANG Wen-Xu, ZHAO Ming, YANG Hui-Jie
Chin. Phys. Lett. 2006, 23 (4): 1046-1049 .  
Abstract   PDF(pc) (283KB) ( 730 )
We consider the effect of clustering coefficient on the synchronizability of coupled oscillators located on scale-free networks. The analytic result for the value of clustering coefficient aiming at a highly clustered scale-free network model, the Holme--Kim model is obtained, and the relationship between network synchronizability and clustering coefficient is reported. The simulation results strongly suggest that the more clustered the network, the poorer the synchronizability.
Epidemic Propagation and Microscopic Structure of Complex Networks
ZHANG Huan, LIU Zong-Hua, MA Wei-Chuan
Chin. Phys. Lett. 2006, 23 (4): 1050-1053 .  
Abstract   PDF(pc) (260KB) ( 932 )
How the microscopic structure of complex network takes influence on the epidemic propagation is investigated. Special attention is paid to the growing network where its average degree changes with time. A formula for the final density of infected individuals is given and is confirmed by numerical simulations. Our results show that the final density of refractory increases nonlinearly with both the average degree of nodes and the adjustable random parameter of network structure.
Bifurcated Current Sheet Structure in a Quiet Time by Cluster Spacecrafts
TANG Chao-Ling, LU Li, LI Zhong-Yuan, LIU Zhen-Xing
Chin. Phys. Lett. 2006, 23 (4): 1054-1056 .  
Abstract   PDF(pc) (218KB) ( 560 )
We analyse the vertical structure of the magnetotail current sheet for two time intervals during which the Cluster spacecrafts crossed the neutral sheet in a quiet time. In the intervals, the current sheet moved slowly, and the value of the AE index was relatively small, about 40--130nT. We find two examples of current sheets, with the current density maximum at the magnetic equator (Bx = 0), as well as an example of off-centre or bifurcated current sheets. In the quiet time, without any fast plasma flow and without significant flapping motion, we also directly observed the bifurcated current sheet. The bifurcated current sheet is probably associated with instabilities in the current sheet. These may be important for researching the mechanism of current sheet bifurcation.

A Possible Mechanism for the Origin of Ultrastrong Magnetic Field of Magnetars
BAI Hua, PENG Qiu-He, LUO Xin-Lian
Chin. Phys. Lett. 2006, 23 (4): 1057-1060 .  
Abstract   PDF(pc) (224KB) ( 789 )
Growing observations reveal that soft gamma-ray repeaters and anomalous x-ray pulsars are magnetars. Their magnetic fields may achieve 1014-1015G. We explore the origin of the superstrong magnetic field by considering the magnetization of the 3P2 superfluid neutrons inside neutron stars (NSs). By solving the Tolman--Oppenheimer--Volkov equations together with the equation of state adopted by Elgaroy it et al. [Phys. Rev. Lett. 77(1996)1428] in the calculation of the neutron pairing gap, we specifically calculate the NS internal structure, the permissible region for 3P2 superfluid neutrons inside the NS, and the total magnetic moment contributed by the orderly arranged neutron vortexes. The result shows that the induced magnetic field may cover a wide range, which is consistent with the magnetic field predicted by the standard magnetic dipole radiation for pulsar spindown.
Stellar Mass Function of Lyman Break Galaxies: Theoretical Perspective
LIU Xiao-Liang, HUANG Yong-Qing, LIU Nian-Hua, LAI Zhen-Quan, SHU Cheng-Gang,
Chin. Phys. Lett. 2006, 23 (4): 1061-0164 .  
Abstract   PDF(pc) (226KB) ( 1098 )
Adopting the observational distributions of star formation rates and half-light radii of Lyman break galaxies (LBGs) in the rest frame UV, we investigate empirically the predicted stellar mass function for LBGs. It is found that a peak exists at mass around 1.5 × 1010M for their stellar mass function and there have been significant amount of LBGs with stellar masses higher than 1011 M at z~ 3. There should be two families for LBG population observed by the Infrared Array Camera (IRAC) (which is a key instrument in the infrared space telescope Spitzer), one is red and the other is blue, which are consistent with recent works. Moreover, the predicted comoving correlation lengths for LBGs with different stellar masses, i.e., with different 8μm magnitudes, are also discussed. The red LBGs should be clustered in space more strongly than the blue LBGs. These predictions can and will be tested by the observations of IRAC, and will provide strong constraints on the current hierarchical galaxy formation model.
83 articles