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Volume 19 Issue 5
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Original Articles
Molecular Dynamics Simulation of the Structure I Empty Gas Hydrate
Chin. Phys. Lett. 2002, 19 (5): 609-612 .  
Abstract   PDF(pc) (545KB) ( 480 )
The 368 water molecule structure I empty gas hydrates with three possible hydrogen orientations are calculated using TIP4P potential molecular dynamical simulations. The thermodynamic properties and hydrogen bonding are compared with ice Ih. The density of states is analysed based on experimental measurements. The empty gas hydrate at low temperature is stable without gas molecules encaged.
Geometric Phases for Photons in an Optical Fiber and Some Related Predictions
GAO Xiao-Chun
Chin. Phys. Lett. 2002, 19 (5): 613-616 .  
Abstract   PDF(pc) (210KB) ( 322 )
We propose a quantum electrodynamic model for the description of the time evolution of the quantum states of the photons in an optical fiber. By means of this model, we are able to make three interesting predictions related to the geometric phases for photons.
Relativistic Energy Spectrum of a Completely Confined Particle and Fowler’s Treatment on Electron Assemblies with Relativistic Energies
REN Shang-Yuan
Chin. Phys. Lett. 2002, 19 (5): 617-619 .  
Abstract   PDF(pc) (179KB) ( 514 )
We give an analytical expression for the relativistic energy spectrum of a particle completely confined in a one-dimensional limited length in real space, based upon the wave property of particles, the relativistic energy-momentum relation and two mathematical formulas. Fowler’s treatment using a relativistic energy momentum relation of progressive waves in the electron assemblies in an enclosure, is justified in the large volume limit, by using the analytical expression obtained.
Quantum Central Processing Unit and Quantum Algorithm
Chin. Phys. Lett. 2002, 19 (5): 620-622 .  
Abstract   PDF(pc) (193KB) ( 403 )
Based on a scalable and universal quantum network, quantum central processing unit, proposed in our previous paper [Chin. Phys. Lett. 18(2001)166], the whole quantum network for the known quantum algorithms, including quantum Fourier transformation, Shor's algorithm and Grover's algorithm, is obtained in a unified way.
Teleportation of M-Qubit Unitary Operations
ZHENG Yi-Zhuang, GU Yong-Jian, GUO Guang-Can
Chin. Phys. Lett. 2002, 19 (5): 623-625 .  
Abstract   PDF(pc) (192KB) ( 516 )
We discuss teleportation of unitary operations on a two-qubit in detail, then generalize the bidirectional state teleportation scheme from one-qubit to M-qubit unitary operations. The resources required for optimal implementation of teleportation of an M-qubit unitary operation by using bidirectional state teleportation scheme are given.
Energy-Momentum Pseudo-tensor of Cylindrical Gravitational Waves of Both the Polarized States
WEN De-Hua, LI Fang-Yu, LIU Liang-Gang
Chin. Phys. Lett. 2002, 19 (5): 626-627 .  
Abstract   PDF(pc) (165KB) ( 319 )
According to the Einstein-Tolman expression of energy-momentum pseudo-tensor (EMPT), we calculate the EMPT of cylindrical gravitational waves (CGW) of both the polarized states (BPS) in cylindrical polar coordinates and Cartesian coordinates, respectively. We find that Cartesian coordinates are the more suitable coordinates to describe the CGW of BPS.
Random Matrix Approach to a Special Kind of Quantum Random Hopping
Chin. Phys. Lett. 2002, 19 (5): 628-631 .  
Abstract   PDF(pc) (484KB) ( 370 )
We use the random matrix method to study one kind of quantum random hopping. The Hamiltonian is a non-Hermitian matrix with some negative subdiagonal elements. Using potential theory, we calculate the eigenvalue density of an N x N matrix when N goes to infinity. We also obtain a least upper bound of the module of eigenvalues. In view of phase string theory in high temperautre superconductor, this model connects with localization-delocalization transition.
Parameter Identification and Tracking of a Unified System
LU Jun-An, TAO Chao-Hai, LÜ, Jin-Hu, LIU Min
Chin. Phys. Lett. 2002, 19 (5): 632-635 .  
Abstract   PDF(pc) (559KB) ( 422 )
The unified chaotic system contains the Lorenz and the Chen systems as two dual systems at the two extremes of its parameter spectrum and the Lü system as a special case. The parameter identification and tracking problem of the unified system are further investigated. In particular, a novel controller is designed for avioding the divergence of the factor 1/x. Numerical simulations are provided to show the effectiveness of these methods.
Light Hadron Masses in Quantum Chromodynamics with Valence Wilson Quarks at β = 6.25 from a Parallel PC Cluster
MEI Zhong-Hao, LUO Xiang-Qian, Eric B. GREGORY,
Chin. Phys. Lett. 2002, 19 (5): 636-639 .  
Abstract   PDF(pc) (390KB) ( 358 )
We present the results for π, ρ, proton and Δ masses from our recently built Pentium cluster and compare with the quenched Wilson fermion data presented by MILC and GF11 collaborations [Nucl.Phys.B (Proc.Suppl.) 60A(1998)3, Nucl. Phys. B 430(1994)179] at β = 6/g2 = 5.7 and 5.85 on the 83 x 32 lattice. New data are shown at β = 6.25 on the 123 x 36 and 163 x 32 lattices. Such a larger β value is useful for extrapolating the lattice results to the continuum limit. The smearing technique is systematically investigated and can greatly improve the spectrum data.
Light Hadron Masses from Lattice Quantum Chromodynamics on Asymmetric Lattices with Improved Actions
LIU Chuan, MA Jian-Ping
Chin. Phys. Lett. 2002, 19 (5): 640-643 .  
Abstract   PDF(pc) (295KB) ( 306 )
We simulate lattice quantum chromodynamics on asymmetric lattices with improved actions, where quenching approximation is used. These lattices have a spatial lattice spacing as at 0.3 and 0.4fm, and a temporal lattice spacing at from 0.14 to 0.08fm. The lattice spacing error due to as is greatly reduced through improving both quark- and gluon-actions at certain level. We find that masses of mesons have weak dependence on both lattice spacings, while the as and at dependence for baryons is more significant. With suitable modelling of these dependencies, we are able to obtain the nucleon mass in agreement with the experiment.
Massive Quark Propagator in the Colour-Superconducting Phase
HUANG Mei, ZHUANG Peng-Fei, ZHAO Wei-Qi,
Chin. Phys. Lett. 2002, 19 (5): 644-646 .  
Abstract   PDF(pc) (200KB) ( 417 )
A more general expression for the quark propagator including both chiral and diquark condensates has been derived by using energy projectors. This makes it possible to study the phase transition from hadron phase to color superconductivity phase in the moderate baryon density region by using the Feynman diagrammatic method or the Green function method.
A Monte Carlo Study on the Identification of Quark and Gluon Jets
YU Mei-Ling, LIU Lian-Shou
Chin. Phys. Lett. 2002, 19 (5): 647-649 .  
Abstract   PDF(pc) (414KB) ( 418 )
Three jets events in e+e- collisions at 91.2 GeV are investigated using both HERWIG and JETSET Monte Carlo generators. The angles among the three jets are used to identify the quark and gluon jets. An analysis at the parton level is carried out to ensure the reasonableness of this method and an angular cut is ultilized to improve the purity of this identification. The multiplicity inside the identified quark or gluon jets agrees with the quantum chromodynamic predictions qualitatively.
Band Structures of the Axial and Triaxial Deformed Nuclei in the Reflection Asymmetric Shell Model
GAO Zao-Chun, CHEN Yong-Shou, MENG Jie,
Chin. Phys. Lett. 2002, 19 (5): 650-653 .  
Abstract   PDF(pc) (209KB) ( 462 )
Band structures for axial and triaxial deformed nuclei are analysed in the reflection asymmetric shell model. The characteristics of the low-lying rotational spectra corresponding to different nuclear intrinsic shapes are given.
Relativistic Corrections to the Zeeman Effect of Helium Atom
GUAN Xiao-Xu, LI Bai-Wen, WANG Zhi-Wen
Chin. Phys. Lett. 2002, 19 (5): 654-656 .  
Abstract   PDF(pc) (211KB) ( 319 )
The high-order relativistic corrections to the Zeeman g-factors of helium atom are calculated. All the relativistic correction the term describing the motion of the mass center are treated as the perturbations. Most of our results are in good agreement with those of Yan and Drake [Phys. Rev. A50 (1994) R1980], who used the wavefunctions constructed by Hylleraas coordinates. For the correction δgL of g-factor of the 33P state in 4He, our result, 2.91415 x 10-7 a.u., should be more reasonable and accurate, although there are no experimental data available in the literature to compare.

Photoexcitation of Bipolaron in Conducting Polymers
LI Sheng, LONG De-Shun, SUN Xin,
Chin. Phys. Lett. 2002, 19 (5): 657-658 .  
Abstract   PDF(pc) (397KB) ( 405 )
We theoretically study the photoexcitation process in a conducting polymer with a non-degenerate ground state, where the carrier without spin is bipolaron. The dynamical simulation reveals a photoinduced phenomenon that a positive bipolaron is split into two polarons by absorbing one photon. The relaxation time of this photoinduced bipolaron-split is about 40 fs. It is predicted that this photoinduced phenomenon can be detected experimentally by observing the change of magnetic susceptibility.
Size Estimation and Time Evolution of Large Size Rare Gas Clusters by Rayleigh Scattering Techniques
LIU Bing-Chen, ZHU Pin-Pin, LI Zhao-Hui, NI Guo-Quan, XU Zhi-Zhan
Chin. Phys. Lett. 2002, 19 (5): 659-662 .  
Abstract   PDF(pc) (436KB) ( 479 )
Large rare gas clusters Arn, Krn and Xen were produced at room temperature in the process of supersonic adiabatic expansion. The cluster size is examined by a Rayleigh scattering experiment. Power variations of the average cluster size Nc with the gas backing pressure P0 give size scaling as Nn ∝ P2.00, resulting in the largest cluster sizes which are estimated in the present work to be about 1.5 x 104, 2.6 x 104 and 4.0 x 104 atoms (the corresponding diameters of the cluster spheres are about 9, 13 and 17 nm) for Ar, Kr and Xe, respectively. A time resolving Rayleigh scattering experiment was conducted to investigate the time evolution of cluster formation and decay processes. A surprising two-plateau structure of the time evolution characteristic of cluster formation and decay processes of Kr and Xe clusters was revealed as compared with a “normal”single structure for the case of Ar gas. In the second plateau, the intensity of the scattered light is enhanced greatly, by even as much as 62 times, over that in the first plateau, indicating a significant increase in cluster size. This finding supports the importance of nuclei in the gas condensation process and may be helpful for further insight into the phenomenon of clustering.
Electronic Structure of One-Dimensional Boron Chains with Density Functional Theory Method
YANG Chuan-Lu, ZHANG Zhi-Hong, REN Ting-Qi, LUO Hang-Zai, XUE Xiang-Yang
Chin. Phys. Lett. 2002, 19 (5): 663-665 .  
Abstract   PDF(pc) (256KB) ( 359 )
One-dimensional chain structures of Bn(n=6-16) are calculated by employing with 6-311G* basis set. The present calculations show that all the chain structures of interest have local minima with large binding energy per atom and short bond length. It is also found that many previous reported structures of B6 and B7 cluster are saddle points and the one-dimensional chain structures are the corresponding ground-state structures of B6 and B7 clusters.
Modified Two-Scale Model for Low-Grazing-Angle Scattering from Two-Dimensional Sea Surface
ZHANG Yan-Dong, WU Zhen-Sen
Chin. Phys. Lett. 2002, 19 (5): 666-669 .  
Abstract   PDF(pc) (488KB) ( 631 )
A hybrid model for describing fully developed two-dimensional sea surface is presented, which incorporates the sea spectrum into a fractal model, and an improved two-scale model is applied to calculate the scattering coefficient. In this model the slope distribution of the large-scale surface is obtained with numerical method instead of being assumed, and the projecting and ray tracing methods are applied to obtain the shadow function for arbitrary incident and scattering angles, moreover the effect of curvature of the large-scale undulating surface on scattered wave is taken into account, hence the precision of results have a great increase at low-grazing angles. Finally the amplitude and fractal characteristics of the scattered wave are analysed, which are of great significance for distinguishing and detecting targets on the sea.
Influence of Atomic Motion on Microlaser in an Optical Standing-Wave Cavity
ZHANG Jing-Tao, FENG Xun-Li, ZHANG Wen-Qi, XU Zhi-Zhan
Chin. Phys. Lett. 2002, 19 (5): 670-673 .  
Abstract   PDF(pc) (371KB) ( 294 )
We study the microlaser in an optical standing-wave cavity
injected with two-level atoms. The results showed the obvious influence of atomic center-of-mass motion on microlaser, such as the photon distribution, the linewidth, and the frequency shift. It was found that when the momentum of atoms is comparable to that of photons, the influence of atomic motion is dominated and the number of photons in microlaser can be greatly enhanced, owing to part of the atomic kinetic energy being transfered to the resonator. This work provides a comparison to the related studies on the atomic motion under special assumptions.

Analysis of Mode Quality Factors for Equilateral Triangle Semiconductor Microlasers with Rough Sidewalls
HUANG Yong-Zhen, GUO Wei-Hua, YU Li-Juan
Chin. Phys. Lett. 2002, 19 (5): 674-676 .  
Abstract   PDF(pc) (438KB) ( 564 )
The eigenmode characteristics for equilateral triangle resonator (ETR) semiconductor microlasers are analysed by the finite-difference time-domain technique and the Padé approximation. The random Gaussian correlation function and sinusoidal function are used to model the side roughness of the ETR. The numerical results show that the roughness can cause the split of the degenerative modes, but the confined modes can still have a high quality factor. For the ETR with 3 μm side length and the sinusoidal fluctuation, we can have the quality factor of 800 for the fundamental mode in the wavelength of 1500 nm, as the amplitude of roughness is 75 nm.
A Z-Scan Study of LiNbO3 Thin Films
WANG Qu-Quan, , SHI Jing, YANG Bai-Feng, LIU Hai-Lin, XIONG Gui-Guang, GONG Qi-Huang, XUE Qi-Kun
Chin. Phys. Lett. 2002, 19 (5): 677-679 .  
Abstract   PDF(pc) (390KB) ( 539 )
Poly-crystal LiNbO3 films on a fused SiO2 substrate are prepared by the rf sputtering technique. The third-order optical nonlinearity of the LiNbO3 films has been investigated by using Z-scan method with picosecond laser pulses at the wavelength of 532 nm. The nonlinear refractive index γ and nonlinear absorption coefficient β are determined to be -7.2 x 10-9cm2/W and 0.39cm/kW, respectively. The third-order optical nonlinearity x(3) of the LiNbO3 film is about 9.1 x 10-7 esu, which is considerably large than the reported value for Z-cut pure LiNbO3 crystals.
Efficient 266 nm Ultraviolet Beam Generation in K2Al2B2O7 Crystal
LU Jun-Hua, WANG Gui-Ling, XU Zu-Yan, CHEN Chuang-Tian, WANG Ji-Yang, ZHANG Cheng-Qian, LIU Yao-Gang
Chin. Phys. Lett. 2002, 19 (5): 680-681 .  
Abstract   PDF(pc) (308KB) ( 1202 )
The ultraviolet beam at 266 nm was obtained by fourth harmonic generation of 1064 nm Nd:YAG laser radiation through a nonlinear crystal K2Al2B2O7 (KABO). The fundamental frequency of a flash-lamp pumped Nd:YAG laser was doubled in a β-Ba2B2O4 crystal to generate a second harmonic output at the wavelength of 532 nm, and then doubled again in KABO crystal to generate the fourth harmonic output at 266 nm. The optical conversion efficiency from 532 to 266 nm was investigated for the first time, and 13% was achieved.

Second-Harmonic and Third-Harmonic Generation in the Thue-Morse Dielectric Superlattice
CAI Xiang-Bao
Chin. Phys. Lett. 2002, 19 (5): 682-684 .  
Abstract   PDF(pc) (303KB) ( 465 )
Theoretical work on the optical properties of the one-dimensional dielectric superlattice is extended. By means of a transfer matrix method, the second-harmonic and third-harmonic generation in a one-dimensional finite Thue-Morse dielectric superlattice is analysed. The electric field amplitude variables of the second-harmonic and third-harmonic can be expressed by the formula of matrices. Taking advantage of numerical procedure, we discuss the dependence of the second-harmonic and third-harmonic on the fundamental wavelength and the field amplitude variables of the fundamental wave. High conversion efficiency of the third-harmonic can be obtained at some special fundamental wavelength.

Photoelastic Effect and Optimal Waveguide Structure in InGaAsP/InP Double Heterostructures
XING Qi-Jiang
Chin. Phys. Lett. 2002, 19 (5): 685-688 .  
Abstract   PDF(pc) (470KB) ( 446 )
Stress field profiles and dielectric constant variations in InGaAsP/InP double heterostructures caused by a 110 nm-thick W0.95Ni0.05 metal thin film strain stripe are calculated. Both theoretical and experimental results demonstrate the form of photoelastic waveguide structure in the InGaAsP/InP double heterostructures. For a 4μm-width W0.95Ni0.05 thin film strain stripe, the difference between dielectric constants of waveguide at the center and the edge of stripe is $9 \times 10-2 - 2 x 10-2 in the depth range from 0.2 to 2μm of the semiconductor. At a given depth, the width of strain stripe for optimal waveguide structure is determined. The maximal change of dielectric constant for the waveguide is an inverse proportion of the depth.
Second-Harmonic Generation of Bessel Beams in Lossy Media
DING De-Sheng, XU Jian-Yi, WANG Yao-Jun
Chin. Phys. Lett. 2002, 19 (5): 689-690 .  
Abstract   PDF(pc) (176KB) ( 418 )
We present a further analysis for the second-harmonic generation of Bessel beams in lossy media. The emphasis is put on the effect of absorption to the radial pattern of the second-harmonic beam. It is shown that within the absorption length of the second harmonic, the Bessel second harmonic beam approches limited-diffracton in the radial direction and behaves as in the case of lossless media.
Experimental Investigation of the Plasma Wake of a Blunt Cone
LI Jun-Feng, Jin-Xiang, ZHANG Chuan-Bao, SONG Fa-Lun
Chin. Phys. Lett. 2002, 19 (5): 691-694 .  
Abstract   PDF(pc) (641KB) ( 310 )
The flow field of plasma wake is studied by analysing the saturated ion current of multiple scanning probes with the method of chaos dynamics. The laminated structure of near-wake is verified. It is observed at x > 250 mm (x is the axis along the flow field) the far-wake flow field is similar to the free flow field, and turbulent structure exists in near-wake, but there is no turbulence in far-wake. The spatially intermittent character of flow field can be discovered, which seems to produce some relationship between the spatially intermittent character and the turbulence. The results show that the analytic method of chaos dynamics is sensitive to non-periodic signal.

Steady State of the Dusty Plasma in a dc Discharge
MA Jin-Xiu, YU Ming Young, LIANG Xiao-Ping, ZHENG Jian, LIU Wan-Dong, YU Chang-Xuan
Chin. Phys. Lett. 2002, 19 (5): 695-697 .  
Abstract   PDF(pc) (315KB) ( 290 )
The steady state formed by the diffusion of plasma particles in an inhomogeneous dusty plasma is investigated theoretically and compared with our previous experimental results [Nucl. Fusion Plasma Phys. 20(2000)180 (in Chinese); Phys. Plasmas 8(2001)1459]. The negatively charged dust grains with average charge number of the order of 105 on a single grain enhance the plasma inhomogeneity by decreasing the diffusion velocity, and can cause significant depletion of electrons. The theoretical electron density profile is in good agreement with the experiment, and the theoretical profile of the electron-to-ion density ratio is in reasonable agreement with experimentally estimated data.

Effect of Laser Pulse Shape on Wake Field in Relativistic Intense Laser-Plasma Interaction
XIE Bai-Song, , LIU An-Dong,
Chin. Phys. Lett. 2002, 19 (5): 698-700 .  
Abstract   PDF(pc) (361KB) ( 386 )
We study the effect of laser pulse shape on plasmas wake field driven by an intense laser beam. It is found that the modified asymmetric laser pulse shape with sharpen rising front and broaden falling back, due to some nonlinear interactions of an intense laser pulse with plasmas, can significantly enhance the magnitude of the wake field.
Preliminary Observation on Coordination of Pellet Injection and Ion Bernstein Wave on a HT-7 Tokamak
YANG Yu, ZHAO Yan-Ping, LI Jian-Gang, WAN Bao-Nian, LUO Jia-Rong, GU Xue-Mao
Chin. Phys. Lett. 2002, 19 (5): 701-703 .  
Abstract   PDF(pc) (403KB) ( 396 )
A pellet injection (PI) experiment was performed during the application of ion Bernstein wave on a HT-7 Tokamak. A preliminary coordination effect was observed. With a lower wave power, shortly after PI, the coupling of the wave was enhanced, and the particle confinement was improved. With higher power, off-axis heating for 15% at about a/3 in the low field side was observed.
Effects of Ambient Pressure on Bubble Characteristics
LU Xin-Pei, LIU Ming-Hai, JIANG Zhong-He, PAN Yuan
Chin. Phys. Lett. 2002, 19 (5): 704-706 .  
Abstract   PDF(pc) (378KB) ( 405 )
The effects of the ambient pressure Pambient on the characteristics of bubble of pulsed discharge in water are investigated. The simulation results show that, when Pambient increases from 1atm to 100 atm, the bubble radius R decreases from 4 cm to 7 mm, and its pulsation period decreases from 8 ms to 0.2 ms. The results also show that the peak pressure of the first shock wave is independent of Pambient, but the peak pressure of the second shock wave caused by the bubble reexpansion decreases when Pambient increases. On the other hand, the larger the ambient pressure, the larger the peak pressure of the plasma in the bubble, while the plasma temperature is independent of Pambient.
Growth and Optical Properties of Double Heterostructure GaN/InGaN/GaN Films with Large Composition
Chin. Phys. Lett. 2002, 19 (5): 707-710 .  
Abstract   PDF(pc) (477KB) ( 691 )
The double heterostructure GaN/InGaN/GaN films with different thickness of the InGaN layer were grown at 780°C or 800°C by metal-organic chemical vapor deposition. The samples were investigated using x-ray diffraction (XRD), room-temperature photoluminescence (PL) and Raman scattering. The dependences of the samples on both the growth temperature and the thickness of the InGaN layer were studied. The composition of InGaN was determined by the results of XRD, and the bowing parameter of InGaN was calculated in term of the PL spectra. When the thickness of the InGaN layer was reduced, the phase separation of InGaN was found in some samples. The Raman frequency of A1 (LO) and E2 (low) modes in all the samples shifted and did not agree with Vegard's law.
Dynamical Behaviour of H2O in Silica Gel
WANG Yan, DONG Shun-Le
Chin. Phys. Lett. 2002, 19 (5): 711-713 .  
Abstract   PDF(pc) (389KB) ( 384 )
The vibrational spectra of silica gel with low concentrations of water, 3% and 10%, were studied with inelastic neutron scattering at 5 K. The experimental spectrum for 3% water in silica gel shows dramatic changes compared to the spectra for the other known ice phases in the energy transfer region of 2-140 meV. Its intermolecular librational band is shifted to lower energy by about 20 meV (or by a factor 1.43) compared to ice Ih, and shows a similar librational band with liquid at 290K. A significant excess of low frequency vibration modes (< 7meV) over normal ice Ih and very wide acoustic peak (4-15 meV) were observed. Experimental data indicate that little H2O (3%) in silica gel exhibits a strong softening of hydrogen bonds compared to bulk normal ice and all the other known ice phases.
Influence of Ba2+ and Pb2+ Ions on the Raman Dominating Active Vibronic Mode in Strontium Nitrate Crystals
LI Chao-Rong, WU Li-Jun, CHEN Wan-Chun,
Chin. Phys. Lett. 2002, 19 (5): 714-716 .  
Abstract   PDF(pc) (497KB) ( 372 )
The composition of Sr(NO3)2 crystals grown from an aqueous solution doped with Ba2+ and Pb2+ were characterized by electron probe microanalysis technique. It was found that Ba2+ is enriched in {100} sectors and Pb2+ in {111} sectors. Raman spectra of different parts in these crystals at room temperature in the ranges of 1038-1070cm-1 and 650-1150cm-1 were investigated. The results indicated that barium and lead shift the Raman dominating peaks to the lower frequency and broaden the full width at half maximum. Furthermore, barium probably degrades the properties of the Sr(NO3)2 Raman shifter while lead is anticipated to improve it.
Electroluminescence of Boron and Nitrogen Doped Diamond Thin Films
WANG Xiao-Ping, WANG Li-Jun, ZHANG Bing-Lin, YAO Ning, MA Hui-Zhong, SONG Tian-Fu, LI Guang-Ting, YANG Shi-E, BIAN Chao, LI Hui-Jun, MA Bing-Xian
Chin. Phys. Lett. 2002, 19 (5): 717-719 .  
Abstract   PDF(pc) (466KB) ( 556 )
An electroluminescence (EL) device is investigated by using boron and nitrogen double-doped diamond films. The characteristics of the EL spectrum and the dependence of EL intensity on boron and nitrogen impurity are investigated. The experiment indicated that the intensity of EL increases obviously and the threshold voltage decreases with increasing nitrogen impurity within our doped level, meanwhile the highest emission line changes from the blue region (peaks at 470 nm) to the yellow region (peaks at 584 nm).
Reaction Limited Aggregation with Anisotropic Island-Edge Exchange in Surfactant-mediated Epitaxy
WANG Dai-Mu, SUN Xia, WU Zi-Qin
Chin. Phys. Lett. 2002, 19 (5): 720-723 .  
Abstract   PDF(pc) (484KB) ( 437 )
We simulate the two-dimensional pattern formation in surfactant-mediated epitaxy using a kinetic model, in which the nucleation and growth of the stable islands are controlled by the exchange process between surfactant atoms and deposited atoms. Our model assumes the following. (1) the exchange barrier preventing an adatom from attaching to an existing island edge depends on the numbers of the adatoms nearest and next-nearest neighbours belonging to the island, (2) The exchange processes at the two different types of steps are associated with different energy barriers. The simulations generate a series of surface morphologies ranging from fractal structures to compact triangular shapes, very similar to those observed in recent experiments.
Effect of Emitter Position on Emission Intensity in an Organic Planar Microcavity
ZHAO Jia-Min, MA Feng-Ying, LIU Xing-Yuan, LIU Yun, CHU Guo-Qiang, NING Yong-Qiang, WANG Li-Jun,
Chin. Phys. Lett. 2002, 19 (5): 724-726 .  
Abstract   PDF(pc) (272KB) ( 410 )
We have fabricated a λ/2-length planar microcavity between two silver mirrors that had the same thickness and consisted of sandwich structure LiF1/Alq3/LiF2. By altering the relative thickness of the two LiF layers, the adjustment of the position of thin layer Alq3 in the microcavity was achieved and the apparent photoluminescence (PL) intensity change was observed. The maximal emission intensity device, corresponding to the luminescence layer located at antinode, is four times of the minimal one whose luminescence layer is near a silver mirror that is close to a node. This indicates that the coupling between vacuum electric-field and dipole strongly affects the emission intensity into the forward direction of the microcavity plane. Compared the PL intensity between the microcavity device and the non-cavity one with the same sandwich structure LiF1/Alq3/LiF2 in free space, at the resonance wavelength a maximal enhancement factor of nine is obtained.
Ground-State Properties of a Local Sine-Gordon Model with Two Frequencies
CHEN Yu-Guang, CHEN Hong, ZHANG Yu-Mei
Chin. Phys. Lett. 2002, 19 (5): 727-729 .  
Abstract   PDF(pc) (411KB) ( 406 )
The local sine-Gordon model with two frequencies is studied by a variational method. The renormalization mass and classical field path are calculated. We find an Ising-like phase transition, which is analogous in the global sine-Gordon model with two frequencies. A full phase diagram is given.
An Exciton Bound to a Neutral Donor in Quantum Dots
XIE Wen-Fang
Chin. Phys. Lett. 2002, 19 (5): 730-732 .  
Abstract   PDF(pc) (220KB) ( 306 )
The binding energies for an exciton (X) trapped in a two-dimensional quantum dot by a neutral donor have been calculated by using the method of few-body physics for the heavy hole (σ = 0.196) and the light hole (σ =0.707). We find that the (D0,X) complex confined in a quantum dot has in general a larger binding energy than those in a two-dimensional quantum well and a three-dimensional bulk semiconductor, and the binding energy increases with decrease of the dot radius. At dot radius R → ∞, we compare our calculated result with the previous results.

Critical Behaviour of Sintered SrRuO3
HOU Deng-Lu, JIANG En-Yong, LI Feng-Wu, BAI Hai-Li, ZHOU Xue-Zhi, Henry KUNKEL, Gwyn WILLIAMS
Chin. Phys. Lett. 2002, 19 (5): 733-735 .  
Abstract   PDF(pc) (434KB) ( 439 )
From the measurements of the ac susceptibility of SrRuO3, we determine the critical temperature Tc =159.7±0.2 K and critical exponents δ =2.50±0.15(from the critical isotherm) or δ =3.17±0.20 (from magnetization versus magnetic field at Curie temperature), γ+β = 1.50±0.05 (from the temperature dependence of the internal field of the crossover line), and γ= 0.96±0.05 (from the temperature dependence of the susceptibility along the same line). These exponent values are very close to those predicted by the mean field model.
Fractal Study of Multi-branched Domains in Garnet Bubble Films
LI Dan, ZHENG De-Juan, ZHOU Yan, HAN Bao-Shan
Chin. Phys. Lett. 2002, 19 (5): 736-738 .  
Abstract   PDF(pc) (1112KB) ( 296 )
The line-measuring dimension Dline has been developed and selected to describe the curved and branched patterns of multi-branched domains (MBDs) formed by using the“low-bias-field method”in magnetic garnet bubble films. The definition of Dline is given. The domain pattern processing and the “double boundary description” of MBDs are introduced. It has been verified that the MBD patterns truly possess the characteristic of fractal structure over a certain range. The meaningful Dline seems to be a better parameter to quantitatively describe the curved and branched structure of MBDs, and can be related to the nucleation of vertical Bloch lines in their walls.

Two-Photon-Absorption Induced Superradiance of a New Organic Dye PSPS
ZHOU Guang-Yong, WANG Dong, WANG Xiao-Mei, YANG Sheng-Jun, XU Xin-Guang, ZHAO Xian, SHAO Zong-Shu, JIANG Min-Hua
Chin. Phys. Lett. 2002, 19 (5): 739-741 .  
Abstract   PDF(pc) (483KB) ( 415 )
The linear and nonlinear optical properties of a new two-photon absorption (TPA) dye, trans-4-(4'-pyrrolidinyl styryl)-N-methyl pyridinium methyl sulfate (abbreviated as PSPS) is reported. Intense red superradiance with a peak located at 625nm can be observed from PSPS solution in benzyl alcohol when pumped by a focused picosecond laser beam operated at 1064nm. The lifetimes of one-photon absorption (OPA) and TPA fluorescence were measured to be 370 and 384ps, respectively. The pulse widths of OPA and TPA superradiance were 60 and 58 ps, respectively. The highest net upconversion efficiency from the absorbed pump laser to the upconverted superradiance is 8.3% at the pump energy of 0.6 mJ.
Updated Multichannel Infrared Solar Spectrograph at Purple Mountain Observatory
LI Hui, YOU Jian-Qi, WU Qin-Di, YU Xing-Feng
Chin. Phys. Lett. 2002, 19 (5): 742-744 .  
Abstract   PDF(pc) (986KB) ( 330 )
We describe the newly updated multichannel infrared solar spectrograph at the Purple Mountain Observatory that now uses three Apogee AP7p grade 1 scientific CCDs as its detectors and works at three wavelengths, HeI 10830Å, cAII 8542Å and Hα, simultaneously. The spectral resolutions of these lines are 0.04776, 0.05113 and 0.05453Å per pixel, respectively. Some observation examples are presented. The observed profiles of the three lines demonstrate that redshift and asymmetry exist in the impulsive phase of the given disc flare and both blueshift and redshift exist in the presented flare spray in the impulsive phase of a limb flare. They also indicate that there exists horizontal expansion in addition to the quick radial motion in the flare spray.
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