Table of contents

12 July 2002, Volume 11 Issue 7 Previous issue    Next issue

GENERAL

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Bäcklund transformation and variable separation solutions for the generalized Nozhnik-Novikov-Veselov equation Zhang Jie-Fang (张解放) Chinese Physics, 2002, 11 (7):  651-655.  DOI: 10.1088/1009-1963/11/7/301 Abstract ( 1068 )   PDF (202KB) ( 754 )   Using the extended homogeneous balance method, the B?cklund transformation for a (2+1)-dimensional integrable model, the generalized Nizhnik－Novikov－Veselov (GNNV) equation, is first obtained. Also, making use of the B?cklund transformation, the GNNV equation is changed into three equations: linear, bilinear and trilinear form equations. Starting from these three equations, a rather general variable separation solution of the model is constructed. The abundant localized coherent structures of the model can be induced by the entrance of two variable-separated arbitrary functions.

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Recurrence spectra of non-hydrogen Rydberg atoms in parallel electric and magnetic fields Song Xiao-Hong (宋晓红), Zhang Qiu-Jü (张秋菊), Xue Yan-Li (薛艳丽), Zhao Ke (赵珂), Li Yu (李玉), Lin Sheng-Lu (林圣路) Chinese Physics, 2002, 11 (7):  656-660.  DOI: 10.1088/1009-1963/11/7/302 Abstract ( 1141 )   PDF (248KB) ( 453 )   We present a new method for computing the recurrence spectra of n ≈ 40, m = 0 lithium Rydberg atoms in strong parallel external electric and magnetic fields. This method is based on an extended closed-orbit theory allowing the computation of the scattering of the electron by the ionic core. We pay particular attention to the scaling properties, which are extremely important for understanding the correspondence between classical and quantum mechanics. The spectra with a constant scaled electric field $\tilde{F}$ = 0.01 and a scaled energy $\varepsilon$ = -0.03 are recorded and compared with those of hydrogen obtained by the standard closed-orbit theory. The result shows that the additional strong resonance structures can be interpreted in terms of the core-scattered classical closed orbits.

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Hawking radiation of Weyl neutrinos in a rectilinearly non-uniformly accelerating Kinnersley black hole Wu Shuang-Qing (吴双清), Cai Xu (蔡勖) Chinese Physics, 2002, 11 (7):  661-665.  DOI: 10.1088/1009-1963/11/7/303 Abstract ( 1112 )   PDF (235KB) ( 439 )   The quantum thermal effect of Weyl neutrinos in a rectilinearly non-uniformly accelerating Kinnersley black hole is investigated using the generalized tortoise coordinate transformation. The equations that determine the location, the Hawking temperature of the event horizon and the thermal radiation spectrum of neutrinos are derived. Our results show that the location and the temperature of the event horizon depend not only on the time but also on the angle.

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Adaptive synchronization of Rossler and Chen chaotic systems Li Zhi (李智), Han Chong-Zhao (韩崇昭) Chinese Physics, 2002, 11 (7):  666-669.  DOI: 10.1088/1009-1963/11/7/304 Abstract ( 1242 )   PDF (195KB) ( 606 )   A novel adaptive synchronization method is proposed for two identical Rossler and Chen systems with uncertain parameters. Based on Lyapunov stability theory, we derive an adaptive controller without the knowledge of the system parameters, which can make the states of two identical Rossler and Chen systems globally asymptotically synchronized. Especially, when some unknown uncertain parameters are positive, we can make the controller more simple and, besides, the controller is independent of those positive uncertain parameters. All results are proved using a well-known Lyapunov stability theorem. Numerical simulations are given to validate the proposed synchronization approach.

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The isolated critical value phenomenon in local－global riddling bifurcation Tan Ning (谭宁), Xu Jian-Xue (徐健学), Chen Yong-Hong (陈永红) Chinese Physics, 2002, 11 (7):  670-677.  DOI: 10.1088/1009-1963/11/7/305 Abstract ( 1030 )   PDF (327KB) ( 410 )   A chaotic synchronized system of two coupled skew tent maps is discussed in this paper. The locally and globally riddled basins of the chaotic synchronized attractor are studied. It is found that there is a novel phenomenon in the local－global riddling bifurcation of the attractive basin of the chaotic synchronized attractor in some specific coupling intervals. The coupling parameter corresponding to the locally riddled basin has a single value which is embedded in the coupling parameter interval corresponding to the globally riddled basin, just like a breakpoint. Also, there is no relation between this phenomenon and the form of the chaotic synchronized attractor. This phenomenon is found analytically. We also try to explain it in a physical sense. It may be that the chaotic synchronized attractor is in the critical state, as it is infinitely close to the boundary of its attractive basin. We conjecture that this isolated critical value phenomenon will be common in a system with a chaotic attractor in the critical state, in spite of the system being discrete or differential.

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A study of a main-road cellular automata traffic flow model Huang Ping-Hua (黄乒花), Kong Ling-Jiang (孔令江), Liu Mu-Ren (刘慕仁) Chinese Physics, 2002, 11 (7):  678-683.  DOI: 10.1088/1009-1963/11/7/306 Abstract ( 1211 )   PDF (241KB) ( 629 )   A main-road cellular automata traffic flow model on two dimensions is presented based on the Biham－Middleton－Levine traffic model. Its evolution equations are given and the self-organization and organization cooperation phenomena in this model are also studied by using computer simulation.

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Mass distribution in n-polymer stochastic aggregation and large-mass behaviour Xue Yu (薛郁), Chen Guang-Zhi (陈光旨) Chinese Physics, 2002, 11 (7):  684-689.  DOI: 10.1088/1009-1963/11/7/307 Abstract ( 858 )   PDF (235KB) ( 372 )   The exact solutions of the rate equations of the n-polymer stochastic aggregation involving two types of clusters, active and passive for the kernel $\prod_{k=1}^{n} s_{i_{k}}\left(s_{i_{k}}=i_{k}\right)$ and $\sum_{k=1}^{n} s_{i_{k}}\left(s_{i_{k}}=i_{k}\right)$, are obtained. The large-mass behaviours of the final mass distribution of the active and passive clusters have scaling-like forms, although the models exhibit different properties. Respectively, they have different decay exponents $\gamma=\frac{2 n+1}{2(n-1)}$ and $\gamma=q+\frac{2 n+1}{2(n-1)}$ for $\prod_{k=1}^{n} s_{i_{k}}\left(s_{i_{k}}=i_{k}\right)$ and $\gamma=\frac{3}{2(n-1)}$ and $\gamma=q+\frac{3}{2(n-1)}$ for$\sum_{k=1}^{n} s_{i_{k}}\left(s_{i_{k}}=i_{k}\right)$, which include exponents of two-polymer stochastic aggregation. We also find that gelation is suppressed for kernel $\prod_{k=1}^{n} s_{i_{k}}\left(s_{i_{k}}=i_{k}\right) $ which is different from the deterministic aggregation.

ATOMIC AND MOLECULAR PHYSICS

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Channel interaction of Ba 6pns (J=1) autoionizing series Li Shi-Ben (李士本), Dai Chang-Jian (戴长建), Zhang Yan (张艳) Chinese Physics, 2002, 11 (7):  690-693.  DOI: 10.1088/1009-1963/11/7/308 Abstract ( 1083 )   PDF (223KB) ( 424 )   The channel interactions between the Ba 6pnl (J=1) autoionizing series with different l and n have been observed by means of unsaturation and saturation excitation methods. The observed interactions were interpreted with the spectral density calculated from the multichannel quantum defect theory, the results of which are quite satisfactory.

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Photoionization properties of an atom with two autoionizing states Guo Hong (郭红), Li Gao-Xiang (李高翔), Peng Jin-Sheng (彭金生) Chinese Physics, 2002, 11 (7):  694-699.  DOI: 10.1088/1009-1963/11/7/309 Abstract ( 1262 )   PDF (235KB) ( 470 )   We have investigated the photoionization properties of an atom with a ladder coupling scheme involving two autoionizing states coupled to each other. The effects of the coherent coupling between two autoionizing states and between the low-lying autoionizing state and the continuum on the ionization yield are discussed. The conditions leading to atomic coherent population trapping and the coherent population trapping states are given explicitly.

GENERAL

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Variation of dielectronic satellite intensity factors with n for dielectronic recombination processes in selected lithium-like ions Sheng Yong (盛勇), Zhu Zheng-He (朱正和) Chinese Physics, 2002, 11 (7):  700-703.  DOI: 10.1088/1009-1963/11/7/310 Abstract ( 1121 )   PDF (197KB) ( 405 )   Satellite intensity factors F*2(s→f) have been calculated for the 1s22s+$\varepsilon l$→(1s23l′nl″)*→1s22sml'''+h$\nu$ dielectronic recombination processes of lithium-like V, Cu, Se, Ag and Ba ions. The relevant atomic parameters have been calculated explicitly for all intermediate resonance states |s〉≡|1s23l′nl″SLJ〉 with n=3－9 in the intermediate coupling scheme. The 1/n3 scaling, which has often been used in extrapolating F*(s→f) for n≥4, is tested against these values of F*2(s→f).

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Electron-impact ionization of Li+(1s2) in the coplanar equal energy-sharing geometry Jia Xiang-Fu (贾祥富), Liu Ming-Hai (刘明海) Chinese Physics, 2002, 11 (7):  704-709.  DOI: 10.1088/1009-1963/11/7/311 Abstract ( 1206 )   PDF (244KB) ( 436 )   In this paper, the triple differential cross section for the low-energy electron impact ionization of the Li+ ion is considered in the coplanar equal energy-sharing kinematics at an incident energy of 114.083 eV. The emergence of structures in the calculated cross sections is explained in terms of isolated two-body final-state interactions and three-body coupling. The cross section shows two peaks originating from ′classical′ is determined by two-body final-state interactions. In addition, it is demonstrated that the signature of three-body interactions is carried by the magnitude and ratio of these two peaks. The direct and exchange amplitudes are also considered.

CLASSICAL AREAS OF PHENOMENOLOGY

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Optically fixed photorefractive correlator Liu You-Wen (刘友文), Liu Li-Ren (刘立人), Zhou Chang-He (周常河), Xu Liang-Ying (徐良瑛) Chinese Physics, 2002, 11 (7):  710-713.  DOI: 10.1088/1009-1963/11/7/312 Abstract ( 1028 )   PDF (220KB) ( 478 )   An optically fixed photorefractive correlator is presented, where two-centre non-volatile holographic recording is employed to write and fix the matched filter in doubly doped LiNbO3 crystals. This correlator shows good correlation characteristics and insensitivity to the writing beam during readout. It can be used in cases requiring stability and not requiring modification for a long period, and it is refreshed optically when new information needs to be registered.

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

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First principles study on the ferroelectricity of the perovskite ABO3 ferroelectrics Wang Yuan-Xu (王渊旭), Zhong Wei-Lie (钟维烈), Wang Chun-Lei (王春雷), Zhang Pei-Lin (张沛霖), Su Xuan-Tao (苏绚涛) Chinese Physics, 2002, 11 (7):  714-719.  DOI: 10.1088/1009-1963/11/7/313 Abstract ( 1184 )   PDF (244KB) ( 814 )   In order to understand well the different ferroelectric behaviour of quantum paraelectrics and ferroelectrics and the origin of the ferroelectricity of the solid solution KTa0.5Nb0.5O3(KTN), we calculated the electronic structure of CaTiO3, BaTiO3 and KTN by first principles calculation. From total energy analysis, it is shown that, with increasing cell volume, the crystals (CaTiO3, SrTiO3) will have a ferroelectric instability. For BaTiO3, the ferroelectricity will disappear as the cell volume is decreased. From the density of states analysis, it is shown that the hybridization between B d and O p is very important for the ferroelectric stability of ABO3 perovskite ferroelectrics. This is consistent with the analysis of band structure.

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Shapiro effect in mesoscopic LC circuit Ji Ying-Hua (嵇英华), Luo Hai-Mei (罗海梅), Ouyang Chu-Ying (欧阳楚英), Lei Min-Sheng (雷敏生) Chinese Physics, 2002, 11 (7):  720-724.  DOI: 10.1088/1009-1963/11/7/314 Abstract ( 1170 )   PDF (215KB) ( 493 )   In this paper we consider the movement of an electron in the single electron tunnel process through a mesoscopic capacitor. The results show that, due to the Coulomb force, there is a threshold voltage Vt in the mesoscopic LC circuit. When the external voltage is lower than the threshold voltage, the tunnel current value is zero, and the Coulomb blockade phenomenon arises. Furthermore, considering that the mesoscopic dimension is comparable to the coherence length in which charge carriers retain the phase remembrance, a weak coupling can be produced through the proximity effect of the normal metal electrons of both electrodes of a mesoscopic capacitor. By varying the external voltage, we can observe the Shapiro current step on the current－voltage characteristic curve of a mesoscopic LC circuit.

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Study of nanocrystalline Fe－Al－N soft magnetic thin films Xie Tian (谢天), Zheng Dai-Shun (郑代顺), Li Xiao-Hong (李晓红), Ma Yun-Gui (马云贵), Wei Fu-Lin (魏福林), Yang Zheng (杨正) Chinese Physics, 2002, 11 (7):  725-729.  DOI: 10.1088/1009-1963/11/7/315 Abstract ( 1200 )   PDF (349KB) ( 525 )   Fe－Al－N films were fabricated by reactive sputtering using a radio-frequency magnetron sputtering system. The effects of Al and N content and annealing temperature on microstructure and magnetic properties were investigated. The Fe－Al－N films, which have good soft magnetic properties, consist of nanocrystalline α-Fe grains and a small amount of other phases in the boundaries of $\alpha$-Fe grains. The average $\alpha$-Fe grain size is about 10－15nm. A slight amount of Fe－N and Al－N compounds precipitate in the boundaries of $\alpha$-Fe grains and suppress their growth. Annealing improves the soft magnetic properties slightly by releasing the residual stress and reducing defects.

ATOMIC AND MOLECULAR PHYSICS

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Surface optical phonon-assisted electron Raman scattering in a semiconductor quantum disc Liu Cui-Hong (刘翠红), Ma Ben-Kun (马本堃), Chen Chuan-Yu (陈传誉) Chinese Physics, 2002, 11 (7):  730-736.  DOI: 10.1088/1009-1963/11/7/316 Abstract ( 1183 )   PDF (275KB) ( 738 )   We have carried out a theoretical calculation of the differential cross section for the electron Raman scattering process associated with the surface optical phonon modes in a semiconductor quantum disc. Electron states are considered to be confined within a quantum disc with infinite potential barriers. The optical phonon modes we have adopted are the slab phonon modes by taking into consideration the Fr?hlich interaction between an electron and a phonon. The selection rules for the Raman process are given. Numerical results and a discussion are also presented for various radii and thicknesses of the disc, and different incident radiation energies.

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Vanadium oxide thin films deposited on indium tin oxide glass by radio-frequency magnetron sputtering Wang Xue-Jin (王学进), Fei Yun-Jie (费允杰), Xiong Yan-Yun (熊艳云), Nie Yu-Xin (聂玉昕), Feng Ke-An (冯克安), Li Lin-De (李林德) Chinese Physics, 2002, 11 (7):  737-740.  DOI: 10.1088/1009-1963/11/7/317 Abstract ( 1408 )   PDF (212KB) ( 663 )   Highly oriented VO2(B), VO2(B) + V6O13 films were grown on indium tin oxide glass by radio-frequency magnetron sputtering. Single phase V6O13 films were obtained from VO2(B) +V6O13 films by annealing at 480℃ in vacuum. The vanadium oxide films were characterized by x-ray diffraction and x-ray photoelectron spectra (XPS). It was found that the formation of vanadium oxide films was affected by substrate temperature and annealing time, because high substrate temperature and annealing were favourable to further oxidation. Therefore, the formation of high valance vanadium oxide films was realized. The V6O13 crystalline sizes become smaller with the increase of annealing time. XPS analysis revealed that the energy position for all the samples was almost constant, but the broadening of the V2p3/2 line of the annealed sample was due to the smaller crystal size of V6O13.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Large magnetic entropy change near room temperature in the LaFe11.5Si1.5H1.3 interstitial compound Chen Yuan-Fu (陈远富), Wang Fang (王芳), Shen Bao-Gen (沈保根), Hu Feng-Xia (胡凤霞), Cheng Zhao-Hua (成昭华), Wang Guang-Jun (王光军), Sun Ji-Rong (孙继荣) Chinese Physics, 2002, 11 (7):  741-744.  DOI: 10.1088/1009-1963/11/7/318 Abstract ( 1455 )   PDF (243KB) ( 643 )   The LaFe11.5Si1.5H1.3 interstitial compound has been prepared. Its Curie temperature TC (288 K) has been adjusted to around room temperature, and the maximal magnetic entropy change (|ΔS|～17.0 J·kg-1·K-1 at TC) is larger than that of Gd (|ΔS|～9.8 J·kg-1·K-1 at TC=293 K) by ～73.5% under a magnetic change from 0 to 5 T. The origin of the large magnetic entropy change is attributed to the first-order field-induced itinerant-electron metamagnetic transition. Moreover, the magnetic hysteresis of LaFe11.5Si1.5H1.3 under the increase and decrease of the field is very small, which is favourable to magnetic refrigeration application. The present study suggests that the LaFe11.5Si1.5H1.3 compound is a promising candidate as a room-temperature magnetic refrigerant.