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Volume 20 Issue 4
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Original Articles
Raman Spectroscopy of Water up to 6 kbar at 290 K
SUN Qiang, ZHENG Hai-Fei, XU Ji-An, XIE Hong-Sen, E. Hines
Chin. Phys. Lett. 2003, 20 (4): 445-447 .  
Abstract   PDF(pc) (388KB) ( 523 )
We study the Raman scattering of the stretching band from liquid water under pressure up to 6 kbar at 290 K. The result shows that the (v1)max intensity decreases with increasing pressure initially and reaches the minimum at about 2 kbar, and increases with the further increase of pressure up to about 4 kbar, then decreases again with the increasing pressure up to 6 kbar. This is in agreement with the behaviour of the average separation rOO between the nearest molecules under pressure. Additionally, the influence of pressure on water structure is also discussed.

Chaotic Dynamical Behaviour in Soliton Solutions for a New (2+1)-Dimensional Long Dispersive Wave System
ZHANG Jie-Fang, ZHENG Chun-Long, MENG Jian-Ping, FANG Jian-Ping
Chin. Phys. Lett. 2003, 20 (4): 448-451 .  
Abstract   PDF(pc) (665KB) ( 711 )
With the help of variable separation approach, a quite general excitation of a new (2+1)-dimensional long dispersive wave system is derived. The chaotic behaviour, such as chaotic line soliton patterns, chaotic dromion patterns, chaotic-period patterns, and chaotic-chaotic patterns, in some new localized excitations are found by selecting appropriate functions.
Thermal Entanglement in Spin-Dimer V4+ with a Strong Magnetic Field
ZHANG Guo-Feng, LIANG Jiu-Qing, YAN Qi-Wei
Chin. Phys. Lett. 2003, 20 (4): 452-455 .  
Abstract   PDF(pc) (370KB) ( 567 )
We study the entanglement in Heisenberg dimer single molecular magnets V4+ with a strong magnetic field by means of the measure of entanglement called “concurrence”and find that thermal entanglement exists for both the ferromagnetic (FM) and antiferromagnetic (AFM) cases. In the FM case, entanglement vanishes for anisotropic parameter λ = 0 while in the AFM case, entanglement exits in the whole region of anisotropic parameter 0 ≤ λ ≤ 1. Entanglement variations with anisotropic parameter λ, magnetic field B and temperature T are evaluated. We find a critical magnetic field at which the concurrence changes sharply from zero to maximum entanglement.

Coherent Control of Transmission Probability of a Cold Atom Through Microcavity Potentials
HE Xiao-Ling, DU Si-De, CHEN Hao, LU Jing
Chin. Phys. Lett. 2003, 20 (4): 456-458 .  
Abstract   PDF(pc) (304KB) ( 519 )
We investigate the transmission probability of a two-level cold atom through a quantum microcavity when the atom is initially prepared in a coherent superposition of its excited state and ground state. We can control the transmissibility of the atom by this initial coherence. Remarkable step and switch effect are discovered in the atomic transmission for the case of weak and intense quantized fields, respectively.

Quantum Correction to Entropy of the Kerr Black Hole due to Rarita-Schwinger Fields
JING Ji-Liang
Chin. Phys. Lett. 2003, 20 (4): 459-461 .  
Abstract   PDF(pc) (212KB) ( 579 )
Quantum correction to entropy of the Kerr black hole arising from Rarita-Schwinger fields is studied by using the Newman-Penrose formalism and brick-wall model. It is shown that contribution of spin to the logarithmic term of the quantum correction is dependent on both the square of spin of the particle and the rotation of the black hole. For different values of a/r+, the subleading term can increase or decrease, or cannot affect the entropy.

Ellipsometric Evaluation of the sp3-Bonded Carbon Fraction in Carbon Thin Films
MO Dang, LI Fang, CHEN Di-Hu, WEI Ai-Xiang,
Chin. Phys. Lett. 2003, 20 (4): 462-464 .  
Abstract   PDF(pc) (303KB) ( 529 )
We prepared amorphous carbon films on Si (100) substrates by using a magnetic-field-filtered plasma stream deposition system. Various samples with different sp3-bonded carbon fraction were obtained by changing the bias voltage applied to the substrates. We measured the ellipsometric spectra of various carbon film samples in the photon energy range of 2.0-5.0 eV. We also measured the Raman spectra for comparison. Our results show that the ellipsometric spectra are dependent on the sp3 carbon fraction. We analysed the measured ellipsometric spectra by a simple method, and determined the sp3 carbon fraction semi-quantitatively. The results from the ellipsometry and the Raman spectroscopy show the same tendency of the sp3 carbon fraction as a function of bias voltage. We found that the spectroscopic ellipsometry is a relatively simple, non-destructive method to evaluate the sp3 carbon fraction of the amorphous carbon films.
Mapping Nanoscale Domains in a Sol-Gel-Derived (Pb,La) (Zr, Ti)O3 Thin Film Using Atomic Force Microscopy
BA Long, SHU Jian, SUN Ping, LU Zu-Hong
Chin. Phys. Lett. 2003, 20 (4): 465-468 .  
Abstract   PDF(pc) (352KB) ( 652 )
Local polarization of a sol-gel-derived (Pb,La)(Zr,Ti)O3 thin film is studied from its piezoelectric response measured by using atomic force microscopy. Topographic and piezoelectric images show that the domain sizes of spontaneous polarization and grain sizes are both within the range of tens to hundreds of nanometers. Nanosized domain arrays have been written in an unpoled region to realize data storage by applying pulse voltage. The results show that the domain sizes grow exponentially when the pulse duration increases.

Green’s Function Method for Perturbed Korteweg-de Vries Equation
CAI Hao, HUANG Nian-Ning
Chin. Phys. Lett. 2003, 20 (4): 469-472 .  
Abstract   PDF(pc) (192KB) ( 524 )
The x-derivatives of squared Jost solution are the eigenfunctions with the zero eigenvalue of the linearized equation derived from the perturbed Korteweg-de Vries equation. A method similar to Green’s function formalism is introduced to show the completeness of the squared Jost solutions in multi-soliton cases. It is not related to Lax equations directly, and thus it is beneficial to deal with the nonlinear equations with complicated Lax pair.

Quenched Chiral Logarithm Diverge in Very Light Quark Region from the Overlap Lattice Quantum Chromodynamics
YING He-Ping, DONG Shao-Jing, ZHANG Jian-Bo,
Chin. Phys. Lett. 2003, 20 (4): 473-474 .  
Abstract   PDF(pc) (286KB) ( 524 )
With an exact chiral symmetry, overlap fermions allow us to reach very light quark region. In the minimum mps = 179 MeV, the quenched chiral logarithm diverge is examined. The chiral logarithm parameter δ is calculated from both the pseudo-scalar meson mass m2ps diverge channel and the pseudo-scalar decay constant fP channel. In both the cases, we obtain δ = 0.25±0.03. We also observe that the quenched chiral logarithm diverge occurs only in the mps ≤ 400 MeV region.

Lifetimes of High Spin Yrast States in Odd-Proton Nucleus 131Pr
LI Guang-Sheng, MENG Rui, ZHU Li-Hua, ZHANG Zhen-Long, WANG Yue, WANG Zhi-Min, WEN Shu-Xian, LU Jing-Bin, ZHAO Guang-Yi, LI Xian-Feng, WEN Li-Jun, ZHENG Yong-Nan, ZHENG Yong, LIU Yun-Zuo, YUAN Guan-Jun, YANG Chun-Xiang
Chin. Phys. Lett. 2003, 20 (4): 475-477 .  
Abstract   PDF(pc) (311KB) ( 585 )
Lifetimes of the high spin yrast states in the odd-proton nucleus 131Pr have been determined by analysing the Doppler broadened line shapes for the de-exciting γ-rays following the 116Sn(19F, 4n)131Pr reaction at a bombarding energy of 95 MeV. The transition quadrupole moments extracted from the measured lifetimes exhibit a considerable reduction near the rotational frequency of 0.42 MeV, at which the J(1) and J(2) moments of inertia indicate a band crossing. The experimental result demonstrates occurrence of the nuclear shape change induced by band crossing associated with the alignment of a pair of h11/2 protons.
Properties of the First 1/2+ Excitation State of 13C by 22 MeV Proton Inelastic Scattering
AN Zhu, CHEN Quan, CHENG Ye-Hao, SHEN Dong-Jun, GUO Gang
Chin. Phys. Lett. 2003, 20 (4): 478-481 .  
Abstract   PDF(pc) (380KB) ( 422 )
The differential cross sections of 22 MeV proton inelastic scattering for the first 1/2+ excitation state (Ex = 3.09 MeV) of 13C have been measured between 9°and 130°. The broad peak located at ~ 120°, which has been systematically observed in the 0+ → 0-, 1/2- → 1/2+, and 1+ → 1- transitions for the 16O, 13C, and 14,15N (p,n) charge exchange reactions at Ep = 35 MeV, has been observed for the first time in the present proton inelastic scattering. The present experimental data are analysed by using microscopic distorted-wave Born approximation. From the comparison of present experimental data and theoretical results at forward angles, our analysis indicates the existence of neutron halo in the first 1/2+ excitation state of the 13C nucleus. In addition, by reasonable modification of shell model wavefunction of the first 1/2+ excitation state, we can well describe the experimental form factors of (e,e') and the experimental differential cross sections of (p,p') at incident energy of 547 MeV.

Influence of Neutron Shell Closure (Nc = 126) on Prescission Particle Emission of Fissioning Systems 216,224Th
YE Wei
Chin. Phys. Lett. 2003, 20 (4): 482-485 .  
Abstract   PDF(pc) (267KB) ( 684 )
The effect of neutron shell closure Nc = 126 on the prescission particle emission of 126Th and 224Th nuclei is investigated within the framework of an extensive Smoluchowski equation. It is found that there is a large difference in the prescission neutron multiplicity for the two Th nuclei, indicating a strong shell effect in neutron emission. Moreover, shell effects on particle emission are also investigated as functions of excitation energy, angular momentum and nuclear viscosity. The results show that with increasing excitation energy shell effects in prefission neutron evolve from continual strongness to gradual weakness. Both high angular momenta and low viscosity weaken the shell effects on the particle emission.
One-Turn Map of Storage Ring with Insertion Devices
LI Yong-Jun
Chin. Phys. Lett. 2003, 20 (4): 486-488 .  
Abstract   PDF(pc) (172KB) ( 427 )
Considering that the one-turn map can provid a useful and powerful tool to understand the nonlinear dynamics in a designing storage ring dedicated to synchrotron radiation and in a damping ring used as the pre-injector of linear collider, we first expand the Hamiltonian of a charged particle moving along the insertion device (ID) axis to the fourth-order Taylor series, and then construct a second-order symplectic integrator using the Lie map product for the particle passing through one period of the ID. The one-turn map can be obtained by concatenating the Lie map of the whole ID and the rest part of ring.

Density Distributions of H and H2 in Pulsed Microwave Hydrogen Plasmas
DUAN Xu-Ru, H. Lange, QIAN Shang-Jie, N. Lang
Chin. Phys. Lett. 2003, 20 (4): 489-492 .  
Abstract   PDF(pc) (452KB) ( 740 )
Temporal distribution of the H atom and H2 densities in a pulsed microwave hydrogen plasmas has been measured simultaneously by two-photon absorption laser-induced fluorescence (TALIF). The measurement of the H-atom absolute density obtained by NO2 titration in a flow tube reactor shows that the density of H2 could be determined by the measured effective lifetime of the TALIF signal via the quenching equation. The H-atom density of about 1.5 x 1015cm-3 in both pulsed and stationary phases does not obviously change. It is found that the gas temperature volume effect plays an important role in governing the distributions of the H-atom density and it is mole fraction. The calculated gas temperature is in good consistent with the rotational temperature of H2 measured by optical emission spectroscopy in pulsed phase.

Computation for High Excited Stark Levels of Hydrogen Atoms in Uniform Electric Fields
Chin. Phys. Lett. 2003, 20 (4): 493-495 .  
Abstract   PDF(pc) (228KB) ( 486 )
We present a new method for the numerical calculation of exact complex eigenvalues of Schrödinger equations for a hydrogen atom in a uniform electric field. This method allows a direct calculation for complex eigenvalues without using any auxiliary treatment, such as the Breit-Wigner parameterization and the complex scale transformation, etc. The characteristics of high excited atoms in electric field have attracted extensive interest in experimental aspect, however, the existing theoretical calculation is only up to n = 40. Here we present the computation results ranging from n = 1 to 100. The data for n ≤ 40 are in agreement with the results of other researchers.
Theoretical Manifestation of the Broadening Effect on Photoelectron Angular Distributions
ZHANG Jing-Tao, ZHOU Lan, ZHANG Wen-Qi, XU Zhi-Zhan, GUO Dong-Sheng, R. R. Freeman
Chin. Phys. Lett. 2003, 20 (4): 496-498 .  
Abstract   PDF(pc) (216KB) ( 476 )
The broadening effect in photoelectron angular distributions (PADs) observed by Freeman et al. is studied theoretically. Using a nonperturbative scattering theory developed for multiphoton ionization with the inclusion of spontaneous emission, we calculate the PADs for above-threshold ionization (ATI) peaks. The numerical calculations from our theory reproduce the kinetic-energy dependence and the laser-intensity dependence of PADs of ATI peaks observed by Freeman et al., [Phys. Rev. Lett. 57 (1986) 3156] and provide an evidence for the existance of the ponderomotive momentum of intense laser fields.
Quantum Electrodynamics Theory of Laser Assisted Recombination
AO Shu-Yan, CHENG Tai-Wang, LI Xiao-Feng, PAN Shou-Fu, FU Pan-Ming
Chin. Phys. Lett. 2003, 20 (4): 499-501 .  
Abstract   PDF(pc) (339KB) ( 557 )
Using a formal scattering theoretical approach, we develop a nonperturbative quantum electrodynamics theory to describe laser assisted recombination (LAR), in which an electron initially in the quantized Volkov state recombines with an ion and emits a high energy photon with frequency defined by energy conservation laws. The transition probability is expressed as an analytic closed form and the spectrum of LAR reflects mainly the properties of general Bessel functions. For the case of a fast electron the LAR spectrum is confined in a well-defined range, while for a slow electron, the LAR spectrum exhibits a double-plateau structure.

Simulation of Low-Grazing Scattering Properties of Vegetation
ZHANG Min, SONG Yue-Xia, WU Zhen-Sen, MA An-Ying
Chin. Phys. Lett. 2003, 20 (4): 502-505 .  
Abstract   PDF(pc) (626KB) ( 357 )
The Monte Carlo method is applied to study the low-grazing scattering from a vegetation medium. Based on the two-layer model, phase of different fields and volume-surface scattering interaction are taken into account. The scattering coefficient is obtained. The numerical results are in agreement well with the measured data and the vector radiative transfer theory. The results are aslo used to explain the backscattering enhancement and the grazing incidence characteristic.

Yb3+-Doped Four-Wavelength Double Clad Laser
XU Zhao-Wen, XIANG Yang, NING Ding, FAN Wan-De, YANG Shi-Quan, YUAN Shu-Zhong, DONG Xiao-Yi
Chin. Phys. Lett. 2003, 20 (4): 506-508 .  
Abstract   PDF(pc) (506KB) ( 501 )
A novel Yb3+-doped four-wavelength double clad fibre laser based on a Fabry-Parot filter, and pumped by a 976 nm laser diode is presented. Its output laser wavelengths are 1085, 1090, 1095, and 1010 nm, respectively. The laser exhibits 0.32 nm line-width, 1.5 W laser output power, 40 dB signal-to-noise ratio and 66% slope efficiency.

Influence of Nonlinear Absorption on Z-Scan Measurements of Nonlinear Refraction
LIU Zhi-Bo, TIAN Jian-Guo, ZANG Wei-Ping, ZHOU Wen-Yuan, ZHANG Chun-Ping, ZHANG Guang-Yin
Chin. Phys. Lett. 2003, 20 (4): 509-512 .  
Abstract   PDF(pc) (451KB) ( 454 )
A simple division of close-aperture Z-scan curve by open-aperture Z-scan is conveniently used to obtain the nonlinear refractive index. It usually causes an error, which even reaches up to over 50% for Z-scan measurements with a pinhole or a medium with a high nonlinear absorption. Here the influence of nonlinear absorption on the determination of nonlinear refraction by Z-scan is analysed. We suggest that the error can be reduced greatly by a simple analysis of the symmetric features (symmetric method) of Z-scan curves from the
closed-aperture Z-scan curve. As an example, experiments were carried out on CS2 solution of C60 derivative, symmetric method agrees well with exact simulation.

Spectral, Thermal and Green-Light Static Recording Properties of Nickel Phthalocynine Thin Film
WU Yi-Qun, WANG Yang, GU Dong-Hong, GAN Fu-Xi
Chin. Phys. Lett. 2003, 20 (4): 513-515 .  
Abstract   PDF(pc) (357KB) ( 544 )
We study the absorption and transmission spectra, the thermal stability and the green-light (514.5 nm) static optical recording properties of nickel phthalocyanine (NiPc) thin film. It is found that this film occupies suitable absorption and transmission properties, excellent thermal stability (decomposition point > 600°C) and outstanding thermal decomposition characteristics (weight loss in one step decomposition > 60%) for green-light (514.5 nm) optical recording. High reflectivity contrast (> 50%) was obtained at low writing power (5 mW) and short writing pulsewidth (100 ns) using an Ar+ laser (514.5 nm) irradiation. Compared with azo in polymer films, the subphthalocyanine film and Sb-Te-Based phase change films, the NiPc film has better green-light static recording properties. These results indicate that metal phthalocyanine is not only a qualified material for near infrared optical recording but also a promising recording medium candidate for green-light DVD-R.

Photonic Band Gaps in Two-Dimensional Crystals with Fractal Structure
LIU Zheng, XU Jian-Jun, LIN Zhi-Fang
Chin. Phys. Lett. 2003, 20 (4): 516-518 .  
Abstract   PDF(pc) (440KB) ( 664 )
We simulate the changes of the photonics band structure of the crystal in two dimensions with a quasi-fractal structure when it is fined to a fractal. The result shows that when the dielectric distribution is fined, the photonic band structure will be compressd on the whole and the ground photonics band gap (PBG) closed while the next PBGs shrinked, in conjunction with their position declining in the frequency spectrum. Furthermore, the PBGs in the high zone are much more sensitive than those in low zones.
A Two-Dimensional Nonlinear Photonic Crystal with a Rectangular Loop
NI Pei-Gen, MA Bo-Qin, CHENG Bing-Ying, ZHANG Dao-Zhong
Chin. Phys. Lett. 2003, 20 (4): 519-521 .  
Abstract   PDF(pc) (339KB) ( 557 )
A novel model of two-dimensional periodically poled lithium niobate designed for second harmonic generation of 1064 nm is proposed, in which a rectangular light route is used. The effective length of the sample is longer than the sample real length by 5/3 21/2 times. The conversion efficiency enhances greatly without prolonging the periodically poled crystal length.

Impact of Polarization Mode Dispersion on Transmission Characteristics of Dispersion-Managed Solitons and Its Suppression
YANG Xiang-Lin, XU Ming, CAI Ju
Chin. Phys. Lett. 2003, 20 (4): 522-525 .  
Abstract   PDF(pc) (290KB) ( 598 )
The coupled nonlinear Schrödinger equations for dispersion-managed soliton (DMS) with the impact of the polarization mode dispersion (PMD) are constructed, and a PMD-suppression approach of DMS is proposed for the first time. Then, based on variational method, the analytical equations of the DMS transmission system with in-line optical filter control are obtained. Finally, in order to investigate the validity of the equations, we present an application sample for practical systems with in-line filter control. The results verify that the control is quite effective and valid.

Influence of Aspect Ratio on the Onset of Thermocapillary Oscillatory Convection in a Floating Half Zone of Large Prandtl Number Fluid
TANG Ze-Mei, HU Wen-Rui
Chin. Phys. Lett. 2003, 20 (4): 526-528 .  
Abstract   PDF(pc) (250KB) ( 501 )
The onset of oscillatory thermocapillary convection in a floating half zone of 10 cst silicon oil (Prandtl number 105.6) is studied by the three-dimensional and unsteady numerical simulation in microgravity environment (g = 10-4 gearth). The results show that the steady and axi symmetric convection, for a fixed liquid bridge volume ratio Vl/V0 = 1, transits directly to the oscillatory convection if geometrical aspect ratio A is larger than the critical value Ac = 1.25, but transits to the oscillatory convection via the steady and non-axisymmetric flow if A is smaller than the critical value Ac. The result means that there are two bifurcation transitions in a liquid bridge of the large Prandtl number fluid with a smaller aspect ratio A.

Theoretical Calculations of Isoelectronic Line-Ratio for Plasma Electron Temperature Diagnosis
WU Ze-Qing, HAN Guo-Xing, YAN Jun, PANG Jin-Qiao
Chin. Phys. Lett. 2003, 20 (4): 529-532 .  
Abstract   PDF(pc) (469KB) ( 390 )
A model is developed to calculate the emission spectrum of non-local thermodynamic equilibrium (LTE) plasmas. The Collisional-Radiative model is adopted for non-LTE population calculations. Configuration-averaged rate coefficients that are needed in the rate equations are obtained based on the first-order perturbation theory. The Hatree-FockSlater self-consistent-field method is used to calculate electron wave functions. The present model is applied to the calculation of isoelectronic line-ratio of Cr and Ti, which is usful for plasma electron temperature diagnosis.

Electron-Acoustic Compressive Soliton and Electron Density Hole in Aurora
Chin. Phys. Lett. 2003, 20 (4): 533-536 .  
Abstract   PDF(pc) (342KB) ( 497 )
Electron-acoustic solitary waves have been studied in an electron-beam plasma system. It is found that the solution of compressive soliton only exists within a limited range of soliton velocity around the electron beam velocity. A compressive electron-acoustic soliton always accompanies with a cold electron density hole. This theoretical model is used to explain the‘fast solitary wave’event observed by the FAST satellite in the mid-altitude auroral zone.

Start-Time of Magnetic Reconnection in Interplanetary Space
FAN Quan-Lin, WEI Feng-Si, FENG Xue-Shang
Chin. Phys. Lett. 2003, 20 (4): 537-540 .  
Abstract   PDF(pc) (813KB) ( 553 )
Start-time of magnetic reconnection under typical interplanetary parameters has been numerically simulated by using the two-dimensional compressible magnetohydrodynamic equations with a third-order compact upwind scheme. Magnetic reconnection would occur near the interplanetary current sheet impacted by a plasmoid. Its initiation is associated with the interplanetary plasma parameter β and the momentum of the plasmoid. The higher the β value is, the faster the reconnection takes place. Meanwhile the reconnection occurs earlier with the increase of the plasmoid momentum, and the increase of driving velocity is more effective in initializing the reconnection than that of the plasma density when the other factors are kept to be the same. The evolution of the reconnection with the heliocentric distance is also investigated.
Shock-Accelerated Flying Foil Diagnostic with a Chirped Pulse Spectral Interferometry
CHEN Jian-Ping, LI Ru-Xin, ZENG Zhi-Nan, WANG Xing-Tao, CHENG Chuan-Fu, XU Zhi-Zhan
Chin. Phys. Lett. 2003, 20 (4): 541-543 .  
Abstract   PDF(pc) (293KB) ( 504 )
A shock-accelerated flying foil is diagnosed with a chirped pulse spectral interferometry. The shock is pumped by a 1.2 ps chirped laser pulse with a power of ~ 1014W/cm2 at 785 nm irradiating on a 500 nm aluminum film and detected by a probe pulse split from the pump based on a Michelson spectral interferometry. A flying foil of ~ 5.595 x 10-6g in ~ 400μm diameter was accelerated to ~ 165 nm away from the initial target rear surface at ~ 1.83km/s before ablation.

Additional Beta due to Fast Fusion Products in D-3He Fusion Plasma
DENG Bai-Quan, G. A. Emmert, PENG Li-Lin
Chin. Phys. Lett. 2003, 20 (4): 544-546 .  
Abstract   PDF(pc) (263KB) ( 559 )
An analytical formula for the additional beta due to fast fusion-born ions is derived by using the slowing-down approximation from the Fokker-Planck equation under the assumption of negligible loss term. It is found that the fast ion beta in a D-3He fusion plasma at a typical temperature of 55 keV is about 20% of the thermal beta, which is the same ratio as that obtained in a D-T plasma at 20 keV.
Energy Distribution of Recycling Particles in Front of the Limiter and the Wall on the HT-7 Tokamak
XU Wei, WAN Bao-Nian, ZHOU Qian, WU Zhen-Wei, MAO Jian-Shan, LI Jian-Gang
Chin. Phys. Lett. 2003, 20 (4): 547-549 .  
Abstract   PDF(pc) (424KB) ( 549 )
The Hα(Dα) line shape in front of the limiter and the wall is measured by two sets of optical spectroscopy multi-channel analysers. The energy distribution is derived directly from the Hα(Dα) line shape, especially showing several molecular processes. The dissociative excitation of molecules is dominating when the local electron temperature is above 10 eV. The Dα line shape is also simulated by the Monte Carlo method, the result shows that the molecular dissociation contributes 57% neutral atoms, 53% emission intensity in front of the limiter, and 85\% neutral atoms, 82% emission intensity in front of the wall. The power loss from molecular dissociation is about 5.6 x 104kW/m-3 and the molecular dissociation is an important cooling mechanism at the plasma edge.
Quasi-One-Dimensional Solid Lattice and Liquid Hydrogen in Single-Walled Carbon Nanotubes
YING Min-Ju, XIA Yue-Yuan, ZHAO Ming-Wen, LIU Xiang-Dong, LI Feng, HUANG Bo-Da, TAN Zhen-Yu
Chin. Phys. Lett. 2003, 20 (4): 550-553 .  
Abstract   PDF(pc) (503KB) ( 559 )
We study the H2 molecules confined in single-walled carbon nanotubes by using molecular dynamics simulations and ab initio calculations. It is found that the H2 molecules at zero-temperature with low density tend to condense. When the linear density of the H2 molecules in the tube increases, various quasi-one-dimensional solid lattices can be observed at low temperature. When the lattices are heated above room temperature, molecular H2 liquids with different density can be observed. The quenching behaviour of the H2 fluids is also examined.

An Envelope Soliton in a Nonlinear Chain with the Power-Law Dependence of Long-Range Interaction
WANG Deng-Long, YAN Xiao-Hong, TANG Yi
Chin. Phys. Lett. 2003, 20 (4): 554-556 .  
Abstract   PDF(pc) (217KB) ( 468 )
We study the Fermi-Pasta-Ulam lattice model in the presence of a power-law dependence of long-range interaction by virtue of the method of multiple scales. Our results show that an envelope soliton still appears, but it is of different property for the group velocity compared with that of the soliton in the model when long-range interaction is absent.
Features of Vortex States in Quantum Dots
HUANG Gang-Ming, LIU Yi-Min, BAO Cheng-Guang
Chin. Phys. Lett. 2003, 20 (4): 557-560 .  
Abstract   PDF(pc) (420KB) ( 564 )
We study the physics of the formation of vortex states. It is found that the formation of vortex states is affected by two factors, one is the center-of-mass (c.m.) motion, the other is the constraints imposed by symmetry. Only if the vortex structure does not violate the symmetry constraints and is relatively lower in potential energy, it would appear in the first-states.
Quantum Fluctuations of a Mesoscopic Capacitance Coupled Circuit with Power Source
ZHANG Shou, ZHAO Yong-Fang, JING Xiao-Gong, QIAN Zheng-Nan, SU Wen-Hui
Chin. Phys. Lett. 2003, 20 (4): 561-563 .  
Abstract   PDF(pc) (215KB) ( 562 )
Starting from classical equations of motion of the charges, we obtain the quantum fluctuations of the charges, and the currents of a mesoscopic capacitance coupled circuit with power source by using a canonical transformation and a unitary transformation. The uncertainty relations between charges and conjugate currents do not satisfy the minimum uncertainty relation, and is independent of the power source.

Influence of Gd Doping at A Site upon the Magnetic Structure of La0.7-xGdxSr0.3MnO3 Systems
PENG Zhen-Sheng, LIU Ning, CAI Zhi-Rang, GUO Huan-Yin, TONG Wei, ZHANG Chang-Jing, ZHANG Yu-Heng
Chin. Phys. Lett. 2003, 20 (4): 564-567 .  
Abstract   PDF(pc) (798KB) ( 555 )
We investigated the magnetism of systems La0.7-xGdxSr0.3MnO3 (x = 0.00, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70) by M-T curves, M-H curves, and electron-spin-resonance (ESR) spectra. The experimental results indicate that the system is in a ferromagnetic long-range order at low-doping level; the samples of x = 0.30 and 0.40 show cluster-spin glass behaviour; and the antiferromagnetic characters are observed at ≥ 0.50. For the samples of x = 0.30 and 0.40, the ESR spectra demonstrate that the phase separation occurs above the Curie temperature.

Preparation and Characterization of GaN Nanowires
XUE Cheng-Shan, YANG Ying-Ge, MA Hong-Lei, ZHUANG Hui-Zhao, MA Jin
Chin. Phys. Lett. 2003, 20 (4): 568-570 .  
Abstract   PDF(pc) (282KB) ( 476 )
GaN Nanowires were prepared by the post-nitridation technique. The morphology and structure of GaN nanowires are investigated by transmission electron microscopy and scanning electron microscopy. A strong blue photoluminescence is observed for room-temperature measurement, which attributes to electron transition from DX center to valence band.
Local Structure of Niobate-Phosphate Glass Using Eu3+ Ion Fluorescence
XIA Hai-Ping, SONG Hong-Wei, WANG Ji-Wei, ZHANG Jian-Li, WANG Jin-Hao, ZHANG Jia-Hua, NIE Qiu-Hua, XU Tie-Feng
Chin. Phys. Lett. 2003, 20 (4): 571-574 .  
Abstract   PDF(pc) (493KB) ( 603 )
The niobate phosphate glasses containing Eu3+ ions were fabricated by the melting method. The fluorescence characteristics of the glass at temperatures from 77 K to 700 K were investigated under the excitation of 488 nm light. The results show that the fluorescence intensity of Eu3+ ions first increases and then decreases as temperature increases. The temperature-dependent parameters of the crystal fields and the local structure surrounding Eu3+ ions were investigated and discussed from the situation of splitting energy level of 5D0-7F1. The results indicate that the distance of europium and oxygen become shorter with the increase of temperature and the coordination number of Eu3+ ion is near 8, which does not change with temperature.

Effect of Water Vapor to Temperature Inside Sonoluminescing Bubble
AN Yu, XIE Chong-Guo, YING Chong-Fu
Chin. Phys. Lett. 2003, 20 (4): 575-578 .  
Abstract   PDF(pc) (613KB) ( 517 )
Using the model based on the homo-pressure approximation, we explain why the maximum temperature is sensitive to the ambient temperature in the single bubble sonoluminescence. The numerical simulation shows that the maximum temperature inside a sonoluminescing bubble depends on how much water vapor evaporates or coagulates at the bubble wall during the bubble shrinking to its minimum size. While the amount of water vapor inside the bubble at the initial and the final state of the compression depends on the saturated water vapor pressure which is sensitive to the ambient temperature. The lower the saturated vapor pressure is, the higher the maximum temperature is. This may lead to more general conclusion that those liquids with lower saturated vapor pressure are more favorable for the single bubble sonoluminescence. We also compare those bubbles with different noble gases, the result shows that the maximum temperatures in the different gas bubbles are almost the same for those with the same ambient temperature.

Nano-crystalline CNx Films and Field Electron Emission Properties
HANG Lan, MA Hui-Zhong, LI Hui-Jun, YANG Shi-E, YAO Ning, HU Huan-Ling, ZHANG Bing-Lin
Chin. Phys. Lett. 2003, 20 (4): 579-581 .  
Abstract   PDF(pc) (379KB) ( 578 )
CNx films with x ≈ 0.5 were prepared onto a titanium coated ceramic substrate by using microwave plasma enhanced chemical vapor deposition. As-deposited films were studied by x-ray photoelectron spectroscopy (XPS), x-ray diffraction, and scanning electron microscopy. The films consist of nano-crystalline grains with sites in a range of 20-40nm approximately. The interplanar distance (d-value) of the nano-crystalline structure determined from the peak position of x-ray diffraction was found to be 0.336 nm. This value is consistent with the d-value of graphite. XPS measurements of the N 1 s and C 1 s core levels for the same sample demonstrate two types of bonding structures between carbon and nitrogen atoms, corresponding to sp2 C-N and sp3 C-N. It is suggested that the N atoms mainly exist in aromatic rings of the nano-graphite layers by substituting carbon positions with nitrogen. Field electron emission characteristics of the film were tested. The turn-on field of the emission was as low as 1.1V/μm.

Characterizations of Cubic ZnMgO Films Grown on Si(111) at Low Substrate Temperature
QIU Dong-Jiang, WU Hui-Zhen, CHEN Nai-Bo, XU Tian-Ning
Chin. Phys. Lett. 2003, 20 (4): 582-584 .  
Abstract   PDF(pc) (330KB) ( 650 )
Cubic ZnMgO thin films in the (100) orientation were grown on Si (111) substrates by reactive electron beam evaporation at low substrate temperature. X-ray photoelectron spectroscopy (XPS) analyses show that Mg content as high as 75 at.% in the cubic ZnMgO film can be obtained. Secondary ion mass spectroscopy (SIMS) measurement indicates the evidence of Mg richness in the interface between the ZnMgO film and the Si substrate, and it is probably the primary reason to form the MgO-like cubic ZnMgO structures rather than the wurtzite one. The optical band gap of cubic ZnMgO is estimated to be 5.76 eV, which was measured by the transmission spectrum of the cubic ZnMgO film grown on the sapphire substrate under the same growth condition with that on Si (111). The band gap is of 2.39 eV blue shifted compared with that of ZnO (3.37 eV), which should render applications in the fabrication of ZnMgO-related heterostructures.
Correlated Noise Effects on Gene Expression
WANG Xian-Ju, AI Bao-Quan, LIU Guo-Tao, LIU Liang-Gang
Chin. Phys. Lett. 2003, 20 (4): 585-588 .  
Abstract   PDF(pc) (494KB) ( 474 )
Based on the model describing the regulation of the PRM operator region of λ phage proposed by Hasty et al. [Proc. Nat. Acad. Sci. 97 (2000) 2075], we study the steady state probability distribution properties of the model in the presence of correlated Gaussian white noise. We find that the degree of correlation of the noises can affect the form of the steady state probability distribution. When the degree of correlation of the noises increases, the form of the steady state probability distribution changes from a bimodal into a unimodal structure. The steady state probability distribution extrema have also been investigated. We find that noise correlation can change the positions of the extreme value of the steady state probability distribution of the model greatly.

Energy Transfer in Isolated LHC II Studied by Femtosecond Pump-Probe Technique
YANG Yi, GUO Li-Jun, LIU Yuan, LIU Wei-Min, ZHU Rong-Yi, QIAN Shi-Xiong, XU Chun-He
Chin. Phys. Lett. 2003, 20 (4): 589-592 .  
Abstract   PDF(pc) (411KB) ( 552 )
Excitation energy transfer in the isolated light-harvesting chlorophyll (Chl)-a/b protein complex of photosystem II (LHC II) was studied by the one-colour pump-probe technique with femtosecond time resolution. After exciting Chl b by 638 nm beam, the dynamic behaviour shows that the ultrafast energy transfer from Chl-b at positions of B2, B3, and B5 to the corresponding Chl-a molecules in monomeric subunit of LHC II is in the time scale of 230 fs. While with the excitation of Chl a at 678 nm, the energy transfer between excitons of Chl-a molecules has the lifetime of about 370 fs, and two other slow decay components are due to the energy transfer between different Chl-a molecules in a monomeric subunit of LHC II or in different subunits, or due to change of molecular conformation.
Exact Solution in Chaotic Inflation Model with Negative Potential
Chin. Phys. Lett. 2003, 20 (4): 593-596 .  
Abstract   PDF(pc) (182KB) ( 476 )
New exact solution to the Einstein equations that describe the evolution of cosmological chaotic inflation model is derived. The inflation is driven by the evolution of scalar field with negative potential V() = -V0 + 1/2m2 2. This includes the solution which is exponential inflation for 0 > > f, and then develops smoothly towards the radiation-like evolution for < f. The spectral indices of the scalar density ns and the gravitational wave fluctuations ng are computed. The value of ns lies well inside the limits set by the cosmic background explorer satellite.

44 articles