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Volume 9 Issue 5
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Original Articles
A Relation Between Gluon Condensates from a Local QCD Sum Rule
LIU Jueping+, LIU Dunhuan
Chin. Phys. Lett. 1992, 9 (5): 225-228 .  
Abstract   PDF(pc) (176KB) ( 478 )
A new approach to get relations between the gluon condensates is shown to be utilization of the local Quantum Chromodynamics (QCD) sum rule via method of analytic continuation by duality in cooperation with the QCD low-energy theorem.
A Computer Simulation of the Rutherford Backscattering Spectra
JIANG Weilin, ZHAI Guangnian+, REN Mengmei, ZHU Peiran
Chin. Phys. Lett. 1992, 9 (5): 229-231 .  
Abstract   PDF(pc) (171KB) ( 459 )
A simulation program for the Rutherford backscattering in the microcomputer has been developed. The energy spectra for any ion incident on any target (up to 10 elements) can be calculated. Energy resolution of the detecting system and energy straggling of ions have been taken into account in the program. Comparisons between experiments and calculations for MeV He and Li ions show a good agreement.

Atomic Hydrogen in Strong Converging Laser Field of Circular Polarization
ZHANG Wenqing, TAN Weihan
Chin. Phys. Lett. 1992, 9 (5): 232-235 .  
Abstract   PDF(pc) (194KB) ( 493 )
We first proved that the modified potential of atomic hydrogen in the converging laser field of circular polarization is an exact uniform field in the range of r ≤ R0(∝ I1/2ω-2), but Coulomb potential in the range of r > R0. Then the energy levels shallow and split, the wavefunction undergoes distortion.

Higher Harmonic in Free Electron Laser with Combined Electromagnetic Wiggler and Axial Guide Magnetic Fields
LU Bo, YU Junsheng+, LIU Shenggang
Chin. Phys. Lett. 1992, 9 (5): 236-239 .  
Abstract   PDF(pc) (181KB) ( 496 )
Following a single-particle approach, a detailed analysis of the higher harmonic in free electron laser (FEL) with combined electromagnetic wiggler and axial guide magnetic fields is derived. The spontaneous emission spectrum and the gain in the low-gain Compton regime are also calculated in detail. This analysis results in a clear resonance condition and shows that this kind of FEL can generate significant coherent harmonic emission of radiation with axial guide magnetic field of suitable strength.
Efficient Generation of Deep Ultraviolet Radiation Using LiB3O5 Crystal
XIE Fali, WU Baichang, MAO Hongwei, CHEN Chuangtian
Chin. Phys. Lett. 1992, 9 (5): 240-242 .  
Abstract   PDF(pc) (178KB) ( 720 )
Efficient generation of deep ultraviolet radiation at wavelength of less than 0.20μm obtained by using LiB3O5 crystal is reported. High power radiation at 0.1914μm has been produced via sum-frequency-mixing of two waves with wavelengths of 0.2128 and 1.9071μm in LiB3O5 crystal. An average output power of about 2.0mW and a conversion efficiency of 8% have been achieved.

Experimental Observation of Bifurcation in Finite-Amplitude Standing Wave Field
LIU Ke, MA Dayou (MAA Dah-you)
Chin. Phys. Lett. 1992, 9 (5): 243-246 .  
Abstract   PDF(pc) (231KB) ( 410 )
The phenomena of bifurcation have been observed in experiments on one-dimensional finite-amplitude standing wave. Besides higher harmonics predicted by the theory, subharmonics fractional also appear in the finite-amplitude standing wave field, as the sound pressuregets higher, and eventually a chaotic state is reached.
Modulated Phase Lag Relations to Determine the Scaling Law of the Electron Thermal Conductivity in Tokamak
XU Yan, WANG Long, ZHENG Shaobai, QI Xiazhi
Chin. Phys. Lett. 1992, 9 (5): 247-249 .  
Abstract   PDF(pc) (145KB) ( 381 )
We propose a method to determine the scaling law of the electron thermal conductivity x0eTeλe with modulating heat pulses. Relation between temperature phase lag and parameters (x0e, λ) is established, from which the electron thermal conductivity in center region of CT-6B tokamak is determined.

Local Ordering Process of (Fe25Ni75)77Si13B10 Amorphous Alloy Under Annealing
WU Qingping, SHEN Zhongyi, YIN Xiujun, CHENG Xianan, WANG Xuwei
Chin. Phys. Lett. 1992, 9 (5): 250-253 .  
Abstract   PDF(pc) (236KB) ( 385 )
In this paper the relaxation behavior of resistance, of temperature coefficient of electrical resistance and of magnetic Curie temperature on (Fe25Ni75)77Si13B10 amorphous alloy in a temperature range from 150°C to 400°C is presented. Having analyzed the possible relaxation mechanism, we proposed a few kinds of local ordering process in the course of annealing. The development of some local ordering processes and the relation between them are analyzed.
Passivating Studies on a P2S5/NH4OH-treated GaAs Surface Using Photoluminescence
WENG Yumin, FAN Zhineng, ZONG Xiangfu
Chin. Phys. Lett. 1992, 9 (5): 254-257 .  
Abstract   PDF(pc) (253KB) ( 429 )
We demonstrated that the photoluminescence intensity and its contrast obtained on liquid encapsulated Czochralski GaAs depend on the surface recombination and they are controlled by chemical surface treatments. We have successfully passivated the surface of GaAs wafer on the basis of P2S5/NH4OH treatment.

Metal-Organic Chemical Vapor Deposition Growth of GaAs.AIAs Double Barrier Resonant Tunneling Diode
REN Hongwen, HUANG Baibiao, XU Xiangang, LIU Shiwen, JIANG Minhua, YU Shuqin
Chin. Phys. Lett. 1992, 9 (5): 258-261 .  
Abstract   PDF(pc) (232KB) ( 457 )
We have growth two structures of AIAs/GaAs/AIAs double barrier resonant tunneling diodes by metal-organic chemical vapor deposition. The resonances to the first excited states were obtained, the measured peak-to-valley current ratio is 1.3 at 77K, room temperature peak current is 8kA/cm2, the resonance voltages are in agreement with the theoretical approach by transfer-matrix method.
Calculated Electronic Structure and Magnetic Properties of a New Ternary Rare-Eart h-Iron Nitride R2Fe17N3
ZENG Zhi, ZHENG Qingqi, LA Wuyan+
Chin. Phys. Lett. 1992, 9 (5): 262-265 .  
Abstract   PDF(pc) (203KB) ( 379 )
Electronic structure and magnetic properties of a new permanent magnetic material R2Fe17N3(R=Sm or Nd) have been studied with self-consistent, spin polarized local spin density functional theory calculation. Several cluster models were used to study the electronic structure of this system. The location
of nitrogen atoms was determined by total energy calculation for clusters with various possible N sites in crystal. The distribution of electrons and the magnetic moments for four kinds ofinequivalent Fe atoms have been obtained. The s-d (s-f) exchange interaction for different Fe sites and Sm atoms was also evaluated. The role of nitrogen atoms in R2Fe17Nδ (δ=0.3) was discussed.

Nano-structure of Iron Formed by Mechanical Grinding
YANG Yuanzheng, MA Xueming, DONG Yuanda, HE Yizhen, WANG Gengmiao*
Chin. Phys. Lett. 1992, 9 (5): 266-268 .  
Abstract   PDF(pc) (198KB) ( 595 )
Nano-crystalline elemental iron powder was successfully formed by high-energy ball grinding. The x-ray diffraction, transmission electron microscopy and Mossbauer spectroscopy were employed to follow the structure changes in the process of mechanical grinding with milling time. The thermal stability of nano-crystalline iron powder was also studied by differential scanning calorimetry. The results showed that the grain size reduces drastically at the initial stage of the milling and reaches 6nm after 40h milling. The broadening of Mossbauer spectrum is attributed to the large fraction of iron atoms existing at the inter-faces for the powder milled.

Hawking hdiation to An Observer with Variable Acceleration
ZHAO Zheng, LUO Zhiqiang, HUANG Chaoguang*
Chin. Phys. Lett. 1992, 9 (5): 269-272 .  
Abstract   PDF(pc) (163KB) ( 475 )
There exists an event horizon and thermal radiation depending on time to a non-uniformly accelerating observer. The Hawking temperature is proportional to its instantaneous acceleration.

Boundary Conditions in Quantum Cosmology in the Brans-Dicke’s Theory
ZHU Zonghong
Chin. Phys. Lett. 1992, 9 (5): 273-276 .  
Abstract   PDF(pc) (193KB) ( 418 )
The Wheeler-DeWitt equation for the Brans-Dicke’s theory of gravitation is solved by two boundary condition proposals of Hartle-Hawking (“no boundary’? and Viienkin (“tunneling from nothing”). It is found that all classical expanding trajectories begin on the classical-quantum boundary and the effective cosmological constant is very small.
Large-scale Pancake Structures in the Universe
LI Xiaoqing, LI Linghuai
Chin. Phys. Lett. 1992, 9 (5): 277-280 .  
Abstract   PDF(pc) (197KB) ( 659 )
On the basis of nonlinear field equations obtained by us, we prove that the fields in the static limit are unstable in the sense of Lyapunov's problem and may collapse, leading to the formation of a pancake-like structure in self-gravitating systems. Our numerical integration shows clearly the same tendency in a much more general condition.

15 articles