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Volume 16 Issue 5
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Original Articles
A Method to Generate New Exact Solutions from a Known Stationary Solution
LIU Zeng-rong, HUANG De-bin
Chin. Phys. Lett. 1999, 16 (5): 313-315 .  
Abstract   PDF(pc) (175KB) ( 477 )
By combining the Backlund transformations and the AKNS system [Study in Appl. Math. 53 (1974) 249.] which is a linear eigenvalue problem of the corresponding evolution equation, a method to find new exact solutions from known stationary solutions for nonlinear integrable equations is proposed. As an example, Korteweg de Vries (KdV) equation is used to illustrate this method, and a class of new exact solutions of KdV equation is obtained.
Geometric Phase in Optical Fiber
ZHOU Yi, WU Zhen-hua, GE Mo-lin
Chin. Phys. Lett. 1999, 16 (5): 316-317 .  
Abstract   PDF(pc) (156KB) ( 338 )
An additional geometric phase viewed as Berry's phase is found in helically coiled monomode optical fiber when linear birefiingences are induced by material. The phase appears when the optical axis and normal vector do not coincide to each other.
General Character of Quantum Regular Motion and Quantum-Classical Correspondence
XU Gong-ou, YANG Ya-tian, XING Yong-zhong
Chin. Phys. Lett. 1999, 16 (5): 318-320 .  
Abstract   PDF(pc) (255KB) ( 397 )
In order to have a complete description of the spatio-temporal evolution of a quantum state, the initial state should be properly specified as the coherent state corresponding to a definite dynamical symmetry. Then we have qualitatively different situations where the initial coherent state evolves under the action of a system having or not having the same dynamical symmetry. In the former case, we have regular motion with the general character which tends to that of the corresponding classical case in the limit ћ → 0. While in the latter case, we may have energy regions of global stochasticity with characters closely related to the initial dynamical symmetry strongly violated.
Motion of Test Particle in Generalized Schwarzschild Geometry
ZHAI Xiang-hua, YUAN Ning-yi, LI Xin-zhou
Chin. Phys. Lett. 1999, 16 (5): 321-323 .  
Abstract   PDF(pc) (184KB) ( 669 )
By the Hamilton-Jacobi formalism, the features of orbits of a test particle moving in generalized Schwarzschild geometries with the parameter 0 < λ ≤ 1 are studied, where the intensity of λ corresponds to the contribution of massless scalar field. In special case λ= 1, it is reduced to the Schwarzschild metric. It is found that λ= 1/2 is a critical point, when 1/2 ≤ λ < 1 the qualitative features are similar to Schwarzschild geometry whereas the case of 0 < λ < 1/2 is different from the case of λ= 1.

On the Significance of Reference System for Active Damping of Vibration Isolators in Gravitational Wave Detection
ZHOU Ze-bing, LUO Jun, FAN Shu-hua
Chin. Phys. Lett. 1999, 16 (5): 324-326 .  
Abstract   PDF(pc) (264KB) ( 388 )
Several active damping methods corresponding to various reference systems are discussed. The theoretical analyses show that a quasi-fixed reference system can be used to improve the high-frequency performance of a multi-stage active damping system because its high-frequency performance is equivalent to that of a low-pass electronic filter with a very low cut-off frequency.
Transient Properties of a Bistable System Driven by Cross-Correlated Noises: Correlation Times are Nonzero Case
MEI Dong-cheng, XIE Guang-zhong, CAO Li, WU Da-jin
Chin. Phys. Lett. 1999, 16 (5): 327-329 .  
Abstract   PDF(pc) (218KB) ( 373 )
The transient properties of a bistable system driven by cross-correlated noises are investigated, the correlation times of the correlations between the noises are nonzero. The explicit expression of the mean ,first-passage time (MFPT) is obtained. From numerical computations we find the following.(l) The MFPT of the system is affected by the correlation time T and the correlation strength λ, T and λ play opposing roles in the MFPT. (2) For the case of perfectly correlated noises (λ = l), the MFPT corresponding to α > D and α < D (α and D are the additive noise and multiplicative noise intensities, respectively) exhibit the same behaviors and the MFPT for
α = D is continuous, which is very different from the case of T = 0 [Phys. Rev. E 53 (1996) 5764].

Equal-Time Transport Theory for Scalar Particles with Width
ZHUANG Peng-fei, Rolf Fauser
Chin. Phys. Lett. 1999, 16 (5): 330-332 .  
Abstract   PDF(pc) (243KB) ( 447 )
For a Ф4-theory the equal-time transport theory is derived with a collision term by including 4-point correlations. Within a ћ expansion a set of coupled equations is presented for the first three energy moments of the Wigner functions and the 4-point correlations. The presence of 4-point correlations. The limit ћ→ 0 is discussed. describing the collision term leads already in this limit to particles with width.
Analyses of Magnetic Force Images of Submicron Magnetic Mn-Ga Particles
LI Dan, HAN Bao-shan
Chin. Phys. Lett. 1999, 16 (5): 333-335 .  
Abstract   PDF(pc) (1044KB) ( 583 )
The sample was prepared by implanting Mn+ ions at energy of 80keV and Mn+ ions of dose of 2 x 1017/cm2 directly into the semi-insulating (100) GaAs wafer, followed by rapid annealing at 830°C for 90s. By using magnetic force microscopy, both the topographic and magnetic force images of the submicron particles in the surface layer of the sample were obtained. The formation of the magnetic particles is more complex, corresponding to more types of magnetic force image patterns. Computer simulation was carried out by integrating the interactions between the tip and the particles, which can be used to judge the magnetization direction of particles more accurately. Moreover, the simulation has confirmed that all submicron magnetic particles are single crystals with a single domain. In fact, the simulated patterns of the single-domain particles are the “elemental” magnetic force patterns for magnetic materials, hence their acquirement and collection are the basis of the analysis and explanation of magnetic force images.
What is Initial State of Scattering at Finite Temperature? *
HOU De-fu, ZUO Jian, LI Jia-rong
Chin. Phys. Lett. 1999, 16 (5): 336-338 .  
Abstract   PDF(pc) (214KB) ( 384 )
This letter addresses a problem concerning temperature corrections to the scattering processes. Although former studies had given the temperature-dependent phase space factors in the corrections, how to derive them from the first principles was not clear. In this letter, we consider this question within the formalism of thermal field dynamics. We find that if the initial and final states in scattering processes at finite temperature are constructed from the expanded vacuum states, the scattering rate in medium can be derived with the desired temperature-dependent phase space factors.
Probing New Physics from CP Violation in Radiative B Decays
WU Yue-liang
Chin. Phys. Lett. 1999, 16 (5): 339-341 .  
Abstract   PDF(pc) (325KB) ( 393 )
When new CP-violating interactions are dominated by flavor changing neutral particle exchanges, which may occur in many extensions of the standard model, we examine a type-3 two-Higgs-doublet model and find that direct CP asymmetries can be as large as about 25% . Time-dependent and time-integrated mixing-induced CP asymmetries up to 85 and 40%, respectively, are possible without conflict with other constraints. It mainly requirs an enhanced chromo-magnetic dipole b →sg decay to be close to the present experimental bound.

Staggering in Rotor Hamiltonians Without C4 Symmetry
LUO Wen-dong, LI Xun-jun
Chin. Phys. Lett. 1999, 16 (5): 342-344 .  
Abstract   PDF(pc) (273KB) ( 569 )
After a brief review of the negative results of the microscopic study, of both the Strutinsky shell correction method and Hartree-Fock approximation, for the C4 symmetry in nuclei, a proposed rotor Hamiltonian to simulate both the microscopic results and the staggering effect is investigated and the staggering resulting from the rotor Hamiltonians without C4 symmetry can be found.
Structure of High Spin States in 87Zr
ZHAO Guang-yi, LI Guang-sheng, WU Xiao-guang, LIU Xiang-an, WEN Shu-xian, LU Jing-bin, YUAN Guan-jun, YANG Chun-xiang
Chin. Phys. Lett. 1999, 16 (5): 345-346 .  
Abstract   PDF(pc) (170KB) ( 425 )
Structure of high spin states in 87Zr was studied through the reaction 59Co(32S, 3pn)87Zr at a beam energy of 118 MeV using in-beam γ-ray spectroscopic method. Measurement of γ-γ coincidence was performed, and directional correlation orientation ratios of some γ rays were determined. The level scheme of 87Zr was established up to spin (37/2+) and (43/2-). Many previously unknown states have been observed. Comparison with neighboring isotones indicates that the effect of neutron on nuclear structure property is predominant compared to proton, and there is a tendency of reduction in band crossing frequency with increasing proton number.
Λ* Resonance Model Calculation of K-p→ηΛ Reaction Near Threshold
JIANG Huan-qing, PENG Guang-xiong, YU Tao
Chin. Phys. Lett. 1999, 16 (5): 347-349 .  
Abstract   PDF(pc) (216KB) ( 302 )
A Λ* resonance model for the η – Λ interaction near threshold is proposed. By assuming the Λ* (1670) excitation dominates in the K-p→ηΛ reaction near threshold, the corresponding η production cross section and the s-wave η - Λ scattering length are calculated. The obtained production cross section is consistent with the available experimental data, which indicates that the Λ* (1670) excitation is dominant in the production reaction near threshold. The η - Λ interaction is found to be attractive.

Possibility of an Optically-Trapped Bose-Einstein Condensation
YIN Jian-ping, , Yifu Zhu, WANG Yu-zhu, Min Xiao
Chin. Phys. Lett. 1999, 16 (5): 350-352 .  
Abstract   PDF(pc) (274KB) ( 406 )
We propose a novel gravito-optical atom trap composed of a blue-detuned, conical dark-hollow-beam propagating upward and the gravity field. When cold atoms are loaded into the conical dark-hollow-beam from a magnetic-optical trap and bounce inside the hollow beam, they experience an efficient hollow-beam induced Sisyphus cooling and repurnping-beam induced geometric cooling. Our investigation shows that an ultracold and dense 87Rb atomic sample with an equilibrium 3D temperature of about 1μK can be obtained and the appearance of an optically-trapped Bose-Einstein condensation may be possible in this pure optical trap.
Modified-PVK-based Photorefractive Three-Component Low-Tg Composites
WANG Feng, CHEN Zhi-jian, GONG Qi-huang, CHEN Yi-wang, CHEN Hui-ying
Chin. Phys. Lett. 1999, 16 (5): 353-355 .  
Abstract   PDF(pc) (252KB) ( 403 )
Two modified poly(N-carbazole), poly (2-carbazolylethyl methacrylate) (PCEMA) and poly(3-carbazolylpropyl methacrylate) (PCPMA), were synthesized. Doped with electro-optic (EO) chromophore 1-n-butoxyl-2,5-dimethyl- 4-(4'-nitrophenylazo)benzene and the photosensitizer 2,4,7-trinitro-9-fl uorenone, the EO response and photore- fractive (PR) effect were studied experimentally. Due to the shorter spacer between the carbazolyl and the main-chain and thus a higher glass-transition-temperature Tg, PCEMA-based composite exhibited an effective EO coefficient as only a quarter as that in PCPMA-based composite. However, a slight higher two-beam coupling coefficient and much faster PR response were observed in the former. It was suggested that both the spacer length and the polymerization degree changed the Tg and the number density of traps, which decided the EO and PR

Flattening Spectrum of a Broadband and Wavelength Stable Erbium Doped Superfluorescent Fiber Source
YANG Bao, MING Hai, GUO Yang, XIE Jian-ping
Chin. Phys. Lett. 1999, 16 (5): 356-357 .  
Abstract   PDF(pc) (183KB) ( 345 )
A technique is used to design the spectra in erbium doped superfluorescent fiber source experimentally and theoretically. In an erbium doped fiber with a 10m length and 300ppm concentration, a line width of about 42nm and high mean wavelength stability (<0.lppm/K, <0.2ppm/mW) were obtained by means of a suitable population distribution, and adjusting the ratio of backward to forward pump power. Also, its thermal characteristic is studied. These results will improve the performance of fiber optical gyroscope and fiber sensors, and will be applied in erbium doped fiber amplifier with flattening gain.
Thermodynamic and Kinetic Characteristics of Glass Transition in an Amorphous Alloy Pd77.5Ni6.0Si16.5
DING Xing-zhao, LIU Xiang-huai, WU Qin-chong, HE Yi-zhen
Chin. Phys. Lett. 1999, 16 (5): 358-360 .  
Abstract   PDF(pc) (239KB) ( 454 )
Variation of some thermodynamic functions of an amorphous alloy Pd77.5Ni6.0Si16.5 in glass transition temperature region during various scans was measured by a differential scanning calorimeter. The Gibbs free energy of glassy state was examined to be larger than that of the undercooled liquid state when the specimen was heated up to the glass transition temperature region, which supports the idea of what there are thermodynamic origins underlying glass transition process. On the other hand, it was found that glass transition behaved differently during heating and cooling scans. Moreover, with increase of heating rate, the glass transition process was delayed gradually to higher temperatures. It can be concluded that glass transition is a kinetically modified thermodynamic phase transformation.
Porous Structures and Short-Wavelength Photoluminescence of C+-Implanted SiO2 Films
ZHAO Jun, MAO Dong-sheng, DING Xing-zhao, LIN Zi-xin, JIANG Bing-yao, YU Yue-hui, YANG Gen-qing, LIU Xiang-huai, S. Jin, H. Bender
Chin. Phys. Lett. 1999, 16 (5): 361-363 .  
Abstract   PDF(pc) (274KB) ( 445 )
C ions of three different energies were sequentially implanted into SiO2 films grown by plasma enhanced chemical vapor deposition. Microstructures of the samples were studied with transmission electron microscopy (TEM) and secondary ion mass spectroscopy As revealed by cross-sectional TEM, porous structures had been created in the implanted region during ion implantation. No photoluminescence (PL) was detected from the as-implanted samples. However, intense short-wavelength PL peaking at 360-370nm and ~ 450nm was observed from the annealed samples. The blue light from samples excited by an Xe lamp can be observed by naked eyes at room temperature. The light emission mechanisms are briefly discussed.

Equilibrium Segregation to Free Surface:Kinet ics and Experiment
CAO Ze-xian, Ralf Mueller, WANG En-ge, NIE Yu-xin
Chin. Phys. Lett. 1999, 16 (5): 364-366 .  
Abstract   PDF(pc) (213KB) ( 306 )
Fick's first law is modified with an additional term df(x)/dx to describe the segregation phenomenon, f(x) is a local, analytical function related to the depth profile at equilibrium. It thus can be determined experimentally by depth profiling technique. Segregation starting in an initially homogeneous solid is described by an inhomogeneous diffusion equation on the half-infinite domain. Segregation with and without formation of overlayer suggests different boundary conditions. The solution for the Ansatz f(x) = as exp(-x/ds) is in perfect agreement with experimental results on sulphur segregation to the surface of titanium. Independent from the detailed kinetics, activation energy can be inferred from the surface concentration evolution under different temperatures. For sulphur segregation in titanium, Eact = 718 meV/atom.
Preparation of GaN Thin Films by Reactive Ionized Cluster Beam Technique
MENG Xian-quan, ZHAO Chun, WANG Qiong, ZHANG Guan-ming, LUO Hai-lin, YE Ming-sheng, GUO Huai-xi, FAN Xiang-jun
Chin. Phys. Lett. 1999, 16 (5): 367-369 .  
Abstract   PDF(pc) (247KB) ( 455 )
GaN thin films were prepared by reactive ionized cluster beam technique at relatively low substrate temperature about 400oC. The composition, structure and morphology of the films were characterized by x-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The binding energy of N Is electron in the film is 397.85eV which shows the formation of Ga-N bonding. The film has a polycrystalline structure revealed by the measurement results of TEM and SEM. It was found that raising nitrogen ion ratio in the beam is helpful to decrease oxygen content in the film.
Growth of Ni Films Observed by Scanning Tunneling Microscopy and X-ray
WANG De-liang, U. Geyer
Chin. Phys. Lett. 1999, 16 (5): 370-372 .  
Abstract   PDF(pc) (591KB) ( 366 )
Scanning tunneling microscopy was used to measure the mean lateral dimensions D of grains at the surface of Ni films with thicknesses ranging from 15 to 200nm. The same films were analyzed by x-ray diffraction to obtain the average linear dimensions δ of coherent scattering regions in the direction normal to the film plane (coherence depths). For thin Ni films condensed on single sapphire substrate at room temperature, these two lengths D and δ are equal and increase with film thickness. But for films thicker than 130nm, these two lengths have different constant values and D > δ. This is because the coherent scattering depth is not only limited by the grain sizes but also by various defects in the grains. The difference between the constant values of D and δ disappears for films after annealing for 30min at 423K in the ultra-high vacuum system.

Spin-Related Electronic Structure of Quantum Wires with an In-plane Magnetic Field
WANG Chuan-kui, WANG Hong-song, ZHANG Qing-gang
Chin. Phys. Lett. 1999, 16 (5): 373-375 .  
Abstract   PDF(pc) (249KB) ( 450 )
Self-consistent calculation of the electronic structure of quantum wires are implemented with an in-plane magnetic field parallel to the wire and spin-density-functional theory of Kohn and Sham is applied [Phys. Rev. A 140 (1965) 1133]. The self-consistent results show that full spontaneous spin polarization takes place in low electron density regime, even at an arbitrary small magnetic field, which demonstrates that the polarization is caused by exchange interactions. The results are consistent with recent measurements of a conductance anomaly in a quantum point contact. Moreover, it is remarkable that a large splitting of spin-related subbands occurs repeatedly whenever the Fermi energy passes the subband threshold energies, although the amplitude of the splitting becomes weaker as more subbands are occupied due to the screen effect. Self-consistent results indicate that a moderate magnetic field tends to suppress the spin polarization caused by the exchange interaction. The diamagnetic shift of the subbands is determined only for those which are close to the Fermi energy.
X-Ray Photoelectron Spectrascopy Investigation of Ceria Doped with Lanthanum Oxide
DU Xue-yan, LI Wen-chao, LIU Zhen-xiang, XIE Kan
Chin. Phys. Lett. 1999, 16 (5): 376-377 .  
Abstract   PDF(pc) (155KB) ( 448 )
The influence of doping lanthana on valent state of CeO2 surface has been studied by using x-ray photoelectron spectrascopy It was found that La3+ doping in host CeO2lattice can promote to convert Ce4+ into Ce3+ and enhance adsorbing-carbonyl capacity of the materials. However, the inversion of Ce4+ to Ce3+ is depressed by dopant La3+ during argon ion bombardment.
Quantum XY Spin Glass Model with Longitudinal Ferromagnetic Coupling
SHANG Yu-min, YAO Kai-un,
Chin. Phys. Lett. 1999, 16 (5): 378-380 .  
Abstract   PDF(pc) (203KB) ( 374 )
The quantum XY spin glass model with longitudinal ferromagnetic coupling is investigated in static replica symmetry limit. Several thermodynamic quantities are calculated numerically. We find that the ferromagnetic coupling enhances the stability of replica symmetric solution. A 2-dimensional Ising model like transition is found, which demonstrates that the ferromagnetic coupling increases the order of spin glass model. Affected by the ferromagnetic coupling, transverse component of the susceptibility has two cusps corresponding to transverse-longitudinal spin-glass phase transition and longitudinal spin glass-paramagnetic transition separately.
Surface Magnetism of One Monolayer Mn Atoms on GaAs(001) Surface
YANG Zong-xian, JIN Xiao-feng, ZHANG Kai- ming, XIE Xi-de
Chin. Phys. Lett. 1999, 16 (5): 381-383 .  
Abstract   PDF(pc) (259KB) ( 389 )
The surface magnetism of one monolayer Mn atoms on GaAs(001) surface is studied by the self-consistent tight-binding linear muffin-tin orbital method. It is found that the magnetic ordered phases (ferromagnetic and antiferromagnetic) are more favorable than the paramagnetic one, the density of states peak far below the Fermi level observed in synchrotron radiation photoemission study has been identified as due to the contribution of Mn 3d majority states.
Efficient Tunable All-Solid-state Pyrromethene Dye Laser Pumped by a Laser-Diode Pumped Nd:YAG Laser
ZHANG Qin-yuan, WANG Jue, HU Li-li, JIANG Zhong-hong
Chin. Phys. Lett. 1999, 16 (5): 384-386 .  
Abstract   PDF(pc) (211KB) ( 488 )
Efficient and stable laser dyes pyrromethene-BF2 complexes were successfully incorporated into organically modified silicate (Ormosil) matrices via sol-gel process. Laser oscillation were easily observed in all hand-polished dye-doped Ormosils pumped by frequency-doubled radiation from a laser-diode pumped Q-switched Nd:YAG laser. A slope efficiency of 57% has been obtained from one of the dyes in Ormosil, the cavity was continuously tunable over 50nm, from 550 to 600nm. The laser output energy has only 10% reduction after 3.0X104 pulses at a pump repetition rate of 30Hz and a pump intensity of 1 J/cm2. An efficient, all-solid-state, compact, long-lifetime, and tunable dye laser has been demonstrated.
A Novel Blue Thin Film Electroluminescent Phosphor Gd3Ga5Ol2:Ag
XU Xiu-lai, , XU Zheng, HOU Yan-bing, WANG Xiao-wei, CHEN Xiao-hong, , XU Xu-rong,
Chin. Phys. Lett. 1999, 16 (5): 387-388 .  
Abstract   PDF(pc) (173KB) ( 396 )
A new blue thin film electroluminescence (TFEL) phosphor Gd3Ga5Ol2:Ag is prepared by electron beam evaporation. Photoluminescence and Electroluminescence of Gd3Ga5Ol2:Ag film were investigated. The luminance of TFEL device excited by an alternating-current sinusoidal voltage with frequency of 1000 Hz is about 2cd/m2.
Preparation and Microstructure of Nanocrystalline Grain Ag-MgF2 Cermet Film
SUN Zhao-qi, SUN Da-ming, LI Ai-xia, XU Zhi-yuan
Chin. Phys. Lett. 1999, 16 (5): 389-390 .  
Abstract   PDF(pc) (278KB) ( 370 )
Nanocrystalline grain Ag-MgF2 cermet films were prepared by using sintered-in-vacuum Ag-MgF2 mixture granules as evaporant. The microstructure and the electronic energy states of the films were examined by x-ray diffraction, transmission electron microscopy, electron diffraction and x-ray photoelectron spectroscopy. The results showed that obtained Ag-MgF2 cermet films consist of mainly amorphous MgF2 matrix with embedded fcc-Ag nanocrystalline grains. The principal x-ray diffraction peaks at d = 3.4245, 2.6102, and 2.0503Ǻ are probably related to Ag-MgF2 cermet composite structure.
28 articles