Table of Content

25 December 2000, Volume 9 Issue 10 Previous Issue    Next Issue

GENERAL

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PERTURBATION TO THE SYMMETRIES AND ADIABATIC INVARIANTS OF HOLONOMIC VARIABLE MASS SYSTEMS Chen Xiang-wei, Mei Feng-xiang 2000, 9 (10):  721-725.  doi: 10.1088/1009-1963/9/10/001 Abstract ( 0 )   PDF (198KB) ([an error occurred while processing this directive])   The perturbation problem of symmetries for the holonomic variable mass systems under small excitation is discussed. The concept of high-order adiabatic invariant is presented, and the form of adiabatic invariants and the conditions for their existence are given. Then the corresponding inverse problem is studied. Finally an example is presented to illustrate these results.

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NORMALLY ORDERED FORMS OF SHAPIRO-WAGNER PHASE OPERATORS AND THEIR APPLICATION Liang Xian-ting 2000, 9 (10):  726-730.  doi: 10.1088/1009-1963/9/10/002 Abstract ( 0 )   PDF (270KB) ([an error occurred while processing this directive])   Based on the quantum mechanical representation |ξ〉=exp[\dfrac12|ξ|+ξ a+1+ξ* a+2-a+1a+2]|00〉constructed by Fan Hong-yi and with the help of the technique of integration within an ordered product of operators, we derive the normally ordered expressions of the Shapiro-Wagner (SW) phase operators. They are in terms of the Bessel functions. As their application we discuss the minimal uncertain relation regarding the two-mode phase and number-difference operators.

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GENERAL FORMULA AND RECURRENCE FORMULA FOR RADIAL MATRIX ELEMENTS OF N-DIMENSIONAL ISOTROPIC HARMONIC OSCILLATOR Chen Chang-yuan 2000, 9 (10):  731-736.  doi: 10.1088/1009-1963/9/10/003 Abstract ( 0 )   PDF (180KB) ([an error occurred while processing this directive])   In this paper, the general formulas and the recurrence formulas for radial matrix elements of N-dimensional isotropic harmonic oscillator are obtained. The relevant results of 2- dimensional and 3- dimensional isotropic harmonic oscillators reported in the reference papers are contained in a more general equations derived in this paper as special cases.

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DYNAMIC SCALING OF GROWING SURFACES WITH GROWTH INHOMOGENEITIES OF SCREENED COULOMBIC FUNCTION Tang Gang, Ma Ben-kun 2000, 9 (10):  737-741.  doi: 10.1088/1009-1963/9/10/004 Abstract ( 0 )   PDF (208KB) ([an error occurred while processing this directive])   The dynamic scaling properties of growing surfaces with growth inhomogeneities are studied by applying a dynamic renormalization-group analysis to the generalized Kardar-Parisi-Zhang(hereafter abbreviated to KPZ) equation, which contains an additional term of growth inhomogeneities. In a practical crystal growth process, these growth inhomogeneities can be induced by surface impurities and defects and are modeled by a screened Coulomb function in this paper. Our results show that the existence of the growth inhomogeneities can significantly change the dynamic scaling properties of a growing surface and can lead to a rougher surface.

ATOMIC AND MOLECULAR PHYSICS

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CALCULATION OF THE RELATIVISTIC CORRECTION ENERGIES OF Ne-LIKE IONS WITH ORBITAL POLARIZATION CORRECTION Li Xiang-dong, Tan Ming-liang, Yi You-gen, Sheng Yong, Jiang Gang, Zhang Zhi-hong, Zhu Zheng-he, Zhao Yong-kuan, Tang Yong-jian 2000, 9 (10):  742-748.  doi: 10.1088/1009-1963/9/10/005 Abstract ( 0 )   PDF (260KB) ([an error occurred while processing this directive])   This paper reports the theoretical calculation of Breit, self-energy, and vacuum polarization corrections in the Ne-like system using multi-configuration Dirac-Fock method with the orbital polarization. The relations of these corrections with the atomic number and the orbital symmetries are shown and the calculated correction energies are compared with other calculated results. Our Breit correction energies are all smaller by 1eV as maximum than the other theoretical Breit correction energies and the differences reveal ystematical relation with atomic number. It is found that the configuration interactions have great effect on Breit corrections while the orbital polarization has much smaller effect on Breit corrections. The self-energy and vacuum polarization obtained by our calculation are much different from that in previous literatures for some transitions.

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L-SHELL IONIZATION MEASUREMENT OF TUNGSTEN BY ELECTRON IMPACT Peng Xiu-feng, He Fu-qing, Long Xian-guan, An Zhu, Luo Zheng-ming 2000, 9 (10):  749-752.  doi: 10.1088/1009-1963/9/10/006 Abstract ( 0 )   PDF (211KB) ([an error occurred while processing this directive])   L-shell partial production cross sections of Lα-, Lβ-, Lγ- rays by electron impact were measured by observing the counts of X-ray from impacted thin tungsten target. Total production cross sections and mean ionization cross sections were deduced from these measured results. The electron beam energy range was from 11 to 36 keV. Tungsten was sputtered onto a carbon backing to reduce bremsstrahlung of the backing. The effect of electrons reflected by the backing has been corrected. Comparison with two theoretical calculations has performed. The experimental results agree rather well with the theoretical predications.

CLASSICAL AREAS OF PHENOMENOLOGY

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THE NONLINEAR SCHR?DINGER EQUATION AND THE CROSS-PHASE MODULATION IN ERBIUM-DOPED FIBER AMPLIFIERS Liu Ning, Liu Song-hao, Liao Chang-jun, Guo Qi, Xu Wen-cheng 2000, 9 (10):  753-756.  doi: 10.1088/1009-1963/9/10/007 Abstract ( 0 )   PDF (209KB) ([an error occurred while processing this directive])   The nonlinear Schr?dinger equation(NLSE) in erbium-doped fiber(EDF) was obtained. The cross-phase modulation (XPM) in the erbium-doped fiber amplifiers (EDFA) was studied based on this NLSE and the rate equations. A more generalized form of the propagation equation in EDFA was obtained which included the phase shifts the EDFA induced. An analytical expression was given to the XPM in the EDFA. It was found that the XPM in the EDFA dose not change very much with the wavelength except at the neighboring wavelengths (around 1531 nm) where the absorption and emission cross-sections of the erbium ions reach their maxima, and the XPMs have opposite signs on the two sides around 1531 nm. Furthermore, it was found that the XPM increases with the increase of the length of EDF.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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A STUDY OF HIGH POWER MICROWAVE AIR BREAKDOWN Liu Guo-zhi, Liu Jing-yue, Huang Wen-hua, Zhou Jin-shan, Song Xiao-xin, Ning Hui 2000, 9 (10):  757-763.  doi: 10.1088/1009-1963/9/10/008 Abstract ( 0 )   PDF (270KB) ([an error occurred while processing this directive])   This paper presents the results of research on microwave breakdown in air, it includes the experimental study and the theoretical analysis. The experimental study has been done in a waveguide with a frequency of 9.37GHz, the peak power up to 200kW, pulse width from 0.3 to 2.0μs. The repetition rate of microwave source is from single pulse to 970 pulse per second. The process of the breakdown of repetition pulse has also been recorded for a burst of ten pulses. A theoretical model for breakdown threshold is presented also. The theoretical are in good agreement with the experimental ones.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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PERTURBATION METHOD SOLVING ELASTIC PROBLEMS OF ICOSAHEDRAL QUASICRYSTALS CONTAINING A CIRCULAR CRACK Peng Yan-ze, Fan Tian-you 2000, 9 (10):  764-766.  doi: 10.1088/1009-1963/9/10/009 Abstract ( 0 )   PDF (174KB) ([an error occurred while processing this directive])   Perturbation method for solving elastic three-dimensional (3D) problems for 3D icosahedral quasicrystals is proposed. Considering an infinite 3D icosahedral quasicrystal weakened by a circular crack, we obtain the uniformly valid asymptotic solutions up to O(R2) for the mode I loading, where R is the elastic constant of phonon-phason coupling.

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LOW TEMPERATURE OPTICAL PROPERTIES OF AMORPHOUS OXIDE NANOCLUSTERS IN POLYMETHYL METHACRYLATE MATRIX V. V. Volkov, Wang Zhong-lin, Zou Bing-suo, Xie Si-shen 2000, 9 (10):  767-773.  doi: 10.1088/1009-1963/9/10/010 Abstract ( 0 )   PDF (239KB) ([an error occurred while processing this directive])   We studied the temperature-dependent steady-state and time-resolved fluorescence properties of very small (1-2 nm) ZnO, CdO, and PbO amorphous nanoclusters prepared in AOT reverse micelles and imbedded in polymethyl methacrylate(PMMA) films. X-ray diffraction and electron diffraction and imaging indicate that these structures are amorphous. These amorphous oxide nanoclusters demonstrate similar structural, electronic, and optical properties. Properties of steady-state fluorescence spectra indicate the unique localization of electronic states due to the amorphous structure. ZnO and CdO show double-band fluorescence structure, which is due to the spin-orbital splitting, similar to Cu2O. Time-resolved fluorescence studies of the nanoclusters in the polymer reveal two lifetime components, as found in solution. The slow component reflects relaxation processes from band-tail states while the fast component may be related to high-lying extended states. The temperature dependence of fast fluorescence component reveals the presence of exciton hopping between anharmonic wells at temperatures higher than 200K. We correlate the barrier height between two wells formed around local atoms with the inter-atomic distance and bond ionicity.

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AuPd CATALYTIC NANOPARTICLE SIZE EFFECT ON THE FORMATION OF AMORPHOUS SILICON NANOWIRES Liu Zu-qin, Sun Lian-feng, Tang Dong-sheng, Zhou Wei-ya, Li Yu-bao, Zou Xiao-ping, Wang Gang 2000, 9 (10):  774-777.  doi: 10.1088/1009-1963/9/10/011 Abstract ( 0 )   PDF (2065KB) ([an error occurred while processing this directive])   Amorphous silicon (a-Si) nanowires have been prepared on SiO2/Si substrates by AuPd nanoparticles / silane reaction method. Field-emission scanning electron microscopy and transmission electron microscopy were used to characterize the samples. The typical a-Si nanowires we obtained are of a uniform diameter about 20 nm and length up to several micrometers. The growth mechanism of the nanowires seems to be the vapor-liquid-solid mechanism. The catalytic particle size effect on the formation of the nanowires and the cause of forming amorphous state Si nanowires are discussed.

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

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POROUS AMORPHOUS FLUOROPOLYMER FILMS WITH ULTRALOW DIELECTRIC CONSTANT Ding Shi-jin, Wang Peng-fei, Zhang Wei, Wang Ji-tao, Wei William Lee, Zhang Ye-wen, Xia Zhong-fu 2000, 9 (10):  778-782.  doi: 10.1088/1009-1963/9/10/012 Abstract ( 0 )   PDF (274KB) ([an error occurred while processing this directive])   With the development of ultralarge scale integrated circuit, new interlayer dielectrics with low dielectric constant for multilevel interconnections are required, instead of conventional SiO2 films. For the sake of seeking perfect dielectrics, amorphous fluoropolymer (AF) thin film with a thickness of about 0.9μm has been prepared by spin-coating method, following the principle of phase separation. By capacitance-voltage (C-V) measurements the dielectric constant of the thin film is equal to 1.57 at 1 MHz, which is attributed to numerous pores contained in the film matrix. X-ray photoelectron spectroscopy (XPS) spectra show that after annealing, about 71% CF3 groups in the AF film have decomposed into CF2, CF, etc. This leads to the increase of CF2 groups by three times and CF groups by 8% in the AF film. In a word, compared with the film without being annealed, about 25% carbon, 7% fluorine and 12% oxygen atoms will be lost after annealing at 400℃ for 30min.

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1.5μm LUMINESCENCE CHARACTERISTIC OF ERBIUM IN B, P DOPED a-SiO:H FILMS Liang Jian-jun, Chen Wei-de, Wang Yong-qian, Chang Yong, Wang Zhan-guo 2000, 9 (10):  783-786.  doi: 10.1088/1009-1963/9/10/013 Abstract ( 0 )   PDF (189KB) ([an error occurred while processing this directive])   Hydrogenated amorphous silicon films co-doped with oxygen (O), boron (B) and phosphorus (P) were fabricated using PECVD technique. The erbium (Er) implanted samples were annealed in a N2 ambient by rapid thermal annealing. Strong photoluminescence (PL) spectra of these samples were observed at room temperature. The incorporation of O, B and P could not only enhance the PL intensity but also the thermal annealing temperature of the strongest PL intensity. It seems that the incorporation of B or P can decrease the grain boundary potential barriers thus leading to an easier movement of carriers and a stronger PL intensity. Temperature dependence of PL indicated the thermal quenching of Er-doped hydrogenated amorphous silicon is very weak.

GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS

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SPECTRAL VARIABILITY AND TRANSIENT INJECTION OF RELATIVISTIC ELECTRONS FOR BL LAC OBJECTS Mei Dong-cheng, Xie Guang-zhong, Chen Luo-en 2000, 9 (10):  787-790.  doi: 10.1088/1009-1963/9/10/014 Abstract ( 0 )   PDF (189KB) ([an error occurred while processing this directive])   The spectral hardening with increasing intensity in optical range for four BL Lac objects have been found by analyzing our observed data. Making use of the synchrotron loss of transient injection of relativistic electrons, we succeeded in explaining the phenomenon of the spectral hardening in the outburst phase. The value of magnetic intensity and the limit condition of the transient injection of relativistic electrons seem to be reasonable.