Table of contents

15 January 2000, Volume 9 Issue 1 Previous issue    Next issue

GENERAL

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ABUNDANT DROMION-LIKE STRUCTURES TO THE (2+1) DIMENSIONAL KdV EQUATION Zhang Jie-fang (张解放) Chinese Physics, 2000, 9 (1):  1-4.  DOI: 10.1088/1009-1963/9/1/001 Abstract ( 1161 )   PDF (157KB) ( 1013 )   The abundant generalized dromion structures for the (2+1)-dimensional KdV equation are obtained using the homogeneous balance method. We give not only the general curve soliton which is finite on a curved line and localized apart from the curve, find but also the dromion solutions which can be driven by two perpendicular line soliton and by two non-perpendicular line soliton and by one line soliton and one curve line soliton. Various types of multi-dromion solutions can be constituted by selecting different arbitrary functions of y. The (1+N) dromion obtained by Radha et al.[3] is only a very special case of our results.

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ENERGY SPECTRUM AND WAVE FUNCTION FOR MULTI-MODE COUPLED NON-IDENTICAL HARMONIC OSCILLATORS Lu Huai-xin (逯怀新), Liu Ke-jia (刘克家), Pan Jian-wei (潘建伟), Zhang Yong-de (张永德) Chinese Physics, 2000, 9 (1):  5-8.  DOI: 10.1088/1009-1963/9/1/002 Abstract ( 1305 )   PDF (199KB) ( 403 )   By means of the linear quantum transformation theory, we consisely derive the exact solution including energy spectrum and wave function for multi-mode coupled non-identical harmonic oscillators.

NUCLEAR PHYSICS

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MICROSTRUCTURE ON COLLECTIVITY IN EVEN 116-122Xe ISOTOPES Shi Zhu-yi (石筑一), Liu Yong (刘庸), Sang Jian-ping (桑建平) Chinese Physics, 2000, 9 (1):  9-12.  DOI: 10.1088/1009-1963/9/1/003 Abstract ( 1107 )   PDF (130KB) ( 568 )   Using microscopic interacting boson-fermion model formalism, the ground-band, $\beta$-band, $\gamma$-band and high spins states in even 116-122Xe isotopes are successfully described. It can explain the recent experimental result that collective structures may coexist with the single-particle states and subshell feature. It predictes the energies of 1+ states.

ATOMIC AND MOLECULAR PHYSICS

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CALCULATION OF THE TRANSITION ENERGIES OF THE Ne-LIKE IONS WITH THE CORRECTION OF CORE POLARIZATION Li Xiang-dong (李向东), Tan Ming-liang (谭明亮), Yi You-gen (易有根), Zhu Zheng-he (朱正和) Chinese Physics, 2000, 9 (1):  13-18.  DOI: 10.1088/1009-1963/9/1/004 Abstract ( 1207 )   PDF (117KB) ( 457 )   The transition energies between n=3 and n=2 of the Ne-like ion Ge22+, Se24+, Zr30+, Rh35+, Ag37+, Sb41+, Xe44+, La47+, Nd50+ and Eu53+ are calculated by adding polarization in the core. The systematic errors in multi-configuration Dirac-Fock calculation are greatly reduced and a good agreement is obtained between the theory and the experiment. This study shows that introducing the polarization of core orbitals is a good method to calculate the atomic structure, and there is a close relation between polarizability and nucleus charge.

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INTERACTION OF A TWO-LEVEL ATOM WITH FINE STRUCTURE MOVING IN AN ELECTROMAGNETIC FIELD Zhang Jing-tao (张敬涛), Chen Zhao-yang (陈朝阳), Xu Zhi-zhan (徐至展) Chinese Physics, 2000, 9 (1):  19-23.  DOI: 10.1088/1009-1963/9/1/005 Abstract ( 1159 )   PDF (122KB) ( 428 )   Dynamics of a moving two-level atom with fine structure interacting with an electromagnetic field is studied. The fine structure increases the damping rate induced by the atomic momentum distribution. When the field is in a Fock state, the Rabi oscillation becomes very complicated; when the field is in a superposition state, the collapse-revival phenomenon disappears for the wider atomic wavepackets. In the presence of the fine structure, each atomic level splits into three sublevels when the field is in a Fock state and the atom has a definite momentum.

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FRINGE STRUCTURE IN THE PHASE-SPACE DYNAMICS OF ATOMIC STABILIZATION IN AN INTENSE FIELD Liu Jie (刘杰), Chen Shi-gang (陈式刚), Li Baowen, Hu Bambi Chinese Physics, 2000, 9 (1):  24-30.  DOI: 10.1088/1009-1963/9/1/006 Abstract ( 1334 )   PDF (427KB) ( 519 )   An analytical expression of a Floquet operator, which describes the evolution of a wave packet in combined atomic and an intense laser field, is obtained approximately in the stabilization regime. Both the classical and quantum versions of the Floquet operator are used to study the phase-space dynamics of atomic stabilization, and the "fringe structure" in the phase-space is clearly demonstrated. Furthermore, we investigate the dynamical mechanism and characters of this striking structure, and find that this structure is very closely related to the classical invariant manifolds.

CLASSICAL AREAS OF PHENOMENOLOGY

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ANALYSES FOR LASING THRESHOLD AT 2 AND 1.5μm WAVELENGTHS IN Tm:YVO4 CRYSTAL Huang Li-lei (黄莉蕾), Hong Zhi (洪治) Chinese Physics, 2000, 9 (1):  31-36.  DOI: 10.1088/1009-1963/9/1/007 Abstract ( 1211 )   PDF (149KB) ( 449 )   From transition-rate-equations and transmission-equations the formulas of threshold power are deduced for an end-pumped laser, in which the probability of cross-relaxation cannot be ignored and the nonradiative transition-probability of the excited state is the same order as the radiative transition-probability of upper level of the lasing transition. The lasing performance of Tm:YVO4 at $\lambda$=1.9 and 1.5μm is discussed by dint of these equations of threshold power.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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TWO-DIMENSIONAL LOCALIZED MODES IN CONJUGATED POLYMERS: THE NONLINEAR ELECTRON-PHONON COUPLING EFFECT An Zhong (安忠), Li Zhan-jie (李占杰), Liu Ying (刘英), Li You-cheng (李有成) Chinese Physics, 2000, 9 (1):  37-41.  DOI: 10.1088/1009-1963/9/1/008 Abstract ( 1264 )   PDF (121KB) ( 454 )   The two-dimensional localized modes around a soliton have been investigated by using an extension of Su-Shrieffer-Heeger model, in which is included the nonlinear term of electron-phonon interaction. The results show that there appears an additional localized mode, and the two modes obtained in the previous work without the nonlinear term disappear. Furthermore, the frequencies of the modes are shifted and their localizations are changed after turning on the nonlinear term.

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STUDY ON ONE-DIMENSIONAL CI PHASE TRANSITION WITH TRIPLE-WELL INTERACTIONS Xu Hai-bo (许海波), Xu Ai-guo (许爱国), Wang Guang-rui (王光瑞), Chen Shi-gang (陈式刚) Chinese Physics, 2000, 9 (1):  42-48.  DOI: 10.1088/1009-1963/9/1/009 Abstract ( 1238 )   PDF (187KB) ( 384 )   To study modulated structures and commensurate-incommensurate (CI) transitions, we generalize the Frenkel-Kontorova model to the Frenkel-Kontorova-Devonshire model where the interparticle interactions are the triple-well potential. By use of the so called effective potential method, numerical solutions of the eigenvalue problem are used to work out the exact phase diagrams of W, a triple-well potential. According to the winding number $\varOmega$ and the rotation number $\omega$, we analyze the periodicity of the phase diagram and find some complex but regular phase structures. These new structures result from the triple-well interatomic interactions. A series of new transition behaviors enrich the traditional understanding on the periodicity of CI transitions.

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SIMULATION OF FRACTAL GROWTH OF THIN FILMS AT LOW TEMPERATURE Wu Feng-min (吴锋民), Zhu Qi-peng (朱启鹏), Shi Jian-qing (施建青), Wu Zi-qin (吴自勤) Chinese Physics, 2000, 9 (1):  49-54.  DOI: 10.1088/1009-1963/9/1/010 Abstract ( 1120 )   PDF (261KB) ( 580 )   Fractal growth of thin films at low temperature (50－175 K) is simulated by Monte Carlo method. It is shown that the thin film growth is quite different from the diffusion-limited aggregation (DLA) model when the coverage is larger than 0.1 ML. The average branch width of clusters increases with increasing temperature and it usually larger than the branch width (1.9 atom) in the classic DLA model. The average fractal dimension of clusters increases also with increasing coverage while the fractal dimension of DLA model remains constant. This difference comes from the weak screening effect during the late stage of thin film growth. The relationship between the saturation island number ns and deposition interval $\Delta t$ is described in a power law: $n_{\rm s}\propto \Delta t^{\gamma}$, where ${\gamma}$ =-0.332 is very close to the theoretical value -1/3 of rate equations from nucleation theory.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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AB INITIO STUDY ON THE ELECTRONIC STRUCTURE AND MAGNETISM OF MnAs, MnSb, AND MnBi Tan Ming-qiu (谭明秋), Tao Xiang-ming (陶向明), Bao Shi-ning (鲍世宁) Chinese Physics, 2000, 9 (1):  55-60.  DOI: 10.1088/1009-1963/9/1/011 Abstract ( 1241 )   PDF (231KB) ( 737 )   We report the results of first-principles calculations on the electronic structure in ferromagnetic and non-magnetic hexagonal MnV (V = As, Sb, Bi). The calculations are based on the local-spin-density approximation (LSDA) of the density-functional theory (DFT) as well as the atomic sphere approximation (ASA) in the linear muffin-tin orbitals (LMTO) method. For the non-spin-polarized case, the calculated bands in these compounds exhibit p-d mixing in the vicnity of Fermi energy and the Mn 3d bands dominate the antibonding parts of p-d hybride. The spin-polarization in ferromagnetic states are mainly due to the splitting of anti-bonding bands from p-d mixing. The calculated spin moments in these compounds agree fairly well with experimental values and refine previous band calculations. In the spin-polarized band structure, the Mn 3d electrons are found to exhibit week dispersions.

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NUMERICAL STUDIES ON THE DYNAMICS OF DISORDERED VORTEX LATTICE Cao Yi-gang (曹义刚), Jiao Zheng-kuan (焦正宽) Chinese Physics, 2000, 9 (1):  61-64.  DOI: 10.1088/1009-1963/9/1/012 Abstract ( 1190 )   PDF (116KB) ( 404 )   Flow behavior of the driven two-dimensional vortex lattice is numerically studied with different densities of randomly distributed pointlike pinning centers. Different features in the curves of velocity-force dependence are found between the elastic and plastic regimes. Scaling fit between force and velocity above the critical driving force can be obtained in the elastic regime but fails in the plastic regime. Transition from the lastic to plastic regimes is accompanied by maximum peaks in the differential curves of velocity-force dependence in the disordered vortex lattice.

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INCREASING TRANSVERSE STABILITY OF OPTICAL TWEEZERS BY USING DUAL-GAUSSIAN BEAM PROFILE Yao Xin-cheng (姚新程), Li Zhao-lin (李兆霖), Cheng Bing-ying (程丙英), Han Xue-hai (韩学海), Zhang Dao-zhong (张道中) Chinese Physics, 2000, 9 (1):  65-68.  DOI: 10.1088/1009-1963/9/1/013 Abstract ( 1264 )   PDF (111KB) ( 468 )   Trapping force was calculated with a homogeneous dielectric sphere model. Results indicate that the transverse trapping force of optical tweezers can be increased effectively through modifying laser beam profile while the axial stability of the system is still assured. This is quite important when optical tweezers are applied to the precise measurements for single biological molecule.

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PHASE DEPENDENCE OF LUMINESCENT EMISSION OF Eu2+ DOPED SrAl2O4 Jia Dong-dong (贾冬冬), Wu Bo-qun (吴伯群), Zhu Jing (朱静) Chinese Physics, 2000, 9 (1):  69-72.  DOI: 10.1088/1009-1963/9/1/014 Abstract ( 1261 )   PDF (123KB) ( 809 )   In this work, we made five samples of SrAl2O4: Eu2+, Dy3+, the $\alpha$ phase and $\beta$ phase SrAl2O4:Eu2+,Dy3+ powder and pellet samples, and $\alpha$ phase single crystal. We have measured the emission spectra of all the samples. All the emission peaks are around 520 nm, which correspond to the transition from 4f65d1(2Eg) to 4f7(8S7/2) of Eu2+ in SrAl2O4 host. The intensity of emission of the $\beta$ phase is stronger than that of the $\alpha$ phase. We believe that it is because the Eu2+ ions have occupied the two types of sites in the $\alpha$  phase SrAl2O4 host and the lifetime of the transition of Eu2+ in the A site is longer than that in the B site. This result also proves that the $\beta$ phase of the material is brighter than the $\alpha$  phase. In addition, the $\beta$ phase can be achieved by quenching technique.