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Volume 20 Issue 7
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Original Articles
A Maple Package for the Painlevé Test of Nonlinear Partial Differential Equations
XU Gui-Qiong, LI Zhi-Bin
Chin. Phys. Lett. 2003, 20 (7): 975-978 .  
Abstract   PDF(pc) (223KB) ( 1090 )
A Maple package, named PLtest, is presented to study whether or not nonlinear partial differential equations (PDEs) pass the Painlevé test. This package is based on the so-called WTC-Kruskal algorithm, which combines the standard WTC algorithm and the Kruskal simplification algorithm. Therefore, we not only study whether the given PDEs pass the test or not, but also obtain its truncated expansion form related to some integrability properties. Several well-known nonlinear models with physical interests illustrate the effectiveness of this package.

An Exact Solution to the Master Equation for the Dissipative Harmonic Oscillator Driven by an External Field
HOU Bang-Pin, WANG Shun-Jin, YU Wan-Lun
Chin. Phys. Lett. 2003, 20 (7): 979-981 .  
Abstract   PDF(pc) (200KB) ( 758 )
By using the algebraic structure in the operator dual space in the master equation for the driven dissipative harmonic oscillator, we have rewritten the master equation as a Schrödinger-like equation. Then we have used three gauge transformations and obtained an exact solution to the master equation in the particle number representation.

Random Phases and Energy Dispersion
LIU Quan-Hui, LIU Tian-Gui, BAN Wei-Quan
Chin. Phys. Lett. 2003, 20 (7): 982-984 .  
Abstract   PDF(pc) (212KB) ( 351 )
Using 2N+1 successive stationary states centered at nth, we construct a rectangular wave packet in which the stationary states are superimposed with the equal weight √2N+1. With the requirement of the wave packet to be a quasi-classical state, the number N is determined by minimizing the uncertainty ΔxΔp. Since the stationary state can only be determined to within an arbitrary multiplicative complex phase factor of unit magnitude, a number of N is obtained as a set of the phases are given. For a harmonic oscillator, when all of the phase factors are essentially the same, we have N ≈ [61/3n2/3] with [x] signifying the integral part of positive number x. When every phase in the phase factors is given by a random number generated in a closed interval [0,2π] and when n ≥ 10, the probability of appearance of N is roughly 1/2N when N = 1 to 7, and does not exceed 0.01 when N ≥ 8.
Quantum Entanglement of Two Atoms Inside an Optical Cavity
LI Shang-Bin, XU Jing-Bo
Chin. Phys. Lett. 2003, 20 (7): 985-987 .  
Abstract   PDF(pc) (280KB) ( 620 )
We investigate the system, which consists of two two-level atoms confined in a linear trap which has been surrounded by an optical cavity, with the Milburn model of intrinsic decoherence, and find an explicit analytical solution of the Milburn equation. The entanglement between the two atoms is then calculated by making use of concurrence. The influence of intrinsic decoherence on the entanglement is also discussed.

Testing the Dissipative Type of a Qubit Interacting with Environment
ZENG Hao-Sheng, KUANG Le-Man, GAO Ke-Lin
Chin. Phys. Lett. 2003, 20 (7): 988-990 .  
Abstract   PDF(pc) (205KB) ( 344 )
We propose a method to test the correctness of the coupling model of a qubit interacting with environment and to determine the type of dissipation. The environment is modeled by a bath of oscillators with infinite degrees of freedom and the qubit-bath coupling is chosen to be a general dissipation-decoherence form. The proposed method can be realized in current experiments.
Universal Quantum Gates Based on Both Geometric and Dynamic Phases in Quantum Dots
YANG Kai-Yu, ZHU Shi-Liang, WANG Zi-Dan,
Chin. Phys. Lett. 2003, 20 (7): 991-994 .  
Abstract   PDF(pc) (212KB) ( 544 )
A large-scalable quantum computer model, whose qubits are represented by the subspace subtended by the ground state and the single exciton state on semiconductor quantum dots, is proposed. A universal set of quantum gates in this system may be achieved by a mixed approach, composed of dynamic evolution and nonadibatic geometric phase.
Big Bounce Singularity of a Simple Five-Dimensional Cosmological Model
XU Li-Xin, LIU Hong-Ya, WANG Bei-Li
Chin. Phys. Lett. 2003, 20 (7): 995-998 .  
Abstract   PDF(pc) (234KB) ( 630 )
The big bounce singularity of a simple five-dimensional cosmological model is studied. Contrary to the standard big bang space-time singularity, this big bounce singularity is found to be an event horizon at which the scale factor and the mass density of the universe are finite, while the pressure undergoes a sudden transition from negative infinity to positive infinity. By using coordinate transformation it is also shown that before the bounce the universe contracts deflationary. According to the proper-time, the universe may have existed for an infinitely long time.
Transition to Phase Synchronization Through Generalized Synchronization
GAO Jian, ZHENG Zhi-Gang, HE Dai-Hai, ZHANG Ting-Xian,
Chin. Phys. Lett. 2003, 20 (7): 999-1002 .  
Abstract   PDF(pc) (587KB) ( 371 )
Synchronization in drive-response chaotic systems is studied. For a small mismatch of the natural frequency of the drive and response oscillators, phase synchronization comes before generalized synchronization. For moderate and even large parameter misfits, generalized synchronization can be achieved before phase synchronization. The mechanism of these two different bifurcations is interpreted in terms of the local-minimal-fluctuation method. It is found that the qualitative changes of local-minimal-fluctuations of the response system well manifests the appearance of generalized synchronization.
Conservation Laws in Sine-Gordon Equation
SHI Li-Na, CAI Hao, LI Cheng-Fang, HUANG Nian-Ning
Chin. Phys. Lett. 2003, 20 (7): 1003-1005 .  
Abstract   PDF(pc) (181KB) ( 709 )
There are two conservation quantities needed to derive conservation laws of sine-Gordon equation in a frame of laboratory reference. One of them could be derived easily with a standard process, but the other could not. After the gauge transformation e-iθσ2/2 is introduced, we simply obtain the other one without any questionable assumption.

New Coherent Structures in the Generalized (2+1)-Dimensional Nizhnik-Novikov-Veselov System
ZHANG Jie-Fang, , MENG Jian-Ping
Chin. Phys. Lett. 2003, 20 (7): 1006-1008 .  
Abstract   PDF(pc) (752KB) ( 467 )
In high dimensions there are abundant coherent soliton excitations. From the known variable separation solutions for the generalized (2+1)-dimensional Nizhnik-Novikov-Veselov system, two kinds of new coherent structures in this system are obtained. Some interesting novel features of these structures are revealed.

Calculation of Free Energy of the Integrable Landau-Lifshitz Model
CAI Cong-Zhong, WANG Wan-Lu, CHEN Yu-Zong,
Chin. Phys. Lett. 2003, 20 (7): 1009-1012 .  
Abstract   PDF(pc) (218KB) ( 316 )
The generalized Bethe-ansatz method of thermodynamic analysis of integrable systems was employed to compute the free energy of a classical integrable model, i.e., the Landau-Lifshitz model. Using the action-angle variables of the model and by imposing a periodic boundary condition, we derive a phase-shifted density of states for the excitations of the system. The free energy, in the thermodynamic limit, can be expressed analytic in terms of two coupled nonlinear integral equations of the finite temperature excited energy for effective phonons and kinks (antikinks). We solve these equations iteratively for a special case that the model is in the limit of anisotropic strong yz coupling.

Δ-scaling and Information Entropy in Ultra-Relativistic Nucleus-Nucleus Collisions
MA Guo-Liang, MA Yu-Gang, WANG Kun, SA Ben-Hao, SHEN Wen-Qing, HUANG Huan-Zhong, CAI Xiang-Zhou, ZHANG Hu-Yong, LU Zhao-Hui, ZHONG Chen, CHEN Jin-Gen, WEI Yi-Bin, ZHOU Xing-Fei
Chin. Phys. Lett. 2003, 20 (7): 1013-1016 .  
Abstract   PDF(pc) (643KB) ( 412 )
The Δ-scaling method has been applied to ultra-relativistic p+p, C+C and Pb+Pb collision data simulated using a high energy Monte Carlo package, LUCIAE 3.0. The Δ-scaling is found to be valid for some physical variables, such as charged particle multiplicity, strange particle multiplicity and number of binary nucleon-nucleon collisions from these simulated nucleus-nucleus collisions over an extended energy ranging from Elab = 20 to 200 A GeV. In addition we derive the information entropy from the multiplicity distribution as a function of beam energy for these collisions.
Scaling Laws and Occurrence Conditions of Nuclear Halo
LIU Zu-Hua, ZHANG Xi-Zhen, ZHANG Huan-Qiao
Chin. Phys. Lett. 2003, 20 (7): 1017-1020 .  
Abstract   PDF(pc) (330KB) ( 416 )
Available data regarding the nuclear halo candidates are systematically analysed in terms of the asymptotic normalization coefficients measured experimentally. On the other hand, we have put forth conditions for nuclear halo formation, and compared with the experimental data. Based on the analytical expressions of the expectation value for the operator r2 in a finite square well potential, we have presented the improved scaling laws for the dimensionless quantity < r2 >/R2 of nuclear halo, which seem to be in reasonable agreement with the experimental data.

Proton Halo or Skin in the Excited States of Light Nuclei
CHEN Jin-Gen, CAI Xiang-Zhou, ZHANG Hu-Yong, SHEN Wen-Qing, REN Zhong-Zhou, JIANG Wei-Zhou, MA Yu-Gang, ZHONG Chen, WEI Yi-Bin, GUO Wei, ZHOU Xing-Fei, MA Guo-Liang, WANG Kun
Chin. Phys. Lett. 2003, 20 (7): 1021-1024 .  
Abstract   PDF(pc) (413KB) ( 604 )
Properties of nuclei 13,15N and 9B are investigated in the relativistic mean-field theory with NLZ and NL3 force parameters. The calculated binding energies are very close to the experimental ones. The calculations show that the first excited state (1p1/2) in 9B, the first excited state (2s1/2) in 13N and the second excited state (2s1/2) in 15N are weakly bound. In particular for 13N and 15N, the proton density distributions in the two above excited states have a long tail and the rms radii of the last proton are greatly larger compared with their respective matter radii. It is predicted that a proton halo exists in the first excited state of 13N and in the second excited state of 15N, respectively. It also indicates that the first excited state in 9B is a proton skin state.
Gamow-Teller Resonance of 90Zr in a Relativistic Approach
MA Zhong-Yu, , CHEN Bao-Qiu,
Chin. Phys. Lett. 2003, 20 (7): 1025-1027 .  
Abstract   PDF(pc) (252KB) ( 661 )
We establish the formalism of nuclear spin-isospin excitations, especially the Gamow-Teller resonance in a fully consistent relativistic random phase approximation. A relativistic form of the Landau-Migdal parameter g' is adopted as a residual spin-isospin correlation force. In the non-relativistic limit it reproduces the excitation energy of the giant Gamow-Teller resonance state obtained in the non-relativistic model. The Gamow-Teller resonance for finite nuclei is investigated in a relativistic approach for the first time. It is found that the Ikeda sum rule of 90Zr is quenched about 8% in the Hartree as well as the correlated strengths due to the poles of the negative Dirac states at energies above 1 GeV.

Evidence for a Possible E(5) Symmetry in 130Xe
ZHANG Da-Li, LIU Yu-Xin,
Chin. Phys. Lett. 2003, 20 (7): 1028-1030 .  
Abstract   PDF(pc) (252KB) ( 537 )
By analysing the energy spectrum and E2 transition branching ratios, we show that the E(5) symmetry predictions agree well with the experimental data of nucleus 130Xe. Compared the calculated results with those in the framework of the interacting boson model, it is found that the nucleus 130Xe is definitely a nucleus in the transitional region from U(5) to O(6) symmetry. 130Xe is then another empirical evidence of the nucleus with E(5) symmetry.

Beta Decay of Neutron-Rich Nucleus 208Hg
ZHANG Li, K. Morita, HU Qing-Yuan, A. Yoshida, ZHAO Jin-Hua, ZHENG Ji-Wen, LI Zhan-Kui, Y. H. Pu, H. Kudo, Y. Yano
Chin. Phys. Lett. 2003, 20 (7): 1031-1033 .  
Abstract   PDF(pc) (417KB) ( 484 )
The β- decaying γ scheme of the neutron-rich nuclide 208Hg has been determined for the first time. The 208Hg was produced in multi-nucleon transfer reaction taking place in the bombardment of 18O-beam on natural lead target, and the Hg-element products were separated with a gas-thermochromatography technique. The γ-ray single and γ-γ coincident spectra were measured. A partial 208Hg γ scheme was proposed. Twenty-six γ rays were assigned to follow the β- decay of 208Hg. At the same time, a new level structure of the daughter nucleus 208Tl was constructed, in which three new levels at 1.72 MeV, 1.652 MeV, and 1.362 MeV were affirmed. The experimental 208Tl level structure was compared with a shell-model calculation.
Measurement of One- and Two-Neutron Transfers in Reaction of 6He+9Be at 25 MeV/u
GE Yu-Cheng, YE Yan-Lin, ZHENG Tao, WANG Quan-Jin, LI Zhi-Huan, LI Xiang-Qing, JIANG Dong-Xing, A. Ozawa, Y. Yamaguchi, C. Wu, R. Kanungo, D. Fang, I. Tanihata
Chin. Phys. Lett. 2003, 20 (7): 1034-1037 .  
Abstract   PDF(pc) (686KB) ( 445 )
The cross sections of one- and two-neutron transfers induced by 6He at 25 MeV/u on a 9Be target were measured in RIKEN. Clear identification of the recoiled Be isotopes was achieved. In total five 11Be and 371 10Be events, the corresponding two- and one-neutron transfers were obtained and analysed for transfer reaction cross sections. The results are useful to determine the spectroscopic factors of the internal halo structure of the 6He nucleus.

Controlling the Orientation and Alignment of Reagent Molecules by a Polarized Laser
CONG Shu-Lin, HAN Ke-Li, LOU Nan-Quan
Chin. Phys. Lett. 2003, 20 (7): 1038-1039 .  
Abstract   PDF(pc) (182KB) ( 490 )
The expressions used for controlling the alignment and orientation of reagent molecules are derived. The problem to the control of the orientation and alignment of reagent molecules by the polarization direction and propagation direction of laser is discussed.

Polarization-Dependence of Coulomb Explosion of CO Irradiated with an Intense Femtosecond Laser Pulse
CHEN Jian-Xin, MA Ri, REN Hai-Zhen, LI Xia, YANG Hong, GONG Qi-Huang
Chin. Phys. Lett. 2003, 20 (7): 1040-1042 .  
Abstract   PDF(pc) (416KB) ( 878 )
Laser-induced Coulomb explosion of CO is studied experimentally using differently polarized femtosecond laser pulses of 2 x 1015W/cm2 intensity at λ = 800 nm. The channels of molecular Coulomb explosion are observed to be independent of the laser polarizations. The critical distance R is deduced to be larger for the circularly polarized light in comparison with the linearly polarized light. The initial emissions of C+, C2+, O+, and O2+ ions are anisotropic for linear polarization and isotropic for circular polarization. The suppression of ionization occurs for the elliptically and circularly polarized lasers.

Birefringence Grating and Surface Grating in Azobenzene Polymer Liquid Crystal Films Investigated by Near-Field Optical Method
ZHANG Jiang-Ying, MING Hai, WANG Pei, SUN Xiao-Hong, LU Yong-Hua, WU Yun-Xia, XIE Jian-Ping, ZHANG Qi-Jin, LIU Jian, XIE Ai-Fang, ZHANG Ze-Bo, GU Ben-Yuan
Chin. Phys. Lett. 2003, 20 (7): 1043-1046 .  
Abstract   PDF(pc) (460KB) ( 501 )
The birefringence grating and the surface grating in azobenzene polymer liquid-crystal (Azo-PLC) films are studied by a near-field scanning optical microscope. With laser irradiation, the refractive index change caused by birefringence and the sinusoidal surface profile are observed at the near-field transmittance image and the surface topography of the grating. The grating period and the peak-to-peak value of the sinusoidal surface profile are 0.8μm and 40 nm, respectively. The maximum diffractive efficiency of the grating is 2%. The dynamic process of the grating formation is probed and analysed. The mass diffusion responsible for the formation of the surface grating due to the temperature rise is analysed.
Insensitivity of Speckle Multiplexing to Multi-longitudinal Modes of Laser in Volume Holographic Storage
WANG Jin-Nan, HE Shu-Rong, HE Qing-Sheng, HUANG Dong, JIN Guo-Fan
Chin. Phys. Lett. 2003, 20 (7): 1047-1050 .  
Abstract   PDF(pc) (403KB) ( 574 )
If a diode pumped solid state laser is used in a holographic storage system, its multi longitudinal modes may damage the angular selectivity of the hologram and introduce more cross talk in the system. By theoretical analysis, we found that with adopting the speckle multiplexing scheme, holographic systems are no longer sensitive to the multi longitudinal modes of the laser source, and consequently the damage described above could be well suppressed. Moreover, the following high density storage experimental results also express strong advocacy of this conclusion. This result may greatly prompt the miniaturization of a holographic storage system.

Diarylethene Materials for Re-writable Volume Holographic Data Storage
LIU Guo-Dong, HE Qing-Sheng, DING De-Hua, WU Min-Xian, JIN Guo-Fan, PU Shou-Zhi, ZHANG Fu-Shi, LIU Xue-Dong, YUAN Peng
Chin. Phys. Lett. 2003, 20 (7): 1051-1053 .  
Abstract   PDF(pc) (360KB) ( 1154 )
The photochromic diarylethene, 1,2-bis(2-methyl-5-(4-formylphenyl)-thien-3-yl)perfluorocyclopentene (1a) is studied and its applicable potential in re-writable volume holographic data storage is verified. Holographic recording films of 10-μm thickness have been fabricated. The refractive index modulation (Δn = 1.15 x 10-3) between the open- and close-ring forms is detected to be large enough so that the films are suitable for the production of volume holographic storage. The experiments of angle multiplexing and rewriting holograms show that the materials are fit for volume holographic data storage.

Atomic Funnel Composed of an HE11-Mode Output Hollow Beam
NI Yun, LIU Nan-Chun, YIN Jian-Ping,
Chin. Phys. Lett. 2003, 20 (7): 1054-1057 .  
Abstract   PDF(pc) (576KB) ( 429 )
Using exact solutions of Maxwell equations based on the vector model, we calculate the diffracted near- and far-field distributions of the HE11-mode output beam from a micron-sized hollow optical fibre under the Fresnel approximation, and compare the differences between the HE11- and LP01-mode output beams. Our study shows that it is unsuitable to calculate the diffracted near-field distribution of the hollow fibre by using weakly waveguiding approximation, and the near- and far-field intensity distributions of the HE11-mode output beam are doughnut-like, which can be used to form a simple atomic funnel as it is blue-detuned.

A Step-by-Step Tunable Compound External Cavity Semiconductor Laser with Two-Side Feedback Coupling
WU Ke-Ying, ZHANG Han-Yi, ZHENG Xiao-Ping, TENG Xiang, SHI Wei-Wei, GUO Yi-Li
Chin. Phys. Lett. 2003, 20 (7): 1058-1060 .  
Abstract   PDF(pc) (573KB) ( 696 )
A kind of compound external cavity semiconductor lasers (CECSL) is presented, by which laser with a discretely tunable wavelength can be obtained to meet the potential demands of the wavelength division multiplexing system. By the introduction of two-side feedback coupling in the CECSL, the CECSL can operate more efficiently, and its side-mode suppression ratio is high up to 50 dB.

Investigation of External Optical Feedback Resistance of IC-DFB and GC-DFB Lasers Using a Very Simple Experimental Set-up
SUN Chang-Zheng, XIONG Bing, LUO Yi, NAKANO Yoshiaki
Chin. Phys. Lett. 2003, 20 (7): 1061-1063 .  
Abstract   PDF(pc) (369KB) ( 757 )
We study the external optical feedback resistance of both index-coupled (IC) and gain-coupled distributed feedback (DFB) lasers using a very simple experimental set-up. Though IC-DFB lasers with large coupling coefficients are found to be less sensitive to external reflection, they suffer from mode instability at high injection level. On the other hand, the introduction of gain-coupling mechanism can significantly improve both the immunity to external optical feedback and the single mode yield of the device.

Diode-Pumped Compact cw Frequency-Doubled Nd:YAG Laser in the Watt Range at 473 nm
LI Ping-Xue, LI De-Hua, ZHANG Zhi-Guo, ZHANG Shi-Wen
Chin. Phys. Lett. 2003, 20 (7): 1064-1066 .  
Abstract   PDF(pc) (312KB) ( 640 )
We report a diode-pumped cw Nd:YAG laser operating on the 4F3/2-4I9/2 transition at 946 nm, for which a maximum output power of 4.5 W with a slope efficiency of 21% is achieved at an incident pump power of 26 W. Two LiB3O5 (LBO) crystals of different lengths (3 x 3 x 10 mm and 3 x 3 x 15 mm), cut for critical type I phase matching at room temperature, have been used for intracavity frequency doubling, and through optimization of the structure and elements of the cavity, a maximum single-ended blue output power of 1.1 W has been obtained with an optical conversion efficiency of 4.2%. A stability better than 4.8% with no mode hopping over a period of 2 h has been achieved.
Z-Scan Characteristics of Cascading Nonlinear Media
ZANG Wei-Ping, TIAN Jian-Guo, LIU Zhi-Bo, ZHOU Wen-Yuan, YANG Xin-Jiang, ZHANG Chun-Ping, ZHANG Guang-Yin
Chin. Phys. Lett. 2003, 20 (7): 1067-1069 .  
Abstract   PDF(pc) (400KB) ( 302 )
We present a method, which combines the Gaussian decomposition method and the “distributed-lens”method, for analysing Z-scan curves of cascading nonlinear medium layers or a complicated cascading structure. A good agreement with the experimental data is obtained. The method would be useful to design optical limiters and to determine the nonlinearities of cascading medium layers.

Enhanced Nonlinear Absorption and Optical Limiting Properties of Organic Material ZnTBP-CA-PhR in a DA-ET System
YU Shi-Rui, ZHAO You-Yuan, LI Lu-Ying
Chin. Phys. Lett. 2003, 20 (7): 1070-1073 .  
Abstract   PDF(pc) (442KB) ( 518 )
Nonlinear absorption of the organic material Zn-tetrabenzoporphin-crotonicacid-phenoxy resin (ZnTBP-CA-PhR) in the donor-acceptor energy-transfer (DA-ET) system is investigated by the irradiation of Ar+ laser on its solid film. A reverse saturable absorption and an enhanced second reverse saturable absorption called the re-reverse saturable absorption are observed in a visible wavelength range. The high performance of optical limiting of the sample possessing low input threshold and an over 95% linear transmission ratio are observed. The physical mechanism of re-reverse saturable absorption is analysed by a five-level rate-equation simulating. According to the Huygens wave diffraction principle and the combination of Kerr effect, thermo-optic effect and optical absorption variation, a mathematical model for the optical limiting of ZnTBP-CA-PhR film limiter is established and the theoretical simulating gives a good agreement with the experimental results.

Mid-Infrared Optical Parametric Oscillator Based on All-Solid-State-Pumped Periodically Poled LiNbO
LIN Xue-Chun, BI Yong, YAO Ai-Yun, KONG Yu-Peng, ZHANG Ying, SUN Zhi-Pei, LI Rui-Ning, CUI Da-Fu, XU Zu-Yan, LI Jian
Chin. Phys. Lett. 2003, 20 (7): 1074-1076 .  
Abstract   PDF(pc) (316KB) ( 466 )
We report the tunable mid-infrared generation with a periodically poled LiNbO3 (PPLN). Using an all-solid-state-pumped Nd:YVO4 laser as the pump source and a PPLN nonlinear crystal with grating periods of 28.2-30.8μm, we have achieved wavelength conversion in the 2.90-4.05μm spectral range by period tuning. The use of confocal cavity design has brought a compact, all-solid-state configuration with an average output powers of idler up to ~ 200 mW. The maximum power of 277 mW was obtained at the wavelength of 3.35μm.

Temperature Tunable Infrared Optical Parametric Oscillator with Periodically Poled LiNbO3
{ZHANG Bai-Gang, , YAO Jian-Quan, , ZHANG Hao, ZANG Gui-Yan, XU De-Gang, WANG Tao, LI Xue-Jin, WANG Peng, ,
Chin. Phys. Lett. 2003, 20 (7): 1077-1080 .  
Abstract   PDF(pc) (450KB) ( 468 )
We demonstrate a temperature tunable infrared optical parametric oscillator (OPO) based on periodically poled LiNbO3 (PPLN) pumped by an acousto-optically Q-switched cw-diode-end-pumped Nd:YVO4 laser with the signal output from 1.48μm to 1.54μm by tuning the work temperature from 60°C to 250°C and the maximum average signal power (1500 nm) of 137 mW. We report the demonstration of the sum frequency of the pump and idler in a single-grating PPLN crystal. In addition, we present the theoretical analysis of the signal wavelength change rate with the changing temperature for a quasi-phase matching OPO, which is in good agreement with our experimental results.

An Electro-Optic Modulator Based on GeO2-Doped Silica Ridge Waveguides with Thermal Poling
CAO Xia, HE Sai-Ling
Chin. Phys. Lett. 2003, 20 (7): 1081-1083 .  
Abstract   PDF(pc) (406KB) ( 590 )
A Mach-Zehnder electro-optic modulator is designed and fabricated based on upper-clad GeO2-doped silica ridge waveguides with thermal poling. The electro-optic coefficient obtained is about 0.05 pm/V and is polarization-insensitive. An extinction ratio of over 17 dB is achieved. The transmission loss of the modulator for the TE mode is 2-3 dB higher than that for the TM mode after the poling.

Decomposition of the Two Lowest Lamb Modes in a Bonded Plate
WANG Xiao-Min, LIAN Guo-Xuan, LI Ming-Xuan
Chin. Phys. Lett. 2003, 20 (7): 1084-1087 .  
Abstract   PDF(pc) (271KB) ( 368 )
Based on the expression of the dispersion equation of Lamb waves in an adhesive two-layered plate presented in our previous paper [Chin. Phys. Lett. 18(2001)1483], the two lowest Lamb modes, the symmetric mode S0 and the anti-symmetric mode A0 are successfully decomposed in the low-frequency regime. Relations between the rigidity of the bond and the velocity of the two Lamb modes are found, which lay a foundation for the estimation of the bond rigidity of the adhesive plate. The influence of the variations of the bond rigidity in terms of the stiffness constants KN and KT of the spring model on the velocity of the two Lamb modes is discussed and numerically evaluated. Numerical results indicate that the deterioration of the bond rigidity causes the phase velocity decrease for Lamb modes of the two lowest order, thus having a possibility for the evaluation of the bonding state of the adhesive plate by using ultrasonic wave velocity measurement.
A Novel Approach to Correct Diffraction Effect in Measurement of Ultrasonic Velocity and Attenuation at High Frequencies
ZHANG Dong, LIU Xiao-Zhou, GONG Xiu-Fen, KUSHIBIKI Jun-Ichi
Chin. Phys. Lett. 2003, 20 (7): 1088-190 .  
Abstract   PDF(pc) (376KB) ( 498 )
A novel method to correct diffraction effect in measurement of ultrasonic velocity and attenuation at high frequencies is developed by using the superposition technique of Gaussian beams. To examine the validity of this numerical approach, the amplitude loss and phase advance due to the diffraction effect for an SiO2 specimen are numerically calculated in 30-240 MHz, and the results are in good agreement with those by the Papadakis method.
Size Segregation in a Vibrated Tilted Compartmentalized Granular Chamber
HU Mao-Bin, WU Qing-Song, JIANG Rui
Chin. Phys. Lett. 2003, 20 (7): 1091-1093 .  
Abstract   PDF(pc) (178KB) ( 592 )
A bidisperse granular mixture in a slightly tilted compartmentalized chamber is experimentally found to show size segregation when vertically vibrated. A surface slope develops and large particles congregate to the lower side. Particles right upon the upper tip of the dividing wall behave in a competitive way, i.e., they can go to either compartment depending on the force exerted on them.
Laboratory Studies of the Stratified Rotating Flow Passing over an Isolated Obstacle
GAO Shou-Ting, PING Fan
Chin. Phys. Lett. 2003, 20 (7): 1094-1097 .  
Abstract   PDF(pc) (256KB) ( 751 )
We study the flow of a density-stratified fluid passing over an isolated obstacle, using towing-tank experiments. Our special concern is the response of the flow with different Froude numbers pasing over a three-dimensional obstacle. A series of experiments of the stratified rotating flow passing over an isolated obstacle was carried out with the towering-tank controlled by the similarity laws and dynamic non-dimension parameters. These experiments show that the Froude number is a very important parameter, and the lee wave and the eddy structure appear simultaneously under an appropriate conditions. The effect of rotation on the lee wave is mainly to change wave amplitude, particularly to restain the development of the lee wave and to promote the formation of an eddy.
New Description Model of Sputtering on Material Surface
DENG Bai-Quan, YAN Jian-Cheng, HUANG Jin-Hua, PENG Li-Lin
Chin. Phys. Lett. 2003, 20 (7): 1098-1101 .  
Abstract   PDF(pc) (342KB) ( 447 )
In order to estimate the erosion rates of some plasma facing component materials, the sputtering yields of Mo, W and deuterium-saturated Li bombarded by fusion charged particles are calculated by application of new sputtering physics description methods based on the bipartition model of ion transport theory. The comparisons with Monte Carlo calculation and experimental results are made. These data might be useful to estimate the lifetime of plasma facing components and to analyse the impurity level in core plasma of fusion reactors.

Variations for Pure Cu Melt Viscosity with Different Atmospheres
GENG Hong-Xia, GENG Hao-Ran, XUE Xian-Ying, YU Ke, LIU Jian-Tong
Chin. Phys. Lett. 2003, 20 (7): 1102-1104 .  
Abstract   PDF(pc) (300KB) ( 1267 )
The viscosity of Cu melt is obtained to be in the ranges from 2.418 to 3.039 mPa.s under vacuum atmosphere (2Pa), from 2.907 to 3.425 mPa.s under nitrogen gas atmosphere and from 3.352 to 4.015 mPa.s under argon gas atmosphere. The activation energy is estimated to be 0.224, 0.162 and 0.150eV for the vacuum atmosphere (2Pa), nitrogen gas atmosphere and argon gas atmosphere, respectively. The results reflect the essential structural change in the Cu melt by using different atmospheres.

Vacancy in 6H-Silicon Carbide Studied by Slow Positron Beam
WANG Hai-Yun, WENG Hui-Min, HANG De-Sheng, ZHOU Xian-Yi, YE Bang-Jiao, FAN Yang-Mei, HAN Rong-Dian, C. C. Ling, Y. P. Hui
Chin. Phys. Lett. 2003, 20 (7): 1105-1108 .  
Abstract   PDF(pc) (367KB) ( 426 )
The defect changes in 6H-SiC after annealing and 10 MeV electron irradiation have been studied by using a variable-energy positron beam. It was found that after annealing, the defect concentration in n-type 6H-SiC decreased due to recombination with interstitials. When the sample was annealed at 1400 °C for 30 min in vacuum, a 20-nm thickness Si layer was found on the top of the SiC substrate, this is a direct proof of the Si atoms diffusing to surface when annealed at high temperature stages. After 10 MeV electron irradiation, for n-type 6H-SiC, the S parameter increased from 0.4739 to 0.4822, and the relative positron-trapping rate was about 27.878 times of the origin sample, this shows that there are some defects created in n-type 6H-SiC. For p-type 6H-SiC, it is very unclear, this may be because of the opposite charge of vacancy defects.

Formation Mechanism and Orderly Structures of an Iron Film System Deposited on Silicone Oil Surfaces
YE Quan-Lin, YU Sen-Jiang, JIN Jin-Sheng, YE Gao-Xiang
Chin. Phys. Lett. 2003, 20 (7): 1109-1111 .  
Abstract   PDF(pc) (213KB) ( 373 )
A new iron film system, deposited on silicone oil surfaces by vapor phase deposition method, has been fabricated and its formation mechanism as well as orderly structures has been studied. It is found that the formation mechanism of the films obeys a two-stage growth model, which is similar to that of the other metallic films on liquid substrates. Large and orderly structures are observed in the continuous iron films. The experiments show that the orderly spatial structures result from the local material gathering in these nearly free sustained films.

Integrability of the Bariev Model with a Hard Core under Open Boundary Conditions
HE Peng-Bin, YUE Rui-Hong
Chin. Phys. Lett. 2003, 20 (7): 1112-1115 .  
Abstract   PDF(pc) (204KB) ( 540 )
For the Bariev model with single electron hopping, pair hopping and hard core potential, we prove the integrability of this model under open boundary conditions and obtained the Bethe ansatz equations by using the reflection equations of the open-boundary XXZ model.

Effect of High Resistance Phases on Metal-Insulator Transition of La0.67Ca0.33MnO3
XIA Zheng-Cai, YUAN Song-Liu, ZHANG Li-Jiang, ZHANG Guo-Hong, FENG Wen, TANG Jie, LIU Li, LIU Sheng, TANG Chao-Qun
Chin. Phys. Lett. 2003, 20 (7): 1116-1119 .  
Abstract   PDF(pc) (473KB) ( 448 )
The temperature dependence of resistivity ρ of YSZ doping composite of (1-x)La0.67Ca0.33MnO3 + xYSZ and Y2O3 doping composite of (1-y)La0.67Ca0.33MnO3 + yY2O3 is investigated, respectively, in a temperature range 77-300 K, where the YSZ represents yttria-stabilized zirconia (8 mol%Y2O3 + 92 mol% ZrO2). Experimental results show that the YSZ doping level has important effects on both the metal-insulator (M-I) transition temperatures and zero field resistivity of the composites of (1-x)La0.67Ca0.33MnO3 + xYSZ. However, the Y2O3 doping level has little effect on the M-I transition temperatures and the zero field resistivity of (1-y)La0.67Ca0.33MnO3 + yY2O3 only increases slightly. The difference between the two types of composites may mainly result from the different distribution of high resistance phases at the grain boundaries and/or surfaces of La0.67Ca0.33MnO3 grains rather than the substitution of La3+ ions with Y3+ ions.
Optical Spectra and Exciton State in Vertically Stacked Self-Assembled Quantum Disks
LIU Jin-Long, LI Shu-Shen, NIU Zhi-Chuan, YANG Fu-Hua, FENG Song-Lin
Chin. Phys. Lett. 2003, 20 (7): 1120-1123 .  
Abstract   PDF(pc) (440KB) ( 457 )
We study the oscillator strengths of the optical transitions of the vertically stacked self-assembled InAs quantum disks. The oscillator strengths change evidently when the two quantum disks are far apart from each other. A vertically applied electric field affects the oscillator strengths severely, while the oscillator strengths change slowly as the radius of one disk increases. We also studied the excitonic energy of the system, including the Coulomb interaction. The excitonic energy increases with the increasing radius of one disk, but decreases as a vertically applied electric field increases.
Spin Polarization Through Resonant Tunneling in a Magnetic Double-Barrier and Double-Well Quantum Structure
GUO Yong, QIN Jian-Hua, CHEN Xin-Yi, GU Bing-Lin
Chin. Phys. Lett. 2003, 20 (7): 1124-1127 .  
Abstract   PDF(pc) (684KB) ( 504 )
Recent studies have indicated that spin polarization of the conductance shows strong oscillation and zero average for electrons resonant tunneling through a magnetic double-barrier and double-well quantum structure. Our studies indicate that strong oscillation of the polarization of the conductance is not physically intrinsic but inaccurate due to problems of numeration and insufficient numerical accuracy. We also indicate that its average of the spin polarization is not zero. The reasonable explanation is presented in details.

Superconducting Properties of MgB2 with Different Lattice Parameters
Chin. Phys. Lett. 2003, 20 (7): 1128-1130 .  
Abstract   PDF(pc) (388KB) ( 869 )
We investigate the electronic structures and superconductivities of new superconductor MgB2 with different lattice parameters by means of multiple-scattered-Xα calculation. It is shown that the lattice parameters have great effect on the superconductivity of MgB2. The results of this paper show that the density of states at the Fermi level decreases with the decreasing lattice parameters. The effects are very more sensitive substantially to the change of the lattice parameter a as compared with that of the lattice parameter c. Correspondingly, the superconducting transition temperature Tc decreases correspondingly mainly with decreasing the lattice parameter a. Our results are in good agreement with the experiments.
Room-Temperature Nonlinear Dielectric Constants and Dielectric Tunability in Poled Pb(Mg1/3Nb2/3) O3-PbTiO3 Single Crystals
ZHAO Xiang-Yong, WANG Jie, Chew Khian-Hooi, Chan Wa-Lai Helen, Choy Chung-Loong, LUO Hao-Su
Chin. Phys. Lett. 2003, 20 (7): 1131-1133 .  
Abstract   PDF(pc) (400KB) ( 463 )
The room-temperature second-, third- and fourth-order nonlinear dielectric constants of poled (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals were determined by measuring the dielectric response at a frequency of 10 kHz and under a dc bias of 0-1000 V/mm. Tunability of the apparent dielectric constant εr was also defined and examined. The results show the phase structure, domain state, composition and orientation dependences of the dielectric nonlinearity and tunability. It is also shown that the <011>-poled monodomain orthorhombic ferroelectric 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 single crystal has the largest nonlinear dielectric constants and the highest tunability of εr in the monodomain crystals. It could be a most promising candidate for applications where a high dielectric nonlinearity is needed.
Size Driven Ferroelectric-Paraelectric Phase Transition from the Surface Energy Viewpoint
ZHONG Wei-Lie, WANG Yuan-Xu, ZHANG Pei-Lin
Chin. Phys. Lett. 2003, 20 (7): 1134-1136 .  
Abstract   PDF(pc) (179KB) ( 721 )
The size driven ferroelectric-paraelectric phase transition in a ferroelectric of small size is studied within the framework of Landau phase transition theory. The transition is a consequence of the competition between the decrease of the volume free energy by polarization and the increase of the surface energy of the ferroelectric phase, which has a surface energy density higher than that in the paraelectric phase. A simple expression for the ferroelectric critical size as a function of the Landau free energy coefficients and the surface energy density is derived.

Photoluminescence of Mg-doped GaN with Different Mg Concentrations After Annealing at Different Temperatures
ZHOU Xiao-Ying, SUN Chang-Zheng, GUO Wen-Ping, HU Hui, LUO Yi
Chin. Phys. Lett. 2003, 20 (7): 1137-1140 .  
Abstract   PDF(pc) (314KB) ( 717 )
The blue band (BB) in low temperature photoluminescence of Mg-doped GaN films with different Mg concentrations is investigated. The BB peak of as-grown samples with higher Mg concentration centers at lower energy. A shift of the BB peak energy is observed after annealing in N2 at different temperatures. Meanwhile, the difference between the BB peak energies diminishes for raised annealing temperature, and the BB peaks for different samples converge to 2.92 eV after annealing at 850 °C. These experimental results can be accounted for by a model based on compensation effect. The shift of BB lines provides a useful criterion for the optimum annealing temperature of the Mg-doped GaN material, and the value is taken to be 850 °C in our case.
Highly Efficient Polymer Light-Emitting Devices Using a New Phosphorescent Material
WANG Jian-Hua, DUAN Lian, WANG Li-Duo, QIU Yong
Chin. Phys. Lett. 2003, 20 (7): 1141-1143 .  
Abstract   PDF(pc) (359KB) ( 479 )
A new phosphorescent material bis(2-phenyl-benzoimiazole) acetylacetonato iridium ((PBI)2IrAcac) is designed and synthesized. The absorption, photoluminescence and electroluminescence are measured. The polymer-based light-emitting devices which use polyvinylcarbazole (PVK) as host and (PBI)2IrAcac as emitter were fabricated. These light-emitting devices show a bright green emission at 548 nm. The device ITO/(PBI)2IrAcac:PVK/BCP/ Alq3/Mg:Ag shows a very high efficiency. A peak external quantum efficiency of 21.5 cd/A (5.8%) was obtained at 0.1 mA/cm2. The maximum brightness is 3840 cd/m2.
Characteristics of Solid State Cathodoluminescence of PPV
QU Chong, XU Zheng, TENG Feng, XU Xu-Rong,
Chin. Phys. Lett. 2003, 20 (7): 1144-1147 .  
Abstract   PDF(pc) (617KB) ( 450 )
Based on our previous discovery [Chem. Phys. Lett. 325 (2000) 420] of the solid-state cathodoluminescence from organic luminescent materials in inorganic/organic heterojunction, we study characteristics of this new kind of electric-field-induced luminescence by means of examining its oscillogram. We prepared three devices with different structures in which PPV was used as luminescent layer, and SiO2 was used as accelerating layer. The experimental results might be understood only by means of the existence of solid-state cathodoluminescence. This new kind of luminescence makes it possible to produce new type of flat panel display.
Time-Resolved Photoluminescence Studies of AlInGaN Alloys
DONG Xun, HUANG Jin-Song, LI Da-Bing, LIU Xiang-Lin, XU Zhong-Ying, WANG Zhan-Guo
Chin. Phys. Lett. 2003, 20 (7): 1148-1150 .  
Abstract   PDF(pc) (434KB) ( 527 )
We study the two samples of AlInGaN, i.e., 1-μm GaN grown at 1030°C on the buffer and followed by a 0.6-μm-thick epilayer of AlInGaN under the low pressure of 76 Torr and the AlInGaN layer deposited directly on the buffer layer without the high-temperature GaN layer, by temperature-dependent photoluminescence (PL) spectroscopy and picosecond time-resolved photoluminescence (TRPL) spectroscopy. The TRPL signals of both the samples were fitted well as a stretched exponential decay at all temperatures, indicating significant disorder in the material. We attribute the disorder to nanoscale quantum dots or disks of high indium concentration. Temperature dependence of dispersive exponent β shows that the stretched exponential decay of the two samples comes from different mechanisms. The different depths of the localization potential account for the difference, which is illustrated by the results of temperature dependence of radiative recombination lifetime and PL peak energy.
Multiple-Scattering of Near-Edge X-ray Absorption Fine Structure of Sulfur-Passivated InP(100) Surface
CAO Song, TANG Jing-Chang, SHEN Shao-Lai, CHEN Geng-Sheng, MA Dan
Chin. Phys. Lett. 2003, 20 (7): 1151-1154 .  
Abstract   PDF(pc) (301KB) ( 588 )
We use the multiple-scattering cluster method to calculate the sulfur 1s near-edge x-ray absorption fine structure (NEXAFS) of S-passivated InP(100) surface. The physical origins of the resonances in the NEXAFS have been unveiled. It is shown that the most important resonance is attributed to the photoelectron scattering between the central sulfur and the nearest indium atoms. The studies show that two S-S dimers with the bond lengthes of 2.05Å and 3.05Å coexist in the surface, meanwhile the bridge and antibridge site adsorption of single S could not be ruled out. We support the scanning tunneling microscopy result that the S-passivated InP(100) surface exhibits significant disorder.
Effect of VI/II Ratio on Structure and Optoelectrical Properties of Zinc Oxide Thin Films Deposited by Metal-Organic Chemical Vapor Deposition
MA Yan, DU Guo-Tong, YANG Shu-Ren, YANG Tian-Peng, YANG Hong-Jun, YANG Xiao-Tian, ZHAO Bai-Jun, LIU Da-Li
Chin. Phys. Lett. 2003, 20 (7): 1155-1157 .  
Abstract   PDF(pc) (323KB) ( 537 )
ZnO thin films with the c-axis orientation on the (0001) sapphire substrate were grown by metal-organic chemical vapor deposition. It was demonstrated that the VI/II precursor flow-rate ratio can influence strongly on the structure and opto-electrical properties. With the increasing VI/II ratio of 130:1, the full width at half maximum of (0002) peak in x-ray diffraction is only 0.184°, the near-band-edge emission enhances remarkably and the intensity ratio of the near-band-edge emission to the deep-level emission reaches 237:1 in the photoluminescence spectrum. At the same time, the resistivity and mobility increases to 3.28 x 102Ω.cm and 25.3cm2V-1s-1. These facts indicates that the quality of the ZnO thin films could be improved by the increase of the VI/II flow rate ratio during the growth.

Statistics and Dynamics for the Aa-Dd Type Hydrogen Bonding System
WANG Hai-Jun, HONG Xiao-Zhong, BA Xin-Wu
Chin. Phys. Lett. 2003, 20 (7): 1158-1160 .  
Abstract   PDF(pc) (183KB) ( 326 )
The kinetics and dynamics for the growth of hydrogen bonding clusters in the Aa-Dd system are considered. The explicit relations between conversions of proton-acceptors and proton-donors and Gibbs free energy are deduced, and then the sol-gel phase transition is predicted to take place and the generalized scaling laws satisfied by the k-th moment and k-th radius near the critical point are given. The conclusions obtained from which are consistent with the statistical descriptions on the system under investigation.
Mössbauer Studies on Spin Transition in Zinc Dilution Complexes [Fe1-xZnx(dpp)2(NCS)2].py (x = 0.05-0.40)
HUANG Hong-Bo, TAO Jian-Qing, YU Zhi, SHAO Ting, HSIA Yuan-Fu
Chin. Phys. Lett. 2003, 20 (7): 1161-1164 .  
Abstract   PDF(pc) (473KB) ( 498 )
A series of spin transition complexes [Fe1-xZnx(dpp)2(NCS)2]py (x = 0.05, 0.10, 0.15. 0.20, 0.25, and 0.40; py=pyridine) has been synthesized and studied by Mössbauer spectroscopy. The high spin structure is frozen at room temperature, and the induced meta-stable high-spin phase by the so-called rapid cooling method is monitored by temperature and time dependent Mössbauer spectra. The investigation on dynamic relaxation of the high-spin state to the low spin state at 80 K reveals sigmoid behaviour and existence of cooperative effect for low diluted complexes. This cooperative effect is wrecked by the dilution of Zn(II) ions in Fe(II) ion sites, and relaxation curves gradually become to obey the first-order kinetics as the ratio of the dilution increases.

Wavelength Dependence of Electro-Optic Coefficients in Chromophore-Incorporated Polymers
YANG Yan-Fang, SHEN Qi-Shun, ZHANG Shui-Ying, CAO Zhuang-Qi, LI Xu-Hua, YUAN Wen
Chin. Phys. Lett. 2003, 20 (7): 1165-1167 .  
Abstract   PDF(pc) (359KB) ( 428 )
Wavelength dependence of electro-optic coefficients in chromophore-incorporated polymers is studied by using the attenuated-total-reflection technique. Experimental result shows that the electro-optic coefficient decreases with the increase of light wavelength, which is in agreement well with the theoretical prediction.
An Intracellular Calcium Oscillation Model and its Property
YING Yang-Jun, LI Wei-Hua
Chin. Phys. Lett. 2003, 20 (7): 1168-1171 .  
Abstract   PDF(pc) (449KB) ( 476 )
Intracellular Ca2+ concentration oscillation is one of the typical nonlinear dynamical phenomena in biophysics. According to the experimental facts that when stimulated by different agonists, the cytosolic Ca2+ oscillations of hepatocytes show nearly constant amplitude for two different oscillation-form, simple spikes and complex bursts, we build a new 4-variables model based on the two models proposed by Hoefer [ Biophys J. 77 (1999) 1244] and Kummer et al. [ Biophys. J. 79 (2000) 1188] Our model can simulate both simple-spike and multi-spike-burst oscillations with amplitude of 0.5-0.7μmol/L in a rather wide range of parameters.

Compressibility of Epidote up to 20 GPa at 298 K
QIN Shan, WU Xiang, LIU Jun, LIU Jing, WU Zi-Yu, LI Xiao-Dong, LU An-Huai
Chin. Phys. Lett. 2003, 20 (7): 1172-1174 .  
Abstract   PDF(pc) (385KB) ( 463 )
We carry out the in-situ high pressure energy dispersive x-ray diffraction measurements on natural epitote by using diamond anvil cell. The pressure dependence of the lattice parameters of natural epidote is reported up to 20 GPa at room temperature. The experimental results show that the compressibility of epidote along the crystal axes is similar with increasing pressure, and the room-temperature isothermal bulk modulus K298 is 207±15 GPa, which is fitted by the Murnaghan equation of state in the case of the pressure derivative K'= 4.
A Hybrid Spin-Down Model and its Application to the Radio Quiet X-Ray Pulsar 1E 1207.4-5209
ZHANG Ling-Di, PENG Qiu-He, , LUO Xin-Lian
Chin. Phys. Lett. 2003, 20 (7): 1175-1178 .  
Abstract   PDF(pc) (216KB) ( 345 )
A series of newly published papers are focusing on the formation of the absorption features discovered by Chandra and XMM-Newton from the young radio quiet x-ray pulsar 1E 1207.4-5209. We try to interpret it as cyclotron absorption lines since this possibility could not be ruled out. With new development and application of a hybrid model, i.e., the magnetic dipole spin-down model combined with the neutrino cyclotron radiation spin-down model, we can easily avoid the contradiction between the normal rotation energy loss rate and the relatively lower magnetic field, and then we obtain the possible initial spin period (~0.420 s). We suppose that the progenitor of 1E 1207.4-5209 may be a white dwarf.

Smooth Transition from Shakura-Sunyaev Disc to Advection-Dominated Accretion Flow
LIN Yi-Qing, LU Ju-Fu, GU Wei-Min
Chin. Phys. Lett. 2003, 20 (7): 1179-1182 .  
Abstract   PDF(pc) (301KB) ( 347 )
We solve a set of basic equations describing black hole accretion flows using the standard Runge-Kutta method and a bridging formula for the radiative cooling, and show that a smooth transition from an Shakura-Sunyaev disc to an advection-dominated accretion flow is realizable for the high-viscosity case, without the need of involving any extra mechanism of energy transport.

Gamma-Ray and Multiwaveband Emission from Gamma-Ray-Loud BL Lacertae Objects
ZHANG Xiong, ZHAO Gang, CHENG Guang-Sheng, ZHANG Li
Chin. Phys. Lett. 2003, 20 (7): 1183-1186 .  
Abstract   PDF(pc) (291KB) ( 548 )
We have collected 18 γ-ray-loud BL Lac with observed data in multiwavedand, we find that γ-ray flux densities correlate better with the near-IR flux densities than those with the optical or x-ray flux densities. There is no correlation between γ-ray and radio flux densities. Possible constraints on the γ-ray emission mechanism are discussed. We suggest that the main γ-ray radiation mechanism is probably the synchrotron self-Compton process. The inverse Compton scattering of the radiation from hot circumscribe dust, by beamed ultrarelativistic electrons, is likely to be an important complementary mechanism.

Comment on “Permanent Electric Dipole Moment of an Rb Atom”
ZHU Zhen-He
Chin. Phys. Lett. 2003, 20 (7): 1187-1187 .  
Abstract   PDF(pc) (141KB) ( 385 )
It is stated that the conjecture that the hydrogen-like atoms may have large permanent electric dipole moments is doubtable. Two kinds of experiments are suggested to check the reliability of the conjecture further.

Reply to Comment on “Permanent Electric Dipole Moment of an Rb Atom”
HUANG Xiang-You, YOU Pei-Lin
Chin. Phys. Lett. 2003, 20 (7): 1188-1188 .  
Abstract   PDF(pc) (120KB) ( 374 )
The result of our experiment on Rb atoms is interesting and surprising. To affirm or to refuse the result should not be by conjectures but by experiments.
63 articles