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Volume 17 Issue 2
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Original Articles
General Cosmological Solutions of Einsteins Equations for Spherical, Plane and Hyperbolic Symmetric Space
Mohammed Ashraful Islam
Chin. Phys. Lett. 2000, 17 (2): 79-81 .  
Abstract   PDF(pc) (138KB) ( 536 )
The analytic cosmological solutions of Einstein's field equations for a type of static metric representing plane, spherical and hyperbolic symmetric spaces are presented and their properties are discussed separately. A general type of solution is obtained which represents the plane, spherical and hyperbolic symmetric cosmological models. Its physical properties are also discussed in details.

Gravitation Without Singularity
CHEN Guang
Chin. Phys. Lett. 2000, 17 (2): 82-84 .  
Abstract   PDF(pc) (165KB) ( 399 )
The coupled Einstein-scalar-vector field equations are found, and their static spherically symmetric solutions are derived under the consideration of self-gravitational interaction of scalar field and proved to be singularity-free and of limited energy.

Transport Properties of a Classical One-Dimensional Kicked Billiard Model
CHEN He-Sheng, WANG Jiao, GU Yan
Chin. Phys. Lett. 2000, 17 (2): 85-87 .  
Abstract   PDF(pc) (299KB) ( 471 )
We study a classical I-dimensional kicked billiard model and investigate its transport behavior. The roles played by the two system parameters α and K, governing the direction and strength of the kick, respectively, are found to be quite crucial. For the perturbations which are not strong, i.e. K < 1, we find that as the phase parameter α changes within its range of interest from –π/2 to π/2, the phase space is in turn characterized by the structure of a prevalently connected stochastic web (-π/2 ≤ α < 0), local stochastic webs surrounded by a stochastic sea (0 < α < π/2) and the global stochastic sea (α=π/2). Extensive numerical investigations also indicate that the system's transport behavior in the irregular regions of the phase space for K < 1 has a dependence on the system parameters and the transport coefficient D can be expressed as D≈D0(α)Kf(α) For strong kicks, i.e. K>> 1, the phase space is occupied by the stochastic sea, and the transport behavior of the system seems to be similar to that of the kicked rotor and independent of α.

Predicting Chaotic Time Series Using Recurrent Neural Network
ZHANG Jia-Shu, XIAO Xian-Ci
Chin. Phys. Lett. 2000, 17 (2): 88-90 .  
Abstract   PDF(pc) (233KB) ( 1045 )
A new proposed method, i.e. the recurrent neural network (RNN), is introduced to predict chaotic time series. The effectiveness of using RNN for making one-step and multi-step predictions is tested based on remarkable few datum points by computer-generated chaotic time series. Numerical results show that the RNN proposed here is a very powerful tool for making prediction of chaotic time series.
Unified Explanation of Quark-Lepton Mass Spectra in q-Deformed Quantum Mechanics
Chin. Phys. Lett. 2000, 17 (2): 91-93 .  
Abstract   PDF(pc) (275KB) ( 516 )
The quark-lepton mass spectra in q-deformed quantum mechanics are investigated. The theoretical formula of the spectrum includes two new quantum numbers: the q-exciting number n describing generations and the scaling indexes Mi describing families. This formula shows two exponential increases in the mass distribution as generation n increases, the intervals of masses in a given family exponentially increase, and the mass splittings among different members in a generation also exponentially increase. The theoretical values of masses of quarks and leptons reasonably agree with the experimental data except for the electron mass which is one order larger.
Influence of Quadrupole Pairing on the Variation of J(2) of the Superdeformed Band 194Hg(1)
XIN Xiao-Bin, LEI Yi-An, LIU Shu-Xin, ZENG Jin-Yan
Chin. Phys. Lett. 2000, 17 (2): 94-95 .  
Abstract   PDF(pc) (162KB) ( 301 )
Using the particle-number-conserving method we show that the observed downturn of J(2) of the superdeformed band 194Hg(1) can be satisfactorily accounted for, provided that both the monopole and quadrupole pairing interaction are included in the cranked shell model Hamiltonian.

Dielectronic Recombinat ion on He+ with Non-isolated Resonance Approach
Chin. Phys. Lett. 2000, 17 (2): 96-98 .  
Abstract   PDF(pc) (294KB) ( 424 )
Based on the relativistic multichannel theory, a non-isolated resonance approach has been developed to calculate the cross sections of dielectronic recombination on He+ for Δn = 1 and 2 transitions. A first order approximation is adopted for the radiative process. The convolved cross sections for the n≤ 3 states in both transitions are in good agreement with those of the observations. It is shown that the l-dependence of the field ionization and the radiative decay during the time-of-flight affect significantly the measurement of the cross sections near the initial state of the field ionization.

High-Energy Ions Emitted from Ar Clusters Irradiated by Intense Femtosecond Laser Pulses
LI Zhong, LEI An-Le, NI Guo-Quan, XU Zhi-Zhan
Chin. Phys. Lett. 2000, 17 (2): 99-100 .  
Abstract   PDF(pc) (205KB) ( 367 )
We have experimentally studied the energy spectra of Ar ions emitted from Ar clusters irradiated by intense femtosecond laser pulses. The Ar clusters were produced in the adiabatic expansion of Ar gas into vacuum at high backing pressures. The laser peak intensity was about 2 Χ10l6W/cm2 with a pulse duration of 45fs. The maximum and the average energies of Ar ions are 0.2MeV and 15keV at a backing pressure of 2.5MPa, respectively. They are almost independent of the backing pressures in the range of 0.6 to 4.5 MPa.
Fluorescence-Detected Ultrafast Free-Induction Decay in Powdered Rare Earth Solids
LUO Qi, DAI De-chang, YU Xiang-yang, QIU Zhi-ren, ZHOU Jian-ying, YAN Chun-hua, CHEN Zhi-da
Chin. Phys. Lett. 2000, 17 (2): 101-103 .  
Abstract   PDF(pc) (254KB) ( 476 )
Fluorescence interferometry is developed and applied to study ultrafast amplitude and phase dynamics for free-induction decay in powdered rare earth solids. The time-resolved phase dynamics of free-induction decay through-out the decaying process is accurately determined by using a novel dual-channel correlation technique and subpi-cosecond dephasing time is measured for Nd3+ solids at room temperature. The phase dynamics is well simulated with linear coherent polarization theory.
Ti:Sapphire-Laser Pumped 20 at.% Yb:YAG Thin Chip with Continuous-Wave Laser Output of 356 mW at 1.053μm
YANG Pei-Zhi, DENG Pei-Zhen, ZHANG Ying-Hua, LIU Yu-Pu, HUANG Guo-Song, CHEN Wei, XU Jun
Chin. Phys. Lett. 2000, 17 (2): 104-105 .  
Abstract   PDF(pc) (158KB) ( 309 )
We analyzed the spectroscopic performances of Yb:YAG and developed an efficient room-temperature 20 at.% Yb:YAG thin chip (6 Χ 6 Χ 0.5 mm) laser operating at 1.053μm pumped by Ti-sapphire laser operating at 940nm. Output power of 356 mW was obtained for an absorbed pump power of 784mW. The slope efficiency was 69%, and the extrapolated threshold was 273mW. The slope efficiency was as high as 72% with absorbed pump power exceeding 730mW.

Multi-wavelength Operation of an Er3+-doped Fiber Laser at Room Temperature with a Novel Optical Fiber Mach-Zehnder Interferometer
AN Hong-Lin, LIN Xiang-Zhi, LIU Hong-Du
Chin. Phys. Lett. 2000, 17 (2): 106-108 .  
Abstract   PDF(pc) (0KB) ( 257 )
A novel multi-wavelength erbium-doped fiber laser with a double-pass Mach-Zehnder fiber interferometer acting both as a comb filter and as a reflection mirror is demonstrated. The spatial hole burning effect introduced by the standing wave cavity configuration enables the simultaneous operation of multiple wavelengths in the homogeneously broadened erbium-doped fiber at room temperature. In the experiment,simultaneous oscillation of four wavelengths at room temperature has been obtained.

Compact Single-Mode Distributed Bragg Reflector Fiber Laser
XUE Yi-Yuan, AN Hong-Lin, FU Li-Bin, LIN Xiang-Zhi, LIU Hong-Du
Chin. Phys. Lett. 2000, 17 (2): 109-111 .  
Abstract   PDF(pc) (248KB) ( 456 )
A compact single-mode distributed Bragg reflector (DBR) fiber laser with narrow spectral linewidth is investigated. Firstly, based on our theoretical analysis the single longitudinal mode operation domain is obtained. Then, a single-mode DBR fiber laser of 7.9cm long with master oscillator power amplifier (MOPA) configuration is designed and constructed to operate in the single-mode domain. The fiber laser is pumped by a semiconductor laser at 975.5nm. The master oscillator operates at 1556.91 nm with a cw output power of 1.43mW for a pump power of 55.35mW . Its slope efficiency is 2.7% and the spectral linewidth is less than 1.2 MHz (instrument resolution limited). With the MOPA configuration the laser output power and slope efficiency are increased to 7.8mW and l6.9%, respectively.

Silica Colloidal Crystals with Ethanol Solvent
LI Zhao-Lin, NI Pei-Gen, CHENG Bing-Ying, JIN Chong-Jun, ZHANG Dao-Zhong, DONG Peng, GUO Xing-Cai
Chin. Phys. Lett. 2000, 17 (2): 112-114 .  
Abstract   PDF(pc) (275KB) ( 562 )
We have prepared a silica colloidal crystal with ethanol, which has a face-centered cubic structure and a corresponding photonic band gap located in the visible region, determined by Kossel ring analysis and the transmission spectra. A special feature is an apparent variation of its lattice constant, as well as the gap frequency, with sample height. The Raman scattering induced by a picosecond laser at different heights of the colloidal crystal has been measured. It is found that the intensity of the Raman scattering is not related sensitively to the photonic gap, even though the Raman-Stokes Wavelength is inside the gap.
Fiber Grating Sensor with Enhanced Pressure and Temperature Sensitivity
LIU Yun-Qi, GUO Zhuan-Yun, LIU Zhi-Guo, ZHAO Dong-Hui, GE Chun-Feng, DONG Xiao-Yi
Chin. Phys. Lett. 2000, 17 (2): 115-116 .  
Abstract   PDF(pc) (157KB) ( 413 )
A technique is used to enhance the pressure and temperature sensitivity of a fiber Bragg grating sensor. The grating is packaged by using polymer jacket, which exhibits no significant chirp due to the adoption of the special technique. The measured pressure and temperature sensitivity of the structured grating is 6.28x10-5/MPa and 5.18 x 10-5/oC. The wavelength shift due to pressure and temperature can be enhanced about 31.5 times for pressure and 7.7 times for temperature.
Solitary Kinetic Alfvén Waves in a Low-β Dusty Plasma
CHEN Yin-Hua, LU Wei
Chin. Phys. Lett. 2000, 17 (2): 117-119 .  
Abstract   PDF(pc) (187KB) ( 406 )
The nonlinear kinetic Alfvén waves in a low-β (0 << β << 1) dusty plasma have been investigated with the fluid model of three-component plasma. The nonlinear equation governing the perturbation density of electrons in a form of the energy integral has been derived. In the approximation of small amplitude, the soliton solution for the perturbation density of electrons is found, and the characteristics of solitons in different range of plasma parameters is studied numerically. The results show that the density dip or hump can be formed in a dusty plasma for different ranges of parameters, the amplitude of density dip is enhanced and the amplitude of density hump is reduced with increasing dust grain content.

Neutron and Pair Production by Interaction of Relativistic Laser Pulses with Plasmas
LIU Shi-Bing, ZHANG Jie, JIANG Wen-Mian
Chin. Phys. Lett. 2000, 17 (2): 120-122 .  
Abstract   PDF(pc) (212KB) ( 579 )
Electron and bremsstrahlung photon number spectra formulas are presented for relativistic laser-plasma interactions. The relevant electron-positron and neutron productions are demonstrated by recent available laser intensities to be possible through high-energy superthermal electrons interacting with solid-targets. The result-implys that the further amelioration to optimal conditions of target is significant for increasing particle yield in photon-induced nuclear reactions.

Bose-Einstein Condensation in a Two-Dimensional System with Sixty Bosons
BAO Cheng-Guang
Chin. Phys. Lett. 2000, 17 (2): 123-125 .  
Abstract   PDF(pc) (263KB) ( 412 )
A 60-boson system confined on a sphere has been qualitatively studied based on symmetry considerations. The low-lying spectrum is dominated by the ground rotation band based on the fullerene structure. In this band all the L = 1 to L = 5 states are found to be prohibited by symmetry. Therefore, there is a large gap lying between the ground state and the first excited state. The magnitude of this gap, which is associated with the critical temperature of Bose-Einstein condensation, has been evaluated. It is found that, the smaller the radius of the sphere of confinement, the higher the critical temperature.

High Bulk Modulus of Nanocrystal γ-Fe2O3 with Chemical Dodecyl Benzene Sulfonic Decoration Under High Pressure
ZHAO Jing, GUO Lin, LIU Jing, YANG Yang, CHE Rong-Zheng, ZHOU Lei
Chin. Phys. Lett. 2000, 17 (2): 126-128 .  
Abstract   PDF(pc) (277KB) ( 446 )
Structural transformation in γ-Fe2O3 nanocrystals (about 10 nm) with dodecyl benzene sulfonic (DBS) coated is studied by using high-pressure energy dispersive x-ray diffraction of synchrotron radiation and high-resolution transmission electron microscopy (HRTEM). Relative to the bulk crystal, the transition pressure showed a decrease while the compressibility increases significantly up to 375 (±9 GPa). HRTEM picture confirmed that there is surface cladding surrounding nanocrystals due to DBS, which formed new special boundaries between nanocrystals and should be different from the ordinary grain boundaries. The experimental results imply that the surface layers of γ-Fe2O3 nanocrystals have strong effect on the compressibility.
Polaronic Band Structure of Holstein Model
WAN Shao-Long, WANG Ke-Lin
Chin. Phys. Lett. 2000, 17 (2): 129-131 .  
Abstract   PDF(pc) (154KB) ( 378 )
A new concise approach is presented for analytic study of the properties of the Holstein model. New analytic results for the polaronic band structure and phonon distribution, of the Holstein molecular crystal model, are given in one dimension. And all analytic results given are in accordance with the known numerical research results.

Magnetization Profiles of Ferromagnetic Ising Films in a Transverse Field
WANG Xiao-Guang, PAN Shao-Hua, YANG Guo-Zhen
Chin. Phys. Lett. 2000, 17 (2): 132-133 .  
Abstract   PDF(pc) (162KB) ( 317 )
Within the framework of the mean field theory, we study the magnetization profiles of ferromagnetic Ising films in a transverse field. By the transfer matrix method, we first derive a general nonlinear equation for phase transition temperatures and then calculate the magnetization profiles of the system. The method proposed here can be applied to ferromagnetic films with arbitrary surface layer number, bulk layer number, exchange interaction constants and transverse fields.
Reaction of Positronium with Proton in Ultra-stable Y Zeolite Studied by Positrons
ZHU Jun, MA Li, WANG Shao-Jie, LUO Xi-Hui
Chin. Phys. Lett. 2000, 17 (2): 134-136 .  
Abstract   PDF(pc) (216KB) ( 479 )
The positron annihilation lifetime spectra were measured as a function of the heating temperature for the ultra-stable Y (USY) zeolites. The lifetime spectra were well resolved into five lifetime components, and the longer lifetimes т3, т4 and т5 are assigned to ortho-positronium annihilating in the β-cage, super-cage and the second pore in USY zeolite, respectively. The interesting observation is that the annihilation rate λ5 (the reciprocal of The т5) of the fifth component increases and its intensity I5 decreases with the increasing heating temperature. The result is interpreted in terms of the increase in proton and the reaction between the positronium and proton in USY zeolite after heated.

Characterization of Pb( Zr0.53Ti0.47)O3 Films on GaN
LI Wei-Ping, ZHANG Rong, ZHOU Yu-Gang, YIN Jiang, SHEN Bo, SHI Yi, CHEN Zhi-Zhong, CHEN Peng, LIU Zhi-Guo, ZHENG You-Dou
Chin. Phys. Lett. 2000, 17 (2): 137-138 .  
Abstract   PDF(pc) (179KB) ( 437 )
GaN/Pb(Zr0.53Ti0.47)O3 structures have been fabricated by light radiation heating low-pressure metal-organic chemical deposition and pulsed laser deposition. These structures show leakage current lower than 10-11A at applied voltage of 5 V. X-ray diffraction shows that ferroelectric Pb (Zr0.53Ti0.47)O3 films directly on GaN are well crystallized with perovskite structure. Because of the high thermal stability and relatively smaller mismatch between GaN and ferroelectrics in comparison with that of Si/ferroelectric structures, GaN looks like more promising as semiconductor active layer for metal-ferroelectric-semiconductor field effect transistors.

Role of Ba2+ Ion in the Crystal Growth of Sr(NO3)2
WU Li-Jun, LI Chao-Rong, CHEN Wan-Chun, LIANG Jing-Kui,
Chin. Phys. Lett. 2000, 17 (2): 139-141 .  
Abstract   PDF(pc) (223KB) ( 411 )
A series of crystals of BaxSr1-x(NO3)2 (x = 0 - 0.98) were grown from aqueous solutions by the evaporation method and characterized by x-ray powder diffraction and high resolution x-ray diffraction. All diffraction data are well indexed according to simple cubic structure. The variation of lattice constants with the concentrations of Ba2+ in the crystals accorded quite well to the Vegard's Law. The results of high-resolution x-ray diffraction show that the crystalline quality of BaxSr1-x(NO3)2 decreases with x increasing. The distribution of Ba2+ between the solution and solid phase indicated that Ba2+ is enriched in the solid phase. It could be attributed to the solubility of Ba(NO3)2 in water being less than that of Sr(NO3)2.

Preparation and Optical Properties of Nanocrystalline Ga0.62In0.38Sb Embedded in SiO2 Composite Films
Chin. Phys. Lett. 2000, 17 (2): 142-144 .  
Abstract   PDF(pc) (233KB) ( 411 )
Nanocrystalline Ga0.62In0.38Sb embedded in SiO2 matrix has been fabricated by radio frequency magnetron cosputtering. X-ray photoelectron spectroscopy strongly supports the existence of nanocrystalhe Ga0.62In0.38Sb embedded in SiO2 matrix. The room-temperature Raman spectrum shows that the Raman peaks of the Ga0.62In0.38SbSiO2 composite film have a larger red shift of about 95.3cm-1 (longitudinal-optic) and 120.1 cm-1 (transverse-optic) than those of the bulk GaSb. This can be explained by the phonon confinement and tensile stress effects. The room-temperature optical transmission spectra show that the absorption edge exhibits a large blue shift of about 2.43 eV compared with that of the bulk semiconductor, suggesting the existence of quantum size effects.

Characterization of Cu-Zn Alloy Nanocrystalline Powders Prepared by Wire Electrical Explosion
WANG Qun, YANG Hai-Bin, GUO Wei-Li, ZOU Guang-Tian
Chin. Phys. Lett. 2000, 17 (2): 145-147 .  
Abstract   PDF(pc) (380KB) ( 462 )
Nanocrystalline powders of Cu-Zn alloy in size ranging from 10 to 140nm was prepared from α-Cu-Zn alloy wire containing 39.8at.% Zn by an electrical explosion method. The particles are identified from x-ray diffraction as a mixture of the α, β, γ, and ε phases of Cu-Zn alloy. Most of the particles are hexagonal in shape, with only a small part being spherical and cubic. The composition of Zn in the explosion products varied from 6.9 to 45.2at.% in different particles as determined by energy dispersive x-ray spectrometer. A possible mechanism for the formation of the alloy nanocrystalline powders is proposed, in which a redistribution process occurred caused by strong collision and diffusion between the two kinds of atoms during the powder formation.

Deceleration Effect of Magnetic Field on Black Hole Accretion Disks
WANG Ding-Xiong
Chin. Phys. Lett. 2000, 17 (2): 148-150 .  
Abstract   PDF(pc) (198KB) ( 349 )
The deceleration effect of magnetic field near the horizon of a spinning black hole (BH) of accretion disk is investigated in the Blandford-Znajek (BZ) process. It is shown that rates of change with respect to time for both the angular velocities of BH horizon and accreting particles at the inner edge of an accretion disk are reduced in the BZ process, behaving with non-monotonous evolution characteristics. This result implies that the magnetic field near the BH horizon has á deceleration effect not only on the spinning BH but also on the surrounding accretion disk.

Causal Viscosity in Global Dynamics of Advection-Dominated Accretion Flows Around Black Holes
GU Wei-Min, LU Ju-Fu,
Chin. Phys. Lett. 2000, 17 (2): 151-153 .  
Abstract   PDF(pc) (235KB) ( 430 )
We modify the viscosity to disappear inside the sonic point in the advection-dominated accretion flows (ADAF’s) around black holes, and obtain the causally connected, physically self-consistent ADAF-thin disk solutions. Such global solutions differ from previous ones in quantitative details. The results show that the range of variation for the value of the outer boundary Rout is very large, from 30Rg to 106Rg. There is a narrow region for which the rotating motion of the flow is super-Keplerian in each global solution. An example global solution with the causal viscosity is given explicitly, for which Rs = 2.28Rg and j = 1.7564(cRg).

Black Hole Creation at the Birth of the Universe
WU Zhong-Chao
Chin. Phys. Lett. 2000, 17 (2): 154-156 .  
Abstract   PDF(pc) (300KB) ( 367 )
We study the quantum creation of black hole pairs in the (anti-)de Sitter space background. These black hole pairs in the Kerr-Newman family are created from constrained instantons. At the Wentzel-Kramers-Brillouin level, for the chargeless and nonrotating case, the relative creation probability is the exponential of (the negative of) the entropy of the universe. Also for the remaining cases of the family, the creation probability is the exponential of (the negative of ) one quarter of the sum of the inner and outer black hole horizon areas. In the absence of a general no-boundary proposal for open universes, we treat the creations of the closed and the open universes in the same way.

A Universal Quantum Network---Quantum Central Processing Unit
WANG An-Min,
Chin. Phys. Lett. 2000, 17 (2): 166-168 .  
Abstract   PDF(pc) (203KB) ( 439 )
A new construction scheme of a universal quantum network which is compatible with the known quantum gate-assembly schemes is proposed. Our quantum network is standard, easy-assemble, reusable, scalable and even potentially programmable. Moreover, we can construct a whole quantum network to implement the general quantum algorithm and quantum simulation procedure. In the above senses, it is a realization of the quantum central processing unit.
29 articles