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Volume 16 Issue 6
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Original Articles
Exact Solution to Landau System with Time-Dependent Electromagnetic Fields
YING Zu-jian, WANG Shun-jin, ZHANG Wen-zhong
Chin. Phys. Lett. 1999, 16 (6): 391-393 .  
Abstract   PDF(pc) (171KB) ( 296 )
Algebraic dynamics is applied to treat Landau system. We consider the case with the vector potential A = B(t)(-y, 0,0) and the scalar potential Ф = -E(t)y +k(t)y2, and find that the system has the dynamical algebra su (1,1) h (3). With a gauge transformation the exact solutions of the system are found, of which the quantum motion in y-direction represents a harmonic oscillator with a moving origin and a varying amplitude of width, the paramertes of the gauge transformation are related to the amplitude, the velocity potential and the expectations of y and py, respectively. The energy of the system, the fluctuations of dynamical variables, the transition amplitudes between different states, and the Berry phase are calculated.

A New Traversable Wormhole Solution in Vacuum Brans-Dicke Theory
HE Feng, LIU liao
Chin. Phys. Lett. 1999, 16 (6): 394-396 .  
Abstract   PDF(pc) (212KB) ( 306 )
A new set of exact solutions in vacuum Brans-Dicke theory is obtained, which is a two-way traversable wormhole for the coupling parameter ω (ω < - 2). This new set of exact solutions satisfies not only the general constraints on the shape function b(R) and the redshift function Φ(R) given by Morris and Thorne [Am. J . Phys. 56 (1988) 395], but also the constraints on them from a trip through wormhole. It also follows that the scalar field Φ plays a role of exotic matter violating the weak energy condition.

Light Scattering Microscopy of Surface and Its Computational Simulation
CHENG Chuan-fu, LIU De-li, QI Dong-ping
Chin. Phys. Lett. 1999, 16 (6): 397-399 .  
Abstract   PDF(pc) (212KB) ( 489 )
The light scattering microscopy is proposed, which reconstructs the height distribution function of a random surface from the speckle intensity of the scattered light wave. In the computational simulation, we generated the random surfaces of Gaussian correlation and the speckle intensities, and reconstructed the surfaces by Gerchberg-Saxton (G-S) and modified G-S algorithm. The simulation proves this microscopy works well.

Casimir Effect Between Plates with Oxide Film
SHAO Cheng-gang, LIU Zhong-zhu, LUO Jun
Chin. Phys. Lett. 1999, 16 (6): 400-402 .  
Abstract   PDF(pc) (196KB) ( 344 )
The Casimir force between the plates with the oxide film in (3+1)-dimensional version is studied by means of the source theory. Theoretical analyses show that the Casimir force between the plates could be affected by the oxide film on the surface of the plate. Numerical simulation shows that the variation due to the oxide film will reach at the level of about 5% for the typical experimental parameters, which means that the oxide film effect should be considered in the high precision experiment.
Why the Constituent Quark Model Works for Baryon Magnetic Moments
CHEN Xiang-song, QING Di, WANG Fan
Chin. Phys. Lett. 1999, 16 (6): 403-405 .  
Abstract   PDF(pc) (218KB) ( 377 )
Starting from quantum chromodynamics, we find that aside from some terms that contribute only via the mixing of different Fock components, the baryon magnetic moment can be expressed as μB = ΣqQq/(2 < k0>q)] (2Sq-2S-q +Lq–L-q) , where < k0>q is the q flavor quark’s average relativistic energy inside the baryon, and Sq, Lq, S-q , L-q are quark and antiquark’s relativistic spin and orbital contributions to baryon spin. We demonstrate that within an error of 1/6, this expression can be parameterized as Σq[Qq/ ( 2mqeff )](2sq-2s-q), (where s is the nonrelativistic Pauli spin contribution and mqeff is of the order of the constituent quark mass) which is just what the nonrelativistic constituent quark model adopts to give a good account of octet baryon magnetic moments.

Identification of a New Isotope 186Hf
YANG Wei-fan, YUAN Shuang-gui, XU Yan-bing, HE Jian-jun, LI Zong-wei, MA Tao-tao, FANG Ke-ming, SHEN Shui-fa
Chin. Phys. Lett. 1999, 16 (6): 406-407 .  
Abstract   PDF(pc) (172KB) ( 302 )
The new neutron-rich isotope 186Hf has been produced through a multinucleon transfer reaction by irradiation of natural tungsten targets with 60 MeV/u 18O projectiles. The 186Hf activities were separated radiochemically from the tungsten and reaction product mixture. The γ-ray singles spectra were measured with a high resolution HPGe detector. The new isotope 186Hf was identified based on the growth and decay of 737.5keV γ rays from the β- decay of its daughter 186Ta. Its half-life has been determined to be 2.6 ± 1.2 min.
129Xe Magnetic Resonance Imaging Experiments Using Laser Polarization in a High Magnetic Field
SUN Xian-ping, HU Hong-bing, ZENG Xi-zhi, MAO Xi-an
Chin. Phys. Lett. 1999, 16 (6): 408-410 .  
Abstract   PDF(pc) (266KB) ( 326 )
129Xe magnetic resonance imaging in a magnetic field of 4.7T and at 311K with laser polarization in the same field is reported. In order to overcome the self-diffusion effect that destroys the transverse magnetization very rapidly, gradient echo is used instead of spin echo. Spectroscopic image is also obtained. Two-dimensional spin nutation spectroscopy under steady state was used to calibrate π/2 pulse of 129Xe in gaseous state. In addition, we have measured the relaxation time of laser-polarized gaseous 129Xe using the saturation-recovery method.
Isotope Shifts in Nd II by Collinear Fast-Ion-Beam Laser Spectroscopy
MA Hong-liang, CHEN Miao-hua, CHEN Zhi-jun, SHI Wei, LU Fu-quan, TANG Jia-yong, YANG Fu-jia
Chin. Phys. Lett. 1999, 16 (6): 411-412 .  
Abstract   PDF(pc) (160KB) ( 296 )
Atomic spectra of singly ionized neodymium have been measured by collinear fast-ion- beam laser spectroscopy. The resonant spectra in the lines of 568.9, 570.8, 572.7, and 574.1 nm in Nd II were obtained and the optical shifts were determined. We obtained the optical shifts of all the five even isotopes (142-150) in Nd II. The accuracy of our results was improved by one order of magnitude compared with other published results.
Simplified Analysis for Leaky Modes in Planar Optical Waveguides
CAO Zhuang-qi, QIU Lin-lin, SHEN Qi-shun, DOU Xiao-ming, CHEN Ying-li
Chin. Phys. Lett. 1999, 16 (6): 413-414 .  
Abstract   PDF(pc) (140KB) ( 395 )
In combination with the transfer matrix method and the concept of an equivalent attenuated coefficient, a first-order perturbation theory is proposed to study the leaky modes in planar optical waveguides. Simplified analytical expressions of the perturbed propagation constants are presented in a more explicit and general manner compared to the existing theory.
Non-Gaussian Pulse Propagation and Pulse Quality Factor Using Intensity Moment Method
LIN Guo-cheng, SUI Cheng-hua, LIN Qiang
Chin. Phys. Lett. 1999, 16 (6): 415-417 .  
Abstract   PDF(pc) (213KB) ( 508 )
The propagation of ultra-short light pulses with nonlinear chirp and arbitrary amplitude profile is treated by using first-order and second-order intensity moments in temporal domain. A generalized pulse complex parameter P-1 is introduced and its propagation law through dispersive systems is derived. The pulse quality factor M2Τ is introduced. As an example, the propagation of pulses with sech-type amplitude profile through dispersive media is included. This method is proved to be a simple way to treat the propagation of non-Gaussian pulses through dispersive system compared with the temporal integral.
Femtosecond Degenerate Four-Wave-Mixing in ZnO Microcrystallite Thin Films
ZHANG Wei-li, WANG Qing-yue, CHAI LU, XING Qi-rong, K. S . Wong, H. Wang, Z. K. Tang, G. K. L. Wong, R. Jain
Chin. Phys. Lett. 1999, 16 (6): 418-419 .  
Abstract   PDF(pc) (160KB) ( 311 )
Transient third-order optical nonlinearity Χ(3) of ZnO microcrystallite thin films is measured at various temperatures by using femtosecond degenerate four-wave-mixing. Room-temperature excitonic enhancement of Χ(3) is observed. The magnitude of Χ(3)) ranges between 10-4 to 10-6 esu from 4.2K to room temperature. The measured Χ(3)response time ranging from 200 to 300fs is ultrafast for temperature down to 4.2K.
Image Storage and Real-Time Distorted Image Correction by Using Photorefractivity in a Stable Photorefractive Polymer Composite
WANG Feng, CHEN Zhi-jian, GONG Qi-huang, CHEN Yi-wang, CHEN Hui-ying
Chin. Phys. Lett. 1999, 16 (6): 420-422 .  
Abstract   PDF(pc) (271KB) ( 544 )
Using a highly stable and excellently performed three-component photorefractive (PR) polymer composite, poly(N-vinylcarbazo1e):l -n- butoxyl-2,5-dimethy1-4(4'-nitrophenylazo) benzene:2,4,7-trinitro-9-fluorenone, optical image storage was demonstrated. The dark storage time was 5-7h. The PR response time was measured to be about 200ms at an intensity of 1W/cm2 with an applied electric field of 84 V/μm. A proof-of-principle experiment on real-time correction of distorted images based on phase conjugattion of four-wave mixing geometry was also carried out.

A Four-Fluid Model and Analysis of m = 1 Internal Kink Instability
QU Hong-peng, GAO Qing-di, SHI Bing-ren
Chin. Phys. Lett. 1999, 16 (6): 423-425 .  
Abstract   PDF(pc) (245KB) ( 298 )
Starting from the four-fluid equation which can simply and effectively describe the motion of trapped particles, we derive the eigenmode equations and the dispersion relation for m=1 internal kink mode with the effects of trapped particles, diamagnetic drifts, finite resistivity and anomalous electron viscosity included. Then, using those results, we find the trapped particles effects have substantial influence on m=1 internal kink mode in the cases with and without high-energy alpha particles in the core plasma.
Preparation of TiOx/γ-AI2O3 Catalyst on Powdery γ-AI2O3 by Using Reactive Sputtering Deposition
LU Wen-qi, XU Zhen-feng, DENG Xin-lu, XU Jun, ZHANG Jia-liang, ZHU Ai-min, GONG Wei-min
Chin. Phys. Lett. 1999, 16 (6): 426-427 .  
Abstract   PDF(pc) (149KB) ( 345 )
A layer of TiOx was deposited on powdery γ-AI2O3 by using flat-target magnetron sputtering in microwave electron cyclotron resonance plasma. A vibrator was developed to coat the γ-AI2O3 particles evenly by TiOx. The conversion efficiency of methane and both the yield and the selectivity of C2 hydrocarbons and C2H2 were revealed to be superior to that by conventional chemical method. The use of vibrator is effective.
Vibrational Analysis of Oxygen Adsorption on Cs and CO Coadsorbate Precovered Ru (0001) Surface
HE Pei-mo, Karl Jacobi
Chin. Phys. Lett. 1999, 16 (6): 428-430 .  
Abstract   PDF(pc) (327KB) ( 410 )
Vibrational analysis of oxygen adsorption on the Cs and CO coadsorbate precovered Ru (0001) surface was carried out by means of high-resolution electron energy loss spectroscopy. For submonolayer Cs coverages on Ru (0001), an appropriate amount of CO adsorption leads to formation of (2 x 2)-Cs+2CO islands. Subsequent oxygen adsorption on this Cs and CO coadsorbate precovered surface results in a remarkable change of high-resolution electron energy loss spectroscopy. The loss peak of C-O stretch mode for 2x2 island species decreases in intensity, which is accompanied by appearance of new bands at about 87 and 240meV. The results show that Cs adatoms and CO molecules are rearranged upon oxygen adsorption, and are correlated with coexistence of bare surface CO and a mixed phase of Cs, CO, and O.
Increase in the Transition Enthalpy of Fibrinogen upon Adsorption onto Hydroxyapatite
CHEN Yong-li, MAO Hai-bin, ZHANG Xiu-fang, GONG Yan-dao, ZHAO Nan-ming
Chin. Phys. Lett. 1999, 16 (6): 431-433 .  
Abstract   PDF(pc) (308KB) ( 467 )
The increase of the protein transition enthalpy upon adsorption onto biomedical material surfaces was observed by measuring the differential scanning calorimetry (DSC) traces of bovine fibrinogen adsorbed onto a hydroxyapatite surface. The mechanism causing the transition enthalpy increase upon adsorption Was clarified by using DSC measurements of bovine fibrinogen for different ionic strength and sodium dodecyl sulfate concentrations. The results suggest that the increased fibrinogen transition enthalpy may be attributed to the electrostatic interactions between the carboxyl of the D domains and the calcium loci of hydroxyapatite, which may result in a more compact protein structure.
Integrable Multi-impurity Open XXZ Chain with Next-Nearest-Neighbor Interaction
LAI Yun-zhong, , ZHANG Ai-zhen, HU Zhan-ning, LIANG Jiu-qing, PU Fu-ke,
Chin. Phys. Lett. 1999, 16 (6): 434-436 .  
Abstract   PDF(pc) (199KB) ( 326 )
The Hamiltonian of one-dimensional integrable multi-impurity XXZ spin chain with open boundary cases is constructed by using the method of adding parameters to the vertical matrices. This is the first approach to add multi-impurity and next-nearest-neighbor interaction to the integrable anisotropic Heisenberg spin chain. It is found that all of the impurity parameters in the bulk must be pure imaginary numbers if the cross parameter is real for getting the hermitian Hamiltonian, or vice versa, when the next-nearest-neighbor interactions are introduced. The Hamiltonian can be also applied to describe the many body systems with two kinds of particles if all of the impurity parameters are equal.
Electronic and Optical Properties of (GaN)n/(AlN)n(001) Superlattices
LI Kai-hang, HUANG Mei-chun, ZHU Zi-zhong, ZHANG Zhi-peng
Chin. Phys. Lett. 1999, 16 (6): 437-439 .  
Abstract   PDF(pc) (255KB) ( 415 )
The band structure of the short period zinc-blende (GaN)n/(AlN)n(001) superlattices has been calculated by means of semi-empirical tight-binding sp3s* method. The superlattices energy gap dependence on layer number n is given out. On the basis of the calculated eigenfunctions and eigenvalues of the superlattices (SL), the imaginary parts of the dielectric function ε2(ω) of (GaN)n/(AlN)n(001) superlattices were obtained. In order to compare with the optical properties of bulk zinc-blende GaN and AlN, we also calculated ε2(ω) of the two compounds. It is shown that there are some discernible effects due to confinement and superlattice periodicity.
Time-Dependent Behavior in Arrays of Two Coupled Quantum-Dot Cells
WANG Chuan-kui, YU Qing-jiang, WANG Hong-song, ZHANG Qing-gang
Chin. Phys. Lett. 1999, 16 (6): 440-442 .  
Abstract   PDF(pc) (192KB) ( 454 )
Time-dependent behavior of two kinds of arrays of two coupled quantum-dot cells is examined. Each square cell composed of four quantum dots in the corners contains two electrons and couples with the neighboring cells by Coulomb interactions. The electrons in one cell tend to occupy antipodal dots which results in a cell “polarization”. We have investigated the temporal evolution of the polarization of one cell under switch of the polarization of the other cell. Our results demonstrate that, with an adiabatic switch, if two cells are arranged in a line their polarizations will align each other, and if they are arranged in a diagonal way their polarizations will invert each other. However, with an abrupt switch, the above features for the polarizations of two cells can not hold. The reason is that the system does not stay in its ground state. It is pointed out that the energy dissipation should be considered in order to obtain the appropriate solutions.

Some Considerations on Energy Levels of Quantum Cascade Lasers
YANG Quan-kui, LI Ai-zhen
Chin. Phys. Lett. 1999, 16 (6): 443-445 .  
Abstract   PDF(pc) (247KB) ( 428 )
Conduction band non-parabolicity is taken into account and a numerical method is proposed to calculate the electron subband energy levels and corresponding wave functions in the active region of quantum cascade lasers. For a coupled double-well vertical transition mode active region, the calculated ΔE21 = 32 meV, ΔE32 = 270 meV correspond, respectively, to the energy of an optical phonon and that of a photon at wavelength λ = 4.5μm. For a coupled triple-well vertical transition active region, the calculated ΔE21 = 32.4meV, ΔE32= 250meV correspond to the energy of an optical phonon and the photon energy at wavelength λ= 5.0 μm.
Relationship Between Superconducting Transition Temperature and Combinative Energy in YBa2Cu3O7-δ
CHENG Li-li, DU Xu, QIN Xiao-chuan, ZHANG Han
Chin. Phys. Lett. 1999, 16 (6): 446-448 .  
Abstract   PDF(pc) (237KB) ( 515 )
Separating the unit cell of YBa2Cu3O7-δ into perovskite and rock salt blocks and considering the interaction between the two blocks, a computer program has been developed to calculate the interaction called combinative energy, between the blocks. The combinative energy in YBa2Cu3O7-δ with different 6 value from 0.07 to 0.62 has been calculated. A close relationship between the superconducting transition temperature and the combinative energy in YBa2Cu3O7-δ has been established, and the change of the combinative energy found to be closely related to the transformation from orthorhombic I to II. It is believed that the interaction between the two blocks in the unit cell is of great importance to the superconductivity in YBa2Cu3O7-δ.
Periodic Revivals of Squeezing in a Mesoscopic Josephson Junction
ZOU Jian, SHAO Bin
Chin. Phys. Lett. 1999, 16 (6): 449-451 .  
Abstract   PDF(pc) (223KB) ( 362 )
The interaction between a mesoscopic Josephson junction and a quantized electromagnetic field is discussed quantum mechanically. Within the external field approximation, it is shown that if the field is prepared in a coherent state and the junction is initially in its lowest energy level, squeezing can occur in such a system.
Giant Magneto-Impedance Effect in As-Deposited Multilayered Amorphous Films
XIAO Shu-qin, LIU De-zhen, LIU Yi-hua, DAI You-yong, ZHANG Lin, MEI Liang-mo
Chin. Phys. Lett. 1999, 16 (6): 452-454 .  
Abstract   PDF(pc) (231KB) ( 311 )
Giant magneto-impedance effects have been observed in as-deposited amorphous FeCuNbSiB/Cu/FeCuNbSiB and FeCuNbSiB/SiO2/Ag/SiO2/FeCuNbSiB multilayered films. The films were deposited onto Si substrates by radio frequency sputtering. In FeCuNbSiB/Cu/FeCuNbSiB films, maximum giant magneto-impedance ratios as large as 32% and 11% were obtained at 13MHz in the longitudinal and transverse fields, respectively. In FeCuNbSiB/SiO2/Ag/SiO2/ FeCuNbSiB films, the maximum giant magneto-impedance ratios were 47% and 57% at the same frequency for the two cases, which are much larger than those obtained in the annealed single layer films.

Stimulated Emission in Blue Wavelength Region from a Copolymer
LIU Xing-yuan, WANG Shu-mei, FENG Ji-meng, LIANG Chun-jun, ZHAO Dong-xu, HONG Zi-ruo, LI Wen-lian, PENG Jun-biao, YU Jia-qi, ZHAO Jia-min, WANG Li-jun, WANG Li-xiang, JING Xia-bin, WANG Fo-song
Chin. Phys. Lett. 1999, 16 (6): 455-457 .  
Abstract   PDF(pc) (188KB) ( 355 )
A dye laser based on the soluble conjugated polymer, Poly[1,8-octanedioxy-2,6-dimethoxy-1,4-phenylene-1,2-Ethenylene-l, 4-phenylene-1,2-ethenylene-3,5-dimethoxy-1,4-phenylene], has been fabricated. The laser was pumped by light pulses from the third harmonic radiation of an Nd:YAG laser. The lasing was observed in the blue wave- length region with the peak at 450nm. The threshold energy is about 19μJ. The energy conversion yield of the laser is about 3.4%. The maximum peak power of the laser output pulse arrives at about 20kW.
Frequency-Size Distribution of Model Seismicity in a Statistical Mechanical Model of Earthquakes
WU Zhong-liang
Chin. Phys. Lett. 1999, 16 (6): 458-460 .  
Abstract   PDF(pc) (236KB) ( 386 )
The frequency-size distribution of model earthquakes in a one-dimensional Burridge-Knopoff spring-block model [Phys. Rev. Lett. 22 (1989) 2632] is studied. Analytical approach is taken to avoid the limitations on the size of models and computation time in numerical calculations. By using the Hamiltonian of the spring-block system a concept of seismic phonon' is proposed which is similar to the concept of phonon in solid state physics. The result of the occurrence frequency of model earthquakes shows a distribution similar to the modified gamma distribution proposed by Main and Burton using information theory.
Modified Magnetohydrodynamic Model of Magnetic Reconnection
ZHOU Guo-cheng, CAI Chun-lin, CAO Jin-bin, ZHANG Yang-ting, CHEN Tao, WANG De-ju
Chin. Phys. Lett. 1999, 16 (6): 461-463 .  
Abstract   PDF(pc) (538KB) ( 331 )
This paper presents the modified magnetohydrodynamic (MHD) model and simulations of solar wind-magnetosphere interactions. We use the two-dimensional and three-component, compressible, resistive, ion gyroviscous and Hall MHD model, i.e., including the ion finite Larmor radius (FLR) and Hall MHD effects, but neglecting the electron inertia and electron FLR effects. The composed dynamic pressure pulses (shear variations in the flow velocity) in the solar wind form gusts that continually buffet the magnetosphere and cause the time-dependent magnetic reconnection a t the magnetopause. The results show that the magnetic field and the flow velocity components perpendicular to the reconnection plane can be generated in magnetopause current layer. The vortical flow structures can also occur in the magnetospheric side region. These results are responsible for non-ideal MHD properties of the plasma fluid, i.e., ion FLR and Hall MHD effects.
Entropy Change of Black Holes in Disk-Accretion
WANG Ding-xiong, DAI Liao-zhong
Chin. Phys. Lett. 1999, 16 (6): 464-466 .  
Abstract   PDF(pc) (202KB) ( 399 )
Entropy change of central black holes of accretion disks (including thin and thick disks) is investigated by considering both accretion and the Blandford-Znajek (BZ) process in detail. It is shown that the contribution of the BZ process to the rate of change of black hole entropy is always less than that arising from accretion process in the case of thin disks, while the former may be greater than the latter for a fast-spinning black hole surrounded by a thick disk. In addition the non-monotonic characteristics of the rate of change of black hole entropy in the BZ process are discussed.

Luminosity Limit of Super-Eddington Accretion onto Black Holes
WANG Jian-min
Chin. Phys. Lett. 1999, 16 (6): 467-468 .  
Abstract   PDF(pc) (181KB) ( 350 )
The luminosity limit is derived for the Super-Eddington accretion by obtaining the self-similar solution. The maximum luminosity is about 4.0 x 1037 erg/s(M/Mסּ) or so (significantly less than the Eddington luminosity) due to photon trapping although the accretion rate is Super-Eddington. The radiation spectrum is found to be universal as Fν ∝ ν-1.

28 articles