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Vol. 52, No. 4 (2003)

2003-02-20
GENERAL
Spatiotemporal relation of prolongable general relativity in the irreversible process of a dissipative system
Li Zong-Cheng
2003, 52 (4): 767-773. doi: 10.7498/aps.52.767
Abstract +
The hypothesis on the equivalence in non-conservative system is set up for irreversible process on the basis of bring-in of the nonconservative-noninertial system;and the hypothesis on the covariance in non-conservative system is put forth for the space-time with complex action on the basis of bring-in of the ultra-gauge. Also the heterogeneity h(ρt)and coarse-grained entropy S(ρtε)of the density distribution ρ in phase space and the derived computational expression of multiscale factor η* are used in the bring-in of the nonconsorvative gravitation mass and nonconservative inertial mass.The analysis here shows that the new result could make the gravitation theory, together with the statistical theory of nonequilibrium state and the nonlinear dynamics reach harmony to some extent, so as to revise and develop general theory of relativity.
Gravitational relation of prolongable general relativity in the irreversible process of a dissipative system
Li Zong-Cheng
2003, 52 (4): 774-780. doi: 10.7498/aps.52.774
Abstract +
The heterogeneity h(ρt)and coarse-grained entropy S(ρtε)of the density distribution ρ in phase space and the derived computational expression of multiscale factor η* are used in the expansion of Weyl curvature into multiscaled curvature R*; and the multifractal in relation to the singular distribution of physical quantities on geometry is used in the preliminary establishment of the multifractal geometry of growing structures set in Riemann space; on this basis, the equation of non-conservative attractive field is set up by the introduction of the general dimension Du in relation to the fractal and informational and incident dimensions. The analysis here shows that the new result could render the suitable basis for the settlement of the questions such as the singularity of cosmology the unidentified matter in the cluster of galaxies, the doubt of information from black hole and the unification between gravitation theory and quantum physics, and so on.
Scattering states of n-dimensional hydrogen atom
Chen Chang-Yuan, Sun Dong-Sheng, Liu Cheng-Lin, Lu Fa-Lin
2003, 52 (4): 781-785. doi: 10.7498/aps.52.781
Abstract +
Characteristics of the scattering states of an n-dimensional hydrogen atom have been studied. The normalized wave functions of scattering states on “k/2π scale” and the calculation formula of phase shift are presented.The analytical properties of phase shift are discussed, and analytical formulas for calculating bound-continuous transition matrix elements are also given. The relevant results of scattering states for the usual hydrogen atom (n=3) reported in the literature are contained in more general conclusions of this paper as special cases.
Discussion on the calculation of radial matrix elements of three-dimensional isotropic oscillator
Di Yao-Min
2003, 52 (4): 786-789. doi: 10.7498/aps.52.786
Abstract +
A concise general formula of the radial matrix element of the three-dimensional isotropic oscillator is derived using the properties of the general Laguerre polynomials. Some important special cases, such as the average value of the integer power of radial vector, the matrix element of the electric dipole transition and the element of the electric quadrupole transition, are obtained from the general formula.
Control of period-doubling bifurcation and chaos in a discrete nonlinear system by the feedback of states and parameter adjustment
Zou Yan-Li, Quan Hong-Jun, Chen Guan-Rong, Luo Xiao-Shu, Wang Bing-Hong, Fang Jin-Qing
2003, 52 (4): 790-794. doi: 10.7498/aps.52.790
Abstract +
In this paper, the control of delaying period-doubling bifurcations and unstable periodic orbits embedded in a chaotic attractor of a discrete nonlinear dynamical system is effectively realized by using the state variables feedback and parameter variation. Moreover, the 2n periodic orbits of the system can be controlled into the 2m (m
Prediction of the chaotic time series using neuro-fuzzy networks
Wang Yao-Nan, Zhou Shao-Wu, Liu Zu-Run, Tan Wen
2003, 52 (4): 795-801. doi: 10.7498/aps.52.795
Abstract +
A novel hybrid neural fuzzy inference system is presented. Only based on the desired input-output data pairs, are the knowledge acquisition and initial fuzzy rule sets available. Then, employing neural networks learning techniques, the fuzzy logic rules,input-output fuzzy membership functions and weights in networks can be easily tuned. So the rule matching is reduced ,inferencing is accelerated, adaptability of the system is greatly improved. To illustrate the performance of the proposed neuro-fuzzy hybrid model, simulations on the chaotic Mackey-Glass time series prediction are performed. Combining either off-line or on-line learning with the proposed hybrid model, we can show that the chaotic Mackey-Glass time series are accurately predicted, and demonstrate the effectivness of the model.
Stochastic resonance in two-dimensional Brownian motion in the weak noise limit
Kang Yan-Mei, Xu Jian-Xue, Xie Yong
2003, 52 (4): 802-808. doi: 10.7498/aps.52.802
Abstract +
The theory of LΩEGF and the scaling theory on multidimensional Fokker-Planck equations with gradient potential are applied to derive the probability transition rate for Brownian motion in a symmetric two-dimensional bistable potential. Based on the rate method in adiabatic elimination, the phenomenon of stochastic resonance is studied in this system. Compared with the known results, the analytic expression for signal-to-noise ratio derived in this study is independent of the intensity of friction,i.e. not only applicable to an overdamped system, but also applicable to a lightly damped system. Numerical simulations fruther verify the significance of the analytically approximate result.
The reflectivity measurement of the 28.5nm multilayer mirror
Huang Wen-Zhong, Gu Yu-Qiu, You Yong-Lu, CunYu Shutai, He Ying-Ling, Lei An-Le, Chen Cheng-Lin, Ma Yue-Yin, Jin Chun-Sui, Zhang Jie, Li Yin-Jun
2003, 52 (4): 809-812. doi: 10.7498/aps.52.809
Abstract +
The reflectivity of the 28.5nm Mo/Si multilayer mirrors are measured at Xingguang-Ⅱ laser facility using a flat-field grating spectrograph with the Ne-like Cr x-ray laser as a soft x-ray source. The reflectivities obtained for two samples are 0031 and 0096.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Effects of quantum electromagnetic dynamics in a cylindrical ring cavity
Jiang Wei-Zhou, Fu De-Ji, Wang Zhen-Xia, Ai Xiao-Bai, Zhu Zhi-Yuan
2003, 52 (4): 813-822. doi: 10.7498/aps.52.813
Abstract +
A charge-free conductor cavity has macroscopic quantum effects that can be explained by the physical picture of vacuum zero-point energy. This paper studies the macroscopic quantum effects in the conductive cylindrical ring,in terms of zero-point oscillating modes. The zero-point oscillating modes are obtained through solving the Maxwell equations without sources under the boundary condition of the cylindrical conductor surfaces. The vacuum energy (i.e. the Casimir energy) per unit length and area for the double-layer concentric cylindrical ring is obtained and it can be decomposed into the three independent and convergent parts that come from the interior, exterior cylindrical surfaces and the portion between them, respectively. For an n-layer cylindrical ring, its Casimir energy comprises of (2n-1) parts, all of which are convergent. Topologically, the geometric structure of the cylindrical ring is analogous to that of the parallel plates. However, the Casimir energy of the cylindrical ring has the non-trivial property that the coefficients of the Casimir energies and potentials vary with the interval between the cylindrical surfaces, compared to the constant coefficient for the parallel plates. This non-trivial property will give rise to an additional Casimir force that does not exist in the case of parallel plates.
NUCLEAR PHYSICS
Density distributions of valence nucleons under single-particle potential model
Lin Cheng-Jian, Zhang Huan-Qiao, Liu Zu-Hua, Wu Yue-Wei, Yang Feng, Ruan Ming
2003, 52 (4): 823-829. doi: 10.7498/aps.52.823
Abstract +
Using the experimental results, we have calculated the density distributions of valence nucleons in terms of the single-particle potential model. The outside probabilities and contributions of valence nucleons given by these calculations are considered as the criterion of halo states. By studying the variation of root-mean-square radius with the separation energy, conditions for the existence of halo states are pointed out, especially of the proton halo states. These have realistic meanings for judging and searching the halo states.
Study of the effect of interface state charges on field-effect mobility of n-channel 6H-SiC MOSFET
Tang Xiao-Yan, Zhang Yi-Men, Zhang Yu-Ming, Gao Jin-Xia
2003, 52 (4): 830-833. doi: 10.7498/aps.52.830
Abstract +
The effect of interface state charges on the field-effect mobility of n-channel 6H-SiC MOSFET is analyzed based on the nonuniform distribution of interface state density in the energy gap. The results of the analysis show that interface state charges have the influence of lowering the field-effect mobility in n-channel SiC MOSFET. A relationship has been established between the ratio of the experimentally determined field-effect mobility to the inversion-layer carrier mobility and interface states.
CLASSICAL AREA OF PHENOMENOLOGY
Temperature character of electromagnetic levitation melting
Ma Wei-Zeng, Ji Cheng-Chang, Li Jian-Guo, Xu Zhen-Ming
2003, 52 (4): 834-839. doi: 10.7498/aps.52.834
Abstract +
Utilizing the formula of electromagnetic force and input power, we have derived the expression of input power of a spherical sample for a general electromagnetic levitation inductor without including the current of the inducer. Combining the power dissipation model of the spherical sample in free-convection gas medium and the expression of input power without including the current of inducer, the relation between processing parameters of electromagnetic levitation and temperature of levitation sample is established. The electromagnetic melting of spherical (TbDy)Fe2 alloys under the protection of Ar is employed as an example to study the effect of processing parameters on the temperature of levitation sample obtained by numerical computation. According to computation results and the character of actual electromagnetic levitation, the methods to decrease the temperature of the levitation melted sample are obtained: i.e. reducing the radius of the levitation melted sample, employing low frequencies of the inducer, adjusting the position of the levitated sample to a position at which the lowest levitation melting temperature can be obtained, reducing the radius of the lower levitation coil, increasing the space interval between the upper stability controlling coil and the lower levitation coil, increasing the radius of the upper stability controlling coil, and increasing the turns of the upper stability controlling coil.
Study of the spectral characters of stimulated Raman scattering in highly elliptical-core optical fibres
Zhang Xi-He, Yao Zhi-Hai, Li Xiao-Ying, Li Chun-Ming, Feng Ke-Cheng, Wang Zhao-Min
2003, 52 (4): 840-843. doi: 10.7498/aps.52.840
Abstract +
In this paper, we systematically study the spectral characters of stimulated Raman scattering(SRS) in the birefringence optical-fibre and give seventh-order Stokes and first-order anti-Stokes spectra, then measure the threshold、spectrum width and Raman gain of SRS. At the same time, we make an analysis of the mechanism of energy transmission between each order of the Raman spectra.
The theory and realization of atomic beam CGH
Shi Jian-Ping, Chen Xu-Nan, Gao Hong-Tao, Chen Xian-Zhong
2003, 52 (4): 844-848. doi: 10.7498/aps.52.844
Abstract +
The realization of atom-beam holography by computer generated hologram have been presented in this paper, which can decrease the difficulty of the atom holography. Firstly the wave nature and cooling mechanism of atoms are analyzed, then the design process and a facture of the atomic SiN film hologram is shown, and finally we present a theoretical plan and the picture of an experiment system.
Generation of tunable intensity difference squeezing light from a quasi-phase-matched OPO
Li Yong-Min, Wu Ying-Rui, Zhang Kuan-Shou, Peng Kun-Chi
2003, 52 (4): 849-852. doi: 10.7498/aps.52.849
Abstract +
A 106μm all-solid-state single frequency Nd∶YVO4 laser was explored to pump a triply resonant optical parametrie oscillator(OPO) based on the periodically poled lithium niobate. When the OPO operated near degeneracy, the amplitude fluctuation correlation of the signal and idler modes was observed as their wavelengths were separated about 200nm. The measured squeezing is 04dB. The amplitude fluctuation correlation existed in a range of 17nm as we tuned the wavelengths of the signal and idler by change the crystal temperature.
Spontaneous emission from a two-level atom embedded in two-band three-dimensional photonic crystals
Chen San, Xie Shang-Yuan, Yang Ya-Ping, Chen Hong
2003, 52 (4): 853-858. doi: 10.7498/aps.52.853
Abstract +
We have studied the properties of the spontaneous emission from a two-level atom embedded in two-band photonic crystals. Due to the anisotropic two-band dispersion relation, the localized and propagating fields cannot coexist, this leads to the non-quasi-oscillation behaviour of the upper level population. Thus the upper level population will tend to a constant as time goes to infinity, or decay with time in a power law, or decay with time exponentially, different from that in the isotropic one-band dispersion relation case. These properties are directly related to the relative position of the upper level from the band edge and the width of the gap.
Study on nonlinear absorption and optical limiting properties in an organic material ZnTBP-CA-PhR
Yu Shi-Rui, Zhao You-Yuan, Li Lu-Ying
2003, 52 (4): 859-863. doi: 10.7498/aps.52.859
Abstract +
In this paper the nonlinear absorption in the organic material ZnTBP-CA-PhR is reported. Saturable absorption, reverse saturable absorption and re-reverse saturable absorption under an Ar+ laser beam in visible light range were observed. This material has fine optical limiting properties. Its intensity threshold is lower than that of other materials and there is no nonlinear optical effect before input intensity reaches the threshold. In order to analyse the physical mechanism of nonlinear absorption of this material, a five-level model is presented using the rate equation theory to simulate the saturable absorption and reverse saturable absorption experimental results.
An experimental proof for the fifth-order harmonic generation by a coherent-controlled two-pulse optical field
Liu Ting-Ting, Wang Da-Wei, Lu Wei-Xin, Sun Quan, Yang Hong, Jiang Hong-Bing, Gong Qi-Huang
2003, 52 (4): 864-869. doi: 10.7498/aps.52.864
Abstract +
We have studied experimentally the intensity characteristic of the fifth-order harmonic radiation produced by two coherent femtosecond laser pulses with a changeable relative phase.The intensities of the harmonic generation are found to increase with the coherent degree.The maximum intensity of harmonics exhibits an asymmetric characteristic with respect to the point where the two components are superposed completely.This fact verifies the influence of deformation of the merged beam on the harmonic generation.Meanwhile,we have carried out some fundamental experiments,based on the theory of stimulated emission.
Compare of characteristics between Martinez and Offner stretchers used in chirped pulse amplifier
Sun Da-Rui, Song Yan-Rong, Zhang Zhi-Gang, Chai Lu, Wang Qing-Yue, Liu Yong-Jun
2003, 52 (4): 870-874. doi: 10.7498/aps.52.870
Abstract +
In this paper, the characteristics and range of application of the Martinez and the Offner stretchers in a chirped pulse amplifier system is analyzed theoretically for a multiple-pass amplifier and a regenerative amplifier respectively. The Martinez stretcher can completely compensate the dispersion introduced either from a multiple-pass amplifier or from a regenerative amplifier within a certain bandwidth. In a regenerative amplifier, if it is necessary to obtain broader pulses, the compact Offner stretcher can be applied.
The influence of channel width and inflow rate on the critical opening-size of granular flow in two-dimensional channels
Xu Guang-Lei, Hu Guo-Qi, Zhang Xun-Sheng, Bao De-Song, Chen Wei, Hou Mei-Ying, Lu Kun-Quan
2003, 52 (4): 875-878. doi: 10.7498/aps.52.875
Abstract +
We have studied experimentlly the transition phenomenon of a granular flow from dilute flow to dense flow in two-dimensional channels. In the dense flow the outflow rate (Q) depends only on the opening (D) given by Q=aD3/2.For different inflow rates Q0 in a dilute flow, the critical opening-size with the channel relation of width (W) is given; and in a larger inflow, the critical opening-size is opproximately proportional to the square root of the inflow rate,Dc∝Q1/20.
The static friction force on a rod immersed in granular matter
Hu Lin, Yang Ping, Xu Ting, Jiang Yang, Xu Hai-Jiang, Long Wei, Yang Chang-Shun, Zhang Tao, Lu Kun-Quan
2003, 52 (4): 879-882. doi: 10.7498/aps.52.879
Abstract +
The dependence of the static friction force exerted on a rod immersed in granular matter on the filling height of granules and the diameter of the rod is studied experimentally. It is observed that the friction force increases with the filling height of granules and increasing diameter of the rod. A model based on the continuous media is given, which can explain the observed results. It is demonstrated that the friction force is proportional to the diameter of the rod and the square of the filling height in the case of shallow granules, while it is a linear function of the filling height in the case of very deep granules,i.e. the friction force is proportional to the area of the interface between the rod and granules.
Numerical analysis of alloy molten pool heated by electron gun
Bo Yong, Wang De-Wu, Ying Chun-Tong
2003, 52 (4): 883-889. doi: 10.7498/aps.52.883
Abstract +
The physical model for a square alloy molten pool heated by an electron gun is described by the Navier-Stokes, energy and species concentration equations. The velocity, temperature and concentration distributions of the two-dimensional pool are analyzed by the finite difference method. The relations between the metal solvent evaporation rate and Rayleigh number Re, Prandtl number Pr, Grashof number Gr and Lewis number are studied in detail. In general, the solvent evaporation rate increases with decreasing Rayleigh number,decreasing Prandtl number, increasing Grashof number and increasing Lewis number, so the power use ratio of the electron gun increases. On this basis, such metal solutes as wolfram, neodymium and chromium is intermingled to such involatile metal solvents as thorium, platinum, ytterbium and ruthenium, and the numerical results indicate that the metal solvent evaporation rate increases.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
Condition of Alfven Gauss wave-packet evolvement to solitons and criterion of Alfven wave modulation instability
Wang Geng-Guo, Zhu Jia-Zhen, Liang Chang-Hong, Zhang Jie-Qiu
2003, 52 (4): 890-895. doi: 10.7498/aps.52.890
Abstract +
By analyzing the integral constant C1 of Alfven solitons, the condition of Alfven Gaussian wave-packets evolvement to solitary waves is put forward as C1≤0. This hypothesis is also confirmed by numerical simulation results. Furthermore,simulation results show that the number of evolving solitons does not depend only on integral constant C0 or C1. The conclusions in Refs. [1] and [2] result from the shorter evolving time. Comparing with other papers, we find that C0≤0 can be used as a criterion of Alfven wave modulation instability.
D-T plasma of self-sustained burning under high performance
Shi Bing-Ren, Long Yong-Xing, Gong Xue-Yu
2003, 52 (4): 896-905. doi: 10.7498/aps.52.896
Abstract +
By adopting a Bohm-type thermal diffusion coefficient related to the energy confinement enhancement factor H within the conventional magnetic shear regime,and a mixed Bohm-gyro-Bohm thermal diffusion coefficient related to the shear within the negative central magnetic shear regime,considering the effect of the α particle anomalous diffusion and the dynamic feedback heating,and starting from energy transport of electrons and ions,we have studied the high performance self-sustaining burning deuterium-tritium plasma under a given plasma density profile for the two different kinds of magnetic shear regimes.Some conclusions are obtained:under the conventional shear,only when H≥3,the D-T burning can produce a large power output,and when H is larger than a certain value(H≈4),D-T plasma self-sustained burning can be maintained without the dynamic feedback heating;under the negative central shear,the plasmas have a higher plasma performance and a larger power output than that under conventional shear,and D-T plasma self-sustained burning can be maintained without the dynamic feedback heating power,the suitable alpha particle diffusion is advantage ous to D-T plasma burning under the conventional shear,and D-T self-sustained burning cannot be maintained under a large α particle anomalous diffusion for the negative central shear.The dynamic feedback heating power is important for sustaining D-T plasma burning under the conventional shear.
Limit cycle oscillating and chaos of the radiation field in a traveling wave tube amplifier
Ding Wu, Hao Jian-Hong
2003, 52 (4): 906-910. doi: 10.7498/aps.52.906
Abstract +
In this paper the evolution of the radiation field from frequency bifurcation to chaos and the temporal and frequency characteristics of the nonlinear unsteady states are investigated, based on the threshold analysis of nonlinear instability for the radiation field in a traveling wave tube amplifier. In the soft nonlinear regime,the nonlinear radiation field is characterized by limit cycle oscillations with frequency bifurcated, and the output power spectrum is discrete and asymmetric around the carrier frequency. This instability is intermittent so that the device can operate in expected steady states or limit cycle oscillation states by slightly adjusting the parameter. In the hard nonlinear regime in which the radiation field is characterized by randomly non-periodic oscillations with frequency chaos, the output power spectrum is continuous and wide, the components with a larger amplitude are restricted in the low-frequency range near zero. This instability is continuous so that it cannot be avoided by slightly adjusting the parameter.
Production of beat waves using S-band klystron amplifier
Fang Jin-Yong, Ning Hui, Zhang Shi-Long, Qiao Deng-Jiang
2003, 52 (4): 911-913. doi: 10.7498/aps.52.911
Abstract +
A method of producing beat waves by a single klystron amplifier is introduced in this paper. The experimental results have been obtained that the main frequency of the beat wave is in S-band, the beat frequency ranges from 10 to 120MHz, the peak power of the pulsed beat wave is 1MW, and the maximal repetitive frequency is 500pps. This method has been successfully used in certain electrical system high-power microwave vulnerability effect experiments.
Study on characteristics of helix-type traveling wave tube filled with plasma
Li Cheng-Yue, Yan Yang, Liu Sheng-Gang, Xie Hong-Quan
2003, 52 (4): 914-919. doi: 10.7498/aps.52.914
Abstract +
A helix-type slow wave structure filled partially with plasma is immersed in a strong longitudinal magnetic field.By means of sheath model and linear field theory,the dispersion relation of the slow wave structure is derived. Hybrid modes which are formed at frequencies at which the phase velocities of electromagnetic and electrostatic waves coincide are found.The trend of change for disperstion characteristic,interaction impedance and gain is analyzed in detail in the cases of various densities of plasma and filling radius by numerical computation. Some useful results are obtained on the basis of the discussion.
The role of ions(N+2) in the dissociation of nitrogen in a direct-current glow discharge
Zhang Lian-Zhu
2003, 52 (4): 920-924. doi: 10.7498/aps.52.920
Abstract +
A model is developed for a nitrogen direct-current glow discharge by a combination of Monte Carlo model of fast electrons and various heavy particles(N+2,N+,Nf),in which N+2-N2 dissociative charge transfer is incorporated,and the role of this process in nitrogen glow discharge is investigated .It is found that this process is dominant in the space of close to the cathode,and that this becomes important with increasing voltage,especially that this plays an important role at higher voltages for the production of fast atomic species(N+,Nf) at the cathode.We have also compared our calculated results with experimental data.
Pattern formation in the dielectric barrier discharge in argon at atmospheric pressure
Yin Zeng-Qian, Chai Zhi-Fang, Dong Li-Fang, Li Xue-Chen
2003, 52 (4): 925-928. doi: 10.7498/aps.52.925
Abstract +
The hexagon and square gridding patterns were observed in Ar(0.5%Air) at atmospheric pressure by using a dielectric barrier discharge set-up with double water electrodes. The temporal behaviour of an individual filament in square gridding was measured. The experimental results show that the time interval between two adjacent discharges are changed between long and short alternately. The influence of the charges deposited on dielectric surface on the self-organized filament pattern has been discussed.
The mapping equation of micro-discharge in dielectric barrier discharges
Yin Zeng-Qian, Dong Li-Fang, Li Xue-Chen, Chai Zhi-Fang, Wang Long
2003, 52 (4): 929-934. doi: 10.7498/aps.52.929
Abstract +
The temporal behaviour of micro-discharge in the dielectric barrier discharge (DBD) in air and argon at atmospheric pressure is measured by an optical method using the special set-up of two water electrodes. The nonsymmetrical character of the filament is discovered. Considering the different effects of wall charges on the adjacent micro-discharges in DBD, we have proposed a mapping equation of discharge moment.The calculated results using different parameters show that the decay time constant of wall charges is much larger than an order of 100μs. The results deduced from the mapping equation give a good explanation to the experimental phenomenon that the time interval between two adjacent discharges of a micro-discharge varies between long one and short one alternatively. The variation range of the decay time constant of the accumulated charge is estimated.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
Structural and photoluminesenct properties of Zn1-xMgxO thin film on silicon
Zou Lu, Wang Lei, Huang Jing-Yun, Zhao Bing-Hui, Ye Zhi-Zhen
2003, 52 (4): 935-938. doi: 10.7498/aps.52.935
Abstract +
High-quality Zn1-xMgxO thin film was grown on Si substrate by pulsed laser deposition (PLD). x-ray diffraction patterns indicated that the film was c-axis oriented, the full width at half maximum of (002) peak was only 0.211°, and no phase separation was observed. Transmission electron microscopy(TEM) verified the c-axis orientation of the Zn1-xMgxO thin film. Regular diffraction spots can be observed by TEM. Photoluminescence spectrum was measured at room temperature. The near-band-energy emission peak of the Zn1-xMgxO thin film has a blue shift of 0.4 eV from that of ZnO, and the ratio of near-band-energy to the defect-level peak intensity was as large as 159. These results indicate that Zn1-xMgxO thin film can have potential applications in optoelectronic devices.
Influence of laser field on interactions between swift molecular ions and solids
Wang Gui-Qiu, Wang You-Nian
2003, 52 (4): 939-946. doi: 10.7498/aps.52.939
Abstract +
Using the linearized hydrodynamic-Poisson equations, we describe electronic excitations of electron gas in solids, and derive general expressions for the induced potential in the target, and the interaction force among the ions within a molecule, in the pre-sence of a laser field. Based on the numerical solution of equations of motion for the constituent ions, the Coulomb explosion patterns and the molecular energy losses are studied for a range of laser parameters. It has been found that by increasing the laser intensity, the wake effects in the interaction potential become weaken. This weans that the deflection of the molecular axis to the direction of the projectile velocity is not significant, and the energy loss of the molecular ions is also reduced.
The specific heat of polyaniline at low-temperature
Wan Mei-Xiang, Luo Jian-Lin, Chen Zhao-Jia, Long Yun-Ze, Bai Hai-Yang, Xu Jie, Wang Wan-Lu
2003, 52 (4): 947-951. doi: 10.7498/aps.52.947
Abstract +
The specific heat of the emeraldine base form of polyaniline and the emeradine salt of polyaniline has been measured at temperatures between 1.8 and 45K. The experimental results have been interpreted in terms of the contributions from both the crystalline and the amorphous phases characterizing the polymer. Anomaly of the specific heat, which is much larger than that expected from the Debye theory, has been successfully explained by the phonon-fracton model at low temperatures. The electronic specific heat has not been observed from the present data.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Investigation of lithium insertion in anode material CuSn for lithium-ion batteries
Liu Hui-Ying, Yang Yong, Hou Zhu-Feng, Zhu Zi-Zhong, Huang Mei-Chun
2003, 52 (4): 952-957. doi: 10.7498/aps.52.952
Abstract +
An ab initio method with mixed-basis norm-conserving non-local pseudopotentials has been employed to investigate the non-carbon-baring anode material-CuSn for lithium-ion batteries. The lithium intercalation energies and their electronic structures have been calculated. The changes of volume, band structures, electronic density of states and charge density contour plots for lithium intercalation in CuSn are also presented. The characteristics of CuSn as an anode material for lithium ion batteries are also discussed. By calculation, we have found that the insertion formation energy of Li insertion CuSn electrode with zinc-blende-type structures as the host framework is about 3.5eV.
The anisotropic phenomena in the D5d minima for the T1uhg Jahn-Teller system
Qiu Qing-Chun
2003, 52 (4): 958-969. doi: 10.7498/aps.52.958
Abstract +
Jahn-Teller (JT) systems contain typically a set of mutually equivalent energy minima in the lowest adiabatic potential energy surface. When one electron occupies the three degenerate electronic states in C60 molecules, the electronic states with a symmetry of T1u and the five degenerate vibrational states with a symmetry of hg will be interacted and form the T1uhg JT system. When the non-linear vibronic interaction is considered, the JT system will contain the D5d minima and D3d maxima, and vice versa. In this paper, on the basis of unitary shift transformation, the modified scale transformation is introduced and the anisotropic phenomenon is studied in the D5d minima for the T1uhg JT system. The results are incorporated into the expressions for the states in the D5d wells and their associate energies. The symmetries and their corresponding energies in the D5d wells in the electronic space are obtained. For finite couplings, the phonon overlap between wells and inversion splitting are also studied. The results obtained in this paper not only show that the anisotropic effect has a significant influence on the above physical quantities, but also are of interest in the studies of anion states (C-60) of the C60 molecules and other C60 anion-related materials.
Structure and electronic properties of the low-dimensional copper systems
Wang Gui-Chun, Yuan Jian-Min
2003, 52 (4): 970-977. doi: 10.7498/aps.52.970
Abstract +
Five different copper structures,including atomic chains atomic monolayers and bulk crystal,have been calculated by full-potential augmented plane wave method.For atomic mono-layers,the hexagon structure was found to be energetic favourable compared with the square structure,and the nearest bond length was also longer.For atomic chains,the same result has been obtained when the equilateral zigzag structure was compared with the linear structure.The calculated density of states (DOS) of the zigzag structure showed some unusual properties,and a band gap has been found.The DOS has been analyzed for different structures to find the relations between the electronic properties and the atomic structures.
Quantum fluctuations in the damped inductive-coupled electric circuit with resistances in the component circuits
Liang Mai-Lin, Yuan Bing
2003, 52 (4): 978-983. doi: 10.7498/aps.52.978
Abstract +
Using a new quantization idea of the damped electric circuit, the inductive-coupled electric circuit is quantized when there exist resistances in the component circuits. Quantum fluctuations are calculated and the temperature effects included.
Study on the kink effect in AlGaAs/InGaAs/GaAs PHEMTs
Liu Hong-Xia, Hao Yue, Zhang Tao, Zheng Xue-Feng, Ma Xiao-Hua
2003, 52 (4): 984-988. doi: 10.7498/aps.52.984
Abstract +
In this paper, two-dimensional devices simulation program-MEDICI has been used to simulate AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistors (PHEMTs). Doping and electron concentrations, current flow and gate characteristic in PHEMTs are studied. The kink effect in PHEMTs is investigated emphatically as a function of temperature and doping concentration of Schottky layer. The results show that the kink effect is related mainly to the trapping/detrapping process of deep levels that lie in the top layers but not related to the impact ionization alone.
The fabrication of nc-Si/SiO2 multilayers and blue-light emission
Sui Yan-Ping, Ma Zhong-Yuan, Chen Kun-Ji, Li Wei, Xu Jun, Huang Xin-Fan
2003, 52 (4): 989-992. doi: 10.7498/aps.52.989
Abstract +
A new fabrication method of a-Si∶H/SiO2 mutilayers (ML) is successfully employed by using layer by layer deposition of a-Si∶H sublayer and in situ plasma oxidation in a plasma-enhanced chemical vapor deposition system. Based on the constrained crystallization principle of a-Si∶H sublayer, the size-controlled nc-Si/SiO2 ML was obtained by the crystallization treatment including a rapid thermal process and furnace annealing. Blue photoluminescence is observed in the crystallized a-Si∶H/SiO2 ML at room temperature. The structure property of the nc-Si/SiO2 ML is investigated by transmission electron microscopy and Raman scattering spectroscopy. The origin of the blue-light emission is briefly discussed in combination with PL and absorption measurements.
Theoretical study of the structure and magnetism of Fe1-xPdx alloys
Shi Yi-Sheng
2003, 52 (4): 993-998. doi: 10.7498/aps.52.993
Abstract +
An ab initio linearized augmented plane wave (LAPW) method has been employed to calculate the electronic and magnetic structures for the fcc and bcc Fe1-xPdx alloys with x=000, 025, 050, 075, and 100, respectively. By decreasing the Pd content, the magnetism of fcc Fe1-xPdx alloys changes from paramagnetism to ferromagnetism, ferrimagnetism, and finally antiferromagnetism or ferromagnetism. On the other hand, the magnetism of bcc Fe1-xPdx alloys changes from paramagnetism to ferromagnetism. Our calculations are in good agreement with previous experimental results. And we predict that the Fe075Pd025 alloys are ferrimagnetism.
Negative thermal expansion of the Ho2AlFe14Mn2 compound
Cui Chun-Xing, Meng Fan-Bin, Hao Yan-Ming
2003, 52 (4): 999-1002. doi: 10.7498/aps.52.999
Abstract +
The structure properties of Ho2AlFe16-xMnx compounds have been investigated by means of x-ray diffraction and magnetic measurements. The Ho2AlFe16-xMnx compounds have a hexagonal Th2Ni17-type structure. Their unit-cell volumes increase nonlinear with increasing x. This implies there is a positive spontaneous volume magnetostriction in the magnetic state of these compounds. x-ray diffraction of the Ho2AlFe14Mn2 compound from 160 to 285 K shows that there appears a negative coefficient of thermal expansion from 220 to 270K and the average thermal expansion is -14×10-4·K-1.
Study on electrochromic performances of amorphous WO3 films
Feng Bo-Xue, Jiang Sheng-Rui, Chen Chong, Lü Shu-Yuan, Dai Fu-Ping
2003, 52 (4): 1003-1008. doi: 10.7498/aps.52.1003
Abstract +
A series of WO3 films are prepared by rf-sputtering under different partial pressures of oxygen. It is found that the films with oxygen partial pressure ratio 1∶10 have better electrochronic(EC) properties than others. Microstructural and compositional characteristics of WO3 films are studied by x-ray diffraction, atomic force microscopy and x-ray photo electro spectroscopy. It is obvious that the samples are amorphous and have more pores that are beneficial for Li+ to inject and eject. The original-state films are composed of tungsten and oxygen. After electrochemical reactions, the main component becomes LixWO3 in which tungsten ions normally exhibit both W6+ and W5+ oxidation states. The films are annealed in air at 230 and 400℃ for 90 min. The cyclic voltammograms and optical transmittance show that the films annealed at 400℃ after more than 10 cycles present better EC properties.
Thermal excitations in SrAl12O19∶Pr3+
Lu Li-Zhu, W M Yen, Wang Xiao-Jun, Lü Shao-Zhe, Chen Bao-Jiu, Huang Shi-Hua
2003, 52 (4): 1009-1012. doi: 10.7498/aps.52.1009
Abstract +
In this paper, we have studied the emission spectra from the thermally excited 3P1 and 1I6 states in SrAl12O19∶Pr3+.The ratio of the emission intensities of 3P1→3H5 and 3P0→3H5 transitions is applied to measure temperature. It is also pointed out that the thermally excited 1I6 emission plays an important role in decreasing the quantum efficiency of the 3P0 visible emission.
Mutual enhancement of cathodoluminescence and organic electroluminescence in SiO2/C9-PPV heterogeneous junction
Liu Ming, Yi Li-Xin, Teng Feng, Xu Zheng, Xu Xu-Rong
2003, 52 (4): 1013-1018. doi: 10.7498/aps.52.1013
Abstract +
We have prepared a device of C9-PPV sandwiched between two SiO2 layers and obtained the blue light in addition to the yellow-green emission under ac electric field excitation. By studying the optical characteristics of the device, we found that the emission was induced by direct bombardment of the accelerated electrons from SiO2. This emission is termed by us as cathodo luminescence-like emission. By using unsymmetrical structure, we realized mutual enhancement of cathodo luminescence-like and Organic electroluminescence.
Interference of Rayleigh scattering and four-wave mixing
Shou Qian, Zhang Hai-Chao, Deng Li, Liu Ye-Xin, Lin Wei-Zhu
2003, 52 (4): 1019-1022. doi: 10.7498/aps.52.1019
Abstract +
A novel interference phenomenon is observed in the femtosecond four-wave mixing experiment of AlGaAs/GaAs multiphe quantum well film, which is interpreted as the interference of Rayleigh scattering and four-wave mixing of the sample. Based on the Rayleigh scattering mode, a dephasing time of 44 fs of the sample is deduced.
Transformation of electronic state of Co3+ and its influence on the structural development in Li(AlxCo1-x)O2
Hao Wan-Jun, Li Chang, Wei Ying-Jin, Chen Gang, Xu Wu
2003, 52 (4): 1023-1027. doi: 10.7498/aps.52.1023
Abstract +
In this paper we have studied the magnetism of a new cathode material with a high energy density, Li(AlxCo1-x)O2(x=01—05), which is used in rechargeable lithium batteries. We found that doping Al can change the spin state of d electron in Co3+, leading to the emergence of high spin d electrons. Accompanied with this, there are also some changes of the structure development which is indicated by the obviously decreasing rate of the increasing value of c/a. This explains the positive deviation of the structure from the Vegard law. This is very important to the design of the microstructure and properties of materials.
Study of the stress observed in diamond films on carbon-implanted alumina surfaces
Fang Zhi-Jun, Xia Yi-Ben, Wang Lin-Jun, Zhang Wei-Li, Ma Zhe-Guo, Zhang Ming-Long
2003, 52 (4): 1028-1033. doi: 10.7498/aps.52.1028
Abstract +
The compressive stress in the diamond films formed on alumina ceramics can be reduced by implantation of carbon ions into alumina substrates before the deposition of diamond films. After carbon ion implantation, there is no new phase identified as interlayer by comparing the x-ray diffraction (XRD) patterns of the un-implanted and implanted substrates. In addition, the stress in the diamond films decreases linearly with the increase of the C+ implantation dose. This is because the implanted ions settle in the interstitial position and induce the residual compressive stress in the alumina lattice. This compressive stress, when the diamond films deposited and cooled down to room temperature, will be released and partly offset the compressive stress in the diamond films.
Study on the optical properties of the nanometer CdS-sulfonic group polyaniline (SPAn) composite multiplayer films
Ma Xi-Ying, Shi Wei-Lin
2003, 52 (4): 1034-1038. doi: 10.7498/aps.52.1034
Abstract +
The nanometer CdS-sulfonic group polyaniline (SPAn) polymer multiplayer films were grown in self-assembled layer-by-layer is reported and the optical properties are investigated. The optical measurement results show that the quantum size effect becomes strong with the decrease of the size of CdS nanocrystals. Blue shift appears on the absorb edgea in the absorption spectrum and also on the exciton band-edge emission peaks in the luminescence spectrum. The observed results of the corresponding annealed samples show that the intensity of the band-edge emission from the exciton direct recombination canbe enhanced about two to three times, and the band width becomes narrower than that of the un-annealed sample, indicating that CdS nanocrystals become more ordering, and their sizes become more uniform in the annealed sample.