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Ground State Properties for Bose-Condensed Gas in Anisotropic Traps
XU Zhi-Jun, LI Hai-Bin, XIN Xiao-Tian, LI Zhen, WANG Dong-Mei
Chin. Phys. Lett. 2006, 23 (6):
1391-1394
.
Based on the energy functional and variational method, we present a new method to investigate the ground state properties for a weakly interacting Bose-condensed gas in an anisotropic harmonic trap at zero temperature. With this method we are able to find the analytic expression of the ground-state wavefunction and to explore the relevant quantities, such as energy, chemical potential, and the aspect ratio of the velocity distribution. These results agree well with previous ground state numerical solutions of the Gross--Pitaevskii equation given by Dalfovo et al. [Phys. Rev. A 53 (1996) 2477] This new method is simple compared to other methods used to solve numerically the Gross--Pitaevskii equation, and one can obtain analytic and reliable results.
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Effects of Nonlinear Time-Delay on a Stochastic Asymmetric System
WANG Jiu-Yun, ZHU Chun-Lian, JIA Ya, LI Jia-Rong
Chin. Phys. Lett. 2006, 23 (6):
1398-1401
.
We numerically investigate the effects of nonlinear time-delay on the stochastic system. With the delay time increasing, it is found that the peak of probability distribution in low steady states is decreased, and the peak of probability distribution in high steady states is increased. The mean of state variable, the normalized variance, and the normalized autocorrelation function which quantifies the concentrated degree are slowly varied for small delay time. However, the mean of state variable is rapidly increased, and the normalized variance and the normalized autocorrelation function is rapidly decreased for large delay time.
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On the Physical Contents of the Light-Cone QCD Effective Hamiltonian on Meson Sector
WANG Shun-Jin, LI Lei, ZHOU Shan-Gui, ZHANG Guang-Biao
Chin. Phys. Lett. 2006, 23 (6):
1426-1429
.
To explore the physical contents of the light-cone QCD effective Hamiltonian on meson sector, the mass spectra of flavour off-diagonal mesons consisting of (u,d,s,c,b) quarks and mesons consisting of heavy quarks cc- and bb- are calculated relativistically and nonperturbatively. Numerical results show that the present light-cone QCD effective Hamiltonian without confining potentials and flavour mixing interactions can well describe the ground states but can not apply for the excited states of the mesons. This result may imply that (i) the confining potential is indispensable for the excited states of mesons, (ii) the valence quark qq1 subspace is only valid for ground states but not for excited states. The above information may be significant for improving the light-cone QCD effective Hamiltonian approach, especially showing the urgent need to implement a confining potential and to enlarge the subspace of the meson sector for a more appropriate description of the excited states of the mesons.
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Average Energy Loss Measured in Single and Double Electron Capture Collisions of He2+ on Ar at Low Velocities
LI Bin, MA Xin-Wen, ZHU Xiao-Long, LIU Hui-Ping, ZHANG Shao-Feng, QIAN Dong-Bin, CHEN Lan-Fang, FENG Wen-Tian, CAO Shi-Ping, SHA Shan, ZHANG Da-Cheng,
Chin. Phys. Lett. 2006, 23 (6):
1452-1455
.
Employing the recoil ion momentum spectroscopy we investigate the collision between He2+ and argon atoms. By measuring the recoil longitudinal momentum the energy losses of projectile are deduced for capture reaction channels. It is found that in most cases for single- and double-electron capture, the inner electron in the target atom is removed, the recoil ion is in singly or multiply excited states (hollow ion is formed), which indicates that electron correlation plays an important role in the process. The captured electrons prefer the ground states of the projectile. It is experimentally demonstrated that the average energy losses are directly related to charge transfer and electronic configuration
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Lengthening the Lifetime of Long Plasma Channel in Air Generated by Femtosecond Laser Pulse
CHEN Xiao, JIANG Hong-Bing, GONG Qi-Huang
Chin. Phys. Lett. 2006, 23 (6):
1482-1485
.
We theoretically investigate the lifetime of self-guided plasma channel in air by launching an auxiliary delayed long-pulsed laser beam following an ultrashort laser. A detailed model makes the electron--ion recombination, the attachment of electrons on neutral particles, and particularly the impact ionization and electron-detachment mechanism incorporate. The calculated results show that the temporal evolution of electron density is greatly flattened and broadened. When the auxiliary laser intensity exceeds the threshold 3.32×104Wcm-2, the channel lifetime is distinctly prolonged from nanosecond to microsecond, or even longer due to the electrical field enhancement. Furthermore, with the laser intensity up to 109Wcm-2, the impact ionization overwhelms the detachment in effect. Thus, it is an effective way to extend the channel lifetime and provides a real opportunity for applications.
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Poled Silica/DR1 Films with Thermally Stability and Large Electro-Optic Coefficient Applying in External Probe Tip
LIU Hong-Fei, HOU A-Lin, LIU Yun-Tao, ZHANG Da-Ming, CHUAI Xiao-Hong, YI Mao-Bin, SUN Wei
Chin. Phys. Lett. 2006, 23 (6):
1486-1489
.
Sol-gel-processed silica films doped with Disperse Red 1(DR1) were prepared at 80°C aging temperature and 120°C baking temperature with corona poling to obtain stable and large electro-optic (EO) coefficient and film strength. A large EO coefficient of γ33=56pm/V was measured for the film of 0.5-μm thickness at the wavelength of 1300nm, and the value was unvaried at room temperature. Moreover, an external EO probe tip using the film was fabricated for the first time, and a signal voltage level corresponding to the EO signal was calibrated successfully.
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Correlation between Post-LASIK Starburst Symptom and Ocular Wavefront Aberrations
LIU Yong-Ji, MU Guo-Guang, WANG Zhao-Qi, WANG-Yan
Chin. Phys. Lett. 2006, 23 (6):
1498-1500
.
Monochromatic aberrations in post laser in-situ keratomileusis (LASIK) eyes are measured. The data are categorized into reference group and starburst group according to the visual symptoms. Statistic analysis has been made to find the correlation between the ocular wavefront aberrations and the starburst symptom. The rms aberrations of the 3rd and 4th orders for the starburst group are significantly larger than those for the reference group. The starburst symptom shows a strong correlation with vertical coma, total coma, spherical aberrations. For 3-mm pupil size and 5.8-mm pupil size, the modulation transfer function (MTF) of the starburst group are lower than those of the reference group, but their visual acuities are close. MTF and PSF analyses are made for two groups, and the results are consistent with the statistical analysis, which means the difference between the two groups is mainly due to the third- and fourth-order Zernike aberrations.
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Optical Planar Waveguides in KTiOPO4 Crystals by MeV Oxygen Ion Implantation
CHEN Feng, WANG Xue-Lin, WANG Ke-Ming, WANG Lei, JIAO Yang, WANG Liang-Ling, LU Qing-Ming, MA Hong-Ji, NIE Rui
Chin. Phys. Lett. 2006, 23 (6):
1501-1503
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We report on the optical planar waveguide formation in KTiOPO4 crystals by single or double oxygen ion implantation at energies of 2.4--3.0MeV and doses of 1015ions/cm2. The dark-line spectroscopy properties are investigated by a prism-coupling method. With an effective refractive index method, the refractive index profiles of the waveguides are reconstructed. The program code TRIM’98 (transport of ions in matter) is used to simulate the implantation process of oxygen ions into the KTiOPO4 crystal. It is found that an inherent relationship exists between the nuclear damage and the refractive index changes induced by the ion-beam implantation.
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Heat Conduction and Characteristic Size of Fractal Porous Media
WANG Wei-Wei, HUAI Xiu-Lan, TAO Yu-Jia
Chin. Phys. Lett. 2006, 23 (6):
1511-1514
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Based on fractal theory, two types of random Sierpinski carpets (RSCs) and their periodic structures are generated to model the structures of natural porous media, and the heat conduction in these structures is simulated by the finite volume method. The calculated results indicate that in a certain range of length scales, the size and spatial arrangement of pores have significant influence on the effective thermal conductivity, and the heat conduction presents the aeolotropic characteristic. Above the length scale, however, the influence of size and spatial arrangement of pores on the effective thermal conductivity reduces gradually with the increasing characteristic size of porous media, the aeolotropic characteristic is weakened gradually. It is concluded that the periodicity in structures of porous media is not equal to the periodicity in heat conduction.
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Relativistic Electron Acceleration in a Wake Field Generated by the Intense Femtosecond Laser Interaction with a Mixture Jet of Deuterium Clusters and Molecules
LIU Hong-Jie, GU Yu-Qiu, ZHENG Zhi-Jian, JIAO Chun-Ye, NAM Sung-Mo, HAN Zai-Min, WANG Xiang-Xian, HE Ying-Ling, WEN Tian-Shu, ZHANG Shuang-Gen, WEN Xian-Lun, ZHOU Kai-Nan, WANG Xiao-Dong, HUANG Xiao-Jun, HUA Jian-Fei
Chin. Phys. Lett. 2006, 23 (6):
1527-1529
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High energy electron acceleration in a wake field generated in the intense ultrashort (30fs) laser pulse cluster gas jet interaction is experimentally demonstrated. Relativistic electrons with energy of 60MeV were observed. These high energy electrons split into two beams due to the relativistic self-focusing of the laser.
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Hydrogen Storage in Benzene Moiety Decorated Single-Walled Carbon Nanotubes
ZHANG Bing-Yun, LIANG Qi-Min, SONG Chen, XIA Yue-Yuan, ZHAO Ming-Wen, LIU Xiang-Dong, ZHANG Hong-Yu
Chin. Phys. Lett. 2006, 23 (6):
1536-1549
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The hydrogen storage capacity of (5, 5) single-walled carbon nanotubes (SWNTs) decorated chemically with benzene moieties is studied by using molecular dynamics simulations (MDSs) and density functional theory (DFT) calculations. It is found that benzene molecules colliding on (5, 5) SWNTs at incident energy of 50eV form very stable configurations of benzene moiety adsorption on the wall of SWNTs. The MDSs indicate that when the benzene moiety decorated (5, 5) SWNTs and a pristine (5, 5) SWNT are put in a box in which hydrogen molecules are filled to a pressure of ~26atm, the hydrogen storage capacity of the benzene moiety decorated (5, 5) SWNT is about 4.7wt.% and that of the pristine (5, 5) SWNT is nearly 3.9wt.%.
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Simulation of Temperature-Dependent Resistivity for Manganite La1/3Ca2/3MnO3
CAO Shuo, ZHOU Qing-Li, GUAN Dong-Yi, LU Hui-Bin, YANG Guo-Zhen
Chin. Phys. Lett. 2006, 23 (6):
1551-1553
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The resistivity of the heavy-doped La1/3Ca2/3MnO3 (LCMO) is simulated using a random resistor network model, based on a phase separation scenario. The simulated results agree well with the reported experimental data, showing a transition from a charge-disordered (CDO) state embedded with a few ferromagnetic (FM) metallic clusters to a charge-ordered (CO) state, corresponding to the transition from a high-temperature paramagnetic (PM) insulating state to a low-temperature antiferromagnetic (AF) insulating state. Furthermore, we find that the number of AF/CO clusters increases with decreasing temperature, and the clusters start to connect to each other around 250K, which causes percolating in the system. The results further verify that phase separation plays a crucial role in the electrical conductivity of LCMO.
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Influence of Mn-Doped Content on Ferromagnetism of Ga1-xMnxN Film Grown by LP-MOVPE
ZHANG Bin, YAO Shu-De, WANG Kun, DING Zhi-Bo, CHEN Zhi-Tao, SU Yue-Yong, ZHANG Guo-Yi, MA Hong-Ji, NIE Rui, ZHANG Ya-Wei
Chin. Phys. Lett. 2006, 23 (6):
1585-1587
.
The diluted magnetic semiconductor Ga1-xMnxN was achieved by low-pressure metal organic vapour-phase epitaxy (LP-MOVPE). Proton-induced x-ray emission was employed non-destructively, quickly and accurately to determine the Mn-doped content. The magnetic property was measured by a superconducting-quantum-interference-device (SQID) magnetometer. Apparent ferromagnetic hysteresis loops measured at or above room temperature are presented. No ferromagnetic secondary phases were detected by high-resolution x-ray diffraction. The experimental results show that the ferromagnetic signal firstly decreases and then increases with the increasing Mn-doped content from 0.23% to 4.69% and it is the weakest when Mn content is 0.51%. The annealing treatment could make the ferromagnetic property stronger.
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Electroluminescence of a Multi-Layered Organic Light-Emitting Diode Utilizing Trans-4-[p-[N-methyl-N-(hydroxymethyl)amino]styryl]-N-Methylphridinium Tetraphenylborate as the Active Layer
FENG Xue-Yuan, ZHANG Jia-Yu, XU Chun-Xiang, QIAO Yi, CUI Yi-Ping
Chin. Phys. Lett. 2006, 23 (6):
1607-1609
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Employing an organic dye salt of trans-4-[p-[N-methyl-N-(hydroxymethyl)amino]styryl]-N-methylphridinium tetra\-phenylborate (ASPT) as the active layer, 8-hydrocyquinoline aluminium (Alq3) as the electron transporting layer and N,N’-diphenyl-N,N’-bis(3-methylphenyl)-[1,1’-biphenyl]-4,4’-diamine (TPD) as the hole transporting layer, respectively, we fabricate a multi-layered organic light-emitting diode and observe the colour tunable electroluminescence (EL). The dependence of the EL spectra on the applied voltage is investigated in detail, and the recombination mechanism is discussed by considering the variation of the hole-electron recombination region.
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Structural and Optical Properties of Nanocrystal In2O3 Films by Thermal Oxidation of In2S3 Films
M. Ö, ztas, M. Bedir, Z. Ö, ztürk, D. Korkmaz, S. Sur
Chin. Phys. Lett. 2006, 23 (6):
1610-1012
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In2S3 nanocrystalline films are prepared on glass substrates by the spray pyrolysis technique using indium chloride and thiourea as precursors. The deposition is carried out at 350°C on glass substrates. The films are then annealed for two hour at 200, 400, 600, and 800°C in O2 flow. This process allows the transformation of nanocrystal In2O3 films from In2S3 films and the reaction completes at 600°C. These results indicate that the In2O3 film prepared by this simple thermal oxidation method is a promising candidate for electro-optical and photovoltaic devices.
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Theoretical Study on Absorption of Magnetically Tunable Terahertz Quantum-Well Photodetectors
CHEN Yu-Ling, GUO Xu-Guang, CAO Jun-Cheng
Chin. Phys. Lett. 2006, 23 (6):
1613-1615
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Because of the Zeeman splitting effect in diluted semiconductor (Zn,Cd,Mn)Se, the absorption spectrum of ZnSe/(Zn,Cd,Mn)Se quantum wells can be adjusted by magnetic field effectively. Within the effective-mass approximation, the conduction electronic structure and the absorption spectrum of ZnSe/(Zn,Cd,Mn)Se quantum wells subjected to in-plane magnetic fields are investigated. Our theoretical results show that it is possible to use the ZnSe/(Zn,Cd,Mn)Se quantum well as magnetically tunable terahertz photodetectors.
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Growth of Strain Free GaN Layers on (0001) Oriented Sapphire by Using Quasi-Porous GaN Template
XIE Xin-Jian, ZHONG Fei, QIU Kai, LIU Gui-Feng, YIN Zhi-Jun, WANG Yu-Qi, LI Xin-Hua, JI Chang-Jian, HAN Qi-Feng, CHEN Jia-Rong, CAO Xian-Cun
Chin. Phys. Lett. 2006, 23 (6):
1619-1622
.
We report the reduced-strain gallium-nitride (GaN) epitaxial growth on (0001) oriented sapphire by using quasi-porous GaN template. A GaN film in thickness of about 1μm was initially grown on a (0001) sapphire substrate by molecular beam epitaxy. Then it was dealt by putting into 45% NaOH solution at 100°C for 10min. By this process a quasi-porous GaN film was formed. An epitaxial GaN layer was grown on the porous GaN layer at 1050°C in the hydride vapour phase epitaxy reactor. The epitaxial layer grown on the porous GaN is found to have no cracks on the surface. That is much improved from many cracks on the surface of the GaN epitaxial layer grown on the sapphire as the same as on GaN buffer directly.
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Dielectric Properties of Fine-Grained BaTiO3 Ceramics under High Pressure
ZHU Jin-Long, XIAO Chang-Jiang, CHI Zhen-Hua, FENG Shao-Min, LI Feng-Ying, JIN Chang-Qing, DENG Xiang-Yun, WANG Xiao-Hui, LI Long-Tu, DAI Zhong-Hua, WANG Jun, XU Zhuo
Chin. Phys. Lett. 2006, 23 (6):
1631-1633
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We investigate the temperature dependence of the dielectric constant of BaTiO3 ceramic with coarse to nano-grain size under different hydrostatic high pressures up to 5000bar in the range between room temperature and 200°C. The ferroelectric-to-paraelectric phase transition temperatures Tc are determined from the peak of dielectric constant versus temperature. The values of average grain-size are estimated from the SEM images. It is found that the magnitude of dTc/dp varies considerably from sample to sample depending on grain size. The Curie point Tc of the sample with small grain size decreases more sharply than that of samples with larger one.
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Fabrication of c-Si:H(p)/c-Si(n) Heterojunction Solar Cells with Microcrystalline Emitters
ZHOU Bing-Qing, LIU Feng-Zhen, ZHANG Qun-Fang, XU Ying, ZHOU Yu-Qin, LIU Jin-Long, ZHU Mei-Fang
Chin. Phys. Lett. 2006, 23 (6):
1638-1640
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The p-type microcrystalline silicon (μc-Si:H) on n-type crystalline silicon (c-Si) heterojunction solar cells is fabricated by radio-frequency plasma enhanced chemical vapour deposition (rf-PECVD). The effect of the μc-Si:H p-layers on the performance of the heterojunction solar cells is investigated. Optimum μc-Si:H p-layer is obtained with hydrogen dilution ratio of 99.65%, rf-power of 0.08W/cm2, gas phase doping ratio of 0.125%, and the p-layer thickness of 15nm. We fabricate μc-Si:H(p)/c-Si(n) heterojunction solar cells without texturing and obtained an efficiency of 13.4%. The comparisons of the solar-cell performances using different surface passivation techniques are discussed.
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Vibrations in Magnet/Superconductor Levitation Systems
F. Y. Alzoubi, H. M. Al-khateeb, M. K. Alqadi, N. Y. Ayoub,
Chin. Phys. Lett. 2006, 23 (6):
1641-1644
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The problem of a small magnet levitating above a very thin superconducting disc in the Meissner state is analysed. The dipole--dipole interaction model is employed to derive analytical expressions for the interaction energy, levitation force, magnetic stiffness and frequency of small vibrations about the equilibrium position in two different configurations, i.e. with the magnetic moment parallel and perpendicular to the superconductor. The results show that the frequency of small vibrations decreases with the increasing levitation height for a particular radius of the superconducting disc, which is in good agreement with the experimental results. However, the frequency increases monotonically up to saturation by increasing the radius of the disc for a particular height of the magnet. In addition, the frequency of vibrations is higher when the system is in the vertical configuration than that when the system is in the horizontal configuration.
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Preparation and Raman Spectrum of Rutile Single Crystals Using Floating Zone Method
GUO Xing-Yuan, XU Da-Peng, DING Zhan-Hui, SU Wen-Hui,
Chin. Phys. Lett. 2006, 23 (6):
1645-1647
.
With anatase-type titanium dioxide as the raw materials, the rutile type titanium dioxide single crystal is prepared using the floating zone method. The results of XRD measurement show that the grown crystal is highly crystalline with a rutile structure, which has orientation to the c-axis. The four Raman vibration characteristic peaks (143, 240, 450 and 610cm-1) at room temperature show that the crystalline structure of the single crystal is a typical rutile phase, meanwhile a new Raman peak at around 690cm-1 is found. The results of the Raman measurement at various temperatures for the single crystal show that the Raman frequency shifts are different.
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Fusion Reaction of 16O+14N and Its Implication for the Production of 26Al in Explosive Oxygen Burning
WANG Peng, PENG Qiu-He, , ZHANG Shui-Nai, LUO Xin-Lian
Chin. Phys. Lett. 2006, 23 (6):
1652-1654
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We suggest that the fusion reaction 16O+14N may be a new way to produce 26Al in interstellar medium. Adopting different mixing modes, we investigate the impact on the production of 26Al in explosive oxygen burning and find that the result is extremely sensitive to mixing mechanisms. In some cases, we obtain an encouraging result, for example, the greatest final abundance of 26Al reaches 7.779×10-6, which means that the explosive oxygen burning may be a new origin of 26Al.
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83 articles
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