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Volume 16 Issue 9
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Original Articles
Differential Completeness Relation in Two-Mode Mass-Weighted |ξ〉- |τ〉Representations
FAN Hong-yi, LIU Nai-le
Chin. Phys. Lett. 1999, 16 (9): 625-627 .  
Abstract   PDF(pc) (176KB) ( 434 )
The explicit form of the common eigenstates |τ〉of the mass-weighted relative coordinate μ2Q1–μ1Q2 and the mass-combinatorid momentum μ1P12P2 of two particles is given. On the basis of |τ〉and their conjugate states |ξ〉, we find that there exist new differential completeness relations (DCR). The applications of the new DCR in deriving the normally ordered two-mode squeezing operators for the mass-related coordinates and momenta are demonstrated. Throughout the discussion the technique of differentiation within an ordered product of operators is fully employed.
A Proposal of Teleportation for Three-Particle Entangled State
YANG Chui-ping, GUO Guang-can
Chin. Phys. Lett. 1999, 16 (9): 628-629 .  
Abstract   PDF(pc) (162KB) ( 494 )
We propose a scheme for teleporting a three-particle entangled Greenberger-Horne-Zeilinger state to three distant users. The scheme operates essentially through the sharing of Einstein-Podolsky-Rosen pairs followed by only local measurements and unitary operations. It can be regarded as a method for generating the entanglement of particles distributed in a communication network.
Transmission Efficiency of X-Rays Through a Cylinder Capillary
CHEN Bao-zhen, YAN Yi-ming
Chin. Phys. Lett. 1999, 16 (9): 630-631 .  
Abstract   PDF(pc) (157KB) ( 318 )
A new model for calculating the transmission efficiency of x-rays through a cylinder capillary is proposed. The model is based on some reasonable physical and mathematical assumptions. The calculation results given by the model have satisfactory intrinsic consistency and can get quite a good fit to the experimental results.
Spin Assignment of the First Discovered Superdeformed Band 152Dy(1) and Some Superdeformed Bands in Neighboring Nuclei
LIU Shu-xin, XIN Xiao-bin, ZENG Jin-yan
Chin. Phys. Lett. 1999, 16 (9): 632-634 .  
Abstract   PDF(pc) (231KB) ( 588 )
By using various approaches to the spin assignment, including the best-fit-method, the variation of moment of inertia with angular momentum, the bandhead moment of inertia J0 systematics, and the signature systematics, the spin of the lowest level observed in the first discovered superdeformed band 152Dy(1)is definitely predicted to be I0 = 26(Eγ(I0 + 2 → I0) = 602.4 keV), rather than the previously predicted I0 = 22,24, or 25. The spin prediction and properties of some superdeformed bands in the A ~ 150 region are discussed.
Identification of Collective Oblate Bands in 138Ce
ZHU Sheng-jiang, LI Ming, ZHU Ling-yan, GAN Cui-yun, M. Sakhaee, YANG Li-ming, PAU San-li, LONG Gui-lu, DENG Jing-kang, WEN Shu-xian, WU Xiao-guang, LIU Xiang-an
Chin. Phys. Lett. 1999, 16 (9): 635-637 .  
Abstract   PDF(pc) (195KB) ( 444 )
High spin states in 138Ce have been investigated following heavy-ion induced reactions carried out at the China Institute of Atomic Energy, Beijing. Two collective rotational bands were established for the first time. These two bands show oblate deformation with γ= -60°and probably originate from the four quasiparticle configurations πg7/2 πh11/2vh11/2 vd3/2 and πg7/2πh11/2 [vh11/2]2, respectively. These oblate bands exhibit strong M1 transitions, no signature splitting and different moments of inertia from those of prolate bands.
A New Method for Calculations of Two-Electron Systems in Magnetic Field
QIAO Hao-xue, LIU Lian-jun, ZHANG Zhe-hua, LI Bai-wen
Chin. Phys. Lett. 1999, 16 (9): 638-640 .  
Abstract   PDF(pc) (214KB) ( 370 )
A method suitable for two-electron systems in a range running from low to high fields is given. ML = -1 triplet state of H- ion and He atom are used to introduce the new means. All the matrix elements in our calculations are formulated as products of simple, independent one-dimensional numerical integrals and analytic ones. As a result, lower energies compared to those obtained with spherical coordinates in low fields, and cylindrical coordinates in high fields are presented.
Quantum Beat Spectroscopy of SO2 in the 235-224nm Range
CHEN Yang, PEI Lin-sen, JIN Jin, CHEN Cong-xiang, MA Xing-xiao
Chin. Phys. Lett. 1999, 16 (9): 641-642 .  
Abstract   PDF(pc) (190KB) ( 311 )
Using time-resolved laser-induced fluorescence(L1F) spectroscopy, the fluorescence quantum beat decay was observed in C ( 1B2 ) ← X(1A1) transition of SO2 molecule. The experimental results show that only the v3 mode and its combination band v1 + v2 + v3 excitation exist the beat decay. Analyzing the result, we attribute the quantum beat states to the coupling of the v3 vibration mode of C state with the high vibrational levels of the electronic ground state.



A Semi-relativistic Distorted Wave Calculation of Electron Impact Excitation of Gold
GAO Jun - fang, PANG Wen-ning, GAO Hong, SHANG Ren-cheng
Chin. Phys. Lett. 1999, 16 (9): 643-645 .  
Abstract   PDF(pc) (202KB) ( 415 )
A semi-relativistic distorted wave method has been developed to calculate the differential cross section (DCS) and Stokes parameters for electron impacting excitation of gold atom at 30 eV. At large angle ( ≥60°) our DCS results are within the experimental error limit. At small angle ( ≤60°) our DCS results deviate a little from the experimental data. In the whole range our DCS data are roughly the same as those of complete relativistic distorted wave (RDW) method. The P1 and P2 calculated from our semi-relativistic method both in structure and tendency are similar to those of the complete RDW method. In particularly, -P3 calculated from two kinds of relativistic methods are almost the same in magnitude and structure. The difference between our results and those of complete RDW method may come from the neglecting direct relativistic of incident electron in our calculation. By comparing the results with those of experiment and complete RDW method it is deduced that the semi-relativistic distorted wave is a convenient and reliable method.
Photon Statistics of Photon-Added and Photon-Subtracted Two-Mode Squeezed Vacuum State
LU Hong
Chin. Phys. Lett. 1999, 16 (9): 646-647 .  
Abstract   PDF(pc) (147KB) ( 648 )
We introduce states a†m |ξ〉and am|ξ〉, where |ξ〉is a two-mode squeezed vacuum state. We examine the properties of these states by analytic derivation. Because of the entanglement between the modes of the field, photon adding (or subtracting) for one of the modes results in interesting outcomes. For a two-mode squeezed vacuum state, the effect of annihilation of m a-photons is just the same as creation of m b-photons. Annihilation of photons of mode a (or mode b) actually increases the mean number of photons of mode a and mode b. We also calculate Mandel Q parameter, cross-correlation function and squeezing of the field.
Squeezed Cascade Two-Quantum-Beat Lasers
HU Xiang-ming, PENG Jin-sheng
Chin. Phys. Lett. 1999, 16 (9): 648-650 .  
Abstract   PDF(pc) (257KB) ( 387 )
Noise squeezing of intensity difference between the pair of sum modes may be generated in a cascade laser of Λ and V quantum-beats. The best achievable squeezing is up to 50% below the shot noise limit. This new kind of squeezed lasers has potential for quantum communications and precision measurements.
Self-Frequency Doubling Laser Performance of Nd:GdCOB Crystal with a Phase-Matching Angle Out of the Principal Plane
LÜ, Jun-hua, LI Guang-ming, LIU Jun-hai, ZHANG Shu-jun, CHEN Huan-chu, JIANG Min-hua, SHAO Zong-shu
Chin. Phys. Lett. 1999, 16 (9): 651-652 .  
Abstract   PDF(pc) (188KB) ( 379 )
The self-frequency doubling laser performance of Nd:GdCOB crystal cut in phase-matching direction (θ = 66.3°, Ф= 134.4 °) was compared with the crystal cut in the direction of (θ= 90 °, Ф = 46°). Results show that the former has a higher second-harmonic conversion efficiency than the latter. Using Ti:sapphire laser as pumping source, a maximum of 11.3mW of green light has been obtained with an incident power of 520mW. This corresponds to an optical-optical conversion efficiency of 2.2%. Laser threshold for self-frequency doubling operation is measured to be 1 mW. To our knowledge, this is the lowest threshold achieved so far.

Nickel-Like Molybdenum and Niobium Soft X-Ray Lasing Driven by 200 ps Laser Pulses with 50 J of Energy
GU Yu-qiu, LI Ying-jun, LI Yu-tong, CHUNYU Shu-tai, YOU Yong-lu, HUANG Wen-zhong, HE Shao-tang, HE Ying-ling, LU Li-zhu, YUAN Xiao-dong, WEI Xiao-feng, ZHANG Chuan-fei, ZHANG Jie
Chin. Phys. Lett. 1999, 16 (9): 653-655 .  
Abstract   PDF(pc) (230KB) ( 559 )
Intense lasing at 18.9 and 20.3nm in nickel-like molybdenum and niobium ions has been observed by using two 200ps laser pulses with total energy of 50 J at 1.053 μm from XingGuang II laser facility. Their gain coefficients were measured to be 1.6 and 1.5cm-1, respectively. This shows the possibility of extending Ni-like x-ray lasing in low-Z elements and paves the way towards small scale x-ray lasers for applications at university laboratories.
Heterodyned Femtosecond Optical Kerr Effect of Substituted Conjugated Polymers
LIN Li, QIAN Wei, WANG Cong-fang, ZOU Ying-hua, WANG Qian, CHEN Hui-ying
Chin. Phys. Lett. 1999, 16 (9): 656-658 .  
Abstract   PDF(pc) (272KB) ( 419 )
The femtosecond optical heterodyne detected optical Kerr effect is described. The real and the imaginary parts of complex third-order optical nonlinearity can be effectively separated and their values and signs can be determined. Using this method, we have thoroughly investigated the substitution effect by adding side-groups on the -(-C=N-)- conjugated system, a new class of nonlinear optical material, and find that the polybenzonitrile (γr = -1.59 x10-31 esu, m = 6 ) is an order of magnitude superior to poly-amino-nitrile. But when we further add substituents on benzoid rings, the enhancement is limited. We can say that for the series of polybenzonitrile, the benzoid ring can improve the x(3) value more effectively than other substitutions.

A Direct Perturbation Method: Nonlinear Schrodinger Equation with Loss
LOU Sen-yue
Chin. Phys. Lett. 1999, 16 (9): 659-661 .  
Abstract   PDF(pc) (266KB) ( 1075 )
Using the nonlinear Schrodinger (NLS) equation, which is used to describe the propagation of the solitons in many real physical systems like fiber and plasma, as a simple example, a direct perturbation method is established. Up to the adiabatic (zero order) approximation, any waves of the NLS equation decay in the same rate. Especially, different from the known claims in literature, the decay rate of the dark soliton in fiber is the same as that of the bright soliton. Starting from any one of the infinitely many adiabatic symmetries (or conservation laws) of the nonperturbative NLS equation, one can get the same adiabatic solutions. An adiabatic symmetry by multiplying a decay factor is just the first order modification. Higher order modifications can be obtained by solving linear equations.
Pinches-Induced Transport Reduction in Reversed Shear/Optimized Shear Tokamak Plasmas
QIU Xiao-ming, WANG Ai-ke
Chin. Phys. Lett. 1999, 16 (9): 662-664 .  
Abstract   PDF(pc) (270KB) ( 366 )
The analytical formulas for anomalous particle and ion thermal diffusivities, Dte and xti, are derived on the basis of the two-fluid equations of our previous paper [Chin. Phys. Lett. 15 (1998) 721]. The two formulas involve five factors: (reversed/optimized) magnetic shear LB( r ) , E x B sheared velocity VE(r), where E is from the gradient of the ion pressure Pi, and the three ways of coupling between them, L-1B(dVE/dr), L-1B VE, and k .VE , where k is the LB-dependent wavevector. It is found that the five factors can produce turbulent particle- and heat-pinch, i.e., Dte< 0 and xti< 0, in the core region of tokamaks, and hence the effective particle and ion thermal diffusivities, Deeff and xieff, reduce significantly in that region. The numerical results for Deeff and xieff are in good agreement with experimental values.
Application of Reactive Ion Etching to the Fabrication of Microstructure on Mo/Si Multilayer
LE Zi-chun, L. Dreeskornfeld, S. Rahn, R. Segler, U. Kleineberg, U. Heinzmann
Chin. Phys. Lett. 1999, 16 (9): 665-666 .  
Abstract   PDF(pc) (174KB) ( 315 )
Mo/Si multilayer mirrors (30 periods, doublelayer thickness 7nm) with the AZ-PF514 resist pattern whose smallest lines and spaces structure was 0.5μm were etched by reactive ion etching (RIE) in a fluorinated plasma. The etch rate, selectivity and etch profile were investigated as a function of the gas mixture, pressure, and plasma rf power. The groove depth and the etch profile were investigated by an atomic force microscope before RIE, after RIE and after resist removal.
Experimental and Theoretical Studies on Composition Limits of Metallic Glass Formation in the Ni-Mo System
LI Zheng-cao, LIU Bai-xin
Chin. Phys. Lett. 1999, 16 (9): 667-669 .  
Abstract   PDF(pc) (281KB) ( 510 )
The Ni-Mo system was selected as a model system to study the composition limits of metallic glass formation by ion mixing experiments as well as by molecular dynamics simulation. The 200keV xenon ion mixing was conducted for ten Ni-Mo mutilayered samples with various concentrations and the results showed that the glass-forming composition range was 39.8-80.4at.% Mo, which is in good agreement with the assessment from an empirical model. Through comparing the stability of the Ni-rich and Mo-rich solid solutions with various concentrations versus their amorphous counterparts, two critical supersaturated solid solubilities were found by molecular dynamics simulation to be 21 at.% Mo in Ni and 25at.% Ni in Mo, from which the glass forming range was deduced to be within 21-75 at.% Mo. The correlation of the simulated glass-forming range with those obtained by ion irradiation and solid-state reaction is also discussed.
Luminescent Properties of Nano-crystalline Silicon Films Embedded in SiO2
LIN Xuan-ying, LIN Kui-xun, YAO Ruo-he, SHI Wang-zhou, LI Mei-ya, YU Chu-ying, YU Yun-peng, LIANG Hou-yun, XU Yan-ping
Chin. Phys. Lett. 1999, 16 (9): 670-671 .  
Abstract   PDF(pc) (202KB) ( 337 )
Nano-crystalline silicon (nc-Si) films embedded in SiO2 exhibited strong visible light luminescence at room temperature. The energies of photoluminescence peak were found to be more than 1.9eV and the peaks shifted to higher energies when nano-Si films were post-oxidized. The photoluminescence intensity depended significantly on the size of the grains and the characteristics of the oxidized surface. Microcrystalline silicon grains of 2-3nm average size and radiation recombination centers located on the nanoscale silicon grain surfaces and located in the Si oxide layers are considered to be the source of the visible luminescence.
Growth, Defects and Electrooptic Properties of RbTiOAsO4 Crystal
WANG Ji-yang, WEI Jing-qian, YIN Xin, HU Xiao-bo, CUI Wei-hong, GUAN Qing-cai, LIU Yao-gang
Chin. Phys. Lett. 1999, 16 (9): 672-674 .  
Abstract   PDF(pc) (299KB) ( 507 )
RbTiOAsO4(RTA) crystals of high optical quality were grown with flux method. The defects of RTA crystals are mainly growth striations, growth sector boundaries and sometimes ferroelectric domains. The refractive indices and electrooptic coefficients were measured together with dielectric constants, ionic conductivity and direct current resistivities. It is shown that RbTiOAsO4 is not only as good a nonlinear optical crystal as KTiOPO4 but also a superior electrooptic crystal.

Optical Absorption and X-Ray Diffraction Studies of Sulfur Under High Pressure
CHEN Liang-chen, WANG Li-jun
Chin. Phys. Lett. 1999, 16 (9): 675-676 .  
Abstract   PDF(pc) (169KB) ( 374 )
In situ high pressure optical absorption measurements of sulfur have been carried out by using DAC device with a TASCO V-550 UV-VIS spectrophotometer at pressures up to 41.6GPa. The curves of absorption edge vs pressure were obtained, in which there are two turning points at about 5 and 12GPa, corresponding to two changes of colour in the optical observation: one is from yellow to red and the other from red to black at 5-6.5 and 10-12GPa, respectively. The absorption edge reaches above 800nm when the pressure is increased to 23GPa. The structure and phase transitions have also been investigated by using in situ high pressure energy-dispersive x-ray diffraction with synchrotron radiation at pressures up to 33.7GPa. No structure phase transition occurs at 5-6 GPa, but there is a new high-pressure phase, caused probably by the reorientation or ordering of S8.
Simulation of Nucleation of Anisotropic Si Islands on Reconstructed Si(100)(2x1) Surface
WU Feng-min, ZHANG Jie-fang, ZHU Qi-peng, WU Zi-qin
Chin. Phys. Lett. 1999, 16 (9): 677-679 .  
Abstract   PDF(pc) (358KB) ( 411 )
The nucleation of anisotropic Si islands on reconstructed Si(100)(2x1) surface has been studied by computer simulation, in which the anisotropic diffusion rate along different direction of the substrate is included. Some results such as anisotropic islands formed at various substrate temperatures, the number of islands (including single Si dimers) with different anisotropic diffusion are obtained. It is shown that the shape and number of anisotropic Si islands are dependent obviously on the substrate temperature and the anisotropic diffusion. The simulation results are consistent with the experimental observations.



Spectra of Hydrogenic Donor States in Quantum-Dot Quantum Well Structures
LUO Ying, XIE Hong-jing, MA Ben-kun, LI Jia-qiang, ZHU Jia-lin,
Chin. Phys. Lett. 1999, 16 (9): 680-682 .  
Abstract   PDF(pc) (248KB) ( 503 )
The series expansion approach has been employed to calculate the exact energy spectra of hydrogenic donor states in a quantum-dot quantum well(QDQW). The result shows that the hydrogenic donor energy levels are very different from those in a quantum dot. In a QDQW, the donor energy levels depend on not only the radius of core and the barrier, but also the numbers of small wells. When there exist two small wells outside the core, the “band gap”exists between donor levels, and its width depends on the depth of the small wells.
Femtosecond Time-Resolved Near-Field Spectroscopy of CdSe Nanocluster Films
YAN Hong, QIAN Wei, DENG Yu-jun, XIA Zong-ju, ZOU Ying-hua, ZHANG Jing-bo, LIN Yuan, XIAO Xu-rui
Chin. Phys. Lett. 1999, 16 (9): 683-685 .  
Abstract   PDF(pc) (292KB) ( 393 )
By using scanning near-field optical microscopy in the femtosecond time-resolved pump-probe experiments, we have studied the time-resolved near-field spectroscopy of CdSe nanocluster films. The submicrometer space dependence of electron dynamics was observed, which is attributed to the non-uniform distributions of interstitial defects in the films.
C-Axis Current -Voltage Characteristics of Mesa Structures on Bi2Sr2CaCu2O8+δ Single Crystals Fabricated by a Simple Technique Without Photolithography
FENG Yi-jun, SHAN Wen-lei, YOU Li-Xing, ZHOU Gan-dong, JI Zheng-ming, KANG Lin, XU Wei-wei, YANG Sen-zu, WU Pei-heng, ZHANG Yu-heng
Chin. Phys. Lett. 1999, 16 (9): 686-688 .  
Abstract   PDF(pc) (283KB) ( 433 )
A simple technique is reported for fabricating the mesa structure on Bi2Sr2CaCu2O8+δ single crystal. In the patterning process, metal masks are used instead of photolithography and argon ion milling is applied to form the small mesa on the Bi2Sr2CaCu2O8+δ crystal surface. Real four-probe transport measurements are made on the mesa structure and typical c-axis current-voltage (I - V) characteristics of the intrinsic Josephson effect have been observed. The superconducting gap parameter can be extracted from the multi-branch structure in the I - V characteristics. Additionally, from the strong hysteresis in the I - V characteristics, the capacitance CJ of the unit intrinsic Josephson junction has been estimated to be 2.3pF, which is in good agreement with that evaluated from the geometric parameters of the unit junction between the two copper oxide layers.
Numerical Study on the Two-Dimensional Vortex System with Random Pinning
CAO Yi-gang, YU Ya-bin, JIAO Zheng-kuan
Chin. Phys. Lett. 1999, 16 (9): 689-691 .  
Abstract   PDF(pc) (266KB) ( 356 )
We study numerically the dynamic behavior of the two-dimensional vortex lattice, moving in a random pinning potential under the action of an external driving force. Different densities of randomly distributed pointlike pinning centers and different vortex-vortex interacting strength are considered. Then the elastic and plastic regimes are found to be dependent on the relation between the vortex-vortex and the vortex-pin interacting potentials. The critical driving force increases with increasing density of pinning centers and with decreasing of the vortex-vortex interacting strength. The simulated results are consistent with the recent experiments, and some of our results fall outside the region of validity of collective pinning theory.
Implementation of a Quantum Algorithm for Deutsch- Jozsa Problem with Improved Nuclear Magnetic Resonance Sequences
ZHANG Yan, LUO Jun, XIAO Li, FU Li-ping, QIU Jian-qing, ZENG Xi-zhi, YE Chao-hui
Chin. Phys. Lett. 1999, 16 (9): 692-694 .  
Abstract   PDF(pc) (210KB) ( 441 )
A quantum algorithm for Deutsch-Jozsa problem was implemented by nuclear magnetic resonance of benzene with heteronuclear decoupling during the readout period. It was demonstrated that decoupling can not only remove the undesired long-range couplings but also save the frequency space taken up by nuclear spins, which was expected to be important when scaling to large systems, and also to enhance the signal-to-noise ratio.
High-pressure Sound Velocity of Perovskite-Enstatite and Possible Composition of Earths Lower Mantle
GONG Zi-zheng, XIE Hong-sen, LIU Yong-gang, HUO Hui, JING Fu-qian, GUO Jie, XU Ji-an,
Chin. Phys. Lett. 1999, 16 (9): 695-697 .  
Abstract   PDF(pc) (226KB) ( 341 )
The compressional sound velocity vp for enstitate of polycrystalline specimens was measured at pressures from 40 to 140 GPa by using the optical analyzer techniques under shock loading. The dependence of vp (in units of km/s) on Hugoniot pressure p (in units of GPa) can be described by: vp = 3.079 - 0.691 lnp + 0.0941n2p. The vp satisfies Birch's law: vp = 6.213 + 1.212 ρ, where ρ is corresponding density, indicating that enstatite is stable throughout the conditions of the lower mantle. Here P wave velocity is 0.5% lower and S wave velocity is 2% higher than those of preliminary reference earth model, respectively. It is concluded that the lower mantle is mainly composed of perovskite-(Mg1-x,Fex)SiO3 and only small amount of (Mg1-x,Fex)O is allowed in it.





Entropy of Kerr-Newman Black Hole Continuously Goes to Zero when the Hole Changes from Nonextreme Case to Extreme Case
ZHAO Zheng, ZHU Jian-yang, LIU Wen-biao
Chin. Phys. Lett. 1999, 16 (9): 698-670 .  
Abstract   PDF(pc) (247KB) ( 446 )
A new formulation of the Bekenstein-Smarr formula of a Kerr-Newman black hole is given. The re-defined black hole entropy continuously goes to zero as the black hole temperature approaches absolute zero, which satisfies the Nernst theorem. Our new result suggests that the Kerr-Newman black hole should be regarded as a composite thermodynamic system composed of two sub-systems, its outer horizon and its inner horizon. There exists a new quantum thermal effect. “Hawking absorption”, near the inner horizon of the black hole.
Bosonic Membranes and the Cosmic Matter-Structure Formation
TAO Bi-xiu
Chin. Phys. Lett. 1999, 16 (9): 701-702 .  
Abstract   PDF(pc) (164KB) ( 297 )
The structures in the universe usually group as they are observed today, in forms such as “walls of galaxies”, hollow spheres and cosmic foam. An interpretation of the origin and evolution of the structures is given by a solution of bosonic membranes, which agrees well with the astronomical surveys.
29 articles