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Volume 11 Issue 12
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Original Articles
Symmetries of the Variable Coefficient KdV Equation and Three Hierarchies of the Integrodifferential Variable Coefficient KdV Equation
ZHANG Jiefang, HAN Ping
Chin. Phys. Lett. 1994, 11 (12): 721-723 .  
Abstract   PDF(pc) (124KB) ( 508 )
By using a simple method to factorize the recursion operator, the inverse recursion operator of the variable coefficient KdV cquqtion is exhibited explicitly. Thee new sets of symmetries of the variable coefficient KdV equation arc given in addition to the known K symmetries and τ symmetries. Starting from these three sets of symmetries, we obtained three hierarchies of the variable coefficient KdV integro-differential equations.

Relationship Between the Coulomb and Oscillator Problems in Arbitrary Dimensions
ZENG Gaojian, SU Kalin, LI Min
Chin. Phys. Lett. 1994, 11 (12): 724-726 .  
Abstract   PDF(pc) (117KB) ( 396 )
It is shown that there is a simpler relationship between the energy eigenstates of a d-dimensional hydrogen atom and those of a D-dimensional harmonic oscillator, which is important in application.
Deflection of an Atomic Beam in a Large Period Quantized Standing Light Wave
WANG Xiaoguang, SUN Changpu
Chin. Phys. Lett. 1994, 11 (12): 727-729 .  
Abstract   PDF(pc) (142KB) ( 357 )
By using the Wei-Norman's method, the deflection of an atomic beam with a large period quantized standing light wave is analyzed for the case with two-level atom and single-mode cavity field. It is concluded that after passing through the standing light wave in cavity, the atomic beam is split into infinite beams symmetrically, and each momentum shift for a split component is proportional to the interaction time. It is also shown that the output momentum distribution of atoms is sensitive to the statistical properties of the cavity field.
Cumulative Reaction Probabilities of Cl+H2 from Quantum Scattering Calculations and Evaluation of Thermal Rate Constant
ZHAO Meishan (Meishan ZHAO)
Chin. Phys. Lett. 1994, 11 (12): 730-733 .  
Abstract   PDF(pc) (199KB) ( 351 )
We report the cumulative reaction probabilities (CRP) of the three-dimensional Cl+H2 → H+HCl calculated on the Stern-Persky-Klein potential energy surface, using the generalized Newton variational principle, for total angular momentum J =0, over a total reaction energy range from 9 to 19 kcal/mol. The relation between CRP and reaction rate constants, as well as the calculation for complete reaction rates (summed over all J), bypassing the direct calculation of the CRP's for J>0, are also discussed.

Sil-xGex/Si Single-Mode Rib Waveguides with 0.5 dB/cm by Molecular Beam Epitaxy
GAO Yong, LIU Enke, LI Guozheng, LIU Xiding, ZHANG Xiangjiu*, LU Xuekun*, WANG Xun*
Chin. Phys. Lett. 1994, 11 (12): 734-736 .  
Abstract   PDF(pc) (191KB) ( 464 )
Sil-xGex/Si single-mode rib waveguides with 0.5dB/cm losses have been fabricated, in which the SiGe layers are grown by molecular beam epitaxy. The single-mode waveguide dimensions determined experimentally are consistent with the single-mode theory of SiGe waveguides.
Exact N-Soliton Solutions for the Higher-Order Nonlinear Schrödinger Equation Under Another Condition
LIU Shanliang*, WANG Wenzheng*, XU Jingzhi
Chin. Phys. Lett. 1994, 11 (12): 737-740 .  
Abstract   PDF(pc) (147KB) ( 407 )
By using a simple transformation approach, we solve the higher-order nonlinear Schrödinger equation under another condition. The obtained exact soliton solutions have the following prominent features: The bright soliton can propagate in both the normal and anormal regions; the soliton travelling speed is proportional to its amplitude square; the phase of the soliton is independent of its amplitude or width; and the component solitons of the bound soliton have the same phase.
Measurement of H/H+D Ratio and Recycling in Ion Cyclotron Resonance Heating HT-6M Tokamak
DING Liancheng, JIANG Guangkuan, WEI Lehan
Chin. Phys. Lett. 1994, 11 (12): 741-743 .  
Abstract   PDF(pc) (0KB) ( 270 )
A scanning Fabry-Perot interferometer has been used to measure the Hα and Dα lines obtain the H/H+D ratio in ion cyclotron resonance heating HT-6M tokamak for determing the energy absorption mechanism. The recycling is observed by changing the working gas from deuterium to hydrogen.
Dynamics of Collisional Sheaths for Spherical and Cylindrical Geometries
WANG Dezhen, MA Tengcai
Chin. Phys. Lett. 1994, 11 (12): 744-746 .  
Abstract   PDF(pc) (126KB) ( 410 )
A model for the source-free, collisional, cathodic plasma sheath in both spherical and cylindrical geometries is developed. The analytic expressions for the sheath scaling law, electric potential profile, ion density and average ion velocity spatial variation in the sheath are derived.
The Effects of Coil Current Distribution in a Cylindrical Electron Cyclotron Resonance Reactor
WU Hanming, D. B. Graves, LI Ming, WANG Qin
Chin. Phys. Lett. 1994, 11 (12): 747-750 .  
Abstract   PDF(pc) (237KB) ( 390 )
Using a 2-D hybrid model, the authors have found that external currents play an important role in the plasma parameters in the reactor. The plasma density, temperature and electrostatic potential would be significantly influenced by the applied external currents.
Molecular-Dynamics Simulation of Surface Relaxation for Tersoff-Dodson Type (100) Si
XIA Yueyuan, TAN Chunyu, XING Yuelin, YANG Hong*, SUN Xiufang*, GONG Bin*
Chin. Phys. Lett. 1994, 11 (12): 751-753 .  
Abstract   PDF(pc) (174KB) ( 423 )
Surface relaxation and lattice dynamics of (100)Si have been studied using Tersoff-Dodson type Si potential. The average temperature of the lattice is studied as well. The temperature fluctuates with a frequency of 9.5x1012 Hz,, that is about the average frequency of the optical phonons in Si. The (100) Si surface relaxes inward by 0.86 Å, and a reduction of 19% in the first interlayer spacing is found.

Strong Coupling Polaron in a Slab of Polar Crystal
HUANG Zhuohe, CHEN Chuanyu, LIANG Shidong, ZHANG Shuqun
Chin. Phys. Lett. 1994, 11 (12): 754-757 .  
Abstract   PDF(pc) (168KB) ( 494 )
By using the extensive Pekar's variational method, the strong coupling polaron energy and the effective mass in a slab of polar crystal including both LO- and SO-phonons are derived as a function of the thickness of slab and the coupling constant. When the slab is thin, the SO-phonons not only influence the ground state energy, but also make the polaronic effective mass become non-isotropic.
Photoluminescence Studies on Very High-Density Two-Dimensonal Electron Gases in Pseudomorphic Modulation-Doped Quantum Wells
LI Wei, WANG Zhanguo, LIANG Jiben, XU Bo, ZHU Zhanping, SONG Aimin, ZHENG Wanhua, YANG Bin
Chin. Phys. Lett. 1994, 11 (12): 758-761 .  
Abstract   PDF(pc) (241KB) ( 424 )
We present photoluminescence studies on highly dense two-dimensional electron gases in selectively Si δ-doped GaAs/ln0.18Ga0.82 As/Al0.25 Ga0.75,As quantum wells (Ns = 4.24 x 1012 cm-2). Five well-resolved photoluminescence lines centered at 1.4194, 1.4506, 1.4609, 1.4695 and 1.4808eV were observed, which are attributed to the subband exciton emission. The subband separations clearly exhibit the feature of a typical quantum well with triangle and square potential. These very intensive and sharp luminescence peaks with linewidths of 2.2 to 3.5meV indicate the high quality of the structures. Their dependence on the excitation intensity and temperatures are also discussed.
Transverse Electric and Transverse Magnetic Active Intersubband Transitions in CaAs/AlGaAs Step Quantum Well
CUI Dafu, CHEN Zhenghao, YUAN Zhenyu, ZHOU Yueliang, LÜ, Huibin, YANG Guozhen
Chin. Phys. Lett. 1994, 11 (12): 762-765 .  
Abstract   PDF(pc) (231KB) ( 586 )
We have observed transverse electric (TE) and transverse magnetic (TM) intersubband infrared absorption peaks in GaAs/AlGaAs step multiquantum wells (SMQW). The energy splitting between TE and TM is 13meV. The high conversion efficiency of second harmonic signal due to intersubband transition in the GaAs/AlGaAs SMQW with a waveguiding surface-emitting structure have been obtained. The second harmonic generation (SffG) obeys wave vector conservation and propagates perpendicular to the waveguide surface which shows that the nonlinear polarization field for SHG may be TE as well as TM active. The existence of strong surface-emitting second harmonic signal also offers solid evidence of TE polarization active intersubband transition in GaAs/AlGaAs SMQW structure.
Electrical Phenomena of C60-Tetracyanoquinodimethane Thin Films
GAO Hongjun, XUE Zengquan, WU Quande (Q. D. Wu)
Chin. Phys. Lett. 1994, 11 (12): 766-769 .  
Abstract   PDF(pc) (243KB) ( 523 )
The electrical properties of C60-tetracyanoquinodimethane (TCNQ) thin films fabricated by using an ionized-cluster-beam method in a high vacuum system were investigated. The films were characterized by transmission electron microscopy (TEM) and electronic spectroscopy. The spectroscopic results evidenced the formation of the charge-transfer complex system in C60-TCNQ thin films and the TEM results revealed the microstructure of the films. The film thickness is of about 100nm. The electromotive intensity at the transition point is a few 107 V/m. The possible mechanism of the electrical phenomena of the films is discussed in the paper.
Thermoelectric Power and l/f Noise in the Normal State of YBa2Cu3O7-δ/PrBa2Cu3O7-δ Superlattice
LIU Guoliang, LIU Sangtian, WANG Min, LIAN Guijun, LI Guohong, XIONG Guangcheng, YAN Shousheng
Chin. Phys. Lett. 1994, 11 (12): 770-771 .  
Abstract   PDF(pc) (127KB) ( 318 )
The thermoelectric power (TEP) and l/f noise of a series of YBa2Cu3O7-δ/PrBa2Cu3O7-δ YBCO/PrBCO) superlattice samples have been measured from 80 to 270K. The TEP of the superlattices has large and positive values. For samples with thick YBCO layers, it varies linearly with temperature and has a positive slope. The noise power of superlattice samples is about two orders of magnitude lower than that in bulk YBCO film.
Self-consistent Phenomenology of the Cuprate Superconductors in the Normal State
LU Wei, GONG Changde
Chin. Phys. Lett. 1994, 11 (12): 772-774 .  
Abstract   PDF(pc) (160KB) ( 496 )
The dynamical susceptibility of the two-dimensional spin fluctuations of local-moment antiferromagnets is proposed and studied self-consistently. The anomalous behaviors of high-Tc cuprates in the normal state are explained in the quantum critical regime, and the momentum averaged dynamical susceptibility reduces to the basic hypothesis of the marginal Fermi liquid theory.
Giant Magnetoresistance of Fe/Ag Multilayer Films with Ultrathin Fe Layers
LI Shuxiang, YU Chengtao, YAN Minglang, LAI Wuyan, WANG Yizhong
Chin. Phys. Lett. 1994, 11 (12): 775-777 .  
Abstract   PDF(pc) (168KB) ( 531 )
A giant magnetoresistive effect in as-deposited Fe/Ag multilayer films with ultrathin Fe layers has been observed. The magnetoresistance in this system is presented first as a function of Fe layer thickness tFe. The sample with Fe layer thickness of 4Å exhibits a magnetoresistance ratio as large as 14.3% at 4.2K. The magnetoresistance ratio decreases approximately an order of magnitude with increasing tFe from 4 to 10Å and then changes slightly with further increasing tFe. From the hysteresis loop measurement, it is found that the interlayer coupling changes from antiferromagnetic to ferromagnetic with increasing tFe. The feature of material at the interface might be responsible for all these findings.

Optical and Structural Properties of AP-MOVPE GaInP/GaAs Heterostructures
REN Hongwen, HUANG Bolin, XU Xian gang, JIANG Minhua, ZHENG Wanhua, XU Junying, ZHUANG Wanru
Chin. Phys. Lett. 1994, 11 (12): 778-781 .  
Abstract   PDF(pc) (215KB) ( 506 )
Lattice matched GaInP/GaAs heterostructures were grown by atmospheric pressuremetal organic vapor phase epitaxy (AP-MOVPE). Compositional intermixing of As/P and Ga/In near the heterointerfaces was studied by photoluminescence (PL) spectroscopy. Indium segregation, memory effect of In into GaAs and the carry-over of As in the GaInP layer during the growth process were considered as three major factors giving rise to the anomalous emissions in the PL spectra. Both thermal annealing and zinc doping strongly enhanced the compositional interdiffusion near the heterointerfaces.
Direct Growth of Diamond Films on Low Carbon Steel
LIAO Xiaoning, LÜ, Fanxiu, WANG Jianjun, YANG Rang
Chin. Phys. Lett. 1994, 11 (12): 782-784 .  
Abstract   PDF(pc) (231KB) ( 527 )
Diamond films have been successfully deposited on a low carbon steel substrate without graphite codeposition. Graphite formation is suppressed by the interlayer formed in situ in pre-treatment process. Grain boundary serves as the preferential site for diamond nucleation.
19 articles