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Volume 10 Issue 9
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Original Articles
Newtonian Limit in Generalized Brans-Dicke Theory
ZHANG Yuan Zhong
Chin. Phys. Lett. 1993, 10 (9): 513-515 .  
Abstract   PDF(pc) (144KB) ( 595 )
Newtonian limit in the generalized Jordan-Brans-Dicke theory is discussed, and some ambiguities are clarified.
Complex Fragment Emission for the Study of the Fermi Energy Domain Nuclear Collisions
LUO Qingzheng
Chin. Phys. Lett. 1993, 10 (9): 516-519 .  
Abstract   PDF(pc) (184KB) ( 499 )
Complex fragment production in the Fermi energy domain heavy ion collisions is studied. The physics used for the description of the various remnants produced in the entrance channel is based on fireball model taking into account the kinematic and dynamic features of the collision partners, and the decay processes are simulated by a version of the statistical binary decay model. Applications are shown to the target-like products for reactions of copper with 24.0,31.1,38.5 and 46.4 MeV/u 12C. Absolute comparisons with experimental data give a very well overall agreement.

Experimental Studies of 374μm 15NH3 Optically Pumped Far-Infrared Laser
ZU Qinxin*, W. A. Peebles, Chun Jing. Lee Cardenas, S. Burns, N. C. Luhmann, Jr.
Chin. Phys. Lett. 1993, 10 (9): 520-523 .  
Abstract   PDF(pc) (276KB) ( 403 )
374μm far-infrared radiation of 15NH3 pumped by CO2 laser has been studied experimentally. The efficiency of pumping, absorption of the pump beam. Stability of the output power diagnostics, a comparison with 432μm of the formic acid laser was also carried out.

Time-Delayed Raman-Enhanced Nondegenerate Four-Wave-Mixing Experiments with Incoherence Light in Carbon Disulfide
YU Zuhe, MI Xin, JIANG Qian, FU Panming
Chin. Phys. Lett. 1993, 10 (9): 524-526 .  
Abstract   PDF(pc) (157KB) ( 440 )
We report for the first time an experiment of the time-delayed Raman-enhanced non-degenerate four-wave-mixing (RENF WM) with incoherence light in carbon disulfide. We studied the RENFWM signal intensity as a function of the relative the delay τ between two beams which originate from a single broadband laser source. Our results indicate that the temporal behavior of the RENFWM is asymmetric with the maximum of the signal shifted from τ=0. From our experiment results the relaxation time of the Raman mode can be extracted directly.

A Soliton Solution for MHD Equation of Unmagnetized Collisionless Plasma
WANG Kelin, DING Weixing*, YU Changxuan*
Chin. Phys. Lett. 1993, 10 (9): 527-530 .  
Abstract   PDF(pc) (178KB) ( 488 )
A new theoretical method has been developed to deal with ion acoustic soliton in collisionless plasma with cold ions (Te»Ti). The analytical solution can be found be from the magnetic hydrodynamics equation other than from the usual KDV equation.
Irradiation Induced Amorphization and Free Energy Calculation in Immiscible Fe-Cu Multilayers
BAI Haiyang, LIU Baixin
Chin. Phys. Lett. 1993, 10 (9): 531-534 .  
Abstract   PDF(pc) (215KB) ( 636 )
Amorphization was achieved by a non-equilibrium process of ion mixing of multilayered films in an immiscible Fe-Cu system with a large positive heat of formation (+19 kJ/mol). The free energy diagram of the Fe-Cu system was constructed. In calculation, the interfacial free energy, ferromagnetic effect and the structure characteristics were considered. The calculated Fe-Cu free energy diagram can explain the amorphization behavior in this immiscible system.
Mechanism for the Nanometer Scale Modification on HOPG Surface by Scanning Tunneling Microscope
WANG Zhonghuai, DAI Changchun. ZHANG Pingchen, HUANG Guizhen. LI Renli. GUO Yi, BAI Chunli
Chin. Phys. Lett. 1993, 10 (9): 535-538 .  
Abstract   PDF(pc) (330KB) ( 478 )
A technique applying voltage across the tunnel junction for writing permanent features on graphite with lines about 10nm width using our home-built scanning tunneling microscope has been presented. Multiple effects while modifying the surface arc often met. The phenomena are explained in terms of the strong electric field existing at the junction between the tip and the surface. In addition, the shape of the structure indented by the tip is in agreement with that of the tip.
Microstructure and Electron Conduction Mechanism of Hydrogenated Nano-crystalline Silicon Films
HE Yuliang, CHU Yiming, LIN Hongyi, JIANG Shusheng
Chin. Phys. Lett. 1993, 10 (9): 539-542 .  
Abstract   PDF(pc) (386KB) ( 551 )
The hydrogenated nano-crystalline silicon (nc-Si:H) films have deposited with plasma enhanced chemical vapor deposition method. The microstructure of these films has been studied by transmission electron microscopy and high resolution transmission electron microscopy. The nc-Si H films show fiber texture structure. The fractal dimension of this structure has been calculated with a Fourier filtered image. The relationship between conductivity and temperature has also been studied and the mechanism of electron conduction is discussed.
Low-Temperature Optical Spectra and Zero-Phonon Transitions of Color Centers in γ-Rayed Sodium Fluoride Crystals
GU Hongen
Chin. Phys. Lett. 1993, 10 (9): 543-546 .  
Abstract   PDF(pc) (195KB) ( 520 )
A lot of narrow lines on R2, R+, N1, N- and some other unknown centers have been observed in γ-rayed pure and doped sodium fluoride crystals in the temperature range of 9-77K. The proper laser irradiation was used for strengthening the zero-phonon lines and the relative explanation was given. The spectral properties and thermostabilities of the lines were investigated systeniaticitl1y at different temperatures.
Interface Optical-Phonon Modes in a C/B/A/B/C Five-Layer Heterostructure of Polar Crystals
SHI Junjie, PAN Shaohua*
Chin. Phys. Lett. 1993, 10 (9): 547-549 .  
Abstract   PDF(pc) (0KB) ( 406 )
The equations of motion for the p-polarization field in a C/B/A/B/C-type five-layer heterostructure of polar crystals arc solved exactly for the interface optical-phonon modes. The eigenvectors arc obtained explicitly. The dispersion relation is derived and discussed in detail for sonic limiting cases. This work can be regarded as a generalization of the formation of that of Shi and Pan [Phys. Rev. B46, 4265(1992)].

Photoinduced Ultrafast Process of Relaxation in Polymer
YU Zhigang, HUANG Qingfeng, SUN Xin
Chin. Phys. Lett. 1993, 10 (9): 550-553 .  
Abstract   PDF(pc) (178KB) ( 420 )
On the basis of multi-phonon transition theory. the origin of the fast component (100 fs) and the slow component(ns) in photoexcitation dynamics is explained and their evolution time is calculated. From these results, it is seen that the fast component is duo to the formation from free electron-hole pair to neutral bipolaron, and the slow one is due to the non-radiative decay of bipolaron.
A New Cluster Updating for 2-D SU(2)xSU(2) Chiral Model
ZHANG Jianbo, JI Daren
Chin. Phys. Lett. 1993, 10 (9): 554-557 .  
Abstract   PDF(pc) (180KB) ( 440 )
We propose a variant version of Wolff's cluster algorithm, which may be extended to SU(N) x SU(N) chiral model, and test it in 2-dimensional SU(2) x SU(2) chiral model. The results show that the new method can efficiently reduce the critical slowing down in SU(2) x SU(2) chiral model.
Surface Effects on Dielectric Susceptibility of a Semi-infinite Ferroelectric
QU Baodong, WANG Chunlei, ZHONG Weilie, WANG Zhonglie
Chin. Phys. Lett. 1993, 10 (9): 558-561 .  
Abstract   PDF(pc) (146KB) ( 444 )
The profile of susceptibility near the surface of a semi-infinite ferroelectric is calculated from Landau free energy. In surface ferroelectric phase, the susceptibility is reduced at surface for |δ| <<β and much enhanced for |δ| ~β Where δ and β are the extrapolation length and the coherent length respectively. In ferroelectric phase, the surface susceptibility is generally reduced for δ<0. But the curve is not monotonic, there is a minimum in the surface layer. For δ >0, the surface susceptibility is reduced for |δ| <<β and enhanced for δ~β. The curve has a maximum in the surface layer.

Magneto-Optical Bistability in Diluted Magnetic Semiconductor Cd1-xMnxTe
LIU Jizhou, WANG Xuezhong, CHEN Chenjia, MA Kejun*
Chin. Phys. Lett. 1993, 10 (9): 562-565 .  
Abstract   PDF(pc) (192KB) ( 443 )
Magneto-optical bistability in diluted magnetic semiconductor Cd1-xMnxTe is realized. The bistability is created by the giant Faraday effect in Cd1-xMnxTe and the saturation characteristic of the magneto-optical feedback system. The bistability characteristic depends on the orientation angle α of the polarizers of the Faraday modulator and on the temperature of the sample.
Angular Dependence of Critical Current in Ag-Seathed Bi(2223) Superconductor Tape
GUQ Shuquan, QIN Xiaomei, ZHANG Jinlong, WU Zu’an, YE Bin*, ZENG Rong*, ZHOU Yiru*, ZHOU Min*
Chin. Phys. Lett. 1993, 10 (9): 566-568 .  
Abstract   PDF(pc) (116KB) ( 475 )
The critical current Ic (B.T.θ) of Ag-sheathed Bi (2223) tape was measured at 4.2 and 77k in magnetic field up to 6T as a function of the field direction. The maximum Ic is observed when the flux line are along the CuO2 planes. This effect is due to an intrinsic pinning between CuO2 layers. When H > 0.5T at 4.2K, Ic decreases very slowly with the magnetic field. The results are consistent with our early-proposed scaling laws for flux pinning in Ag-sheathed tape.

Brillouin Scattering from Metallic Ta/Al Fibonacci Multilayers
XIA Hua, PENG Ruwen, ZHANG Wei, HU An, JIANG Shusheng, ZHANG Xingkui
Chin. Phys. Lett. 1993, 10 (9): 569-572 .  
Abstract   PDF(pc) (209KB) ( 437 )
Surface phonon spectra from Ta/Al Fibonacci multilayers are studied via Brillouin scattering. Determination of the frequency positions of the Rayleigh wave and the intensity dip corresponding to the longitudinal threshold has enabled us to extract two effective elastic constants C44 and C11 of the whole structure. The 22.6% enhancement of the shear modulus is found in our experiment.
Stability of the Soliton Excited in Protein in the Biologic Temperature Range
PANG Xiaofeng
Chin. Phys. Lett. 1993, 10 (9): 573-576 .  
Abstract   PDF(pc) (209KB) ( 435 )
The thermal stability of the soliton excited in protein in the biological temperature range of 300 –310K have been studied by means of the quantum theory in our theory. The lifetimes of the soliton obtained are in the range of 10-9–10-8 s from 300-310K. This result shows that the soliton is very stable in the biologic temperature range and quite useful in biological processes.
17 articles