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Volume 20 Issue 11
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Original Articles
A Simplified and Obvious Expression of Concurrence in Wootters’Measure of Entanglement of a Pair of Qubits
Chin. Phys. Lett. 2003, 20 (11): 1907-1909 .  
Abstract   PDF(pc) (181KB) ( 371 )
We obtain a simplified and obvious expression of“concurrence” in Wootters’measure of entanglement of a pair of qubits having no more than two non-zero eigenvalues in terms of concurrences of eigenstates and their simple combinations. It not only simplifies the calculation of Wootters’measure of entanglement, but also reveals some general and important features. Our conclusions are helpful to further understand and application of quantum entanglement.
A Robust Scheme for Two-Qubit Grover Quantum Search Alogrithm Based on the Motional and Internal States of a Single Cold Trapped Ion
QIN Tao, GAO Ke-Lin
Chin. Phys. Lett. 2003, 20 (11): 1910-1912 .  
Abstract   PDF(pc) (216KB) ( 488 )
We propose a scheme to implement two-qubit Grover quantum search algorithm. The novelty in the proposal is that the motional state is introduced into the computation and the internal state within a single cold trapped ion. The motional and internal states of the ion are manipulated as two qubits by the laser pulses to accomplish an example of Grover algorithm based on the two qubits. The composite laser pulses which are applied to implement the Grover algorithm have been designed in details. The issues concerning measurement and decoherence are discussed.
Hawking Radiation of an Arbitrarily Accelerating Kinnersley Black Hole: Spin-Acceleration Coupling Effect
WU Shuang-Qing, YAN Mu-Lin
Chin. Phys. Lett. 2003, 20 (11): 1913-1916 .  
Abstract   PDF(pc) (228KB) ( 372 )
The Hawking radiation of Weyl neutrinos in an arbitrarily accelerating Kinnersley black hole is investigated by using a method of the generalized tortoise coordinate transformation. Both the location and temperature of the event horizon depend on the time and on the angles. They are in agreement with the previous results, but the thermal radiation spectrum of massless spinor particles displays a type of spin-acceleration coupling effect.
Coupling of a Linearized Gravitational Wave to Electromagnetic Fields and Relevant Noise Issues
LI Fang-Yu, WU Zhang-Han, ZHANG Yi
Chin. Phys. Lett. 2003, 20 (11): 1917-1920 .  
Abstract   PDF(pc) (233KB) ( 318 )
According to electrodynamical equations in curved spacetime we consider the coupling of a linearized weak gravitational wave (GW) to a Gaussian beam passing through a static magnetic field. It is found that unlike the properties of the “left-circular” and “right-circular” waves of the tangential perturbative photon fluxes in the cylindrical polar coordinates, the resultant effect of the tangential and radial perturbations can produce the unique nonvanishing photon flux propagating along the direction of the electric field of the Gaussian beam. This result might provide a larger detecting space for the high-frequency GWs in GHz band. Moreover, we also discuss the relevant noise issues.
Quantum Statistics of a Forced Oscillator with a Time-Dependent Driving Force
LIU Wen-Sen
Chin. Phys. Lett. 2003, 20 (11): 1921-1923 .  
Abstract   PDF(pc) (189KB) ( 413 )
Quantum statistics of a forced harmonic oscillator acted upon by a time-dependent external force is derived using the Wilcox trick and time-dependent inhomogeneous Bogoliubov transformation formalism. The internal energy, fluctuation of the particle-number average and entropy of this nonequilibrium system are presented explicitly.
Control Method of Cooling a Charged Particle Pair in a Paul Trap
ZHANG Guang-Cai, ZHANG Hong-Jun,
Chin. Phys. Lett. 2003, 20 (11): 1924-1927 .  
Abstract   PDF(pc) (707KB) ( 609 )
We propose a simple feedback cooling method, including both the component feedback and the velocity feedback, for cooling a charged particle pair in a Paul trap. It is found that the system can be cooled to periodic orbits; and if control intensity is strong, the system can be cooled to a one-periodic orbit, which is only in a horizontal plane. The result shows that the cooled system is also robust for noise.
First Overtone Frequency Stimulated Quartz Tuning Fork Used for Shear-Force Scanning Near-Field Optical Microscopy
LIU Sheng, SUN Jia-Lin, SUN Hong-San, TAN Xiao-Jing, SHI Shuo, GUO Ji-Hua, ZHAO Jun
Chin. Phys. Lett. 2003, 20 (11): 1928-1931 .  
Abstract   PDF(pc) (419KB) ( 565 )
The conventional 32.768 kHz tuning fork is stimulated at its first overtone resonant frequency of ~190 kHz for shear-force distance control. The time constant is measured to be 0.54 ms and it decreases about 40 times faster than that of the fundamental frequency (20.76 ms). The cross section of a corn root with height difference of ~3 μm is imaged at a scan speed of 12 μm/s for 256 x 256 pixels.
Negative Parity Bands and Signature Splitting Inversion in 80Rb
WEN Shu-Xian, HE Chuang-Ye, ZHU Li-Hua, WANG Zhi-Min, LI Guang-Sheng, MA Rui-Gang, WU Xiao-Guang, YUAN Guan-Jun, YANG Chun-Xiang, WANG Yue, ZHANG Zhen-Long, MENG Rui, M. Oshima, Y. Toh, A. Osa, M. Koizumi, Y. Hatsukawa, M. Matsuda, T. Hagakawa, M. M. Ndontcheng
Chin. Phys. Lett. 2003, 20 (11): 1932-1935 .  
Abstract   PDF(pc) (565KB) ( 485 )
High spin states in 80Rb were studied via the 65Cu+19F, 66Zn+18O and 68Zn+16O reactions. The 75-MeV 19F, 76-MeV 18O and 80-MeV 16O beams were provided by the CIAE HI-13 Tandem accelerator and JAERI Tandem accelerator. The prompt γ-γ coincidence and the directional correlation from oriented nuclei (DCO) were measured by the detector arrays in CIAE and JAERI. Twenty-three new states with 28 new transitions have been assigned to 80Rb. The states were observed up to spins 20+ and 22- in the α = 0 branch for the positive and negative parity yrast bands respectively. The negative parity non-yrast bands were significantly extended up to spins of 22- and 15-. The band crossings with frequencies 0.51 MeV and 0.61 ,MeV in the α = 0 cascade were observed for the first time. The signature splitting was observed in both the negative parity bands. The signature inversions at about spins 7ħ and 15ħ were observed.
Deformed Potential Energy of 263Db in a Generalized Liquid Drop Model
CHEN Bao-Qiu, MA Zhong-Yu, , Zhao Yao-Lin
Chin. Phys. Lett. 2003, 20 (11): 1936-1939 .  
Abstract   PDF(pc) (301KB) ( 798 )
The macroscopic deformed potential energy for super-heavy nuclei 263Db, which governs the entrance and alpha decay channels, is determined within a generalized liquid drop model (GLDM). A quasi-molecular shape is assumed in the GLDM, which includes the volume-, surface-, and Coulomb-energies, the proximity effects, the mass asymmetry, and an accurate nuclear radius. The microscopic single particle energies are derived from a shell model in an axially deformed Woods-Saxon potential with the quasi-molecular shape. The shell correction is calculated by the Strutinsky method. The total deformed potential energy of a nucleus can be calculated by the macro-microscopic method as the summation of the liquid-drop energy and the Strutinsky shell correction. The theory is applied to predict the deformed potential energy of the experiment 22DNe + 241Am → 263Db*259Db + 4n, which was performed on the Heavy Ion Accelerator in Lanzhou. It is found that the neck in the quasi-molecular shape is responsible for the deep valley of the fusion barrier due to the shell corrections. In the cold fusion path, the double-hump fusion barrier is predicted by the shell correction and complete fusion events may occur.
A Quantitative Theory Model of a Photobleaching Mechanism
CHEN Tong-Sheng, ZENG Shao-Qun, ZHOU Wei, LUO Qing-Ming
Chin. Phys. Lett. 2003, 20 (11): 1940-1943 .  
Abstract   PDF(pc) (275KB) ( 1636 )
A photobleaching model; D-P (dye-photon interaction) and D-O (Dye-oxygen oxidative reaction) photobleaching theory, is proposed. The quantitative power dependences of photobleaching rates with both one- and two-photon excitations (1 PE and TPE) are obtained. This photobleaching model can be used to elucidate commendably our and other experimental results. Experimental studies of the photobleaching rates for rhodamine B with TPE under unsaturation conditions reveals that the power dependences of photobleaching rates increase with the increasing dye concentration, and that the photobleaching rate of single molecule increases in the second power of the excitation intensity, which is different from the high-order (> 3) nonlinear dependence of ensemble molecules.
Optical Potential Calculation of Elastic Collision for Electron Scattering by H2
LIU Wen-Wang, ZHOU Ya-Jun, WANG Zhi-Gang
Chin. Phys. Lett. 2003, 20 (11): 1944-1946 .  
Abstract   PDF(pc) (307KB) ( 447 )
Differential cross sections for the elastic scattering of the electrons by H2 at 100 eV and 150 eV have been calculated and compared with experiments. We use the momentum space method in which the electron-molecule system has a single centre and effect of higher reaction channels on electron-molecule elastic scattering is approximated by an ab initio equivalent-local potential. It is added to the exact static-exchange potential for e-H2 scattering.
An Atomic Force Microscopy Investigation of the Tracks Made by C+1-C+4 Bombardment on CR-39 Detectors
ZHAO Kui, WU Xiu-Kun, GUO Ji-Yu, SUI Li, MEI Jun-Ping, NI Mei-Nan, BAO Yi-Wen
Chin. Phys. Lett. 2003, 20 (11): 1947-1949 .  
Abstract   PDF(pc) (388KB) ( 415 )
Carbon micro-clusters are accelerated by an HI-13 tandem accelerator. The plastic nuclear track detectors CR-39 are irradiated by C1-C4 beams from the HI-13 tandem accelerator and the tracks in CR-39 are studied using an atomic force microscope (AFM). The depths and diameters of C1-C4 tracks are measured for the first time in a nanometer scale. An enhancement of energy loss is obtained for carbon cluster related to single carbon ions with the same velocity. The results show that the AFM observation is very useful in the quantitative analysis of clusters in the track detector CR-39.

Effects of the Center-of-Mass Motion on the Population Trapping of Ultracold Atoms
Chin. Phys. Lett. 2003, 20 (11): 1950-1953 .  
Abstract   PDF(pc) (310KB) ( 353 )
We investigate the effects of the atomic center-of-mass motion on atomic population trapping in a two-mode micromaser injected with ultracold Λ-type three-level atoms. We find that in the mazer regime (the case in which the atomic kinetic energy is much smaller than the atom-field interaction energy), the interplay between reflection and transmission of the ultracold atom leads to the destruction of the atomic population trapping.

Direct Measurement of Light Speed Reduction in a Rubidium Vapor Medium Coherently Prepared by Electromagnetically Induced Transparency
TU Xian-Hua, WANG Jin, JIANG Kai-Jun, HE Ming, LI Ke, ZHONG Jia-Qi, ZHAN Ming-Sheng
Chin. Phys. Lett. 2003, 20 (11): 1954-1956 .  
Abstract   PDF(pc) (374KB) ( 888 )
We have experimentally observed the reduction of light speed in a rubidium vapor medium coherently prepared by electromagnetically induced transparency. The light speed reduction was deduced by directly measuring the time delay of a probe light when it passed through the medium. The time delay varies with the intensity of the coupling laser, and the typical time delay we recorded was 1.8μs, corresponding to a light speed of 56000m/s.

High-Power Blue Light Generation by External Frequency Doubling of an Optical Parametric Oscillator
BI Yong, ZHANG Hong-Bo, SUN Zhi-Pei, BAO Zhao-Ri-Ge-Tu, LI Hui-Qing, KONG Yu-Peng, LIN Xue-Chun, WANG Gui-Ling, ZHANG Jie, HOU Wei, LI Rui-Ning, CUI Da-Fu, XU Zu-Yan, SONG Li-Wei, ZHANG Ping, CUI Jian-Feng, FAN Zhong-Wei
Chin. Phys. Lett. 2003, 20 (11): 1957-1959 .  
Abstract   PDF(pc) (365KB) ( 807 )
We report on an all-solid-state high-power quasi-continuous blue light source by frequency doubling of the signal wave from an optical parametric oscillator (OPO). A 50-mm-long LiB3O5 (LBO) crystal is used for the OPO, which is pumped by a diode-pumped Nd:YAG green laser (10 kHz, 50 ns). Tunable blue emission in a new nonlinear crystal BiB3O6 (BiBO) is obtained with a wavelength range from 450 nm to 495 nm. The average power of the signal output is as high as 9.3 W from 924 nm to 970 nm. The maximum output of the blue laser with the second harmonic walk-off compensation is 1.3 W average power at 470 nm for 6.2 W of OPO signal light at 940 nm.
A Passively Mode-Locked Diode-End-Pumped Nd:YAG Laser with a Semiconductor Saturable Absorber Mirror Grown by Metal Organic Chemical Vapor Deposition
WANG Yong-Gang, MA Xiao-Yu, LI Chun-Yong, ZHANG Zhi-Guo, ZHANG Bing-Yuan, ZHANG Zhi-Gang
Chin. Phys. Lett. 2003, 20 (11): 1960-1962 .  
Abstract   PDF(pc) (285KB) ( 481 )
We report the experimental results of a mode-locked diode-end-pumped Nd:YAG laser with a semiconductor saturable absorber mirror (SESAM) from which we achieved a 10 ps pulse duration at 150 MHz repetition rate. The SESAM was grown by metal organic chemical vapor deposition at low temperature. The recovery time was measured to be 0.5 ps, indicating the potential pulse compression to sub-picoseconds.
Broad Omnidirectional Reflection Band Forming using the Combination of Fibonacci Quasi-Periodic and Periodic One-Dimensional Photonic Crystals
DONG Jian-Wen, HAN Peng, WANG He-Zhou
Chin. Phys. Lett. 2003, 20 (11): 1963-1965 .  
Abstract   PDF(pc) (485KB) ( 804 )
By combining two Fibonacci quasi-periodic structures and a periodic structure to form a heterostructure, a broad omnidirectional reflection band is obtained. From the numerical results performed by the transfer matrix method, it is found that the reflection bands of the two Fibonacci quasi-periodic sub-structures and the periodic sub-structure can be compensated for each other. This method is expected to be useful in constructing a one-dimensional quasi-periodic photonic crystal structure with a broad omnidirectional reflection band.
A Novel Method for Measuring Photo-Induced Birefringence of Photosensitive Fibres Based on a Fibre Loop
ZHANG Dong-Sheng, JIANG Li, LIU Bo, ZHANG Wei-Gang, KAI Gui-Yun, DONG Xiao-Yi
Chin. Phys. Lett. 2003, 20 (11): 1966-1968 .  
Abstract   PDF(pc) (242KB) ( 505 )
We report a novel method for measuring photo-induced birefringence of photosensitive fibres based on a fibre loop. The method is simple and is only slightly affected by the surroundings. The experimental results show that the photo-inducing normalized birefringence of the photosensitive fibre is multi-decaying-exponentially proportional to the exposure and it can attain 10-5.
Tracer Dispersion Between Two Lines in Two-Dimensional Percolation Porous Media
LIU Zhi-Feng, WANG Xiao-Hong, MAO Pan, WU Qing-Song
Chin. Phys. Lett. 2003, 20 (11): 1969-1972 .  
Abstract   PDF(pc) (465KB) ( 407 )
we study the statistical behaviour of the tracer motion between two lines in two-dimensional percolation porous media, based upon the direct numerical solutions of the Stokes equations on 20000 different percolation structures. At the critical threshold p = pc, the travelling length has the exponential distribution rather than the power-law distribution. Numerical simulations show that the ensemble average travelling length ~ L1.21 and ~ L for p = pc and p > pc, respectively. The region of the tracer dispersion is wide when p = pc and rather narrow when p > pc. Numerical simulations indicate that the transverse fluctuation has the same scale as the correlation length of the percolation structure, which is the system size L when p = pc and is constant for the large system size L when p > pc. It is also shown that the travelling time has the power-law behaviour when p = pc.
Electron Heat Transport in an HL-1M Tokamak ECRH Plasma
FU Hong-Jun, DING Xuan-Tong, LIU Yi, XU De-Ming
Chin. Phys. Lett. 2003, 20 (11): 1973-1976 .  
Abstract   PDF(pc) (818KB) ( 407 )
Electron temperature profiles, the normalized temperature gradient length and the electron heat diffusivity calculated by the heat pulse transfer method in the plasma confinement region, are investigated during electron cyclotron resonance heating (ECRH) in an HL-1M tokamak. The electron temperature profiles keep almost to be constant. The normalized temperature gradient length is in the range of 7-13. Electron heat diffusivity in the ECRH plasmas is larger than that in the ohmically heated plasmas. Electron heat diffusivity during off-axis (ρ < 0.3) ECRH discharge is similar to that during on-axis ECRH discharge.
Quasi-Optical Cavity Virtual Cathode Oscillator for Microwave Generation
LING Gen-Shen, CHEN Bo, ZHOU Jin-Juan
Chin. Phys. Lett. 2003, 20 (11): 1977-1980 .  
Abstract   PDF(pc) (542KB) ( 679 )
A new configuration of a virtual cathode oscillator (VCO), i.e., quasi-optical cavity VCO, is proposed for high-power microwave generation. The analysis and simulation are carried out to investigate the characteristics of this configuration. In the numerical simulation, the microwave output power of 2.93 GW is obtained with an electron beam of 610 keV in electron energy and 26.7 kA in the beam current. The beam-to-microwave power efficiency is 18%. The frequency is 17.5 GHz, and the output microwave mode is TEM10.
Fusion Reactivity in the Case of Ion Cyclotron Resonant Heating
YU Guo-Yang, CHANG Yong-Bin, SHEN Lin-Fang
Chin. Phys. Lett. 2003, 20 (11): 1981-1983 .  
Abstract   PDF(pc) (203KB) ( 430 )
By applying the integral-variable-change technique, an explicit expression of deuterium-tritium fusion reactivity in the case of second harmonic ion cyclotron resonant heating on deuterium is obtained.
Sheet Plasma Produced by Hollow Cathode Discharge
ZHANG Long, ZHANG Hou-Xian, YANG Xuan-Zong, FANG Chun-Hua, QIAO Bin, WANG Long
Chin. Phys. Lett. 2003, 20 (11): 1984-1987 .  
Abstract   PDF(pc) (392KB) ( 847 )
A sheet plasma is produced by a hollow cathode discharge under an axial magnetic field. The plasma is about 40 cm in length, 4 cm in width and 1 cm in thickness. The electron density is about 108cm-3. The hollow cathode is made to be shallow with a large opening, which is different from the ordinary deep hollow cathode. A Langmuir probe is used to detect the plasma. The electron density and the spatial distribution of the plasma changed when the voltage, the pressure and the magnetic field vary. A peak and a data fluctuation at about 200 G-300 G are observed in the variation of electron density (or thickness of the sheet plasma) with the magnetic field. Our work will be helpful to characterize the sheet plasma and make the production of dense sheet plasma more controllable.
Diagnostics of Atmospheric Pressure Surface Discharge Plasmas in Argon
ZHANG Rui, ZHAN Ru-Juan, WEN Xiao-Hui
Chin. Phys. Lett. 2003, 20 (11): 1988-1990 .  
Abstract   PDF(pc) (301KB) ( 597 )
Atmospheric pressure surface discharge is shown to have great prospects for a number of industrial applications. To acquire better results in application fields and considering that the study of the basic parameters including electron temperature and electron density is desirable, we develop an equivalent circuit model and the diagnostic techniques based on optical emission spectroscopy and electrical measurement in our laboratory. The electron temperature has been determined to be about 0.7 eV by a Fermi-Dirac model. The electron density has been calculated to be near 1010cm-3 from a time resolved electrical measurement (Ohmic heating method).
Controlled Growth of Carbon Nanotubes and Its Field Emission Properties
FAN Zhi-Qin, ZHANG Bing-Lin, YAO Ning, LU Zhan-Ling, YANG Shi-E, MA Bing-Xian
Chin. Phys. Lett. 2003, 20 (11): 1991-1993 .  
Abstract   PDF(pc) (302KB) ( 457 )
Uniform films of aligned carbon nanotubes were grown on a patterned Ni coated ceramic substrate by microwave plasma chemical vapor deposition (MWPCVD). A laser writing technique was used to make some patterns on the substrate. The controlled selective growth of nanotubes on the patterned substrate can be obtained directly during the reaction process in the MWPCVD chamber. The Raman spectrum shows a good graphitization of the carbon nanotubes. In the field emission test, turn-on field of V/μm and emission current density of 5 mA/cm2 at 3.3 V/μm were achieved.

Ion-Implanted Waveguides in a Nd3+-Doped Silicate Glass
LI Shi-Ling, CHEN Feng, WANG Xue-Lin, FU Gang, WANG Ke-Ming, LU Qing-Ming, LI Xi-Shan, SHEN Ding-Yu, MA Hong-Ji, NIE Rui
Chin. Phys. Lett. 2003, 20 (11): 1994-1996 .  
Abstract   PDF(pc) (371KB) ( 526 )
Monomode enhanced-index Nd3+-doped silicate glass waveguides fabricated by ion implantation are reported. The Nd3+-doped silicate glass was implanted by 3.0 MeV B+ ions, 3.0 MeV O+ ions and 4.5 MeV Ni2+ ions, respectively. A prism-coupling method was carried out to measure dark modes in the Nd3+-doped silicate glass using a model 2010 prism coupler. The moving fibre method was applied to measure the waveguide propagation loss. After a moderate annealing, the 3.0-MeV B+-ion implanted waveguide loss is about 3.54 dB/cm; the 3.0-MeV O+-ion implanted waveguide loss is about 5.36 dB/cm; and the 4.5-MeV the Ni2+-implanted waveguide loss is about 7.55 dB/cm. The results show that with the increasing ion mass, the loss in implanted waveguide is increased.
Formation of Infrared Femtosecond Laser Induced Colour Centers in Tb3+-Doped and Tb3+/Ce3+-Codoped Heavy Germanate Glasses
CHEN Guo-Rong, YANG Yun-Xia, QIU Jian-Rong, JIANG Xiong-Wei, K. Hirao
Chin. Phys. Lett. 2003, 20 (11): 1997-2000 .  
Abstract   PDF(pc) (385KB) ( 431 )
Formation of infrared femtosecond laser induced colour centers was observed in the Tb3+-doped and Tb3+/Ce3+-codoped heavy germanate glasses. A rectangle scanning was made by focusing the laser beam inside the glass samples. A three-dimensional yellowish block was created from the path and it corresponded to the appearance of broad absorption bands in the absorption spectra. Irradiation induced absorption coefficient μ (λ) was used to characterize the distribution of radiation induced colour centers in the samples, whose peak was located at 380 nm and extended to the longer wavelength. Ce3+ ions were found not only to inhibit the formation of colour centers, but also to enhance the recovery.
Strain and Phonon Confinement in Self-Assembled Ge Quantum Dot Superlattices
YANG Zheng, SHI Yi, LIU Jian-Lin, YAN Bo, HUANG Zhuang-Xiong, PU Lin, ZHENG You-Dou, WANG Kang-Long
Chin. Phys. Lett. 2003, 20 (11): 2001-2003 .  
Abstract   PDF(pc) (312KB) ( 456 )
Raman scattering measurements were carried out in self-assembled Ge quantum dot superlattices grown by molecular beam epitaxy. The characteristics of the Ge-Ge, Si-Ge, Si-SiLOC and Si-Si peaks were investigated, especially the Ge-Ge optical phonon frequency shift was emphasized, which was tuned by the phonon confinement and strain effects. The experimentally observed frequency shift values of the Ge-Ge peak frequency caused by optical phonon confinement and strain in Ge quantum dots were discussed with quantitative calculations.

Application of Corner Transfer Matrix Renormalization Group Method to the Correlation Function of a Two-Dimensional Ising Model
HE Chun-Shan, LI Zhi-Bing
Chin. Phys. Lett. 2003, 20 (11): 2004-2007 .  
Abstract   PDF(pc) (351KB) ( 432 )
The correlation function of two-dimensional Ising model is calculated by the corner transfer matrix renormalization group method. We obtain the critical exponent η = 0.2496 with few computer resource.
Scaling Approach to the Growth Equation with a Generalized Conservation Law
TANG Gang, ZHANG Li-Ping, WU Yu-Xi, XIA Hui, HAO Da-Peng, CHEN Hua
Chin. Phys. Lett. 2003, 20 (11): 2008-2010 .  
Abstract   PDF(pc) (202KB) ( 333 )
The Flory-type scaling approach proposed by Hentschel and Family [Phys. Rev. Lett. 66 (1991) 1982] is generalized to the analysis of the growth equation with a generalized conservation law, which contains the Kardar-Parisi-Zhang, Sun-Guo-Grant, and molecular-beam epitaxy growth equations as special cases and allows for a unified investigation of growth equations. The scaling exponents obtained here can be in agreement well with the corresponding results derived by the dynamic renormalization group theory and the previous scaling analyses.
Analysing Imaging Signals of Negative-Charging Contrast in Scanning Electron Microscopy
ZHANG Hai-Bo, FENG Ren-Jian, Katsumi URA
Chin. Phys. Lett. 2003, 20 (11): 2011-2014 .  
Abstract   PDF(pc) (423KB) ( 436 )
Negative charging of a specimen may produce the image contrast of yielding the information under the insulating thin film in scanning electron microscopy. To clarify and make good use of the recently developed negative-charging contrast (NCC), we propose a simplified procedure for quantifying secondary electron (SE) imaging signals and report the calculated results. The theoretical considerations and calculations are validated by comparing the calculated relation between the SE signal and the surface potential with measured dynamic characteristics of the NCC images. The results show that in the region of weak negative charging the NCC formation is due to the SE redistribution. The intensity of SE signals decreases with the increase of the amount of the SEs returning to the negatively charged surface whose local electric field may attract electrons. This results in the NCC transient characteristics.
Nonlinear Excitation in a Ferrimagnetic Zigzag Chain
WANG Wei-Zhong
Chin. Phys. Lett. 2003, 20 (11): 2015-2018 .  
Abstract   PDF(pc) (371KB) ( 396 )
We study the nonlinear excitation (solitons) in a ferrimagnetic polymer chain by using a total Hamiltonian consisting of Su-Schrieffer-Heeger Hamiltonian and a Hubbard term. At half-filling, the distortion of lattices forms domain wall solitons while the spin configuration forms the envelope solitons. The soliton pair is obtained in a range of the electron-electron (e-e) interaction U, which depends on the electron-phonon (e-ph) interaction. The spin solitons corresponding to the left domain wall and the right domain wall of the displacement are quite different.
First-Principles Calculations of Scanning-Tunneling-Microscopy Images of Ar Atoms Adsorbed on a Graphite Sheet
BAI Yu-Lin, ZHOU Xiao-Lin, CHEN Xiang-Rong, GOU Qing-Quan
Chin. Phys. Lett. 2003, 20 (11): 2019-2022 .  
Abstract   PDF(pc) (871KB) ( 908 )
Local density approximation in the framework of the density functional theory is applied to calculate the scanning tunneling microscopy (STM) images of Ar atoms adsorbed on a graphite sheet (Ar/graphite system). It is found that the optimal site of adsorbed Ar atom is at the top of the center of the carbon hexagon and its equilibrium distance from the graphite surface is about 3.20Å. We demonstrate that it is the hybridization of the C 2p electronic states with the Ar 3p and 4s electronic states, which renders Ar atoms visible in the STM experiment.
Evolution of Spin and Charge in a System with Interacting Impurity and Conducting Electrons
ZHANG Yong-Mei, XIONG Shi-Jie
Chin. Phys. Lett. 2003, 20 (11): 2023-2026 .  
Abstract   PDF(pc) (581KB) ( 659 )
We investigate the dynamics of spin and charge in an interacting system consisting of impurity and conducting electrons. The time evolution of spin and charge in the impurity is given by solving the time-dependent Schrödinger equations for the many-body states of the interacting system. By switching on the interaction between impurity and conducting electrons, the spin and charge of the impurity begin oscillations with frequencies which reflect the elementary excitations of the interacting system. The dynamics reflects the basic picture of the Kondo effect.
Electronic State of Bismuth in BaBiO3 up to 9 GPa Investigated by Optical Spectroscopy
LIU Xiao-Jun, MORITOMO Yutaka
Chin. Phys. Lett. 2003, 20 (11): 2027-2029 .  
Abstract   PDF(pc) (1290KB) ( 321 )
Effects of hydrostatic pressure on the mixed-valence (MV) bismuth complex BaBiO3 have been investigated up to ~9 GPa by means of high-pressure Raman scattering and absorption spectra at 300 K. The pressure-induced hardening behaviour of the Bi-O stretching mode suggests that the predicted pressure-induced MV to the single-valence (SV) phase change cannot occur. Investigation of absorption spectra with pressure shows the enhanced optical gap Egap, which further indicates the remained MV state of Bi ions.
Infinite-Range Quantum Dzyaloshinskii-Moriya Spin Glass Model
SHANG Yu-Min, YAO Kai-Lun
Chin. Phys. Lett. 2003, 20 (11): 2030-2032 .  
Abstract   PDF(pc) (401KB) ( 671 )
Based on the replica method and the imaginary time functional-integral technique, we investigate the infinite-range quantum Dzyaloshinskii-Moriya spin glass model. It is found that the quantum Dzyaloshinskii-Moriya spin glass model behaves in a Heisenberg-like manner. The specific heat has the crossover behaviour. The broad Maximum in specific heat is shifted to higher temperature with increasing applied field. These features are in good agreement with the observation of Brodale et al. [J. Magn. Magn. Matter. 31-34 (1983) 1331] The susceptibility of the system has the typical spin glass feature.
Magnetic Microstructures of PryFe90-yB10(y = 8-11.76) Nanocrystalline Ribbons by Using Magnetic Force Microscopy
PANG Zhi-Yong, FANG Yi-Kun, CHANG Huang-Wei, HAN Sheng-Hao, HAN Bao-Shan, CHANG Wen-Cheng
Chin. Phys. Lett. 2003, 20 (11): 2033-2035 .  
Abstract   PDF(pc) (302KB) ( 395 )
Magnetic microstructure of melt-spun PryFe90-yB10 (y = 8, 8.5, 9, 9.5, 10 and 11.76) nanocrystalline ribbons in an as-grown state has been studied by using a magnetic force microscope. The magnetic domains are characterized by dark areas adjacent with bright areas in a sub-micron scale and in random distribution. By comparing with the size of the micro-crystals measured from the TEM image, the exchange coupling effect was confirmed to exist in all the ribbons. By using the roughness analysis, the variation of the root mean square values of the phase shifts obtained from the magnetic force images versus the content y of Pr were measured, which is well consistent with the curve of the residual induction Br versus the content y.
Solutions for a Mode III Growing Crack in a Piezoelectric Plane Under Two Kinds of Electric Boundary Conditions
ZHANG Xing-Wu, LIU Kai-Xin
Chin. Phys. Lett. 2003, 20 (11): 2036-2038 .  
Abstract   PDF(pc) (220KB) ( 375 )
The solutions for a mode III crack growing along an arbitrary propagation path in a piezoelectric plane are studied under the impermeable surface condition and the electrical contact surface condition respectively. According to the two kinds of electric boundary conditions, the Hilbert and Riemann boundary value problems in a half-plane including opening smooth arc are obtained from the theoretical analysis. Moreover, the equipollence of the solution forms under these two electric boundaries is proven, and unified solutions for the stress and electric displacement distribution in the crack-tipfield of the piezoelectric plane are achieved.
Electrical and Pyroelectric Properties of Sol-Gel Derived (Pb, Ca)TiO3 Thin Films with Various Orientations
TANG Xin-Gui, DING Ai-Li, CHAN Helen Lai-Wah
Chin. Phys. Lett. 2003, 20 (11): 2039-2041 .  
Abstract   PDF(pc) (384KB) ( 542 )
(Pb0.76Ca0.24)TiO3 (PCT) thin films with various orientations were grown on Pt/Ti/SiO2/Si substrates by using a sol-gel process and by controlling the temperature of heat-treatment. The PCT thin films with (100) and random orientation showed well-saturated hysteresis loops at an applied field of 800 kV/cm, with remanent polarisation and coercive electric field of 23.6 μC/cm2 and 225kV/cm, 17.8 μC/cm2 and 195 kV/cm, respectively. For highly (100)- and random-oriented PCT films, the dielectric constant and dielectric loss values of these films are 121 and 0.016, 121 and 0.024 at 1 kHz, respectively. The pyroelectric coefficients p of the PCT thin films are measured by a dynamic technique. At room temperature, the p values and figures of merits of the highly (100)- and random-oriented PCT films are 185 μC/m2K and 1.79 xm 10-5Pa-0.5, 176μC/m2K and 1.39 x 10-5Pa-0.5, respectively.
Photoluminescence of SiOx Thin Films After Annealing at Various Temperatures
FANG Ying-Cui, LI Lu-Ying, ZHAO You-Yuan, Qi Le-Jun, LI Wei-Qing, ZHANG Zhuang-Jian, LU Ming
Chin. Phys. Lett. 2003, 20 (11): 2042-2044 .  
Abstract   PDF(pc) (327KB) ( 368 )
We study photoluminescence (PL) of SiOx (0< x <2) thin films after annealing at temperatures in the range of 700-1100°C. The SiOx thin films were prepared by evaporation of SiO powder onto the substrate of Si(100). Two PL emission structures were observed in the measuring range of 580 -755 nm. The one centered around ~ 730 nm was confirmed to be due to Si nanocrystals. The origin for the other one spanning the range of 580-650 nm was investigated by using hydrogen and oxygen passivations, and by short time annealing at 1100°C followed by hydrogenation. Our results support the model of structural defects in SiO2 matrix for the origin of the 580-650 nm PL peak.

Comparative Study of Properties of ZnO/GaN/Al2O3 and ZnO/Al2O3 Films Grown by Low-Pressure Metal Organic Chemical Vapour Deposition
ZHAO Bai-Jun, YANG Hong-Jun, DU Guo-Tong, MIAO Guo-Qing, YANG Tian-Peng, ZHANG Yuan-Tao, GAO Zhong-Min, WANG Jin-Zhong, FANG Xiu-Jun, LIU Da-Li, LI Wan-Cheng, MA Yan, YANG Xiao-Tian, LIU Bo-Yang
Chin. Phys. Lett. 2003, 20 (11): 2045-2048 .  
Abstract   PDF(pc) (451KB) ( 621 )
ZnO films were deposited by low-pressure metal organic chemical vapour deposition on epi-GaN/Al2O3 films and c-Al2O3 substrates. The structure and optical properties of the ZnO/GaN/Al2O3 and ZnO/Al2O3 films have been investigated to determine the differences between the two substrates. ZnO films on GaN/Al2O3 show very strong emission features associated with exciton transitions, just as ZnO films on Al2O3, while the crystalline structural qualities for ZnO films on GaN/Al2O3 are much better than those for ZnO films directly grown on Al2O3 substrates. Zn and O elements in the deposited ZnO/GaN/Al2O3 and ZnO/Al2O3 films are investigated and compared by x-ray photoelectron spectroscopy. According to the statistical results, the Zn/O ratio changes from Zn-rich for ZnO/Al2O3 films to O-rich for ZnO/GaN/Al2O3 films.
Temperature-Dependent Photoluminescence of ZnTe Films Grown on Si Substrates
SHAN Chong-Xin, FAN Xi-Wu, ZHANG Ji-Ying, ZHANG Zhen-Zhong, LU You-Ming, LIU Yi-Chun, SHEN De-Zhen
Chin. Phys. Lett. 2003, 20 (11): 2049-2052 .  
Abstract   PDF(pc) (462KB) ( 521 )
ZnTe films have been prepared on Si substrates by metal-organic
chemical vapor deposition (MOCVD), and the temperature-dependent
photoluminescence (PL) properties were investigated. The near-band-edge (NBE) emission of the ZnTe sample at 83 K shows an asymmetry line shape, which can be decomposed into two Gaussian lines labeled by FE and BE. Temperature-dependent PL intensity of the NBE peak shows two variation regions, and an expression with two dissociation channels fits well to the experimental data. The results of the temperature-dependent full width at half maximum (FWHM) and peak energy were well understood under the framework of the two-dissociation-channel model. That is, at low temperature, the emission from bound excitons governs the NBE peak, while above 157 K, the free exciton emission becomes dominant gradually. A simple model with three energy levels was employed to describe the variation in emission intensity of BE and FE with temperature.
Single Bubble Sonoluminescence Driven by Biharmonic Ultrasound
LI Sheng-Qiong, CHEN Wei-Zhong, JIANG Li-An, ZHU Yi-Fei, WANG Chao
Chin. Phys. Lett. 2003, 20 (11): 2053-2055 .  
Abstract   PDF(pc) (429KB) ( 569 )
Based on the spectrum measurement, we have investigated the single bubble sonoluminescence (SBSL) driven by a biharmonic ultrasound. The spectral temperature is sensitive to the relative phase of the second harmonic with respect to the fundamental. At the optimal phase, about 160°, the SBSL reaches its most efficient state in which the temperature is lifted by over 10000 K. Our experimental results have also been reproduced by numerical calculation in the theoretical framework of Rayleigh bubble dynamics.
Novel Chemically Stable Er3+-Yb3+ Codopded Phosphate Glass for Ion-Exchanged Active Waveguide Devices
CHEN Bao-Yu, ZHAO Shi-Long, HU Li-Li
Chin. Phys. Lett. 2003, 20 (11): 2056-2057 .  
Abstract   PDF(pc) (217KB) ( 402 )
A novel Er3+-Yb3+ codoped phosphate glass, which combines good chemical durability with good spectroscopic properties, is developed for the ion-exchange process. The relevant properties of this glass are presented for reference in the design and modeling of ion-exchanged active waveguide devices. The weight-loss rate of this glass is 1.45 x in boiling water, which is comparable to that of Kigre's Q-246 silicate glass. The emission cross section of Er3+ in this glass is calculated to be 0.72 x 10-20cm2 using the McCumber theory. It is found that a planar waveguide with three modes at 632.8 nm is readily realized in this glass from our primary ion-exchange experiments.
Synthesis, Characterization and Magnetic Property Measurements of Zn1-xMnxO Nanoparticles via Vapor Phase Growth
CHANG Yong-Qin, LUO Xu-Hui, XU Xiang-Yu, LI Lin, CHEN Jin-Ping, WANG Rong-Ming, YU Da-Peng
Chin. Phys. Lett. 2003, 20 (11): 2058-2060 .  
Abstract   PDF(pc) (355KB) ( 546 )
Nanosized Mn-doped ZnO particles were synthesized using a vapor phase growth method. The x-ray analysis reveals a wurtzite ZnO structure with small expansion of the lattice constants due to the doping of Mn in ZnO. The TEM analysis shows that the nanoparticles have an average diameter around 37 nm, and energy dispersive spectroscopy detection on single nanoparticle indicates that the manganese concentration is around 3.5 at.%. Magnetization measurements under field cooling conditions reveal that the as-grown Mn-doped ZnO nanoparticles show paramagnetic behaviour. This work demonstrates that Mn can be doped into nanosized ZnO structures via vapor phase growth, which represents an important step towards the synthesis of nanosized diluted magnetic semiconductors.
Photoluminescence of Self-Assembled InAs/GaAs Quantum Dots Covered by InAlAs and InGaAs Combination Strain-Reducing Layer
FANG Zhi-Dan, GONG Zheng, MIAO Zhen-Hua, XU Xiao-Hua, NI Hai-Qiao, NIU Zhi-Chuan
Chin. Phys. Lett. 2003, 20 (11): 2061-2063 .  
Abstract   PDF(pc) (316KB) ( 425 )
Self-assembled InAs/GaAs quantum dots covered by the 1-nm InxAl1-xAs (x = 0.2,0.3) and 3-nm In0.2Ga0.8As combination strain-reducing layer are fabricated, whose height can take up to 30-46 nm. The luminescence emission at a long wavelength of 1.33 μm and the energy separation between the ground and the first-excited state of 86 meV are observed at room temperature. Furthermore, the comparative study proves that the energy separation can increase to 91 meV by multiple stacking.
Self-Assembled Monolayers Exposed by Metastable Helium for Nano-Patterning: Octanethiol and Dodecanethiol
JU Xin, KURAHASHI Mitsunori, SUZUKI Taku, YAMAUCHI Yasushi
Chin. Phys. Lett. 2003, 20 (11): 2064-2066 .  
Abstract   PDF(pc) (348KB) ( 714 )
A large-area gold pattern with nanoscale edge on muscovite mica was fabricated by using a metastable helium beam and octanethiol (OT) and dodecanethiol (DDT) self-assembled monolayers (SAM), in which the width of edge was typically ~70 nm for the OT SAM and ~90 nm for the DDT SAM, respectively. The mask was reproduced with high fidelity. Combined the analysis of roughness with grain size, more flat surface and sharper edge of patterns were obtained by using the shorter chain molecules such as the OT. All the information indicated that the OT SAMs on atomically flat surfaces can be used as a resist for exposure to metastable atom beams.
Effect of Electric Field on Conductivity and Vickers Hardness of an Al-Li Alloy
LIU Bing, CHEN Da-Rong, CHEN Zheng, WANG Yong-Xin, LI Xiao-Ling
Chin. Phys. Lett. 2003, 20 (11): 2067-2069 .  
Abstract   PDF(pc) (525KB) ( 521 )
Static electric fields were applied on aluminum-lithium alloy during solution treatment. The conductivity and Vickers hardness of the quenched Al-Li alloy is changed with the effect of electric field. The Vickers hardness increases with the applied electric field for a certain solutionizing time but decreases with the time under an electric field. In the absence of the electric field, the Vickers hardness and the conductivity increase synchronously, while reversed after electric field treatment. Positive and negative electric fields had the similar effect. The change of the local electron density in alloy caused by electric field is presented to explain the effect.
Dynamics Behaviour of Nanoscale Electrostatic Actuators
LIN Wen-Hui, ZHAO Ya-Pu
Chin. Phys. Lett. 2003, 20 (11): 2070-2073 .  
Abstract   PDF(pc) (409KB) ( 443 )
The dynamics behaviour for nanoscale electrostatic actuators is studied. A two parameter mass-spring model is shown to exhibit a bifurcation from the case excluding an equilibrium point to the case including two equilibrium points as the geometrical dimensions of the device are altered. Stability analysis shows that one is a stable Hopf bifurcation point and the other is an unstable saddle point. In addition, we plot the diagram phases, which have periodical orbits around the Hopf point and a homoclinic orbit passing though the unstable saddle point.
Evidence for Grain Boundary Transport from Impedance Spectroscopy of Gabbro at 1-2 GPa up to 890°C
BAI Li-Ping, DU Jian-Guo, LIU Wei, GUO Jie, ZHOU Wen-Ge
Chin. Phys. Lett. 2003, 20 (11): 2074-2077 .  
Abstract   PDF(pc) (547KB) ( 333 )
Impedance spectra of gabbro were measured at 1-2 GPa and up to 890°C with applied frequency of 12 to 105Hz. At temperatures below 680°C, only one impedance arc corresponding to the grain interior conduction process occurs. Owing to the grain boundary transport with increasing temperature, the impurities occur at the grain boundaries, resulting in the second arc corresponding to the grain boundary conduction process over the frequency range of 12 to 103Hz above 680°C, and the resistivities of the grain interior and the grain boundary conduction mechanisms add in series. The total conductivity of this rock is dominated by the grain interior conductivity and the impurities have no significant effect on the total electrical conductivities.
Simulated Melting Curve of NaCl up to 200 kbar
CHENG Xin-Lu, LIU Zi-Jiang, CAI Ling-Cang, ZHANG Fang-Pei
Chin. Phys. Lett. 2003, 20 (11): 2078-2080 .  
Abstract   PDF(pc) (278KB) ( 467 )
The melting curve of NaCl is studied up to 200 kbar by means of the shell-model molecular dynamics method using massive shell core interaction potentials. The model for the interatomic interaction is shown to produce reasonable results at a wide range of pressures in bulk transitions. The pressure dependence of the melting curve of NaCl was calculated and the result is modified on the assumption of overheating due to the small system size and small time scale simulation. The final result is in good agreement with the corrected experimental values account for the melting mechanism such as surface heating or superheating. Therefore, it is believed that bulk transition simulation at constant pressure indeed provides a useful tool for studying the melting transition.

Pressure-Balance Consistency in Magnetospheric Modeling
XIAO Yong-Deng, CHEN Chu-Xin
Chin. Phys. Lett. 2003, 20 (11): 2081-2083 .  
Abstract   PDF(pc) (332KB) ( 379 )
There have been many magnetic field models for geophysical and astrophysical bodies. These theoretical or empirical models represent the reality very well in some cases, but in other cases they may be far from the reality. We argue that these models will become more reasonable if they are modified by some coordinate transformations. In order to demonstrate the transformation, we use this method to resolve the “pressure-balance inconsistency” problem that occurs when plasma transports from the outer plasma sheet of the Earth into the inner plasma sheet.
R-Process Nucleosynthesis and Galactic Chemical Evolution of the Ba Peak Elements
SONG Han-Feng, ZHANG Bo, ZHANG Jiang, WU Hai-Bin, PENG Qiu-He
Chin. Phys. Lett. 2003, 20 (11): 2084-2087 .  
Abstract   PDF(pc) (320KB) ( 419 )
Nucleosynthesis yield is a very important parameter of the Galactic chemical evolution model. We adopt the same method of Tsujimoto to derive the r-process yields of various mass SNe II at low metallicities from the new observed [Ba/Fe]-[Fe/H] trend. %but we get rid of the stars such as CS22892-052, CS31082. Furthermore, we present a new formula of r-process nucleosynthesis yields. We also consider the various neutron sources and set up four cases, namely A, B, C and D to calculate the abundance evolution of Ba peak elements in the solar neighborhood. Our results show that the r-process could be associated with a secondary event in massive stars (i.e., 18M < M < 50). Therefore, the r-process could be associated with a secondary event in massive stars. Both the neutron source and the seed nuclei must be freshly manufactured by the stars instead of depending upon the initialmetallicity abundance.
Equilibrium Correlations in a Clustering Universe
ZHANG Hang, HUANG Xia, LI Xiao-Qing
Chin. Phys. Lett. 2003, 20 (11): 2088-2090 .  
Abstract   PDF(pc) (180KB) ( 604 )
It is shown that the observed result of two-point galaxy correlation function and three-point correlation function in the universe agrees with a quasi-equilibrium assumption of mass distribution. Utilizing the form of the three-point correlation, we find that the two-point correlation function can be obtained by solving an equation derived from maximizing an entropy under some constraints in a self-gravitating particle model. A generalized non-extensive entropy is also introduced to improve our result.
54 articles