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Volume 19 Issue 11
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Original Articles
Entanglement Swapping and Disentanglement via an Entangled State of Atoms Interacting with a Cavity Field
LIU Tang-Kun, WANG Ji-Suo, FENG Jian, ZHAN Ming-Sheng
Chin. Phys. Lett. 2002, 19 (11): 1573-1575 .  
Abstract   PDF(pc) (196KB) ( 396 )
We consider entanglement swapping and disentanglement schemes via an entangled state of three two-level atoms interacting with a coherent field. When a two-level atom C, entangled with other two two-level atoms A and B, is injected into a high-Q cavity and atoms A and B are far away from the cavity, the entanglement swapping or disentanglement can be realized by carrying out the measurement on the atom C and by selecting appropriate interaction time of atom C with the coherent field.
Resolution of Unity of Generalized Bargmann Spaces by means of Displaced Fock States
Nour Eddine Askour, Zouhair Mouayn
Chin. Phys. Lett. 2002, 19 (11): 1576-1578 .  
Abstract   PDF(pc) (203KB) ( 456 )
We resolve the unity of generalized Bargmann spaces in Cn [J. Math. Phys. 41(2000)3507] by means of displaced Fock states.
Remote Quantum Adding Machine
ZHANG Sheng-Xing, LONG Gui-Lu, , LIU Xiao-Shu,
Chin. Phys. Lett. 2002, 19 (11): 1579-1580 .  
Abstract   PDF(pc) (171KB) ( 410 )
We desigh a scheme to perform additions of N remote addends. This adder is useful for some quantum information processing purposes, such as statistics and multi-party quantum game. The quantum remote adder is constructed by using a multi-party superdense coding scheme.
Relative Phase with the Overlap Region of Two Bose-Einstein Condensates
ZHOU Xiao-Ji, LI Wei-Dong, CHEN Xu-Zong, WANG Yi-Qiu
Chin. Phys. Lett. 2002, 19 (11): 1581-1583 .  
Abstract   PDF(pc) (279KB) ( 733 )
We present an expression of the relative phase for two interacting Bose-Einstein condensates released from an isotropic trapping potential. We discuss the interference condition between condensates and the visibility of interference pattern reflected the interaction between the condensates.
Can Quintessence Be the Rolling Tachyon?
LI Xin-Zhou, HAO Jian-Gang, LIU Dao-Jun
Chin. Phys. Lett. 2002, 19 (11): 1584-1586 .  
Abstract   PDF(pc) (190KB) ( 621 )
In the light of the recent works by Sen [hep-th/0203211, hep-th/0203265, hep-th/0204143] and Gibbons[hep-th/0204008], we present a phase-plane analysis on the cosmology containing a rolling tachyon field in a potential resulted from string theory. We show that there is no stable point on the phase-plane, which indicates that there is a coincidence problem if one consider tachyon as a candidate for quintessence. Furthermore, we also analyse the phase-plane of the cosmology containing a rolling tachyon field for an exactly solvable toy
potential in which the critical point is stable. Therefore, it is possible for rolling tachyon to be quintessence if one gives up the strict constraint on the potential or find a more appropriate effective potential for the tachyon from M/string theory.
Perturbation of Massive Scalar Field in Three-Dimensional Spherical de Sitter Space-time
QIU Wei-Gang, WANG Bin, SU Ru-Keng
Chin. Phys. Lett. 2002, 19 (11): 1587-1588 .  
Abstract   PDF(pc) (177KB) ( 307 )
We obtain exact expressions of quasi-normal modes in three-dimensional spherical de Sitter space-time. Exact agreement is found between the quasi-normal frequencies and the location of poles of the retarded correlation function of the corresponding perturbations in the dual conformal field theory. Our results exhibits the Sitter/conformal-field theory correspondence in three-dimensional spherical spacetime.
Vacuum Polarization of Twisted Scalars in a Non-simply Connected Space-time and Its Effects
WU Pu-Xun, YU Hong-Wei
Chin. Phys. Lett. 2002, 19 (11): 1589-1591 .  
Abstract   PDF(pc) (197KB) ( 440 )
The vacuum polarization the due to twisted scalar fields is investigated in a non-simply connected space-time. It is found that some photon modes acquire an imaginary topological mass, thus traveling at a superluminal speed. Topological bi-refringence is expected for photons propagating perpendicularly to the compactification direction. The effect of a topological photon mass on the static properties of electromagnetic fields is also considered for the cases of both twisted and untwisted scalar fields. Our result shows that in the untwisted case the magnetic field is screened along the radial direction for massive photon modes while in the twisted case no screening occurs and the magnetic fields merely oscillate.
J/ψ →γBB Decays and the Quark Pair Creation Model
PING Rong-Gang, JIANG Huan-Qing, , SHEN Peng-Nian, , ZOU Bing-Song, ,
Chin. Phys. Lett. 2002, 19 (11): 1592-1595 .  
Abstract   PDF(pc) (289KB) ( 338 )
We generalize the quark-pair creation model to a study of the radiative decays J/ψ →γBB by assuming that the u, d, or s quark pairs are created with the same interaction strength. From the calculation of the ratio of the decay widths Γ(J/ψ →γpp)/Γ(J/ψ →γpp), we extract the quark-pair creation strength gI = 15.40 GeV. Based on the SU(6) spin-flavor basis and the “uds”basis, the radiative decay branching ratios containing strange baryons are evaluated. Measurements for these decay widths from the BESII data are suggested.
Impacts of the Soft-Gluon Exchanges on B →ππ Decays
WU Xiang-Yao, LI Zuo-Hong, CUI Jian-Ying, HUANG Tao
Chin. Phys. Lett. 2002, 19 (11): 1596-1598 .  
Abstract   PDF(pc) (223KB) ( 756 )
We have investigated the role of soft-gluon exchanges in B →ππ, using the light-cone sum rules in quantum chromodynamics. The calculations are carried out not only for the tree operators but also for the penguin operators. We conclude that soft-gluon exchanges contribute to the decay amplitudes, noticeably on some decay channels, and thus cannot be neglected.
Possible 1d5/2 and 2s1/2 Level Inversion in the Proton-Rich Nucleus 23Al
ZHANG Hu-Yong, SHEN Wen-Qing, REN Zhong-Zhou, MA Yu-Gang, CAI Xiang-Zhou, ZHONG Chen, WEI Yi-Bin, CHEN Jin-Gen
Chin. Phys. Lett. 2002, 19 (11): 1599-1601 .  
Abstract   PDF(pc) (285KB) ( 438 )
The discovered proton halo nucleus of 23Al is investigated in the nonlinear relativistic mean-field (RMF) model with deformation using the NL075 force parameter. It is shown that there is an energy inversion between the (5/2)+(202) and (1/2)+(211) orbital in the 23Al nucleus, which may produce a large enhancement of the reaction cross section compared with the neighboring nuclei. Meanwhile, the NL075 force parameter may be better than the other RMF parameters for calculation of large deformed nucleus 23Al.
Nucleon-xcJ Dissociation Cross Sections
FENG You-Ceng, XU Xiao-Ming, ZHOU Dai-Cui
Chin. Phys. Lett. 2002, 19 (11): 1602-1605 .  
Abstract   PDF(pc) (314KB) ( 344 )
Nucleon-xcJ dissociation cross sections are calculated in a constituent interexchange model in which quark-quark potential is derived from the Buchmüller-Tye quark-anti-quark potential. These new cross sections for dominant reaction channels depend on the center-of-mass energy of nucleon and the charmonium.
Magnetically Guiding Atoms with Current-Carrying Conductors
LIU Nan-Chun, GAO Wei-Jian, YIN Jian-Ping
Chin. Phys. Lett. 2002, 19 (11): 1606-1609 .  
Abstract   PDF(pc) (494KB) ( 435 )
We propose a novel magnetic guide for cold neutral atoms using some current-carrying conductors. The spatial distributions of the magnetic fields from a V-shaped or U-shaped current-carrying conductor are calculated, and the relationship between the resulting magnetic field and the parameters of the current-carrying conductors is analysed in details. The result shows that these current-carrying conductors can be used to realize a single or a controllable double magnetic guide of cold atoms in the weak-field-seeking state, and to construct various atom-optical elements, and even to realize a single-mode atomic waveguiding under certain conditions.

Ionization of Hafnium L-Shell by Electron Impact
LUO Zheng-Ming, FU Yu-Chuan, AN Zhu, PENG Xiu-Feng, HE Fu-Qing, LONG Xian-Guan
Chin. Phys. Lett. 2002, 19 (11): 1610-1612 .  
Abstract   PDF(pc) (350KB) ( 322 )
A lower-electron beam has been directed on to a hafnium thin
target with thick backing to investigate the process of L-shell ionization. By using a Si (Li) detector to count the x-rays from the L-subshell, the partial and total production cross sections and mean ionization cross sections versus electron energies were deduced simultaneously (from threshold to 36 keV). The influence of the electron reflected from the backing on measurements was corrected. The path of the electron multi-scattered in the target itself was also calculated by using the Monte Carlo programme (EGS4). A comparison with both theoretical predictions is given.
Scattering from Rough Surfaces with Extended Self-Similarity
ZHANG Yan-Dong, WU Zhen-Sen
Chin. Phys. Lett. 2002, 19 (11): 1613-1616 .  
Abstract   PDF(pc) (558KB) ( 352 )
An extended self-similarity (ESS) model is developed by extending the self-similarity condition in fractional Brownian motion (FBM), then the incremental Fourier synthesis algorithm is introduced to generate ESS rough surfaces, and an estimation algorithm is presented to extract the generalized multiscale Hurst parameter which can also be modified to estimate the Hurst parameter for FBM more accurately. Finally, the scattering coefficient from ESS rough surfaces is calculated with the Scalar Kirchhoff approximation, and its variation with the parameters in the ESS model is obtained. Compared with experimental measurements, it can be concluded that the ESS model provides a good tool to model natural rough surfaces.


Moment Method with Wavelet Expansions for Fractal Rough Surface Scattering
GUO Li-Xin, WU Zhen-Sen
Chin. Phys. Lett. 2002, 19 (11): 1617-1620 .  
Abstract   PDF(pc) (533KB) ( 354 )
We study the moment method (MM) to deal with Harr wavelet basis due to the problem of electromagnetic scattering from the fractal rough surface. The vanishing moment properties and the capability of the wavelets to adjust themselves to the fractal surface lead to a sparse impedance matrix and faster computation. Compared to the measured data and conventional MM, the result shows that the wavelet basis functions provide substantial reductions in both memory requirements and computation time.
Emission Probability of the Cascade Three-Level-Atom Mazer with Injected Atomic Coherence
XIONG Jin, ZHANG Zhi-Ming
Chin. Phys. Lett. 2002, 19 (11): 1621-1624 .  
Abstract   PDF(pc) (297KB) ( 404 )
We investigate the effects of the injected atomic coherence on the atomic emission probability of the micromaser injected with ultracold cascade three-level atoms by considering that the atoms are initially in the coherent superposition states of the two upper levels. We show that there is no interference between the transitions from the two upper levels to the lowest level. In the large atom-field-detuning case, the atomic emission probability decreases as the coherent parameter increases. In the zero atom-field-detuning case, the atomic emission probability has three sets of resonance peaks. The reason for these results has been explained.
A Class of New Nonlinear Bogoliubov Transformations
YANG Xiao-Xue, WU Ying,
Chin. Phys. Lett. 2002, 19 (11): 1625-1627 .  
Abstract   PDF(pc) (181KB) ( 629 )
We find a class of new nonlinear Bogoliubov transformations and solve the eigenvalue problem of the model Hamiltonian describing the second harmonic generation with intensity-dependent coupling. These transformations differ from the previously known nonlinear quadrature-dependent Bogoliubov transformations.
Effects of the Spectral Line Broadened Model on the Performance of a Flowing Chemical Oxygen-Iodine Laser
GAO Zhi, HU Li-Min
Chin. Phys. Lett. 2002, 19 (11): 1628-1631 .  
Abstract   PDF(pc) (335KB) ( 405 )
A new gain saturation model of chemical oxygen-iodine lasers (COILs) is deduced from the conservation equations of the population number of upper and lower lasing levels. The present model is compared with both the Voigt profile function model and its low-pressure limit model. The differences between the Voigt profile function model or its low pressure limit model and the model presented here are pointed out, such as the length of power extraction, the optimal range of the threshold gain. These differences are useful for the optimization of COIL adjustable parameters.
Compact High-Power Blue Light from a Diode-Pumped Intracavity-Doubled Nd:YAG Laser
LI De-Hua, LI Ping-Xue, ZHANG Zhi-Guo, ZHANG Shi-Wen
Chin. Phys. Lett. 2002, 19 (11): 1632-1634 .  
Abstract   PDF(pc) (288KB) ( 552 )
We report an efficient continuous wave (cw) operation of 946 nm and 473 nm laser beams generated from a diode-pumped composite Nd:YAG rod. A very simple compact linear cavity was employed with cavity length of 35 mm. A composite Nd:YAG laser rod was used to release thermal effects. The maximum cw output of 3.3 W at 946 nm was obtained with slope efficiency of 22% at incident pump power of 17.5 W. By intracavity doubling with an LBO crystal, as much as 590 mW of single-ended blue output at 473 nm was achieved with an optical-optical conversion efficiency of 3.4%. The total blue output would be 1.06 W with overall conversion efficiency of 6.1% if the lasers emitted in both the directions were taken into account.
Levitation and Oscillation of Dust Grains in Plasma Sheath with Wake Potential
LIAN Hai-Jun, XIE Bai-Song, ZHOU Hong-Yu
Chin. Phys. Lett. 2002, 19 (11): 1635-1638 .  
Abstract   PDF(pc) (413KB) ( 496 )
We investigate the equilibrium and levitation of dust grains in a plasma sheath with various forces, in particular the wake potential force. The vertical oscillation frequency of dust chains is also obtained by including the wake-potential term. It is found that the wake-potential has a significant role for the levitation and oscillation of dust grains.
Three-Dimensional Propagation of Magnetohydrodynamic Waves in the Solar Chromosphere and Corona
LI Bo, ZHENG Hui-Nan, WANG Shui
Chin. Phys. Lett. 2002, 19 (11): 1639-1642 .  
Abstract   PDF(pc) (641KB) ( 450 )
We study the three-dimensional magnetohydrodynamic (MHD) wave
propagation in the solar atmosphere consisting of the chromosphere and corona. Pressure enhancement and velocity shear are implemented simultaneously at the bottom of the chromosphere. The global propagation of the incurred MHD waves, including fast- and slow-mode magnetoacoustic waves as well as Alfvén wave, can be identified. Wave front positions obtained numerically with respect to specific waves fit well with those calculated with local MHD wave speeds.
Role of Advanced Refueling and Heating on Edge Reynolds Stress-Induced Poloidal Flow in HL-1M
HONG Wen-Yu, WANG En-Yao, LI Qiang, CAO Jian-Yong, YAN Long-Wen
Chin. Phys. Lett. 2002, 19 (11): 1643-1645 .  
Abstract   PDF(pc) (380KB) ( 406 )
The radial profile of electrostatic Reynolds stress, plasma poloidal rotations, radial and poloidal electric field have been measured in the plasma boundary region of the HL-1M tokamak using a multiarray of Mach/Langmuir probes. In the experiments of Ohmic discharge, lower hybrid current drive, supersonic molecular beam injection (SMBI) and multi-shot pellet injection, the correlation between the Reynolds stress and poloidal flow in the edge plasma is presented. The radial profile changes of the Reynolds stress and poloidal flow velocity Vpol with lower hybrid wave injection power and SMBI injection are obtained. The results indicate that the sheared poloidal flow can be generated in tokamak plasma due to the radially varying Reynolds stress.
A Compact Vircator with Feedback Annulus Operated in Quasi-Single TM01 Mode Within C Band
SHU Ting, WANG Yong, QIAN Bao-Liang, TAN Qi-Mei
Chin. Phys. Lett. 2002, 19 (11): 1646-1648 .  
Abstract   PDF(pc) (386KB) ( 625 )
An axially extracted virtual cathode oscillator (vircator) with a feedback annulus is proposed and configured through particle-in-cell simulation. This compact device needs no guiding magnetic field. Its experimentally radiated microwave is measured to be of quasi-single TM01 mode with a frequency range of 4.41-4.69 GHz and a power level of above 300 MW, when the diode voltage ranges in 400-480 kV and the beam current in 20-25 kA; this conforms the simulation results.

ormation of Nanosized Inclusions in Cubic Boron Nitride Single Crystals
LIU Yu-Xian, XIAO Li-Mei, YIN Long-Wei
Chin. Phys. Lett. 2002, 19 (11): 1649-1652 .  
Abstract   PDF(pc) (435KB) ( 423 )
Cubic boron nitride (c-BN) crystals with dimensions of 0.3-0.4 mm, which have been synthesized using lithium nitride (Li3N) as a catalyst with a high-pressure high-temperature method, were examined by transmission electron microscopy (TEM). The TEM result shows that there exits some nanostructrued areas containing several types of nanosized foreign particles within the as-grown c-BN crystals. We find that the nanometer inclusions are hexagonal BN with the lattice constants of a = 2.054Å and c = 6.66Å, tetragonal B25N with a = 8.79Å and c = 5.08Å, tetragonal B53N with a = 8.79Å and c = 5.08Å, and hexagonal Li3N with a = 3.648Å and c = 3.875Å.
Crystallization of the Amorphous Zr70Cu20Ni10 Alloy
WANG Huan-Rong, LIU Yu-Xian, XIAO Li-Mei, HUI Xi-Dong
Chin. Phys. Lett. 2002, 19 (11): 1653-1656 .  
Abstract   PDF(pc) (447KB) ( 366 )
Crystallization behaviour of amorphous the Zr70Cu20Ni10 alloy within the supercooled liquid region has been investigated by means of differential scan calorimetry (DSC) and transmission electron microscopy (TEM). It is found that the relationship between the incubation time, which is necessary for amorphous Zr70Cu20Ni10 alloy to nucleate and grow, and the annealing temperature obeys an exponential function. Similar relationship can also be observed between the peak time corresponding to the minimum of the exothermic reaction in the DSC scan and the annealing temperature. TEM observations confirm that the first exothermic peak in the DSC trace of amorphous Zr70Cu20Ni10 alloy mainly corresponds to the precipitation of the Zr2Cu phase, while the second one mainly corresponds to the precipitation of the nanoscale Zr2Ni phase.
Kinetics and Mechanism of Nanostructures in Oxidation of Si1-xGex Alloys
HUANG Wei-Qi, CAI Shao-Hong
Chin. Phys. Lett. 2002, 19 (11): 1657-1659 .  
Abstract   PDF(pc) (350KB) ( 448 )
We investigate the oxidation behaviour of Si1-xGex alloys (x= 0.05, 0.15, and 0.25). The oxidation of SiGe films with different compositions was carried out in O2 (dry) atmosphere at 800 °C , 900 °C, and 1000 °C, respectively, for various lengths of time. The thickness and property of nanoparticle and nanolayer in oxide films and germanium segregation in oxidation of SiGe alloys are measured by using a high precision ellipsometer. The results are in good agreement with the Rutherford backscattering spectrometry, profile dektak instrument and high-resolution scanning transmission electron microscopy. We found that the Ge content in the oxide layer increases with the Ge content in SiGe alloys, the Ge content in the oxide film decreases with the increasing oxidation temperature and time. Rejection of Ge results in piling up of Ge at the interface between the growing SiO2 of nanostructure of oxide and Ge segregation in oxidation of
Si1-xGex alloys.
Zener Relaxation Peak in an Fe-Cr-Al Alloy
ZHOU Zheng-Cun, CHENG He-Fa, GONG Chen-Li, WEI Jian-Ning, HAN Fu-Sheng
Chin. Phys. Lett. 2002, 19 (11): 1660-1662 .  
Abstract   PDF(pc) (426KB) ( 393 )
We have studied the temperature spectra of internal friction and relative dynamic modulus of the Fe-(25 wt.%)Cr-(5 wt.%)Al alloy with different grain sizes. It is found that a peak appears in the internal friction-temperature plot at about 550 °C. The peak is of a stable relaxation and is reversible, which occurs not only during heating, but also during cooling. Its activation energy is 2.5 (± 0.15) eV in terms of Arrhenius relation. In addition, the peak is not obvious in the specimens with smaller grain size. It is suggested that the peak originates from Zener relaxation.
Effective Stress Reduction in Diamond Films on Alumina by Carbon Ion Implantation
FANG Zhi-Jun, XIA Yi-Ben, WANG Lin-Jun, ZHANG Wei-Li, MA Zhe-Guo, ZHANG Ming-Long
Chin. Phys. Lett. 2002, 19 (11): 1663-1665 .  
Abstract   PDF(pc) (451KB) ( 487 )
We show the effective stress reduction in diamond films by implanting carbon ions into alumina substrates prior to the diamond deposition. Residual stresses in the films are evaluated by Raman spectroscopy and a more reliable method for stress determination is presented for the quantitative measurement of stress evolution. It is found that compressive stresses in the diamond films can be partly offset by the compressive stresses in the alumina substrates, which are caused by the ion pre-implantation. At the same time, the difference between the offset by the pre-stressed substrates and the total stress reduction indicates that some other mechanisms are also active.
High-Pressure X-Ray Diffraction and Raman Scattering of LiTaO3
ZHANG Wei-Wei, CUI Qi-Liang, PAN Yue-Wu, DONG Shu-Shan, LIU Jing, ZOU Guang-Tian
Chin. Phys. Lett. 2002, 19 (11): 1666-1668 .  
Abstract   PDF(pc) (430KB) ( 679 )
We study the energy-dispersive x-ray diffraction and Raman
scattering of LiTaO3 at high pressure. The result keeps stable up to 36 GPa. The average isothermal bulk modulus and its pressure derivative are obtained to be k0 = (225±6) GPa and k`0 = 1.3±0.5 at zero pressure by the Birch-Murnaghan equation of state and the “universal”equation of state. The linear incompressibility of LiTaO3 between the a- and c-directions differs by a factor of four, which shows that the compression is anisotropic.
A Generalized Kawasaki-Type Dynamics with Spin-Pair Redistribution Mechanism
ZHU Jian-Yang, ZHU Han
Chin. Phys. Lett. 2002, 19 (11): 1669-1671 .  
Abstract   PDF(pc) (206KB) ( 872 )
We generalize Kawasaki's dynamics, spin-pair exchange mechanism, to a spin-pair redistribution mechanism, and we present a normalized redistribution probability. As an application, we treat the one-dimensional kinetic Gaussian model and obtain the exact diffusion equation and the temperature-dependent diffusion coefficient. We find that the diffusion process can slow down infinitely near the critical point and obtain the critical dynamic exponent z = 2 that is independent of the assumed mechanism, either Glauber-type or Kawasaki-type.
Luminescent Properties of Eu3+-Doped Yttrium Oxide Chloride Embedded in Nanoporous Glass
ZENG Xiao-Qing, LIN Feng-Ying, GAN Fu-Xi, YUAN Sui-Hua
Chin. Phys. Lett. 2002, 19 (11): 1672-1674 .  
Abstract   PDF(pc) (286KB) ( 407 )
The photoluminescence of Eu3+-doped yttrium oxide chloride embedded in nanoporous glass was observed. The emission lines of Eu3+ ions become much broader and blue shift were observed in the lines due to 5D07F2 transitions and Eu-O charge transfer excitation band in comparison with those in the powder phosphor. The ratio intensities of the 5D07F1 transitions to the 5D07F2 transitions of Eu3+ ion becomes higher and change at different excitation wavelengths such as 393 nm and 254 nm. The two excitation wavelengths belong to the 4f → 4f transition of Eu3+ ion and the Eu-O charge transfer, respectively. This material may be developed into a new luminescent glass.
Correction to the Metal-Insulator Transition Temperature due to Cation Size and Strain Effects for Colossal Magnetoresistance Perovskites
YUAN Song-Liu, LIU Jie, XIA Zheng-Cai, PENG Gang, TANG Jie, ZHANG Guo-Hong, ZHANG Li-Jiang, FENG Wen, LI Zhong-Yi, YANG Ying-Ping, LIU Li, XIONG Cao-Shui
Chin. Phys. Lett. 2002, 19 (11): 1675-1678 .  
Abstract   PDF(pc) (419KB) ( 422 )
A phenomenological expression of the metal-insulator transition temperature is proposed for AMnO3 manganese perovskites by taking into account the distortion of Mn-O-Mn bond due to A-cation size and the strain-dependent effect due to performed Jahn-Teller distortions, independently. Using reasonable physical parameters, the calculated results give excellent agreement with experimental data obtained in polycrystalline samples of La2/3(Ca1-xBax)1/3MnO3, providing a strong support to this approach.
Auto-correlation Effects on the sp3-d Exchange Interaction in Cd1-xMnxTe/CdTe Multilayers
K. Afif, A. Benyoussef, J. Diouri
Chin. Phys. Lett. 2002, 19 (11): 1679-1682 .  
Abstract   PDF(pc) (378KB) ( 343 )
Band offsets and total energy of wannier excitons in multilayers are affected by dimensional and auto-correlation effects, sp3-d coupling is consequently modified. Thus, the calculation of the Zeeman splitting in the quantum wells has to take into account these effects, especially when the mismatch cannot be disregarded. In this work, theoretical study of these combined effects has been performed for Cd1-xMnxTe/CdTe multilayers embedded by Cd1-yZnyTe as the substrate (or the buffer) on one side and as a cladding layer in the other side. This sample allows us to highlight the role played by the substrate (buffer) and the growth direction on the Zeeman splitting in such multilayers.

Distribution Function of Mesoscopic Hopping Conductance
HE Li-Qun, Eugene Kogan, Moshe Kaveh, Shlomo Havlin, Nehemia Schartz, LUO Dawei
Chin. Phys. Lett. 2002, 19 (11): 1683-1686 .  
Abstract   PDF(pc) (414KB) ( 378 )
We study mesoscopic hopping conductance by computer simulation
distribution functions (DF). It is found that the distributions obtained by choosing randomly the chemical potentials (for a fixed impurity configuration), which corresponds to a typical experimental situation, coincide with those obtained when both impurity configuration and chemical potential are chosen randomly, in agreement with the ergodicity hypothesis. The DFs in shape obtained for one-dimensional systems are found to be quite close to the predictions of the theory by Raikh and Ruzin. For the two-dimensional case, the DFs both for a narrow system and thin film look to be similar (and close to the one-dimensional case). The distribution function for the conductance of the square sample is nearly Gaussian.
Electron Spin Pairing and Excitations in High-Tc Superconductors
GUO Wei, HAN Ru-Shan, ZHENG Yi
Chin. Phys. Lett. 2002, 19 (11): 1687-1690 .  
Abstract   PDF(pc) (256KB) ( 656 )
Effective spin coupling between conduction electrons mediated by local Cu moments in the doped CuO2 plane may induce the instability of the normal states of conduction electrons and pairing at Cu sites, where the superexchange interaction between local moments influenced by hole doping is found to be Ising-like in recent experiments. By a mean field approach, we show that spin pairing and strong pair-pair interaction in the doped antiferromagnetic ordered Ising-like CuO2 plane gives rise to high temperature superfluid condensation and the exceptional features of quasi-particle excitation in cuprates such as spin gap, pseudogap, and the linear temperature dependence of resistivity ρab in the normal states.
Heat-Activated Effect of Exchange Coupling Between Two Ferromagnets Separated by an Amorphous Semiconducting Barrier
XIAO Ming-Wen, LI Zheng-Zhong, XU Wang
Chin. Phys. Lett. 2002, 19 (11): 1691-1694 .  
Abstract   PDF(pc) (264KB) ( 367 )
We try to extend our previous zero-temperature tunneling theory for the exchange coupling between two ferromagnets separated by an amorphous semiconducting barrier to the case of finite temperature. The result exhibits that the tunneling electrons can absorb or emit phonons when they tunnel through the amorphous barrier at finite temperatures so that the interlayer exchange coupling is heat activated. This agrees with the experiments.
Dielectric Characterization of Free-Standing Diamond Films
ZHANG Heng-Da, CHEN Guang-Chao, LI Cheng-Ming, TANG Wei-Zhong, LÜ, Fan-Xiu
Chin. Phys. Lett. 2002, 19 (11): 1695-1696 .  
Abstract   PDF(pc) (271KB) ( 436 )
The dielectric properties of free-standing diamond films grown by the dc arc-jet plasma method are measured by an impedance analyser in the temperature range of 298-573 K and at frequencies between 1000 Hz and 1 MHz. In the temperature and frequency ranges, the loss tangent can be expressed as a function of temperature and frequency. The loss tangent increases slightly with increasing temperature and frequency. The dielectric properties of the diamond films decrease with the increasing deposited temperature. The structure and quality of diamond films have been analysed by scanning electron microscopy, x-ray diffraction and Raman spectroscopy.
Carrier Transport Behaviour of Molecularly Doped Poly (N-Vinylcarbozole) in Polymer Light-Emitting Diodes
CHEN Xiao-Hong, , XU Zheng, HOU Yan-Bing, LIU Shu-Man, TENG Feng, XU Xu-Rong,
Chin. Phys. Lett. 2002, 19 (11): 1697-1699 .  
Abstract   PDF(pc) (393KB) ( 575 )
Single-layer polymer light-emitting diodes (PLEDs) are prepared from blends of poly (N-vinylcarbozole) (PVK) doped with tris (8-hydroxy-quinoline) aluminum (Alq3) of 2 wt% (sample a) and 0.2 wt% (sample b). The onset of PVK transient electroluminescence (EL) is delayed with respect to that of Alq3 in sample a under pulsed excitation, While the EL onset of Alq3 and PVK in sample b are simultaneous. The total carrier mobility of Alq3-rich regions in sample a is larger than that of PVK-rich regions. However, the total carrier mobility is homogenous in sample b. The phase image of atomic force microscopy and photoluminescence spectra of sample a and sample b indicate that the separated phase of samples a and b exists in PVK-rich regions and Alq3-rich regions. The variance of the doping concentration and separated phase in blends results in the different carrier transport mobility of Alq3-rich regions and PVK-rich regions.
Optical Constants of Palladium Phthalocyanine Derivative Thin Films
WU Yi-Qun, GU Dong-Hong, GAN Fu-Xi, WANG Jun-Dong, CHEN Nai-Sheng
Chin. Phys. Lett. 2002, 19 (11): 1700-1703 .  
Abstract   PDF(pc) (445KB) ( 712 )
Ellipsometric parameters of a series of spin-coating thin films of palladium phthalocyanine derivatives with bromine and tetraalkoxyl substitutes [PdPc(OC8H17 4Brm, m = 0,2,3,4] are determined from a rotating analyser-polarizer type of scanning ellipsometer. The optical, dielectric constants and absorption coefficients of the films in the 500-800 nm wavelength region are reported. The results show that refractive index N (N = n-k), dielectric constant ε (ε = ε1 - ε2) and absorption coefficient α in the region 500-800 nm are influenced by bromine atom substituted on the conjugated phthalocyanine ring regularly. It is found that there is approximately linear relationship between the resonance absorption wavelengths of the films and the number of bromine atoms substituted on the phthalocyanine ring.

Photoluminescence Properties of Silicon Nanowires and Carbon Nanotube-Silicon Nanowire Composite Arrays
LI Meng-Ke, LU Mei, KONG Ling-Bin, WANG Cheng-Wei, GUO Xin-Yong, LI Hu-Lin
Chin. Phys. Lett. 2002, 19 (11): 1703-1706 .  
Abstract   PDF(pc) (357KB) ( 796 )
Composite arrays of multi-wall carbon nanotubes (MWNTs) and silicon nanowires (SiNWs) are fabricated by means of the chemical vapor deposition method in porous anodic aluminum oxide (AAO) templates. The results of the scanning electron microscopy, high-resolution transmission electron microscopy, and transmission electron microscopy have shown that SiNWs are successful nested or filled in the hollow cavities of synthesized MWNTs array in AAO templates to form MWNTs-SiNWs composite arrays. The photoluminescence (PL) intensity degradation and a blue shift of PL peak position, usually created from the chemical instability of the SiNWs surface, are decreased and eliminated clearly in the composite arrays. The composite arrays of MWNTs-SiNWs exhibit more enhanced intensity and stability of PL performance than the SiNWs arrays deposited in AAO templates.
Characterization of Growth Hillocks on the Surface of High-Pressure Synthetic Diamonds
YIN Long-Wei, LI Mu-Sen, YUAN Quan, XU Bin, HAO Zhao-Yin
Chin. Phys. Lett. 2002, 19 (11): 1707-1710 .  
Abstract   PDF(pc) (416KB) ( 553 )
Diamond crystals, with dimensions of about 0.5-0.6 mm, were synthesized in the presence of Fe-Ni and Fe-Ni-Si catalyst solvents under high-pressure-high-temperature (HPHT) conditions. The as-known dendritic pattern was clearly seen on the (111) or (100) planes of diamond single crystals grown using Fe-Ni as a catalyst solvent. However, the conventional dendritic pattern was not observed in diamonds grown in the presence of Fe-Ni-Si alloy catalyst. Trigonal-type, pyramid-type, polygonal-type, and rectangular-type growth hillocks were clearly observed on the (111) and (100) surfaces of diamonds grown from the Fe-Ni-Si-C system, and the density of the hillocks is very higher at some position. Clear successive growth layers can also be found on the (111) planes of the high-pressure diamond single crystals grown in the presence of Fe-Ni Si alloy catalyst. The growth hillocks distributing on the (111) and (100) planes of the diamonds generally occur on or near growth steps, and some of the hillocks terminate at certain solid inclusions and voids. Growth hillocks on the (111) and (100) surfaces directly indicate the spiral growth mechanism under high temperature-high pressure (HPHT). A possible formation process for growth hillocks is proposed.
Ablation of GaN Using a Femtosecond Laser
LIU Wei-Min, ZHU Rong-Yi, QIAN Shi-Xiong, YUAN Shu, ZHANG Guo-Yi
Chin. Phys. Lett. 2002, 19 (11): 1711-1713 .  
Abstract   PDF(pc) (304KB) ( 867 )
We study the pulse laser ablation of wurtzite gallium nitride (GaN) films grown on sapphire, using the femtosecond laser beam at a central wavelength of 800 nm as the source for the high-speed ablation of GaN films. By measuring the back-scattered Raman spectrum of ablated samples, the dependence of the ablation depth on laser fluence with one pulse was obtained. The threshold laser fluence for ablation of GaN films was determined to be about 0.25 J/cm2. Laser ablation depth increases with the increasing laser fluence until the amount of removed material was not further increased. The ablated surface was investigated by an optical surface interference profile meter.
Comparisons of Structural and Optical Properties of ZnO Films Grown on Sapphire and Si (001)
QIU Dong-Jiang, WU Hui-Zhen, XU Xiao-Ling, CHEN Nai-Bo
Chin. Phys. Lett. 2002, 19 (11): 1714-1717 .  
Abstract   PDF(pc) (353KB) ( 423 )
Zinc oxide films were grown on sapphire and Si (001) substrates by reactive electron beam evaporation at low substrate temperatures. Atomic force microscopy (AFM), x-ray diffraction (XRD), and photoluminescence excitation (PLE) are employed to characterize the as-grown films. The AFM measurements have shown that all of the ZnO films present the pillar-like growth properties, but the dimensional uniformity of the ZnO crystal pillars grown on sapphire was better than
that on Si (001). The XRD results indicated that the prepared ZnO films both on sapphire and Si (001) were all highly c-axis oriented, their linewidth of ZnO (002) are only 0.19° and 0.28°, respectively. The PLE characterizations revealed the continuum absorption of the samples grown on sapphire. However, in the PLE spectra of the ZnO films grown on Si(001) substrates, a broad peak appears at the high energy region, which indicates the formation of ZnO quantum dot structures on Si(001).
Geometrical Deviation and Residual Strain in Novel Silicon-on-Aluminum-Nitride Bonded Wafers
MEN Chuan-Ling, XU Zheng, WU Yan-Jun, AN Zheng-Hu, XIE Xin-Yun, LIN Cheng-Lu
Chin. Phys. Lett. 2002, 19 (11): 1718-1720 .  
Abstract   PDF(pc) (414KB) ( 543 )
Aluminum nitride (AlN), with much higher thermal conductivity, is considered to be an excellent alternative to the SiO2 layer in traditional silicon-on-insulator (SOI) materials. The silicon-on-aluminum-nitride (SOAN) structure was fabricated by the smart-cut process to alleviate the self-heating effects for traditional SOI. The convergent beam Kikuchi line diffraction pattern results show that some rotational misalignment exists when two wafers are bonded, which is about 3°. The high-resolution x-ray diffraction result indicates that, before annealed at high temperature, the residual lattice strain in the top silicon layer is tensile. After annealed at 1100°C for an hour, the strain in the top Si decreases greatly and reverses from tensile to the slightly compressive as a result of viscous flow of AlN.
Thermodynamical Phase Equilibrium of Iron Nitrides at Low Temperatures
LEI Ming-Kai, WANG Xing-Jun
Chin. Phys. Lett. 2002, 19 (11): 1721-1723 .  
Abstract   PDF(pc) (278KB) ( 472 )
The presence of α-Fe(N), γ'-Fe4N, and ε-Fe4N1-x phases and the phase equilibrium between α-Fe(N) and γ'-Fe4N, and γ'-Fe4N and ε-Fe4N1-x have been studied at the low temperatures below 350°C, according to the binary Fe-N phase diagram calculated using the sublattice-compound energy model. The α-Fe(N), γ'-Fe4N, and ε-Fe4N1-x phases would be thermodynamically stable at the low temperatures. Thermodynamic phase equilibrium of the iron nitrides is supported by the experimental results, explaining the phase formation and its stability in the Fe-N system at low temperatures.
Characterization of Mn-Doped Ba1-xSrxTiO3 Thin Films Prepared by the Sol-Gel Method
REN Tian-Ling, BAO Jun-Bo, WANG Xiao-Ning, LIU Jian-She, LIU Li-Tian, LI Zhi-Jian, LI Xing-Jiao
Chin. Phys. Lett. 2002, 19 (11): 1724-1726 .  
Abstract   PDF(pc) (437KB) ( 748 )
Undoped and Mn-doped Ba1-xSrxTiO3 (BST) thin films have been fabricated on Pt/Ti/SiO2/Si by an aqueous acetate sol-gel method. The BST stock solution can be easily mixed with an aqueous metal ion solution and is stable at room temperature. The annealing temperature of the doped and undoped films is between 650-750°C. The x-ray photoelectron spectra (XPS) results show that the Mn 2p3/2 valence state in the BST is the same as that of the original Mn(II) dopant. The dielectric constant of the BST thin films can be increased to 800, and the loss tangent can be decreased to 0.01 due to the Mn(II) doping. The leakage current of the BST films can also be greatly reduced.
Calibration of Membrane Viscosity of the Reconstituted Vesicles by Measurement of Rotational Diffusion of Bacteriorhodopsin
WANG Ao-Jin, HU Kun-Sheng
Chin. Phys. Lett. 2002, 19 (11): 1727-1729 .  
Abstract   PDF(pc) (326KB) ( 620 )
Membrane viscosity of the reconstituted vesicles was calibrated by rotational diffusion of bacteriorhodopsin (BR) in
dimyristoylphosphatidylcholine (DMPC) and egg phosphatidylcholine (PC) vesicles. Rotational diffusion of BR in the vesicles was measured by flash-induced absorption anisotropy decay. BR was, for the first time, reconstituted successfully into DMPC and egg PC vesicles. From the measurement of flash-induced absorption anisotropy decay of BR, the value of rotational diffusion coefficient D was obtained from each curve fitting by a global fitting procedure and, in turn, membrane viscosity η was estimated from D. The results showed that membrane viscosity is temperature-dependent. It was decreased as temperature increased, but a transition occurred in the region of the respective phase transition of DMPC and egg PC, respectively. The decrease of η was fast near the phase transition for DMPC and egg PC. Few effects of lipid/BR ratio and glycerol or sucrose in suspension medium on membrane viscosity were found.

Parameter Space for Evolution of Black Hole Systems and Gamma-Ray Bursts
WANG Ding-Xiong, LEI Wei-Hua, MA Ren-Yi
Chin. Phys. Lett. 2002, 19 (11): 1730-1733 .  
Abstract   PDF(pc) (416KB) ( 323 )
An analytical model of black hole (BH) evolution is proposed by considering the Blandford-Znajek process with a transient magnetized accretion disc, which is used as a central engine for powering gamma ray bursts (GRBs). The state of BH evolution can be described by the representative points in the corresponding sub-regions of a parameter space. It is shown that the BH spin might be spun up rather than slowed down, provided that the ratio of the angular velocity of the magnetic field lines to that of the BH horizon is greater than a critical value. In addition, the effects of some initial values of the BH system on the evolution terminals and the output energy for GRBs are discussed in the parameter space.
Evolutionary Population Synthesis for Single Stellar Populations
ZHANG Feng-Hui, HAN Zhan-Wen, LI Li-Fang, Jarrod R. Hurley
Chin. Phys. Lett. 2002, 19 (11): 1734-1737 .  
Abstract   PDF(pc) (609KB) ( 308 )
Using the evolutionary population synthesis technique, we present the latest integrated colours for instantaneous burst single stellar populations (SSPs) of different metallicities and we investigate their colour evolution. Different from the previous research we adopt the stellar evolutionary models that employ, amongst other things, recent opacities and a revised equation of state (EOS), and include evolutionary processes such as convective overshooting, thermal pulses and dredge-up. The models are used in the convenient form of analytic fitting functions. In addition, we use the BaSeL model for the library of stellar spectra. This model provides an extensive low-resolution theoretical flux distribution and UBVRIJHKLM colours, which have been calibrated empirically or semi empirically, for a wide range of stellar parameters.
Thin Circular Disc Shells of Radio Sources Around Supernova Remnant G16.2-2.7
YU Zhi-Yao
Chin. Phys. Lett. 2002, 19 (11): 1738-1740 .  
Abstract   PDF(pc) (306KB) ( 309 )
We propose a new model of distinct thin circular disc shells to analyse the radio map of the supernova remnant (SNR) G16.2-2.7 from NRAO VLA Sky Survey at 1.4 GHz and the radio sources around it. It is obtained that the 20 radio sources around the SNR G16.2-2.7 distribute on the four thin circular disc shells. The results support the shell-like structure strongly and further indicate that the shell-like structure is several thin circular disc shells. Because the shell-like structure dominate the total sample, our results is important for the research of radio mophology of SNRs.

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