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Volume 15 Issue 5
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Original Articles
The Most General Harmonic Coordinates for Kerr Metric
LIU Quan-hui
Chin. Phys. Lett. 1998, 15 (5): 313-314 .  
Abstract   PDF(pc) (147KB) ( 451 )
The most complete harmonic coordinates for Kerr metric, which include the previous results as special cases, are given. It correctly reduces to the flat space-time metric at infinity or when both mass and angular momentum vanish, and to the complete Schwarzschild metric when only the angular momentum is zero.

Can a Correlation Ratchet Operate Under Spatial Symmetry and Temporal Symmetry ?
JIA Ya, LI Jia-rong
Chin. Phys. Lett. 1998, 15 (5): 315-317 .  
Abstract   PDF(pc) (195KB) ( 398 )
The simplest imaginable ratchet system which cantains two noises correlated with each other is discussed. It is found that ( 1 ) the correlation between noises can induce transport, even when the ratchet potential is completely symmetric in space and the driving forcing is symmetric in time, and (2) the system can exhibit a current in either direction, and the direction can be controlled by the intensity of the correlation between noises.
Classical Dynamics of a Nucleon in Heavy Nuclei
GU Jian-zhong, ZHAO En-guang, ZHUO Yi-zhong, WU Xi-zhen, ZONG Hong-shi
Chin. Phys. Lett. 1998, 15 (5): 318-320 .  
Abstract   PDF(pc) (248KB) ( 424 )
Within the framework of the two-center shell model, the classically dynamical behaviour of a nucleon in heavy nuclei is investigated when nuclear shape parameters are changed systematically. It is found that there is a good quantum-classical correspondence of nucleonic regular (chaotic) motion so that Bohigas, Giannoni and Schmit conjecture is confirmed once again.
Induced Chern-Simons Term at High Temperature in Intrinsic Regularization
GUO Han-ying, ZHAO Wan-yun
Chin. Phys. Lett. 1998, 15 (5): 321-322 .  
Abstract   PDF(pc) (150KB) ( 322 )
By perturbative calculations of the high temperature ground-state axial current in intrinsic regularization, an anomalous Chern-Simons topological mass term is induced in the three-dimensional effective action. The anomaly in three dimensions appears just in the ground-state current rather than in the divergence of ground-state current. In the abelian case, the contribution comes only from the vacuum polarization graph, whereas in the nonabelian case, contributions come from the vacuum polarization graph and the two triangle graphs.
Construction of Paired States in Axially Symmetric Nuclei and Diabolic Pair Transfer
LEI Yi-an, ZENG Jin-yan
Chin. Phys. Lett. 1998, 15 (5): 323-325 .  
Abstract   PDF(pc) (227KB) ( 475 )
In axially symmetric nuclei, three forms of paired states can be constructed, i.e., monopole pair, signature pair and ±Ω pair, which are the eigenstates of (J2, Jz), (J2z, Rx(π)), and Jz, respectively. In the cranked shell model, though the energy spectra at ω = 0 are the same for three types of pair interactions, the spectra and spin alignments for ω≠0 are different to a certain extent. It is found that the ω variation of the pair transfer amplitude, particularly the diabolic pair transfer, is quite different for different pair interactions.

Molecular Dynamics Simulation of Binary Fluorozirconate Glass ZrF4.BaF2
ZHOU Lin-xiang, J.R. Hardy, XU Xin
Chin. Phys. Lett. 1998, 15 (5): 326-328 .  
Abstract   PDF(pc) (256KB) ( 374 )
Binary fluorozirconate glass ZrF4.BaF2 has been studied by molecular dynamical simulation using parameter-free Gordon-Kim potentials. In these simulations a novel technique is employed to monitor the motion of ions, thus the structure pictures of glass and the microscopic motion mechanism of ionic conduction are clearly and directly obtained. The glass networks commonly are formed by ZrF8, ZrF7 or ZrF6 polyhedra, cross linked by Ba-F ionic bonds. The mean distance of the ionic nearest neighboring at 300K is about 3.90Å (Zr-Zr), 3.87Å(Zr-Ba), and 1.96Å(Zr-F). The two stronger peaks of five main peaks of vibrational spectra are at about 540-600 and 460-510cm-1 and three weaker peaks at about 386-416, 322-348, and 183-196cm-1. The other properties of glass: density, thermal expansion coefficient, polarization, and glass transition temperature are also examined.
Energy of ls2snp 4P States for the Lithium Isoelectronic Sequence
QU Lian-hua, WANG Zhi-wen, LI Bai-wen
Chin. Phys. Lett. 1998, 15 (5): 329-331 .  
Abstract   PDF(pc) (198KB) ( 390 )
The nonrelativistic energies of the core-excited ls2snp 4P (n =2, 3, 4, 5) states for the lithium isoelectronic sequence from Be II to O VI are calculated with a full core plus correlation method using multiconfiguration interaction wavefunctions. The relativistic and mass-polarization effects on the energy are evaluated as the first order perturbation theory. Our predicted energies are lower than other theoretical results. They show that this full core plus correlation method is useful for the core-excited systems.

Identification of the 2l2l nl 2P0 Hollow Lithium Systems
Kwong T. Chung, GOU Bing-cong
Chin. Phys. Lett. 1998, 15 (5): 332-334 .  
Abstract   PDF(pc) (226KB) ( 427 )
In a recent letter [L. Journel et al., Phys. Rev. Lett. 76, 30 (1996)], first experimental determination of the partial photoionization cross sections of lithium near the hollow atomic states was reported. Very extensive R-matrix calculation has also been carried out for the 2l2l nl 2P0 hollow states and assignments for the excited states have been made. However, these assignments are substantially different from those of other theoretical methods. This points out the need for more information and discussion which are necessary for a meaningful comparison.
An Improved Magneto-Optical Trap for Cesium Atom
HOU Ji-dong, LI Yi-min, YANG Dong-hai, WANG Yi-qiu
Chin. Phys. Lett. 1998, 15 (5): 335-337 .  
Abstract   PDF(pc) (210KB) ( 488 )
Based on the realization of magneto-optical trap for cesium atom in China, great improvement is achieved on its performance. In the new experimental setup, a laser battery in stepwise injection-locking scheme is developed as laser source, which has more output power and better beam quality than the previous one. Under the optimum working condition, cesium atoms of more than l09 with the density of 1011 atoms/cm3 are trapped to form an atomic cloud with the diameter of 3mm. Compared with previous results, both the number of trapped atoms and the density of atomic cloud are increased in two orders of magnitude.
Effect of Phase Factor in Kick Approximation for Super Intense Field Ionization
CHENG Tai-wang, LIU Jie, CHEN Shi-gang
Chin. Phys. Lett. 1998, 15 (5): 338-340 .  
Abstract   PDF(pc) (291KB) ( 557 )
Based on a simple consideration, the kick approximation used by Sundaram et al. in describing the interactions between super intense laser field and single atom is modified. Two different phase factors of the two kicks during one optical period are considered. It is found that we can introduce the factors in a very simple way and derive a new map which can be written in a closed form, and that to include these factors really improves the dynamical description of the system.
Valence Orbitals of Ethane by Electron Momentum Spectroscopy
PANG Wen-ning, GAO Nai-fei, ZHANG Wen-xin, SHANG Ren-cheng, DENG Jing-kang, CHEN Xue-jun
Chin. Phys. Lett. 1998, 15 (5): 341-342 .  
Abstract   PDF(pc) (126KB) ( 500 )
The valence electron binding energy spectra and orbital electron momentum distributions of ethane(C2H6) have been measured by high resolution (ΔE=0.9eV, Δp = 0.1 a.u.) symmetric non-coplanar electron momentum spectroscopy, at an impact energy of 1200eV+binding energy. The high energy resolution is adequate for us to be observe clearly the separated valence orbitals of C2H6.
Generation of cw Radiation of 273mW at 671nm from a Diode-Pumped Intracavity-Doubled Nd:YVO4 Laser
HE Jing-liang, ZHANG Heng-li, HOU Wei, WU Ling-an, XU Zu-yan, YANG Guo-zhen, WANG Jian-ming, WU Xing, ZHAO Zong-yuan, WANG Ji-Yang
Chin. Phys. Lett. 1998, 15 (5): 343-344 .  
Abstract   PDF(pc) (136KB) ( 515 )
We have demonstrated a diode-pumped Nd:YVO4 laser that produced 273mW cw output at 671 nm by using KTP intracavity doubling. The optical-optical efficiency of the all-solid-state red laser was 5.1 %. The maximum output power of the fundamental wave at 1342nm from Nd:YVO4 was 2.3W with slope-efficiency of 43%.
Temperature Dependence of Optically Erased Two-Wave Mixing in Ce:KNSBN
LIU Jin-song, LU Ke-qing, LIANG Chang-hong, ZHANG Du-ying, TANG Tian-tong
Chin. Phys. Lett. 1998, 15 (5): 345-347 .  
Abstract   PDF(pc) (222KB) ( 457 )
The intensity response of an optically erased photorefractive two-wave mixing to the erase beam is studied by using the coupling wave equation and the band-transport model. The concepts of response strength and the minimum response intensity are introduced and their temperature dependence is investigated. A 2-fold increase in the response strength and 4-fold decrease in minimum response intensity have been experimentally observed in Ce:KNSBN at 633 nm when the crystal temperature is raised from 320 to 370K. These experimental results are in agreement with theoretical analysis and show that the response property can be improved by changing the crystal temperature.

Measurement of Photorefractive Two-Wave Coupling Exponential Gain Coefficient of LiNbO3 : Fe Crystal
SUN Qian, LI Yu-dong, XU Jing-jun, LIU Si-min, ZHANG Guang-yin, ZHANG Xin-zheng, ZHANG Guo-quan
Chin. Phys. Lett. 1998, 15 (5): 348-350 .  
Abstract   PDF(pc) (199KB) ( 474 )
For a photorefractive crystal, the exponential gain coefficient of two-wave coupling,Г, is a constant. In this paper, the constant Г of a LiNbO3: Fe crystal is measured by using Gaussian beams and quasi-uniform beams. The difference between the results is attributed to the self-defocusing effect of the crystal.
Response Time Characteristics and Holographic Gratings in an Azo-Dye Doped Photorefractive Polymeric Composite
WANG Feng, CHEN Zhi-jian, GONG Qi-huang, CHEN Yi-wang, CHEN Hui-ying
Chin. Phys. Lett. 1998, 15 (5): 351-353 .  
Abstract   PDF(pc) (249KB) ( 453 )
Theoretical and experimental investigation on the applied electric field- and intensity-dependent photorefractive response in a photorefractive polymeric composite is presented. The decay time constant and the corresponding grating-amplitude for the composite consisting of 1-n-butoxy1-2,5-dimethy1-4-(4 ’- nitrophenylazo) benzene : poly(N-vinylcarbazole) : 2,4,7-trinitro-9-fluorenone with a weight ratio 44:55:1 were measured. The results revealed that there existed two gratings simultaneously, one was caused by the photorefractive effect, and the other was contributed from the photo-isomerization process. The dynamic process for the photorefractive grating was explained with a modified band transport model.
Excitation of Slow Electromagnetic Waves in a Dielectric-Lined Waveguide Having a Thin Annular Plasma Sheet
WU Jian-qiang, LIU Sheng-gang
Chin. Phys. Lett. 1998, 15 (5): 354-356 .  
Abstract   PDF(pc) (184KB) ( 422 )
Excitation of slow electromagnetic waves for a configuration, in which a thin annular relativistic electron beam (TAREB) propagates through a cylindrical, dielectric-lined waveguide having a thin, annular plasma sheet at the same radial position as the TAREB, is studied in the presence of an infinite longitudinal guide magnetic field. Determinant dispersion equation is derived and directly numerically solved. The operation frequency and the growth rate of the waves are obtained and discussed.

Order-Disorder Transition in C60: Possible Role of Stacking Faults
GU Min, Tong B. Tang, WANG Ye-ning, YAN Feng, FENG Duan
Chin. Phys. Lett. 1998, 15 (5): 357-359 .  
Abstract   PDF(pc) (254KB) ( 406 )
Differential scanning calorimetry revealed a secondary transition at a lower temperature besides the order-disorder phase transition near 260K in powders, not in single crystals, of C60 from which solvents and impurities had been carefully excluded. This is attributed to phase transformation facilitated by nucleation around stacking faults. This proposal is supported by internal friction measurements on films, which confirmed the presence of this secondary transition, and by x-ray diffraction, which detected an hcp structure within the fcc lattice of C60 at room temperature.

New Potential Energy Functions for Diamond and α-Tin Crystals
LIU Xin-hou, ZHEN Zhen, ZHANG Jian-cheng
Chin. Phys. Lett. 1998, 15 (5): 360-361 .  
Abstract   PDF(pc) (130KB) ( 280 )
A new model of potential energy functions for atomic solids is given and applied to diamond and α-tin crystals. In the new model, a factor expressing the characters of covalent bonds has been included. Therefore it is suitable for covalent crystals. New pontentials of C and α-Sn crystals accurately reproduce experimental elastic constants and phonon dispersion curves and so on. The set of new potentials is accurate enough for computer simulations.
Ground State Structure of the Metallic Hydrogen
ZHU Zai-wan, LI Jun-jie
Chin. Phys. Lett. 1998, 15 (5): 362-363 .  
Abstract   PDF(pc) (142KB) ( 372 )
By using Heine-Abarencov pseudopotential method with mono-parameter rc , the expressions for ground state energy ε(rs ) , pressure P (rs), and bulk modulus B(rs) of metallic hydrogen (fcc, bcc, and hcp structures) are derived. Based on Gibbs free energy function criterion, the calculation shows that cold metallic hydrogen lattice (T = 0K) belongs to hcp structure.
Theoretical Study of the Specific Heat of Helium II
Pao Lu
Chin. Phys. Lett. 1998, 15 (5): 364-366 .  
Abstract   PDF(pc) (150KB) ( 345 )
We present the calculation of the specific heat of helium II under pressure of 1 atm from very low temperature to approximately 1.8K (the transition temperature Tλ= 2.712 K). Experimentally, the specific heat jumps from a finite value to infinity at Tλ. We have been able to reproduce the specific heat theoretically up to 1.8K.
Ordered and Abrupt fcc Fe/Cu {111}Interface Observed with Angle-Resolved Photoemission
REN Wan-wan, DONG Yu-hui, QIAN Hai-jie, LIU Feng-qin, ZHAO Ru-guang, LÜ, Si-hua, WU Si-cheng
Chin. Phys. Lett. 1998, 15 (5): 367-369 .  
Abstract   PDF(pc) (242KB) ( 389 )
The electronic structure of fcc Fe/Cu {111} interface has been studied by angle-resolved photoemission with synchrotron radiation. The existence of the interface state and absence of intermixture between Fe and Cu atoms in the Fe/Cu {111} interface show that the Fe/Cu {111} system has an abrupt and ordered interface.
Perimeter Effects on Heavy Doping GaAs Diodes
SHI Xiao-zhong, WANG Le, XIA Guan-qun
Chin. Phys. Lett. 1998, 15 (5): 370-372 .  
Abstract   PDF(pc) (188KB) ( 458 )
The influence of perimeter effects on dark I-V characteristics of GaAs diode is investigated experimentally. The results indicate that the diodes with high energy states density will be more easily shorted than that with low energy states density during alloying. The possibility of shunt short of GaAs diode increases with the decrease of the distance between the front contact and pn junction. The AlGaAs layers enhance the dark current.
Epitaxial Growth of Bi2Sr2-xLaxCu1O6+δ Thin Films by In-Situ dc Magnetron Sputtering
ZHANG Ying-zi, YANG Duo-gui, LI Lin, ZHAO Bai-ru, JIA Shun-lian, CHEN Hong, WU Fei, CHE Guang-can, ZHAO Zhong-xian
Chin. Phys. Lett. 1998, 15 (5): 373-375 .  
Abstract   PDF(pc) (226KB) ( 339 )
Bi2Sr2-xLaxCu1O6+δ (La-2201) thin films were successfully prepared on (100) SrTiO3 and (100) LaAIO3 substrates by in-situ dc-magnetron sputtering process. A series compensated 2201 targets of La3+ substitution contents for Sr2+ were studied for growing 2201 phase thin films. The superconducting zero resistance temperature Tc,0 reached 19K. X-ray diffraction analyses showed that films oriented with c-axis perpendicular to the substrate surface and their lattice parameters are around 2.43-2.46nm. Ф-scan and rocking curve show a good epitaxial growth and crystallisation of the films.
Magneto-Optical Properties of PtCu/Co Multilayers
MA Ping-ping, ZHENG Wu, WANG Ai-ling, CHEN Jin-chang, WANG Yin-jun, LI Jian, CHEN Liang-yao
Chin. Phys. Lett. 1998, 15 (5): 376-378 .  
Abstract   PDF(pc) (206KB) ( 484 )
The effect of Cu doping in Pt spacer layers on the magneto-optical properties of sputtered Pt/Co multilayers has been investigated. It was found that the polar Kerr rotation θk, ellipticity εk, refractive index n and absorptive index k show an oscillation behavior as a function of the Cu content x, reflective index R keeps almost constant with the decreasing wavelength λ, three θk peaks appear at x = 0.03, 0.12, 0.25, respectively. Values of conductivity tensor σ1xx, σ2xx, σ1xy, and σ2xy in the PtCu layers have been derived from experimental θk, εk, n, and k values at wavelength 770nm. The oscillation of the polar Kerr rotation θk may be resulted from spin polarized quantum size effects in the PtCu layers.
Magnetostriction of the Oriented Crystals in a TbDyFe Alloy
JIANG Cheng-bao, ZHOU Shou-zeng, WANG Run
Chin. Phys. Lett. 1998, 15 (5): 379-381 .  
Abstract   PDF(pc) (350KB) ( 390 )
The preferred growth directions of Tb0.3Dy0.7Fe1.95 grown by a super-high temperature gradient zone melting directional solidification technique were examined over a large range of the crystal growth velocity (0.5-30 mm/min). The [110] preferred growth direction was found in most case, and the [112] orientation only existed with a certain solidification condition. The magnetostriction of the[110] oriented samples was poor and had no obvious “stress effect”, which exists in [110] perfect crystals according to alculation. The difference of the magnetostriction between the actual and perfect [110] oriented crystal was discussed in detail. The poor magnetostriction of the [110] oriented samples was attributed to the special 109.5°angular with two (111) twin growth mechanism, which resulted in the [114] direction along axis in twins, and only the[110] along axis in master.
Monoexponential Microsecond Decay of Blue Photoluminescence in Aged Porous Silicon Prepared with Ar+ 488nm
LI Peng, MA Yu-rong, WANG Guan-zhong, FANG Rong-chuan
Chin. Phys. Lett. 1998, 15 (5): 382-384 .  
Abstract   PDF(pc) (260KB) ( 338 )
Blue photoluminescence is observed in aged porous silicon samples anodized under Ar+ 488 nm laser illumination. No samples have been undergone any heating treatment process. Both nanosecond and microsecond decay of blue photoluminescence have been measured. Samples show a good monoexponential microsecond decay with lifetimes of about 5.3μs . Photoluminescence excitation spectra of blue and red Photoluminescence indicate there is a large Stokes shift (about 800-900meV) in the excitation spectra of red photoluminescence while no this marked Stokes shift in that of blue photoluminescence. The possible origin of the photoluminescence is discussed based on the experimental results.
Contacting Probability Dependence of Folding Dynamics of a Modeling Protein
Chin. Phys. Lett. 1998, 15 (5): 385-387 .  
Abstract   PDF(pc) (299KB) ( 354 )
The folding dynamics of a model of polypeptides is studied by Monte Carlo simulations. The effect of contacting probability between monomers is discussed. A specific temperature T* corresponding to the fastest folding process is found. At the temperature T*, the folding process appears more conservative than at other temperatures. In addition a cooperative characteristic, the length dependence of T*, is also illustrated. These show some instructive insights into the generic features of protein folding in nature.
Collimation of High Velocity Molecular Outflows
WU Yue-fang, HUANG Mao-hai
Chin. Phys. Lett. 1998, 15 (5): 388-390 .  
Abstract   PDF(pc) (235KB) ( 314 )
Statistics of apparent collimation factors for molecular outflows catalogued is presented. Intrinsic collimation factor is calculated with the project effects removed. There is collimation difference between high and low mass outflows. It may concern the stellar sources in the flow regions, the outflow driving process, and the evolution time.
28 articles