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Volume 17 Issue 7
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Original Articles
Broadcasting of Entanglement in Three-Particle Greenberger-Horne-Zeilinger State via Quantum Copying
TONG Zhao-Yang, KUANG Le-Man
Chin. Phys. Lett. 2000, 17 (7): 469-471 .  
Abstract   PDF(pc) (254KB) ( 579 )
We introduce entanglement measures to describe entanglement in a three-particle system and apply it to studying broadcasting of entanglement in the three-particle Greenberger-Horne-Zeilinger (GHZ) state. The results show that the entanglement of the three-qubit GHZ state can be partially broadcasted with the help of local or non-local copying processes. It is found that non-local cloning is much more efficient than local cloning for the broadcasting of entanglement.
Semiclassical Evaluation of the Quantum Propagator of Chaotic Systems
ZHANG Fei-Zhou, WANG Jiao, GU Yan,
Chin. Phys. Lett. 2000, 17 (7): 472-474 .  
Abstract   PDF(pc) (209KB) ( 373 )
The propagators of quantum chaotic systems in configuration space are calculated semiclassically. For the strongly chaotic system whose phase space is torus, such as baker’s map, we find that, long after a logarithm time, the quantum propagator can be evaluated approximately as the local average of the semiclassical one on each quantum cell h.
Studying High Energy Final State Interactions by N / D Method
YUAN Feng, ZHENG Han-Qing
Chin. Phys. Lett. 2000, 17 (7): 475-477 .  
Abstract   PDF(pc) (309KB) ( 405 )
We discuss the final state interaction effects at high energies via a multi-channel N/D method. We find that a 2 by 2 charge-exchange final state rescattering typically contributes an enhancement factor of a few times 10-2 in the B meson decay amplitude, for both the real and the imaginary parts. We also make some discussions on the elastic rescattering effects.
Spins of Triaxial Superdeformed Bands in 86Zr
LIU Zu-Hua, YANG Chun-Xiang
Chin. Phys. Lett. 2000, 17 (7): 478-479 .  
Abstract   PDF(pc) (156KB) ( 346 )
Transition energies of three triaxial superdeformed bands in 86Zr were fitted by the power-series expansion of spin I in odd powers of rotational frequeney ω and by the two-parameter expression for rotational spectra. Level spins of these bands were assigned by means of the least-squares fits.
Observation of a Collective Oblate Band in 137Ce
ZHU Sheng-Jiang, ZHU Ling-Yan, LI Ming, GAN Cui-Yun, M. Sakhaee, YANG Li-Ming, ZHANG Zheng, JIANG Zhuo, LONG Gui-Lu, Jon Myang-Gil, WEN Shu-Xian, WU Xiao-Guang, LIU Xiang-An
Chin. Phys. Lett. 2000, 17 (7): 480-482 .  
Abstract   PDF(pc) (211KB) ( 425 )
High spin states in 137Ce have been studied by using the heavy-ion induced reaction 124Sn(18O, 5n) carried out at China Institute of Atomic Energy. Partial level scheme with spin up to (43/2-), including a high spin collective rotational band observed for the first time, has been established. The collective band shows the properties similar to those oblate bands with γ~ -60o in neighboring nuclei and probably originates from the five quasi-particle configuration vsl/2 [vh11/2]2 πg7/2 πh11/2. The characteristics of this oblate band have been discussed.

Experimental Study on High-Spin States in 119Xe
HUANG Wen-Xue, GUO Ying-Xiang, SUN Xiang-Fu, LEI Xiang-Guo, ZHOU Xiao-Hong, LIU Zhong, ZHANG Yu-Hu, ZHU Shao-Fei, XU Xiao, FENG Xi-Chen, LIU Ming-Yi, LUO Yi-Xiao, WEN Shu-Xian, WU Xiao-Guang, YUAN Guan-Jun, LI Guang-Sheng, YANG Chun-Xiang
Chin. Phys. Lett. 2000, 17 (7): 483-484 .  
Abstract   PDF(pc) (157KB) ( 344 )
High-spin states of 119Xe have been investigated by in-beam y-ray spectroscopy via the reaction of l6O bombarding a 106Cd target at beam energies of 67-80MeV. No enhanced El transition was observed, the non-existence of octupole correlations in 119Xe.

Analysis of the Low-Lying Spectra of Five-Nucleon Systems
BAO Cheng-Guang
Chin. Phys. Lett. 2000, 17 (7): 485-487 .  
Abstract   PDF(pc) (267KB) ( 509 )
The wavefunctions are decomposed into components. The inherent nodal structure and the stability of these components are investigated. It is assumed that the low-lying states wound be dominated by the components without inherent nodal surfaces. Based on this assumption, the composition of the wave functions of the low-lying states of 5He has been suggested and the qualitative feature of the spectrum has been explained.

Prediction of Triaxial Superdeformation in the A ~ 160,80 Region
SHEN Cai-Wan, CHEN Yong-Shou, ZHAO En-Guang,
Chin. Phys. Lett. 2000, 17 (7): 488-490 .  
Abstract   PDF(pc) (261KB) ( 396 )
The discovery of the triaxial superdeformed bands provide a new opportunity to understand the axial symmetry breaking even in highly elongated nuclei. A total of 17 triaxial superdeformed nuclei in the mass A ~ 160 region and 11 in the mass A ~ 80 region are predicted by the three dimensional total routhian surface calculations. A possible way to identify the triaxiality of triaxial superdeformed nuclei is suggested.

Subfemtosecond X-ray Pulses Produced Directly by High Harmonic Generation
WANG Ying-Song, XU Zhi-Zhan
Chin. Phys. Lett. 2000, 17 (7): 491-492 .  
Abstract   PDF(pc) (181KB) ( 349 )
The generation of subfemtosecond pulses in hydrogen-like atoms through high-harmonic generation by using superintense multicycle driver pulses is numerically investigated. It is shown that a single subfemtosecond pulse can be directly generated when the driver pulse is strong enough to deplete the neutral atoms within several optical cycles. The propagation effect is neglected during the numerical examinations.
Dynamics of Interaction of H2+ with Intense Ultrashort Laser Pulse
QU Wei-Xing, CHEN Zhao-Yang, ZHANG Wen-Qi, XU Zhi-Zhan
Chin. Phys. Lett. 2000, 17 (7): 493-495 .  
Abstract   PDF(pc) (269KB) ( 395 )
The dynamic process of H2+ in intense ultrashort laser pulses with intensities of 1014 ~ 1015 W/cm2, wavelength of 532nm and duration of 22fs is theoretically investigated by using collinear model and numerically solving the time-dependent Schrodinger equation. The results show that: (1) the dissociation and dissociative ionization compete each other in the case of intensities between 2.5 x 1014 and 4.0 x 1014 W/cm2; (2) both the dissociation and the dissociative ionization are much smaller and appear at about 5 cycles (≈ 9 fs ) later than the ionization. In addition, we estimate the spectrum of high harmonic generation and find that the well-known cutoff rule is invalid for the ultrashort laser pulse (e.g. the duration ≤ 25fs), because the shorter pulse can produce higher order harmonics than the longer one.

Electron Scattering by Ar Atoms in a Laser Field
ZHANG Sheng-Hai, QIAN Xing-Zhong, JIANG Yu-Hai, SUN Jin-Feng
Chin. Phys. Lett. 2000, 17 (7): 496-497 .  
Abstract   PDF(pc) (192KB) ( 323 )
The differential cross sections of electron-Ar atom scattering for free-free transition with one and two photons absorption in the presence of CO2 laser field is obtained by the second Born approximation, the direction of laser polarization being perpendicular to the change of electron momentum. Compared with the more recent available experimental data, the present results are very good.
Light Transmission Through Symmetric Fibonacci-Class Multilayers
WANG Yong, HUANG Xiu-Qing, GONG Chang-De
Chin. Phys. Lett. 2000, 17 (7): 498-500 .  
Abstract   PDF(pc) (220KB) ( 407 )
We have studied the optical transmission of one-dimensional Fibonacci-class quasiperiodic multilayers, which possess a mirror symmetry. We find that the transmission coefficient is unity for all studied sequences at the central wavelength λ=λ0, where λ0= (1/4)nA(B)dA(B) with nA(B) and dA(B) being the index of refraction and thickness of two kinds of layers, respectively. Two-cycle or three-cycle has been found around λ=λ0, which is different from the features of the sequences without symmetric structure.

Absorption Spectrum of a Driven Two-Level Atom in a Tunable Cavity with Injected Squeezed Vacuum
LI Gao-Xiang, HUANG Guang-Ming, PENG Jin-Sheng
Chin. Phys. Lett. 2000, 17 (7): 501-503 .  
Abstract   PDF(pc) (244KB) ( 734 )
The absorption spectrum of a driven two-level atom in a frequency tunable cavity with injected squeezed vacuum is investigated. The line shape of the spectra depends on the relative phase between the driving field and the squeezed vacuum, and the frequency detuning between the driving field and the cavity mode. Line narrowing and probe gain can occur and be enhanced by adjusting the phase and detuning.
Macroscopic Quantum Superposition States in a Model of Photon-Supersonic Phonon Interaction
CHAI Jin-Hua, WANG Yan-Bang, LU Yi-Qun
Chin. Phys. Lett. 2000, 17 (7): 504-506 .  
Abstract   PDF(pc) (191KB) ( 576 )
A model of photon-hypersonic phonon interaction is proposed. The evolution of macroscopic quantum superposition states is analyzed, including the wave function and number distribution. It is shown that a superposition state of hypersonic phonon modes can be generated in the case of nondetuning and no losses.
Noise Reduction in Photorefractive Image Amplification by Contradirectional Two-Wave Mixing in Rh-Doped BaTiO3 Crystal
XU Xin-Guang, MU Xiao-Dong, SHAO Zong-Shu, DU Chen-Lin, JIANG Min-Hua, LUO Hao-Su, XU Hai-Qing
Chin. Phys. Lett. 2000, 17 (7): 507-509 .  
Abstract   PDF(pc) (268KB) ( 475 )
Low noise image amplification owing to contradirectional two-wave mixing (CTWM) is proposed and demonstrated in Rh-doped BaTiO3 crystal. Comparing with the conventional forward two-wave mixing scheme, an enhancement of signal-to-noise ratio in the order of 103 is obtained. The theoretical analyses are presented and give a reasonable explanation for the experimental results. The further discussion shows that CTWM scheme can also reduce the influence of the crystal absorption and crystal size on the two-wave mixing process to rise the signal beam gain.

Analysis of the Influence of Thermal Effect on Z-Scan Measurements with a Nanosecond Pulse Laser
TIAN Jian-Guo, WANG Hao-Hua, ZHOU Wen-Yuan, LI Tao, ZHANG Chun-Ping, ZHANG Guang-Yin
Chin. Phys. Lett. 2000, 17 (7): 510-512 .  
Abstract   PDF(pc) (190KB) ( 500 )
The influence of thermally induced optical nonlinearities on Z-scan measurements with a nanosecond pulse laser is investigated theoretically. The results demonstrate that thermal effect plays an important role in certain circumstance. As an example, the optical nonlinearities of CS2 with an adjustable linear absorption coefficient which is used to alter the magnitude of thermally induced optical nonlinearities are analysed, and the results show that thermal effect even makes the change of the sign of optical nonlinearities.

Domain Reversal Characteristics of Near-Stoichiometric LiNbO3 Crystals
YAO Jiang-Hong, XU Jing-Jun, ZHANG Guang-Yin, CHEN Xiao-Jun, LI Bing, LI Guan-Gao,
Chin. Phys. Lett. 2000, 17 (7): 513-514 .  
Abstract   PDF(pc) (273KB) ( 405 )
The domain reversal characteristics of near-stoichiometric LiNbO3([Li]/[Li+Nb]=0.496) single crystals, which are grown by the Czochralski method with K2O flux, are investigated. The switch field for 180o ferroelectric domain reversal in the near-stoichiometric LiNbO3 crystal is 8.0±0.5kV/mm, which is only one third of the switching field required for the congruent LiNbO3 crystals. We have successfully achieved 180o domain reversal in near-stoichiometric LiNbO3 samples of 1.0 mm thickness.
Upconversion Luminescence of the Er3+ and Yb3+ Codoped Transparent Vitroceramics
LI Yun-Bai, HOU Yan-Bing, ZHAO Su-Ling, YI Li-Xin, XU Xu-Rong
Chin. Phys. Lett. 2000, 17 (7): 515-516 .  
Abstract   PDF(pc) (175KB) ( 337 )
The upconversion luminescence of oxyfluoride transparent vitroceramics codoped with Er3+ and Yb3+ has been studied experimentally. There are microcrystallites to form in the oxyfluoride glass which is treated over its transition temperature, and the transparent vitroceramics are obtained. The vitroceramics has the better transparency and a high upconversion luminescent efficiency. Our results show that there is strong energy transfer between Er3+ and Yb3+ in the vitroceramics, which results in the change of the upconversion spectra with intensity of excitation laser.
Dipole Alfven Vortex with Finite Ion Larmor Radius in a Low-Beta Plasma
WANG XU-YU, HE Xian-Tu, LIU Zhen-Xing, CAO Jin-Bin
Chin. Phys. Lett. 2000, 17 (7): 517-518 .  
Abstract   PDF(pc) (156KB) ( 339 )
A set of nonlinear fluid equations which include the effects of ion gyroradius is derived to describe Alfven vortex. The correction of finite ion gyroradius to the Alfven vortex in the inertial region is much more significant than that in the kinetic region. The amplitude of the vortex is enhanced in both regions. The scale of the vortex in the kinetic region becomes larger whereas it becomes smaller in the inertial region.

Effects of Plasma Density and Toroidal Magnetic Field on Lower Hybrid Current Drive Efficiency on HT-7 Tokamak
DING Bo-Jiang, KUANG Guang-Li, LIU Yue-Xiu, LIU Deng-Cheng, ZHENG Guang-Hua, WU Jun-Shuan, LIU Fu-Kun, SHEN Wei-Ci, LIN Jian-An, YANG Chun-Sheng, XU Han-Dong, YU Jia-Wen, HUANG Yi-Yun, SHANG Lian-Quan, SHI Yue-Jiang, WU Zhen-Wei, ZHANG Jin-Song, YIN Fu-Xian, XIE Ji-Kang, WAN Yuan-Xi
Chin. Phys. Lett. 2000, 17 (7): 519-521 .  
Abstract   PDF(pc) (285KB) ( 521 )
Lower hybrid current drive experiments on the HT-7 device have been carried out by scanning the following parameters: central line averaged electron density (ne = 0.6 - 2.0 x 1019m-3) and toroidal magnetic field (Bt = 1.62 - 2.0 T). The dependence of current drive efficiency on these parameters has been studied and the experimental curves of current drive efficiency as a function of ne and Bt have also been obtained. from these experimental results, it can be seen that current drive efficiency rises with the increase of toroidal magnetic field. As plasma density increases, the current drive efficiency first increases to a certain value, then gradually decreases, that is, there exists an optimized density regime where a better drive efficiency can be obtained. The analysis shows that the current drive efficiency is mainly affected by wave accessibility and impurity concentration, and the competition of these two factors determines the current drive efficiency.

Effect of the Vibrational Modes on the Ag-Cu Phase Diagram
DUAN Su-Qing, ZHAO Xian-Geng, LIU Shao-Jun, MA Ben-Kun
Chin. Phys. Lett. 2000, 17 (7): 522-524 .  
Abstract   PDF(pc) (230KB) ( 464 )
We calculated the vibrational free energies of the selected ordered compounds in the Ag-Cu system by using two kinds of methods: (1) calculating the phonon dispersion and density of states and the consequently vibrational free energies by using the method of ab initio inverted interatomic potentials and dynamic matrix; (2) the vibrational free energies determined by a Debye-Griineisen approximation. The Ag-Cu phase diagram is calculated by the cluster variation method. The results show that the solubility at Ag-rich end of the calculated phase diagram considering vibrational modes by using the first method is in better agreement with the experimental.
Adsorption and Thermal Decomposition of SiH44 on Cu(111) by Multiple-Scattering Cluster Method
HE Jiang-Ping, TANG Jing-Chang
Chin. Phys. Lett. 2000, 17 (7): 525-527 .  
Abstract   PDF(pc) (293KB) ( 557 )
Adsorption and thermal decomposition of SiH4 on Cu(111) at 110 K has been studied by the calculation of silicon K-edge near edge x-ray absorption fine structure spectra using multiple-scattering cluster method. It is found that the cleavage of Si-H bond yields SiH3 species adsorbed on the fcc 3-fold hollow sites on Cu (111) surface at 110K .

Quantum Wavefunctions and Fluctuations of Mesoscopic RLC Circuit
WANG Ji-Suo, LIU Tang-Kun, , ZHAN Ming-Sheng
Chin. Phys. Lett. 2000, 17 (7): 528-529 .  
Abstract   PDF(pc) (178KB) ( 474 )
The quantum wavefunctions and the corresponding energy levels of a RLC (Resistance-Inductance-Capacity) electric circuit are obtained by using canonical quantization method and unitary transformation from the classical equation of motion. The quantum fluctuations of charge and current in an arbitrary eigenstate of the system have also been given as well as the uncertainty relation. It is showed that even if at 0 K charge and current in the circuit exhibit quantum fluctuations, which originates from fluctuations of zero point vibrations of the system.
Nonlinear Electrical Behaviour of the TiO2.Sb2O3 System
WANG Jin-Feng, CHEN Hong-Cun, ZHANG Xing-Hua, ZHANG De-Jun, ZHONG Wei-Lie
Chin. Phys. Lett. 2000, 17 (7): 530-531 .  
Abstract   PDF(pc) (120KB) ( 300 )
The Sb2O3-doped TiO2 varistors were obtained by conventional ceramic processing. The 0.75 mol%Sb2O3.99.25mol%TiO2 varistor has a nonlinear coefficient α = 7 and a minimum breakdown electrical field of 6V/mm. The nonlinear electrical behaviour of TiO2.Sb2O3 ceramics was explained by the introduction of defects in the crystal lattice that are responsible for the formation of Schottky potential barriers at grain boundaries.
Cascade Energy Transfer in CeF3 Crystals
SHI Chao-Shu, DENG Jie, WE Ya-Guang, ZHANG Guo-Bin, G. Zimmerer, J. Becker, SHEN Ding-Zhong, HU Guan-qin
Chin. Phys. Lett. 2000, 17 (7): 532-533 .  
Abstract   PDF(pc) (0KB) ( 56 )
The emission spectra of the CeF3 crystals in UV-visible region and their temperature dependence in the range of 6-453K under UV, VUV excitation as well as their excitation spectra (4-25eV) have been studied. The 350nm emission band from perturbed Ce3+ can be excited by 295.2 and 302.4nm emissions from the regular Ce3+. The 350nm emission band, in turn, can excite the emission bands centered at 470 and 535nm caused by some defects below room temperature. These results show that there is a cascade energy transfer process from regular Ce3+ to quenching centers via perturbed Ce3+ and defect centers in the CeF3. Meanwhile, thermoluminescence, giving peaks at about 240 and 300°C has been discovered, and the corresponding deep traps with depth~ leV are found to be a kind of quenching center for CeF3 luminescence at room temperature.

A White Emitting Organic Diode with a Doped Blocking Layer
ZHANG Zhi-Lin, JIANG Xue-Yin, XU Shao-Hong
Chin. Phys. Lett. 2000, 17 (7): 534-536 .  
Abstract   PDF(pc) (244KB) ( 530 )
A novel white emitting organic diode has been simply realized by inserting a doped hole-blocking layer between the hole transporting layer (HTL) and the electron transporting layer (ETL). The structure of this device is ITO/CuPc/NPB/blocking layer : rubrene/Alq/MgAg. Copper phthalocyanine(CuPc) was used as a buffer layer, N,N’-bis-(I-naphthy1)-N,N’-diphenyl-1,1’-bipheny1-4,4’-diamine (NPB) as the HTL, and trimer of N-arylbenzimidazoles (TPBi) as the blocking layers, in which rubrene is doped. Tris(8-quinolino1ato)aluminum complex(A1q) as ETL. Indium tin oxide and MgAg were the anode and cathode, respectively. The emission spectrum of this device covers a wide range of visible region and can be sensitively adjusted by the concentration of rubrene. The white emission with the CIE (Commission International de 1’ Eclairage) color coordinates x = 0.31, y = 0.32, a maximum luminance of 8635cd/m2, and the luminous efficiency 1.391m/W at the luminance of 100cd/m2 were obtained in the device with 1.5% rubrene concentration in TPBi.

Formation and Optical Absorption of Photo-reduced Gold Nanoparticles Inside Pores of Mesoporous Silica
SHI Hua-Zhong, YAO Bao-Dian, ZHANG Li-De, BI Hui-Juan, CAI Wei-Ping, WU Yu-Cheng
Chin. Phys. Lett. 2000, 17 (7): 537-539 .  
Abstract   PDF(pc) (291KB) ( 464 )
Mesoporous silica with gold nanoparticles inside its pores was synthesized by soaking and photo-reduction method. This new material was characterized by transmission electron microscopy, x-ray photoelectron spectroscopy and Brunauer-Emmett-Teller techniques. The results showed that gold nanoparticles were isolated from each other and uniformly dispersed inside the pores of silica, most of which were less than 4 nm in diameter. It was found that in optical absorption spectrum, surface plasma resonance peak of nanosized gold particles assumed a significant redshift (about 55nm) with respect to that predicted by Mie theory. This can be explained in terms of interface interaction (boundary coupling) between gold particles and pore walls of porous silica.

Deposition of Diamond-Like Carbon Films with Femtosecond KrF Laser Pulses
YAO Dong-Sheng, LIU Jing-Ru, WANG Li-Ge, YU Chang-Xuan, ZHAN Ru-Juan
Chin. Phys. Lett. 2000, 17 (7): 540-541 .  
Abstract   PDF(pc) (207KB) ( 393 )
Hydrogen-free diamond-like carbon (DLC) films with the optical band gaps of 2.0-2.7eV and the microhardness of 40-55 GPa are deposited by femtosecond KrF laser pulses. The film microstructure of nanometer spheroid is observed. The film microhardness is improved with the increase of ion kinetic energy of plasma plume from 300 to 600eV. The characteristics of DLC film deposition with fs pulses is discussed.

Magnetic Anisotropy in the Radula of Chiton
ZHAO Jian-Gao, QIAN Xia, LIU Wei, LIU Chuan-lin, ZHAN Wen-Shan
Chin. Phys. Lett. 2000, 17 (7): 542-543 .  
Abstract   PDF(pc) (283KB) ( 360 )
Radular teeth of chitons were studied by using magnetic torque-meter and transmission electron microscopy (TEM). The magnetic torque curves give clear evidence of presence of strong uni-axial magnetic anisotropy The easy axis is along the length direction of tonguelike radula. The TEM pattern shows that long chip-like magnetite nano-scaled particles packed in the radular teeth with both uni-axial shape anisotropy and magneto-crystalline anisotropy.

On the Light Curve and Spectra of X-Rays and Gamma-Rays from the Crab Pulsar
ZHANG Li, K. S. Cheng, ME Dong-Cheng
Chin. Phys. Lett. 2000, 17 (7): 544-546 .  
Abstract   PDF(pc) (255KB) ( 480 )
We use a three-dimensional pulsar magnetosphere model to study the light curve and spectra of x-rays and gamma-rays from the Crab pulsar. In this model, the vertical size of the outer gap is first determined by a self-consistent model in which the outer gap is limited by pair production from collisions of thermal photons produced by polar cap heating of backflow outer gap current and curvature photons emitted by gap accelerated charged particles. The transverse size of the outer gap is determined by local pair production conditions. In principle, there are two topologically disconnected outer gaps present in the magnetosphere of a pulsar, and both incoming and outgoing particle flows are allowed. However, doublepeak light curves with strong bridges are most common, Making use of the three-dimensional structure of the outer gap and its local properties, we compare the results of our model with the light curve and phase-resolved spectra of the Crab pulsar.

30 articles