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Volume 11 Issue 3
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Original Articles
Detection of Plasma Produced in the Interaction Between YAG Laser and CCD
NI Xiaowu, LU Jian, HE Anzhi
Chin. Phys. Lett. 1994, 11 (3): 129-132 .  
Abstract   PDF(pc) (181KB) ( 416 )
A Q-switched YAG laser is used to act repeatedly upon a charge-coupled devices (CCD) having metal-oxide-semiconductor structure, and plasmas in the process are investigated by a Mach-Zehnder interferomcter. According to the production and development of the plasmas, the damage mechanism of the optoelectronic device is analyzed.
Dynamical Process of Charge Transfer in Fullerene C60
FU Rongtang, YU Zhigang, HUANG Qingfeng, SUN Xin, FU Rouli*
Chin. Phys. Lett. 1994, 11 (3): 133-136 .  
Abstract   PDF(pc) (0KB) ( 538 )
We consider lattice relaxation in doped C60 using the tight-binding model applied to a single C60 molecule. To simulate the dynamical evolution processes of string polaron in charged C60, we use a classical dynamical method where all the tangential collective coordinates are chosen. The nonlinear response time of lattice relaxation can be obtained in view of the present theory.
Time-Resolved Fluorescence Study of C60 Solution
SONG Jie, LI Feiming, QIAN Shixiong, LI Yufen, PENG Wenji, ZHOU Jianying, YU Zhenxin
Chin. Phys. Lett. 1994, 11 (3): 137-140 .  
Abstract   PDF(pc) (196KB) ( 473 )
Using a picosecond excitation source and a time-resolved streak camera detection system, the time-resolved fluorescence spectra of purified C60 have been recorded from toluene solution at room temperature. A fluorescence peak at about 730nm was detected and its lifetime was directly determined to be 1.1±0.1 ns. Two fluorescence peaks obtained from the mixture of C60 and C70 at 676 and 696nm were mainly related to C70 content.
Analytical Expression of Ampere’s Force Between Two Current Rings in a Compensated Torsion Balance
LUO Jun, FAN Shuhua
Chin. Phys. Lett. 1994, 11 (3): 141-144 .  
Abstract   PDF(pc) (166KB) ( 541 )
An analytical expression of ampere’s force between two current rings in a compensated torsion balance is deduced here, the properties and stability of this force are discussed. The result of numerical estimation for typical experimental parameters shows that the uncertainties of the force are smaller than 1 x 10-4 orders, which is very important for precise measurement of gravitational constant G.
Two-Wave Mixing and Self-pumped Phase Conjugation with Photorefractive BaTiO3 at Near-Infrared Wavelengths
ZHANG Zhiguo, ZHU Yong, KANG Jin, WU Xing, JIANG Qian, FU Panming
Chin. Phys. Lett. 1994, 11 (3): 145-148 .  
Abstract   PDF(pc) (168KB) ( 426 )
We studied the wavelength dependence of the exponential gain coefficient and response time of the two-wave mixing at near-infrared regime with an undoped BaTiO3. We also report a highly efficient self-pumpkd phase conjugation (SPPC). A 80% SPPC reflectivity at 741 nm was achieved.
Effect of Longitudinal Momentum Spread in Ion-Ripple Laser
LIU Pukun, QIAN Shangjie, TANG Changjian, LIU Shenggang
Chin. Phys. Lett. 1994, 11 (3): 149-152 .  
Abstract   PDF(pc) (167KB) ( 449 )
Using kinetic coupling mode theory of three waves, the effect of longitudinal momentum spread in ion-ripple laser (IRL), which is an advanced new scheme to generate tunable-coherent radiation with frequency ranging from microwaves to x-rays, is investigated. For a Gaussian distribution in beam longitudinal momentum, the results show that the growth rate of IRL falls off rapidly with increasing momentum spread, and the momentum spread causes linear damping of beam space-charge wave, weakening the beam-radiation mode coupling and lowering the output radiation frequency apart from broadening the radiation spectrum. The dispersion relation and phase matching conditions are also obtained.
Energy Walk-off in Nonlinear Acoustics
JIANG Wenhua, DU Gonghuan
Chin. Phys. Lett. 1994, 11 (3): 153-156 .  
Abstract   PDF(pc) (160KB) ( 455 )
It is found that acoustic internal conical refraction occurs for both fundamental and second harmonic of transverse wave propagating dong threefold axis of crystals. Energy walk-off which usually does not exist in acoustic collinear harmonic generation appears as well.
Particle Confinement Properties of Lower Hybrid Current Drive Plasma on the HL-1 Tokamak
DUAN Xuru, YUAN Chengjie, QIAN Shangjie, DING Xuantong, YUAN Bin, YANG Guang, DIAO Guangyue
Chin. Phys. Lett. 1994, 11 (3): 157-160 .  
Abstract   PDF(pc) (196KB) ( 464 )
The particle confinement property of LHCD (lower hybrid current drive) plasma on the HL-1 tokamak is mainly affected by the line-averaged density of electrons (ne). With ne < 2.0 x 1013cm-3 the particle confinement time (TP)is improved with the suppression of Hα(Dα) fluctuation at the edge, and tends to increase with the power PLH. The peak of Tp appears near the critical density ( 1.0x1013cm-3). These results are not influenced by the current drive directions.
Edge Ohmic Heating Experiment on HT-6M Tokamak
GAO Xiang, FAN Shuping, LI Jian’gang, MENG Yuedong, LUO Jiarong, YIN Fhxian, ZENG Lei, DING Liancheng. LIN Bili, ZHANG Wei, HAN Yuqing, TONG Xingde, LUO Lanchang, GONG Xianzu, JIANG Jiaguang, WU Mingjun, YIN Fei
Chin. Phys. Lett. 1994, 11 (3): 161-164 .  
Abstract   PDF(pc) (181KB) ( 456 )
An improved ohmic confinement has been achieved on HT-6M tokamak after application of edge ohmic heating pulse which makes plasma current rapidly ramp up (0.4 ms) in a ramp rate of 12 MA/s. The improved ohmic confinement phase is characterized by (a) energy and particle confinement time increase, (b) non-symmetric increased density ne, (c) reduced Hα radiation, (d) increased Te and steeper Te, ne profile at the edge. The results from soft x-ray sawteeth inversion radius and βp +li/2 implied the anomalous current penetration.
Room Temperature Visible Photoluminescence from Thermally Annealed Hydrogenated Amorphous Silicon Films
LIN Xuanying, WANG Hong, YU Yunpeng, LIN Kuixun
Chin. Phys. Lett. 1994, 11 (3): 165-168 .  
Abstract   PDF(pc) (208KB) ( 520 )
A visible photoluminescence from a thermally annealed boron doped hydrogenated amorphous silicon (a-Si : H) film has been observed at room temperature. The wavelength at the peak of the photoluminescent spectra is about 600nm. The intensity of photoluminescence is dependent on the annealing temperature strongly and relative to the deposition technology parameters of the films, especially to the hydrogen dilution of the boron doped silane and the deposition rate of the films. There exists a quantum size effect of nanometer-scale porosity on the surface of the annealed a-Si: H film. The quantum-confined structures may form due to the evolution of hydrogen from the surface of the films during the annealing procedure. The density of the porosity is relative to the quantity of evolved hydrogen from the film and the evolution rate of the hydrogen.
Effects of Annealing on Pt/Co Multilayer Films
JIANG Zhihong, SHEN Defang, SHI Tiansheng, GUO Changlin*, GUO Rongfa*
Chin. Phys. Lett. 1994, 11 (3): 169-172 .  
Abstract   PDF(pc) (177KB) ( 482 )
Annealing effects are helpful guides to study Pt/Co multilayer interface diffusions. However, the results reported till now are different. Here we report the increase in coercivity Hc and the decrease in Kerr rotation θk after being annealed in vacuum or argon atmosphere. We attribute these effects to the formation of CoPt3 compound.
Polarization Effect in Co-Nb/Pd Multilayer Films
LIU Yihua, ZHENG Min, MA Xiaoding
Chin. Phys. Lett. 1994, 11 (3): 173-176 .  
Abstract   PDF(pc) (201KB) ( 536 )
Co-Nb/Pd multilayer films with different thicknesses of Co-Nb layers have been prepared by rf sputtering. X-ray diffraction showed that the Co-Nb layers for all samples were in amorphous state. Magnetic measurements showed that the Pd atoms near the Go-Nb layers are polarized by Co atoms. The total thickness of polarization for each Pd layer is about 3.2Å. A perpendicular easy axis in Co-Nb/Pd films can be obtained when the Co-Nb layers are very thin.
Haldane Gap Related Energy States in Spin s = 1 Linear Chain Heisenberg Antiferromagnet
LU Wei, LIU Pulin, SHEN Xuechu, M. von Ortenberg, J. Tuchendler, J . P. Renard
Chin. Phys. Lett. 1994, 11 (3): 177-180 .  
Abstract   PDF(pc) (189KB) ( 512 )
Some fundamental properties are found for the singlet ground state and lowest triplet excited state in the spin s = 1 linear chain Heisenberg antiferromagnet with arbitrary chain length. The influence of the anisotropic term on these states is evaluated by spin polarization on the site of the chain. The energy levels based on these analyses are in good agreement with the experimental spectroscopes.
Synthesis of Diamond Films on Stainless Steel Substrates
ZHAN Rujuan, CHEN Jifong, ZHU Xiaodong, JIANG Xicheng, WANG Xueyi, WU Hao
Chin. Phys. Lett. 1994, 11 (3): 181-184 .  
Abstract   PDF(pc) (201KB) ( 658 )
The continuous diamond films have been deposited on the stainless steel substrate using the hot cathode dc discharge plasma chemical vapor deposition method. The characteristics of diamond film are reported and the pretreatment of stainless steel substrate before deposition is also described.
Diamond Nuclei on the Silicon Mirror Surface by Direct-Current Glow Discharge Chemical Vapor Deposition
GAO Chunxiao, ZOU Guangtian, JIN Zengsun
Chin. Phys. Lett. 1994, 11 (3): 185-188 .  
Abstract   PDF(pc) (238KB) ( 429 )
A new method is proposed for generation of high density diamond nuclei in the dc glow discharge chemical vapor deposition. Application of dc negative valtage together with high methane content has been found to generate diamond nuclei as high as 1010/cm2 on mirror-polished Si wafer. It has been indicated that carbon over-saturation, negative voltage and hydrogen play an important role in this new pretreatment process.
Classical Instability of Anti-de Sitter Universe
XU Jianmei, LI Lixin, LIU Liao
Chin. Phys. Lett. 1994, 11 (3): 189-192 .  
Abstract   PDF(pc) (142KB) ( 575 )
This article discusses the gravitational stability of anti-de Sitter universe. It turns out that anti-de Sitter universe with closed timelike curves is unstable to gravitational perturbations.
16 articles