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Volume 17 Issue 6
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Original Articles
Test of the Symmetrization Postulate for Phonons in an Ion Trap
ZHENG Shi-Biao, ZHU Xi-Wen
Chin. Phys. Lett. 2000, 17 (6): 391-392 .  
Abstract   PDF(pc) (188KB) ( 331 )
We propose a scheme for testing the symmetrization postulate (SP) for phonons in an ion trap. In the scheme a two-level ion is trapped in a harmonic potential and driven by a laser beam tuned to the carrier. The violation of the SP is manifested by the probability that the ion makes a transition from the ground state to the excited state after an appropriate interaction time.

Antiparticle in the Light of Einstein-Podolsky-Rosen Paradox and Klein Paradox
NI Guang-Jiong, GUAN Hong, ZHOU Wei-Min, YAN Jun
Chin. Phys. Lett. 2000, 17 (6): 393-395 .  
Abstract   PDF(pc) (254KB) ( 449 )
The original version of Einstein-Podolsky-Rosen paradox and the Klein paradox of Klein-Gordon equation are discussed to show the necessity of existence of antiparticle with its wave function being fixed unambiguously. No concept of “hole” is needed.
Quantum Corrections to the Entropy of a Barriola-Vilenkin Black Hole due to Spin Fields
LI Zhong-Heng
Chin. Phys. Lett. 2000, 17 (6): 396-397 .  
Abstract   PDF(pc) (143KB) ( 316 )
The radial parts of the gravitational, electromagnetic, neutrino, and massless scalar fields in Barriola-Vilenkin spacetime are transformed to the form of the Teukolsky-type master equation. The first quantum corrections to the entropy of the black hole due to the spin fields are calculated by using the brick wall model. It is shown that the contribution of any one of the spin fields is quadratically divergent at the event horizon and is proportional to the surface area of the event horizon.
A New Feature in Some Quasi-discontinuous Systems
WU Shun-Guang, HE Da-Ren
Chin. Phys. Lett. 2000, 17 (6): 398-400 .  
Abstract   PDF(pc) (235KB) ( 339 )
Many systems can display a very short, rapid changing stage (quasi-discontinuous region) inside a relatively very long and slowly changing process. A quantitative definition for the “quasi-discontinuity” in these systems has been introduced. We have shown by a simplified model that extra-large Feigenbaum constants can be found inside some period-doubling cascades due to the quasi-discontinuity. As an example, this phenomenon has also been observed in Rose-Hindmash model describing neuron activities.
Shell Model Analysis of Ξ- Hypernuclei Spectra for Mass A = 12 and A = 16
TAN Yu-Hong, LUO Yan-An, NING Ping-Zhi, CAI Chong-Hai
Chin. Phys. Lett. 2000, 17 (6): 401-402 .  
Abstract   PDF(pc) (197KB) ( 347 )
The excitation spectra for (Ξ12-Be) and (Ξ16-C) are obtained in the frame of a shell model. The experimental values of the ground state binding energies of the Ξ- hyperon in (Ξ12-Be) and (Ξ16-C) are used to determine the well depth of the Ξ-- nucleus potential. The information on the residual interaction is emphasized. It is found that the residual interaction does not have much effect on the spectra of the Ξ--hypernucleus.

A Calculation of Electron Impact for the 3d5/2 → 2p3/2 Line Emission of Fe23+
CHEN Chong-Yang, QI Jing-Bo, WANG Yan-Sen, XU Xue-Ji, SUN Yong-Sheng
Chin. Phys. Lett. 2000, 17 (6): 403-404 .  
Abstract   PDF(pc) (195KB) ( 328 )
By using the semi-relativistic distorted-wave Born exchange method, electron impact cross sections for the Fe23+line emission 3d5/2 + 2p3/2 are calculated. The calculation involves line formation by direct electron-impact excitation, radiative cascade, resonant excitation, and dielectronic recombination satellites with captured electron in the n ≥ 5 levels. The results show a good agreement with the recent measurements.

Autoionizing Distribution of the Triply Excited Double Rydberg States in La Atom
SUN Wei, XIE Xiu-Ping, HUANG Wen, ZHONG Zhi-Ping, XU Cheng-Bin, XUE Ping, XU Xiang-Yuan,
Chin. Phys. Lett. 2000, 17 (6): 405-407 .  
Abstract   PDF(pc) (259KB) ( 373 )
The autoionization distribution o f the triply excited double Rydberg states (TEDRS) 5d5/2NLnl (N ≤ 2 2 ; n≤ 50; L, l < 4) of La has been investigated by using five-laser resonance excitation in combination with a method of sequential ionization by a pulsed electric field and a constant electric field. The experimental results exhibit that the La atoms in TEDRS predominantly single-autoionize to the ionic Rydberg states located in a few Rydberg manifolds. Furthermore, a difference of autoionization mechanisms between TEDRS above and those below the double ionization threshold is found.

Effect of Resonant Photoionization in Non-Local Thermodynamical Equilibrium Plasmas
Chin. Phys. Lett. 2000, 17 (6): 408-409 .  
Abstract   PDF(pc) (177KB) ( 362 )
Based on the detailed configuration accounting model(DCA), a method is developed to calculate the rate of the resonant photoionization(RP) in the average atom(AA) model. Using this method, the RP rates are calculated for an average ion and compared with DCA calculation. The comparison shows the reasonableness of the proposed method. The RP process is included in the AA rate equations and the numerical results show that RP can cause an additional ionization up to 10% or so in some cases.
Preparation of GHZ States via Grover’s Quantum Searching Algorithm
ZENG Hao-Sheng, KUANG Le-Man
Chin. Phys. Lett. 2000, 17 (6): 410-412 .  
Abstract   PDF(pc) (188KB) ( 427 )
We propose an approach to prepare GHZ(Greenberger, Horne, Zeilinger) states of an arbitrary multi-particle system in terms of Grover's fast quantum searching algorithm. The approach can be used to produce other entangled states with various degrees of entanglement.

Supercontinuum Generation in Atmospheric-Pressure Nitrogen Using a Tightly Focused Intense Femtosecond Laser Beam
QIN Yuan-Dong, ZHU Chang-Jun, YANG Hong, GONG Qi-Huang
Chin. Phys. Lett. 2000, 17 (6): 413-415 .  
Abstract   PDF(pc) (270KB) ( 508 )
Supercontinuum generation in atmospheric-pressure nitrogen by a focused intense femtosecond Ti: sapphire laser was studied at various pulse durations and energies. The generated supercontinuum was greatly blue-broadened due to self-phase modulation in the plasma produced. The measured blue-broadening Δω is proportional to pulse intensity for fixed pulse duration, and values up to 0.7ω (ω being the original laser frequency) was obtained with a pulse energy of 9.5 mJ and minimum duration of 100 fs.

Deposition of Small Clusters on Surface: a Molecular Dynamics Simulation
DUAN Xiang-Mei, GONG Xin-Gao
Chin. Phys. Lett. 2000, 17 (6): 416-418 .  
Abstract   PDF(pc) (272KB) ( 421 )
By using the molecular dynamics simulation, we have studied the dynamic behaviors of small energetic clusters deposited on the surface. We find that, at incident energy as low as1.0eV/atom, the structure of the cluster is destroyed and cluster atoms form an epitaxial layer above the surface. At high energy incidence, the site exchange between cluster atom and surface atom is observed. The effects of the cluster size and orientation are discussed.

Structural Origin of the Formation of Odd-Numbered Carbon Clusters from Fullerene Derivatives
KONG Qing-Yu, ZHUANG Jun, ZHAO Li, WANG Jia-Yu, QIAN Shi-Xiong, LI Yu-Fen, LI Xu, ZHONG Chao-Fan, CAI Rui-Fang, YU Yong, HOU Hui-Qic
Chin. Phys. Lett. 2000, 17 (6): 419-422 .  
Abstract   PDF(pc) (256KB) ( 416 )
We report the mass spectrometric investigation on fullerene derivatives C60CH2, C60RH , C60R2(R = C6H5 CO-) and C60On under the 308nm laser ablation. In the negative ion mass spectra of C60CH2, C60R2 and C60On odd-numbered clusters C-57,C-55, C-53, C-51 are observed clearly in addition to the even-numbered fullerene fragment ions, while for the monoadduct C60 RH,, odd-numbered species can not be detected. In the positive ion channel, the fragmentation patterns of the three derivatives are similar

Generation of Tunable Amplitude-Squeezed Light by Injection Locking of a Laser Diode
WANG Jun-Min, HE Ling-Xiang, ZHANG Tian-Cai, XIE Chang-De, PENG Kun-Chi
Chin. Phys. Lett. 2000, 17 (6): 422-424 .  
Abstract   PDF(pc) (239KB) ( 439 )
Tunable amplitude squeezing around the D2 line of cesium has been experimentally accomplished at room temperature in a quantum-well laser diode with light injection from a single-mode distributed Bragg-Reflector laser diode. While the master laser frequency is tuned, amplitude squeezing of the output light from the slave laser can be maintained at about 0.9dB throughout a tunable range of ~1.7GHz around the cesium D2 line.

Quantum Interference in Spontaneous Emission from a V-Type Three-Level Atom in a Two-Band Photonic Crystal
YANG Ya-Ping, Chen Hong, ZHU Shi-Yao
Chin. Phys. Lett. 2000, 17 (6): 425-427 .  
Abstract   PDF(pc) (289KB) ( 366 )
The spontaneous emission from a V-type three-level atom embedded in a two-band photonic crystal is studied. Due to the quantum interference between the two transitions and existence of two bands, the populations in the upper levels display some novel behavior: anti-trapping, population oscillation, and population inversion.
Pattern Formation and Quasicrystal Structure in Azobenzene Polymer Film
XU Ze-Da, CAI Zhi-Gang, ZHANG Ling-Zhi, LIU Yan-Fa, YANG Jie, SHE Wei-Long, ZHOU Jian-Ying
Chin. Phys. Lett. 2000, 17 (6): 428-430 .  
Abstract   PDF(pc) (597KB) ( 445 )
Pattern formation in azobenzene polymer film by degenerate four-wave mixing is reported. Island arrays with specific patterns are analyzed with scanning electron microscopy and polarizing optical microscopy. It is demonstrated that the control of photo-induced nanostructure sized micropattern in the nonlinear organic film is possible by using properly polarized writing beams with the total incident power exceeding a certain threshold.

Pump Intensity Dependence of Two-Beam Coupling in Doped Lithium Niobate Crystals
Nouel Y. Kamber, XU Jing-Jun, Sonia M. Mikha, SONG Feng, ZHANG Guo-Quan, ZHANG Xin-Zheng, LIU Si-Min, ZHANG Guang-Yin
Chin. Phys. Lett. 2000, 17 (6): 431-432 .  
Abstract   PDF(pc) (197KB) ( 366 )
We demonstrated experimentally the dependence of two-beam coupling on the incident pump intensity in our samples of doped LiNbO3 crystals. Our results show that there is an optimum pump intensity for the signal beam amplification, which can be easily controlled by doping the LiNbO3 crystal with suitable concentrations of Fe and damage-resistant dopants such as Mg, In, and Zn.
Determination of the Refractive Index Profile of a Polymer Waveguide by Photobleaching
SHAN Ji-Xiang, SHEN Qi-Shun, ZHANG Ai-Hua, CAO Zhuang-Qi, CHEN Ying-Li
Chin. Phys. Lett. 2000, 17 (6): 433-434 .  
Abstract   PDF(pc) (199KB) ( 350 )
The shrinkage effect of polymer films, which was demonstrated in our photobleaching experiment, can be fitted approximately by an exponentially decaying function. After taking the shrinkage effect into account, the index profile of the polymer waveguide was determined to be a Fermi function with the help of the m-line method and the exact transfer matrix theory.
InAsP/InGaAsP Strained Microstructures Grown by Gas Source Molecular Beam Epitaxy
CHEN Yi-Qiao, CHEN Jian-Xin, ZHANG Yong-Gang, LI Ai-Zhen, K. Frö, jdh*, B. Stotz*
Chin. Phys. Lett. 2000, 17 (6): 435-437 .  
Abstract   PDF(pc) (231KB) ( 508 )
Device quality InAsP/InGaAsP strained multiquantum-well (MQW) structures are successfully grown by using gas source molecular beam epitaxy method. The grown MQW and InGaAsP quanternary alloy are characterized by using x-ray diffraction, room temperature photoluminescence measurements, confirming that optimum growth condition and high quality material have been obtained for device application. The grown laser structures are processed into ridge waveguide lasers. A threshold current as low as 16mA at 25°C for 300µm long device has been obtained. Temperature-dependent light-current measurement shows a characteristic temperature of 75 K.

Cluster Model for K(Ta0.56Nb0.44)O3 Solid Solution
PENG Yi-Ping, LI Hua, WANG Chun-Lei, ZHANG Lei, ZHANG Pei-Lin, ZHONG Wei-Lie
Chin. Phys. Lett. 2000, 17 (6): 438-440 .  
Abstract   PDF(pc) (240KB) ( 499 )
Based on the results of total-energy calculations for embedded clusters using self-consistent-field Xα-scattered-wave method, we determined the tetragonal fine structure of K(Ta0.56Nb0.44)O3, i.e., the equilibrium configuration of B-site cations (Ta and Nb) in the ferroelectric phase. Ta is found to have an off-center displacement of about 0.02Å along [001]. The off-center displacement of Nb is much larger than that of Ta, thus it makes a major contribution to the occurrence of the ferroelectric instability.

Electronic Structure of High-pressure Alumina Polymorphs
LIU Xiao-Lei, DUAN Wen-Hui, GU Bing-Lin
Chin. Phys. Lett. 2000, 17 (6): 441-443 .  
Abstract   PDF(pc) (383KB) ( 397 )
Electronic properties are investigated for three alumina polymorphs (corundum, Rh2O3 (II) and Pbnm perovskite), which are predicted as the stable structures under different pressure range, by means of the first-principles molecular dynamics method within local density functional framework. The similarity in electronic properties of the polymorphs of alumina is observed. The effect of possible phase transitions on ruby (Cr+3-doped Al2O3) fluorescences is discussed.
Calculation of the Exchange Interaction Constant Between the Rare-Earth and the Transition Metal Sub-lattices in R2Fe17-xMx(M = AI or Ga)
HAO Yan-Ming
Chin. Phys. Lett. 2000, 17 (6): 444-445 .  
Abstract   PDF(pc) (120KB) ( 373 )
A precise calculation of the exchange interaction constant JRT between the rare-earth sub-lattice and the transition metal sub-lattice in R2Fe17-xMx(R: rare-earth, M = Al or Ga) compounds is given. The calculated values for Tb2Fe17-xGax(x = 6 and 7) and Dy2Fe17-xAlx(x = 5, 6, 7 and 8) compounds are in excellent agreement with the values derived from the high-field measurement.

Influence of Fe in the local Structure of Perovskite Compound La2/3Cal/3Fel-xMnxO3
WE Long, WANG Yun-Bo, WANG Hui-Yao, YUE Yong, WANG Tian-Min, ZHANG Tian-Bao, CAO Guo-Hui,
Chin. Phys. Lett. 2000, 17 (6): 446-447 .  
Abstract   PDF(pc) (214KB) ( 327 )
The ceramic samples with nominal composition of La2/3Cal/3Mnl-xFexO3 (0.01 ≤ x ≤ 0.20) were prepared by solid state reaction method. The effect of Fe doping on the Mn site was measured by the positron annihilation technique and Mössbauer spectroscopy. Upon doping, no appreciable structure change and electronic structure change in Mn-O plane were observed in the series of compounds. The Mössbauer parameters show that the iron probe has stable 3+ valance with the high spin state in all samples. Moreover, by examining the shape of the spectra, the tendency can be found that the isomer shift and quadruploe splitting increase with the increasing Fe+3 content. This phenomenon shows the local lattice distortion and the localization of d-electrons with the increasing Fe-doping content.

Thermal Expansion of CsNiCI3 by Electron Paramagnetic Resonance and Optical Absorption Spectra
GUO Sheng-Li, ZHANG Yong, YOU Xiao-Zeng, MIN Nai-Ben
Chin. Phys. Lett. 2000, 17 (6): 448-450 .  
Abstract   PDF(pc) (209KB) ( 379 )
Electron paramagnetic resonance (EPR) measurement of CsNiCl3 compound has been performed at 192 GHz in the temperature range from 300 to 5K, along the axes of main g tensor. The energy levels and the g-factors are calculated. The linear thermal expansion coefficient ( 2.77x10-5 K-1 ) for the Ni2+-CI- bond distance is studied by combining EPR and optical absorption spectra with changing temperature.

Preparation of Si Nanocrystals Using Anodic Porous Alumina Template Formed on Silicon Substrate
WU Jun-Hui, PU Lin, ZOU Jian-Ping, MEI Yong-Feng, ZHU Jian-Min, BAO Xi-Mao
Chin. Phys. Lett. 2000, 17 (6): 451-453 .  
Abstract   PDF(pc) (383KB) ( 847 )
A novel technique to extend template application of anodic porous alumina to Si has been reported. First, porous alumina template about 400nm thick was prepared on silicon substrate by anodizing thin aluminum film with high purity of 99.99% in 15 wt.% sulfuric acid under a constant voltage of 20 V and at an electrolyte temperature of 5oC. Then, amorphous Si layer approximately 50nm in thickness was deposited onto the surface of template by using electron beam evaporation technique followed by an Xe ion beam bombardment, upon which as-coated Si layer at the pore mouth could be removed into pores smoothly. Three runs were performed by repeating above process of deposition and post bombardment. Finally, samples were annealed at 800oC for 30min in nitrogen. Transmission electron microscopy and x-ray diffraction analysis reveal Si nanocrystals with a size of 15-20nm being formed in the pores of template.

Organic Light-Emitting Diodes Based on New Oxadiazole and Pyrazoline Derivatives
ZHANG Zhi-Ming, ZHANG Rui-Feng, WU Fang, MA Yu-Guang, LI Guo-Wen, TIAN Wen-Jing, SHEN Jia-Cong
Chin. Phys. Lett. 2000, 17 (6): 454-456 .  
Abstract   PDF(pc) (210KB) ( 427 )
The bilayer heterojunction devices were fabricated successfully by using a novel oxadiazole derivative: 2, 2'- (2,5-thiophenediyl) bis (5-(4-methyl) phenyl-l,3,4-oxadiazole) (T-OXD) as the electron-transporting layer (ETL) and a pyrazoline derivative:l-phenyl-3-(dimethylamino)styry1-5-(p(dimethylamino) pheny1)pyrazoline (PDP) as the light-emitting layer and the hole-transporting layer. The emission at 500nm was derived from PDP layer. In comparison with the bilayer device of tris (8-hydroxyquinoline) aluminum (Alq) as the ETL, the luminous efficiency of the PDP/T-OXD heterojunction device was enhanced by 104 times.

Positron Annihilation Mechanism Correlated with Microstructure of C60-Contained Chitosan
DAI Yi-Qun, HE Chun-Qing, LI Shi-Qing, FANG Peng-Fei, CHEN Yuan-Yin, WANG Shao-Jie
Chin. Phys. Lett. 2000, 17 (6): 457-459 .  
Abstract   PDF(pc) (309KB) ( 438 )
Positron annihilation lifetime spectra measurements were performed on C60-containing chitosan as a function of temperature ranging from 290 to 380K. Both the ortho-positronium annihilation lifetime т3 and its intensity I3 increase with increasing temperature, however, the values of I3 in C60-containing chitosan are smaller than that in pure chitosan, and the slope of т3 with temperature is also suppressed after C60 linked. The existing three models for positron annihilation in polymer have been compared to analyze the experiment result. It is realized that only the spur reaction model, combined with the free volume model, can explain it satisfactorily. The ortho-positronium lifetime and intensity were affected by the local physicochemical environment of material, i.e., free-volume structure, electron scavenging and trapping sites, etc. The linked C60 that play a significant chemical inhibition and quenching role on positronium formation and annihilation is first observed. The microstructure change brought by C60 group has also been discussed.
The First Spectral Analysis of Solar Radio Spike Event
XU Fu-Ying, LIU Yu-Ying, FU Qi- Jun, WU Hong-Ao
Chin. Phys. Lett. 2000, 17 (6): 460-462 .  
Abstract   PDF(pc) (242KB) ( 332 )
The first spectral analysis of a spike event has been performed. It was found that the peak frequency of spectrum of the spike event on Oct. 2, 1993 drifted from higher to lower frequency for the first group of spikes, but the frequency remained almost the same for the second group. Only if the mean energy of electron beam is a monotonic or random function of time and its pitch angle is a monotonically decreasing function of mean energy, then the different observed characteristics of evolution of the peak frequency with time may be interpreted by the location of resonant circle. The spike radio emissions with one and the same peak frequency probably originated from the same region of electron cyclotron maser instability.
Unusual Evolution Characteristics in Black Hole Disk-Accretion,
WANG Ding-Xiong
Chin. Phys. Lett. 2000, 17 (6): 463-465 .  
Abstract   PDF(pc) (193KB) ( 435 )
It is shown that evolution characteristics of black hole (BH) parameters in the pure disk-accretion are determined uniquely by BH spin parameter a*. Some unusual evolution characteristics of the parameters of BH accretion disks, such as angular velocity, temperature and event horizon radius, are investigated in both thin and thick disk-accretion. And the corresponding turning points, a*c. are derived. In addition, two characteristic functions describing the evolution of BH parameters are derived for thin and thick disks, respectively.

A New Method to Determine the Thickness of Spiral Galaxies: Apply to M31
LI Meng, LUO Xin-Lian, PENG Qiu-He, ZOU Zhi-Gang
Chin. Phys. Lett. 2000, 17 (6): 466-468 .  
Abstract   PDF(pc) (268KB) ( 367 )
A new method is presented to determine the thickness of spiral galaxies. Based on the rigorous solution of the Poisson equation for logarithmic density disturbance in three-dimensional spiral galaxies, we have derived an accurate dispersion relation for the stellar and gaseous disk with a finite thickness. From this relation, a new method is put forward here for determining the thickness of galaxies. We apply this way to M31 and get the thickness of about 0.7kpc, which is in good agreement with the previous results.

29 articles