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Volume 8 Issue 1
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Original Articles
Supercritical Characteristics of a Relaxation Oscillator
JI Feng, LIU Hui, YANG Zhenghai, SHI Kangjie, HE Daren, WANG Dakai
Chin. Phys. Lett. 1991, 8 (1): 1-4 .  
Abstract   PDF(pc) (212KB) ( 395 )
A relaxation oscillator can be described by two maps: one circle and one inverse circle. The order of map depends on the function form of the modulation signal . Supercritical behaviors of the oscillator were studied experimentally and numerically. Two scaling laws S( f) ∝ f and τ ∝ |f – fc| were verified. Both the scaling exponents δ and γ2 increase when the order is getting larger.

G Pair Included Fermion Dynamical Symmetry Model for Medium and Heavy Mass Nuclei
PAN Feng*, CAO Yufang and PAN Zhenyong
Chin. Phys. Lett. 1991, 8 (1): 5-8 .  
Abstract   PDF(pc) (142KB) ( 429 )
A new description of the hexadecapole degree of freedom in the medium and heavy mass region in the framework of the fermion dynamical symmetry model is proposed. In this letter, the k-active case is discussed in detail, in which the pairing and multipole operators generate Sp10 group. The energy spectra are derived for two limiting cases. The results show that these limits and those in the s. d. g ZBM have one to one correspondence when N1 (=N boson number in the s. d. g IBM)≤ Ω1/5.

Phase Portraits and Flow Regimes in a Circular Couette System with Counter-Rotating Cylinders
LIU Shusheng*, SHA Ernan, YAO Lan, WANG Mingtan
Chin. Phys. Lett. 1991, 8 (1): 9-12 .  
Abstract   PDF(pc) (234KB) ( 368 )
Experiments have been conducted on the circular Couette system, established recently in our laboratory. By using an optical-electronic modulation feedback Laser Doppler Velocimetry technique, the velocity time series data with higher signal-noise ratio, power spectra, phase ort traits and Poincare sections were obtained. Two scenarios to chaos were observed. One is the Ruelle-Takens scenario, while the other (when both cylinders of the Couette system are counter-rotating) is quite different from it. A tremendous variety of flow regimes and a new state were observed. A tentative explanation is made for the new state.
Evolution of Ultrastrong Langmuir Turbulence
MU Jianlin, CAI Shidong
Chin. Phys. Lett. 1991, 8 (1): 13-16 .  
Abstract   PDF(pc) (189KB) ( 441 )
We report here our recent studies of ultrastrong Langmuir tubulence by numerical simulation in two-fluid plasma. Many nonlinear phenomena, such as the formation and collapse of solitons, the onset of wavebreaking, the burnout and reborn of cavitons and so on, are observed in the simulation. Very intense cavitons ( |E|2/2ε0Te3 and δn/n0 0.3 ) caused by relative weak pump ( (|E0|2/2ε0Te 0.05 ) and fluctuations ( δn/n0 0.003 ) can exist in the system which are beyond the approximation of the Zakhorov model.

Dissociation of CO on Oxygen Contaminated Ni{00l}c(2x2)-A1 Surface at Room Temperature
YAO Jun, ZHU Li, LÜ, Sihua, WU Sicheng
Chin. Phys. Lett. 1991, 8 (1): 17-20 .  
Abstract   PDF(pc) (258KB) ( 336 )
The dissociation of CO on oxygen contaminated Ni{00l}c(2x2)-A1 surface at room temperature has been observed by electron energy loss spectroscopy. The CO dissociation rate is proportional to the oxygen contamination on the surface.
Calculation of Dielectric Constants for Semiconductors-an Application of Ab Initio Pseudopotential Method
WANG Jianqing, GU zongquan, LI Mingfu
Chin. Phys. Lett. 1991, 8 (1): 21-24 .  
Abstract   PDF(pc) (220KB) ( 340 )
We have used ab initio pseudopotential method to generate basis wavefunctions and eigen energies to carry out first principle calculations of the static macroscopic dielectric constant for GaAs and Gap. The resulted converged random phase approximation (RPA) value is 12.55 and 10.71, in excellent agreement to the experimental value of 12.4 and 10.86, respectively. The inclusion of the exchange correlation contribution makes the calculated result slightly worsen. A convergence test with respect to the number of k points in Brillouin zone (BZ) integration was carried out. Sixty irreducible BZ k points were wed to achieve the converged results. Integration with only 10 special k points increased the RPA value by 15%.
Coverage Dependence of Charge Transfer Between Cs Overlayer and 5d Transition Metal Subtrates
GAO Shiwu, WANG Dingsheng
Chin. Phys. Lett. 1991, 8 (1): 25-28 .  
Abstract   PDF(pc) (254KB) ( 404 )
A recently developed embedded cluster scheme is applied to study the coverage dependence of charge transfer between Cs and the (001) surface of all 5d transition metals, which agrees with the jellium-slab model calculation given by the first principle band method. The correlation between the initial drop of work function during cesiation caused by this charge transfer and the unfilled d band of the substrates is revealed
Anisotropy of Bi2Sr2CaCu2Oy Superconducting Single Crystals Under High Pressure
LIU Zhenxing, ZHENG Dongning, YAN Yifeng, WANG Jihong, WANG Lijun, ZHAO Zhongxian
Chin. Phys. Lett. 1991, 8 (1): 29-32 .  
Abstract   PDF(pc) (185KB) ( 381 )
It is shown that there exists the anisortropic nature of pressure dependence for the superconducting transition temperature and resistivity in Bi2Sr2CaCu2Oy single crystals. The maximum superconducting critical temperature and the minimum resistance along a-b plane under about 8kbar have been observed, no obvious structure phase transition was observed at room temperature under pressure, and there is not the same behaviour along the c axis up to 13kbar. A slight difference between the rates dTc/dP along a-b plane and c axis was also found. This anisotropy may have close relation to the coupling between layers.
Resistance to Photorefraction and Phase Matching Temperature of Nd:MgO:LiNbO3 Crystals
LI Jiang, LI Bing, WEN Jinke, WANG Huafu
Chin. Phys. Lett. 1991, 8 (1): 33-35 .  
Abstract   PDF(pc) (255KB) ( 426 )
The influence of Nd:MgO:LiNbO3 composition on the optical quality and resistance to photorefraction has been studied. Nd:MgO:LiNbO3 (1mol% Nd2O3, 7.5 mol% MgO) crystal has been found to have enhanced resitance to photore-fraction, lower phase matching temperature and good optical quality. This crystal is promising material for self-frequency-doubled and self-Q-switched laser devices.
Far-Infrared Reflectance of the Sintered Samples of Y-Ba-Cu-O at Different Quenching Temperature
ZENG Wensheng, ZHANG Guizhong, LI Zengfa, ZHANG Guangyin, YANG Xiaoming*, YAN Jie*, SONG Deying*
Chin. Phys. Lett. 1991, 8 (1): 36-39 .  
Abstract   PDF(pc) (202KB) ( 349 )
The sintered samples of Y-Ba-Cu-O were quenched in air at different temperatures from 950 to 300℃ and their room-temperature far-infrared reflectance spectra were obtained. The spectra were studied by using the Drude model and Lorentzian phonon. From the curve of carrier density us quench temperature, an orthorhombic-tetragonal phase change is indicated. The phonon oscillation strength changes were explained by the abnormal sensibility in the reflectance spectra.
Time-resolved Fluorescence Decay Study of Hematoporphyrin Derivative
LIU Wenqing, XIA Yuxing, LIU Songhao, R. Ramponi*, R. Cubeddu*
Chin. Phys. Lett. 1991, 8 (1): 40-43 .  
Abstract   PDF(pc) (218KB) ( 447 )
Time-resolved fluorescence decays were first performed on hematoporphyrin derivative laser No.3 in buffer at different micelles concentration. The fluorescence lifetime constants, measured with a time-correlated single photon counting system, could be fitted by two or three exponential components with different relative peak amplitudes depending on the observation wavelength, thus indicating the presence of different emitting molecular species and/or of molecular species in different aggregational states.
Sputtering Angular Distributions of Individual Elements for Low-Energy Ar Ion Irradiation of PtCu Alloy
ZHENG Liping, LI Risheng*, LI Mingyao, SHEN Weizu, LIN Junying, ZOU Zhiyi
Chin. Phys. Lett. 1991, 8 (1): 44-47 .  
Abstract   PDF(pc) (226KB) ( 381 )
The dynamic Monte Carlo program including a bombardment-induced Gibbsian segregation process was used to calculate angular distributions of individual elements from sputtered Cu0.5Pt0.5 alloy in the Ar ion energy range between 0.2 and 1.5keV. Calculated results show that for each investigated incident energy, the angular distribution of the Pt clement is more forward-pointed than that of the Cu one; the reason may be that different percentage of sputtered atoms (37~45% of Pt and 12~19% of Cu) come from beneath the topmost layer.
Excitation Intensity Dependence of Photoluminescence in a-C:H and a-C Films
LI Qingshan, GUO Hua, MA Yurong, FANG Rongchuan, XU Cunyi
Chin. Phys. Lett. 1991, 8 (1): 48-51 .  
Abstract   PDF(pc) (224KB) ( 412 )
We present the novel results of excitation intensity dependent photoluminescence (PL) in a-C:H and a-C thin films. Sublinear and superlinear phenomena of PL have been observed for a-C:H films. There are two PL bands in a-C films under lower excitation intensity. These results are qualitatively explained in the light of band tail state saturation and the contribution of gap states.
Third Quantization of a Solvable Model in Quantum Cosmology in Brans-Dicke Theory
XIANG Yingming and LIU Liao
Chin. Phys. Lett. 1991, 8 (1): 52-55 .  
Abstract   PDF(pc) (133KB) ( 324 )
In this paper we constructed the formula of the third quantization of a solvable model in quantum cosmology based on the Brans-Dicke theory and got an abnormal distribution.
14 articles