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Volume 15 Issue 3
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Original Articles
Derivation of 2 × 2 Thermal Propagator Without Factorization
ZUO Jian, GUI Yuan-xing
Chin. Phys. Lett. 1998, 15 (3): 157-158 .  
Abstract   PDF(pc) (149KB) ( 334 )
The real time thermal propagator with 2 × 2 matrix structure is derived in the functional formalism of the field theory in η-ξ spacetime. It is emphasized that the trouble-shooting factorization of generating functional in the time-path method can be avoided in this derivation.
Electrodynamical Response to a High Frequency Standing Gravitational Wave
LI Fang-yu, TANG Meng-xi
Chin. Phys. Lett. 1998, 15 (3): 159-161 .  
Abstract   PDF(pc) (220KB) ( 382 )
Electrodynamical response (ER) to the high frequency standing gravitational wave (GW ) of a composite toroidal electromagnetic resonant system is investigated, corresponding perturbation solutions are given, the advantages and shortcomings of electromagnetic detection to the standing GW by means of a static magnetic field and superconducting resonant cavity are compared. A concrete numerical calculation shows that under the reasonable states of the present technology, the ER to the standing GW can probably be displayed at the level of the single photon avalanche effect.
In-Situ Control of Oxygen Fugacity in Water-Free Systems at High Temperature and High Pressure
LI He-ping, XIE Hong-sen, GUO Jie, ZHANG Yue-ming, XU Zu-ming, XU Ji-an
Chin. Phys. Lett. 1998, 15 (3): 162-164 .  
Abstract   PDF(pc) (588KB) ( 355 )
By using two oxygen specific electrolyte discs and applying a dc voltage between the sample and an oxygen buffer, oxygen can be driven into or pumped from the sample at a fixed temperature and pressure. By measuring the voltage between the sample and a reference buffer, the oxygen fugacity in the sample is simultaneously monitored. Therefore, the oxygen fugacity in the sample at high temperature and high pressure can be in situ controlled independently of temperature and pressure.
Laser Induced Light-Force Interaction in the Optical Near-Field Region
ZHU Xing, LING Yong, HUANG Gui-song, ZHOU He-tian, DAI Yuan-dong, WU Ke, GAN Zi-zhao
Chin. Phys. Lett. 1998, 15 (3): 165-167 .  
Abstract   PDF(pc) (298KB) ( 491 )
Laser light can induce many effects on the vicinity of the sample surface due to the proximity effects, such as the field enhancement at the surface of a small conducting particle; plasma exchange effect between the metallic tip and substrate surface. We have observed a new optical tip-sample interaction: laser induced force as the results of light pressure in the near-field region. Under the side illumination of a laser light, an additional attractive force was observed between a dielectric tip and various samples of C60, optical glass, YBa2Cu3O7-d(YBCO) thin film. No such effect was observed in metallic samples. This optical binding force is due to the multiple scattering of light between two close objects. The results are in good agreement with the recent theoretical calculation. The effects of the optical refraction index, thermal expansion of probe tip due to laser radiation are discussed.
Collective Behavior of Negative Parity States in 126Ba at High Spin
LI Guang-sheng, DAI Zheng-yu, LIU Xiang-an, ZHANG Lan-kuan, WEN Shu-xian, WU Xiao-guang, YUAN Guan-jun, WENG Pei-kun, LI Sheng-gang, YANG Chun-xiang
Chin. Phys. Lett. 1998, 15 (3): 168-169 .  
Abstract   PDF(pc) (166KB) ( 310 )
Lifetimes of the high spin states in the negative parity band of 126Ba were measured by using the Doppler shift attenuation method in conjunction with the reaction 116Sn(16O, 2p4n)126Ba at a beam energy of 73 MeV. This band shows a typically collective behavior and possesses a near-axial prolate shape with a deformation parameter β2 = 0.27 ± 0.01 and triaxiality γ ~ -5°.
Description of Superdeformed Triaxial Band in 163Lu
XING Zheng, WANG Zi-Xing, CHEN Xing-qu,
Chin. Phys. Lett. 1998, 15 (3): 170-172 .  
Abstract   PDF(pc) (190KB) ( 340 )
Using triaxial-particle-rotor model, the γ-transition energies, kinematic and dynamic moments of inertia and the transition quadrupole moments for π [660 1/2] band in 163Lu are calculated and compared with the observed data. The results prove that this band is a superdeformed triaxial band.
Two-Dimensional Hydrogen Molecule and Its Ions
WANG Huai-yu, SUN Jin-zuo, YANG Fu-min
Chin. Phys. Lett. 1998, 15 (3): 173-174 .  
Abstract   PDF(pc) (160KB) ( 512 )
The lowest four states of two-dimensional (2D) hydrogen molecule H2 and the lowest two states of its ions H+2 and H-2 are calculated with an applicable 2D hydrogen anion wave function properly chosen. The results are compared with their three-dimensional correspondents. It becomes possible to calculate transitions between states of clusters containing two shallow impurities in semiconductor thin films.

Relativistic Multichannel Theory: Doubly Excited States of Atomic Helium
ZOU Yu, FANG Quan-yu, LI Jia-ming
Chin. Phys. Lett. 1998, 15 (3): 175-177 .  
Abstract   PDF(pc) (214KB) ( 378 )
In the report, the recently developed relativistic multichannel theory (RMCT) is a full relativistic non-perturbative method and can be applied to the high-Z atomic ions which have given rise to some recent interests because of researches of inertial confinement fusion and x-ray laser. Based on the RMCT, the positions and widths of doubly excited sp2n+, sp2n-, and 2pnd 1P1 resonances are calculated, which are in agreement with the recent experimental measurements. It sets up a sound foundation on which the RMCT should be applicable to high Z atomic ions.
Changes in Mean Square Nuclear Charge Radii of Nd II from Optical Isotope Shifts by Collinear Fast-Ion-Beam Laser Spectroscopy
MA Hong-liang, SHI Wei, YAN Bing, CHEN Miao-hua, CHEN Zhi-jun, FANG Du-fei, LU Fu-quan, TANG Jia-yong, YANG Fu-jia
Chin. Phys. Lett. 1998, 15 (3): 178-179 .  
Abstract   PDF(pc) (164KB) ( 378 )
High-resolution collinear fast-ion-beam-laser spectroscopy has been applied to investigate the optical isotope shifts for transition 4f45d6K11/2-(24445)°11/2 of Nd II. From the measured optical isotope shifts, changes in mean-square nuclear charge radii δ(r2) (fm2) among five even-even neodymium isotopes have been deduced: (142,144) 0.282, (144, 146) 0.242, (146, 148) 0.274, (148, 150) 0.404. The results are in good agreement with experimental data from electronic x-ray spectroscopy and combined optical and x-ray spectroscopy.
Calculation of Total Cross Section for Positron Scattering on Helium
ZHOU Ya-jun, PAN Shou-fu
Chin. Phys. Lett. 1998, 15 (3): 180-182 .  
Abstract   PDF(pc) (236KB) ( 394 )
Total scattering cross sections for positron scattering on helium are calculated at intermediate energies and compared with experimental measurements. The method used is the coupled-channels-optical method with an ab initio complex polarization potential, which takes all channels into account. Calculated results show that the ionization continuum and positronium formation rearrangment channels are very important parts in total scattering cross section of positron-helium collision.
Statistical Properties of the Output Light Intensity in a Single-Mode Laser Driven by Correlated Noises
ZHOU Xiao-ji, CAO Li, WU Da-jin,
Chin. Phys. Lett. 1998, 15 (3): 183-185 .  
Abstract   PDF(pc) (216KB) ( 404 )
By using linear approximation we derive expressions for the correlation function, power spectrum and correlation time of the output light intensity in a single-mode laser driven by additive white noise and multiplicative colored noise with an exponential correlation form. The effects of correlation strength and correlation time of the noises on the above quantities are discussed and compared with the case of a delta function correlation form for the noises.
Nonlinear Jaynes-Cummings Dynamics of a Trapped Ion Under a Dressed-State Description
YANG Xiao-xue, WU Ying, LUO Xue-li, GAO Ke-lin, XIAO Yi
Chin. Phys. Lett. 1998, 15 (3): 186-188 .  
Abstract   PDF(pc) (211KB) ( 393 )
Introducing a dressed-state description, we show that a trapped ion in a standing wave field can be described by a nonlinear Jaynes-Cummings model different from the counterpart of Vogel and Matos Filho [Phys. Rev. A 52 (1995) 4214] in several aspects, which may carry important implications for the preparation and reconstruction of the nonclassical states of a trapped ion.
Nonlinear Optical Properties of Some New Conjugated Copolymers
YANG Qi-guang, SI Jin-hai, LIU Xu-chun, XU Gang, YE Pei-xian, LEI Zi-qiang, ZHAN Xiao-wei, YANG Mu-jie
Chin. Phys. Lett. 1998, 15 (3): 189-191 .  
Abstract   PDF(pc) (273KB) ( 385 )
The ground- and the excited-state nonlinearities of two new copolymers are investigated in nanosecond scale at 1064 nm. It is found that the excited-state susceptibility is dramatically larger than the corresponding ground-state susceptibility for each sample. The experimental results also give evidence that superlattice structure of the copolymers can enhance, especially for the excited state, the molecular hyperpolarizabilities significantly. This enhancement may be attributed to the confinement effect of the pump-induced carriers.
Femtosecond Optical Kerr Effect of Surface Modified PbS Nanocrystals
AI Xi-cheng, JIN Rong, WANG Jing-jing, XIA Zong-ju, ZOU Ying-hua, GUO Lin, LI Qian-shu, ZHU He-sun
Chin. Phys. Lett. 1998, 15 (3): 192-194 .  
Abstract   PDF(pc) (212KB) ( 458 )
Surface modified PbS nanocrystals were fabricated by a novel method and their ultrafast optical nonlinearity was studied by the femtosecond time-resolved optical Kerr effect. A large nonlinear effect (x(3)~ 5 ×10-12 esu) with a laser pulse limited response was observed. This may be attributed to the reduction of surface trapped electrons due to the surface modification.
High-Order Harmonic Generation in the Presence of Static Electric Field
WANG Bing-bing, LI Xiao-feng, FU Pan-ming
Chin. Phys. Lett. 1998, 15 (3): 195-197 .  
Abstract   PDF(pc) (194KB) ( 526 )
We study the effects of the static electric field on the high-order harmonic generation (HOHG). It is found that the presence of the static electric field breaks the inversion and reflection symmetry, as a result, the HOHG spectrum exhibits a double plateau structure. Furthermore, the cutoff of the HOHG is no longer corresponding to the maximum kinetic energy the ionized electron can obtain from the laser field. Instead, it corresponds to the maximum kinetic energy of the electron with one return.
Gas Exchange by Bubbles in Waves
ZHOU Xian-chu, LIU Chun-rong
Chin. Phys. Lett. 1998, 15 (3): 198-199 .  
Abstract   PDF(pc) (160KB) ( 617 )
A simple and feasible model for the calculation of the gas transfer by bubble clouds is proposed in this article. N2, O2, and CO2 transfered by bubble clouds are obtained. At wind speed of 10m/s, the calculated supersaturation of dissolved oxygen is 1.92-3.89% in agreement with the measurement.
Magnetic Field Dissipation in Dense Molecular Clouds
MAO Xin-jie, TONG Yi
Chin. Phys. Lett. 1998, 15 (3): 200-202 .  
Abstract   PDF(pc) (235KB) ( 412 )
In dense molecular clouds the grains become the main charged particles. When the hydrogen gas density reaches as high as nH = 1011cm-3 and the grains are assumed to be small polycyclic aromatic hydrocarbons(PAHs), the lower hybrid drift instability develops, leading to the creation of anomalous electric conductivity, which makes the magnetic Reynold's number of the system RM ~ 1 indicating the dissipation of magnetic fields. When the gas density continues to go up and over1011cm-3, the collision frequency between PAHs and gas particles becomes larger than the plasma frequency, resulting in the collision process being dominant. In that case the magnetic field also dissipates because RM ~ 1 is still kept.
Near-Edge X-Ray Absorption Fine Structure Analyses of the Chain Model of Solid CS2
XU Chun-yi, TANG Jing-chang
Chin. Phys. Lett. 1998, 15 (3): 203-204 .  
Abstract   PDF(pc) (164KB) ( 327 )
The S K-shell near-edge x-ray absorption fine structure spectra of solid CS2 have been calculated by means of the multiple-scattering cluster method. The results show the existence of two kinds of absorption spectra which correspond to single-bond (C-S) and double-bond (C=S), respectively, and their superposition of the two spectra fits the experimental spectrum well. Our calculation supports the zigzag chain model of solid CS2 with C-C distance of 3.60±0.01Å.
Solid/Liquid Interface of Ag/Sn/Ag Trilayers by In Situ Resistivity Measurement
ZHAO Jian-hua, LIU Ri-ping, ZHANG Xiang-yi, CAO Li-min, ZHANG Ming, HE Duan-wei, DAI Dao-yang, XU Ying-fan, WANG Wen-kui,
Chin. Phys. Lett. 1998, 15 (3): 205-207 .  
Abstract   PDF(pc) (251KB) ( 562 )
The in situ four-point probe resistivity measurement was used as a main method to study the solid/liquid interfacial characteristics in Ag/Sn/Ag trilayers at temperatures ranging from 150 to 305°C. It is found from the variation of resistivity that three processes take place on annealing: the dissolution of silver atoms, the diffusion of silver atoms, and the formation of Ag3Sn in liquid tin layer. The first one plays the leading role in the variation of resistivity during annealing process. The apparent diffusivity of silver in liquid tin at 305°C is determined to be 7.3×10-17cm2/s.


Effects of La-Doping on Strontium Titanate Thin Films
GUO Jun, XIE Kan, LIU Zhen-xiang
Chin. Phys. Lett. 1998, 15 (3): 208-209 .  
Abstract   PDF(pc) (157KB) ( 589 )
La-doping effects of strontium titanate (SrTiO3) thin films were studied by x-ray photoelectron spectroscopy. The results indicated that the oxygen adsorption properties of SrTiO3 thin film surface could be significantly affected by La substitution. Besides, a shoulder was observed on the high binding energy side of the main O1s, peak in La-doped thin films.
Transport Properties of Ferromagnet/Ferromagnetic-Insulator/Ferromagnet Junctions Attached by a Paramagnetic Metal on Two Sides
LI Yun, LI Bo-zang, ZHANG Wu-shou, DAI Dao-sheng
Chin. Phys. Lett. 1998, 15 (3): 210-212 .  
Abstract   PDF(pc) (216KB) ( 380 )
The electronic-transport properties of ferromagnet/ferromagnetic-insulator/ferromagnet junctions attached on two sides by a paramagnetic metal are analyzed. The tunnel conductance and magnetoresistance are oscillatory functions of the ferromagnet thickness. The exchange coupling between ferromagnets depends on both the magnetic polarization of the conduction electrons and the exchange splitting in all the magnetic layers.
Effective Scattering Time in Zener Transition Between Bloch Bands
YAN Wei-xian, ZHAO Xian-geng,
Chin. Phys. Lett. 1998, 15 (3): 213-215 .  
Abstract   PDF(pc) (210KB) ( 363 )
Based on a two-band tight-binding model, the dynamics of electrons under the action of static electric fields with Markoffian dephasing is investigated. The effective scattering time is obtained under the conditions of long-time limit and small interband communication through a perturbative calculation, from which the signature of Zener resonances and relatively long time evolution behavior are predicted.
Electron Tunneling in nc-Si/a-SiO2 Double-Barrier Diode
LU Hai, GU Xiao-feng, QIN Hua, LI Wei, CHEN Kun-ji, HUANG Xin-fan
Chin. Phys. Lett. 1998, 15 (3): 216-218 .  
Abstract   PDF(pc) (303KB) ( 400 )
A single layer of nc-Si dots with 10nm in diameter embedded in a-SiO2 matrix is formed by the plasma enhanced chemical vapor deposition in a high hydrogen diluted silane plasma and followed by thermal annealing treatment. Based on this structure, an a-SiO2/nc-Si/a-SiO2 double barrier diode is fabricate. The transport characteristics of this diode exhibit a series of reproducible conductance peaks at room temperature. An equivalent circuit method is introduced to determine the real voltage spacing between adjacent conductance peaks. The results are in good agreement with the calculated values based on the Coulomb blockade effect.

Ellipsometric Studies of Polyaniline-Effective Dimension of “Conducting”States
YU Zhao-xian, LIN Yong-yao, MO Dang
Chin. Phys. Lett. 1998, 15 (3): 219-220 .  
Abstract   PDF(pc) (178KB) ( 336 )
A model of fractional-dimensional space is employed to study the measured ellipsometric spectra of polyaniline with acid doping treatment. Aside from some band parameters, the important dimensional properties of electronic states in the system associated with direct interband transitions can be obtained. The results indicate that as doping density is increased, the effective dimension (D) of electron states in the polyaniline changes from about 1.5D t o near 2.6D, in the same time the polyaniline shows an insulator-metal transition. A brief discussion about the results is given.

Examination on the Optical Absorption and Electron Paramagnetic Resonance Spectra of Cr3+ ions in α-LilO3 Crystal
HU Ping
Chin. Phys. Lett. 1998, 15 (3): 221-222 .  
Abstract   PDF(pc) (130KB) ( 371 )
The optical and electron paramagnetic resonance spectra of Cr3+ ions in the α-LilO3 crystal are explained based on the complete diagonalization procedure and a crystal-field-like model. The results agree well with experimental data.
Magnetic Properties of Gd2Co17-xSix Compounds
SHEN Bao-gen, LIANG Bing, CHENG Zhao-hua, ZHANG Shao-ying, ZHANG Hong-wei, ZHAN Wen-shan, ZHANG Li-gang
Chin. Phys. Lett. 1998, 15 (3): 223-225 .  
Abstract   PDF(pc) (244KB) ( 422 )
Effects of substituting small amounts of Si for Co on the structure and magnetic properties of Gd2CO17 compounds were studied by means of x-ray diffraction and magnetization measurements. All samples are of single phase with the rhombohedra1 Th2Zn17, type structure. The substitution of Si for Co leads to an approximately linear decrease in the unit cell volume. The saturation moment at 1.5 K decreases linearly with increasing Si concentration, being an approximately linear rate of about 4.1μB per substituted Si. The Curie temperature of Gd2Co17-xSix is found to decrease monotonously from 1213 to 651 K, as x increases from 0 to 3. X-ray diffraction measurements on magnetically aligned powders show that the easy magnetization direction of Gd2Co17-xSix compounds changes from basal plane to c-axis with increasing Si concentcation. The samples with x = 2, 3 exhibit a room temperature uniaxial anisotropy.
Positron Annihilation Studies in the Sm2/3Sr1/3MnO3+δ
JI Yuan, CAO Guo-hui, , LI Yang, MA Qing-zhu, LI Shen, WANG Yun-bo, SHEN Bao-gen
Chin. Phys. Lett. 1998, 15 (3): 226-227 .  
Abstract   PDF(pc) (169KB) ( 370 )
We measured lifetime and doppler broadening spectra of Sm2/3Sr1/3MnO3+δ as functions of temperature by positron annihilation technology In terms of lifetime spectrum, we found that the lattice effects triggered by ferromagnetic transition give rise to the change of the coefficient of the average linear thermal expansion of Sm2/3Sr1/3MnO3+δ at Tc. In terms of doppler broadening spectrum, we found the delocalization of low-momentum electrons occurs in Sm2/3Sr1/3MnO3+δ at metal-insulator transition temperature.
Effects of Alcohol Addition on the Deposition of Diamond Thick Films by dc Plasma Chemical Vapor Deposition Method
BAI Yi-zhen, JIANG Zhi-gang, WANG Chun-lei, JIN Zeng-sun, LÜ, Xian-yi, ZOU Guang-tian
Chin. Phys. Lett. 1998, 15 (3): 228-229 .  
Abstract   PDF(pc) (202KB) ( 355 )
Diamond films have been deposited by dc plasma chemical vapor deposition method. The addition of alcohol in the resource gas largely increases the deposition rate. The effects of alcohol addition on deposition rate and film quality are analyzed by scanning electron microscopy and Raman spectrometry. The mechanism of experimental phenomena is discussed.
Investigation of Preparing Cubic Boron Nitride Films by Magnetron Arc-Discharge Plasma Ion Plating
ZHAO Yong-nian, HE Zhi, WANG Bo, TAO Yan-chun, ZOU Guang-tian
Chin. Phys. Lett. 1998, 15 (3): 230-231 .  
Abstract   PDF(pc) (149KB) ( 296 )
A method of synthesizing cubic boron nitride (c-BN) films by the magnetron arc-discharge plasma ion plating was investigated. A nearly pure c-BN film was obtained by reacting boron vapor with high-density nitrogen ions, and using hot cathode arc-discharge plasma in a parallel magnetic field around the substrate. The structure of the films obtained was characterized by using infrared absorption spectroscopy and x-ray diffraction analysis. After numerous experiments, the phase pattern of the bias vs the current in synthesizing c-BN was found.
Mechanical Properties of Electrorheological Fluids
ZHAO He-ping, LIU Zheng-you, SHEN Jia-rui, LIU You-yan, Hui P. M.
Chin. Phys. Lett. 1998, 15 (3): 232-234 .  
Abstract   PDF(pc) (180KB) ( 400 )
The Rayleigh identity based on a multipole expansion theory is extended to analyze the mechanical properties of electrorheological fluids. Evaluation of the effective dielectric constant is emphasized. The dependence of the shear stress on the shear strain and the shear modulus for chains of particles arranged on a square lattice are presented.
30 articles