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Volume 13 Issue 6
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Original Articles
General Approach to Antinormally Ordering Boson Exponential Quadratic Operators and Its Applications
WANG Xiang-bin, ZHANG Yong-de, PAN Jian-wei
Chin. Phys. Lett. 1996, 13 (6): 401-404 .  
Abstract   PDF(pc) (144KB) ( 395 )
A general approach to antinormally ordering the boson exponential quadratic operators (EQOs) is presented. By the approach, some important EQOs, including squeezed operator of one mode and two mode, linear quantum transformation operator, Bogolubov transformation operator are antinormally ordered.

Wormhole Solution in Vacuum Brans-Dicke Theory with Cosmological Constant
XIAO Xing-guo, ZHU Jian-yang,
Chin. Phys. Lett. 1996, 13 (6): 405-408 .  
Abstract   PDF(pc) (130KB) ( 601 )
In this paper, we give an Euclidean wormhole solution in the Brans-Dicke theory with cosmological constant. We show that this wormhole is unlike all the others, its configuration is non-static. The throat radius of the wormhole will increase as Euclidan cosmic time increases.
About the Energy of the Universe
FENG Shi-xiang, DUAN Yi-shi
Chin. Phys. Lett. 1996, 13 (6): 409-411 .  
Abstract   PDF(pc) (97KB) ( 502 )
We use the general covariant conservation law of energy-momentum, which is general covariant and therefore preferable to the non-covariant conservation laws, to analyse the energy of the universe and obtained vanishing energy. A physical interpretation of the vanishing energy and some discussions are also presented.
Remarks on the Three-dimensional Lattice Model
HU Zhan-ning
Chin. Phys. Lett. 1996, 13 (6): 412-415 .  
Abstract   PDF(pc) (151KB) ( 371 )
We find the connection between the weight functions of the three-dimensional (3D) Bazhanov-Baxter model and the 3D vertex model proposed by Mangazeev et al. And the weight function of the 3D integrable model with the modified tetrahedron can be formulated as the vertex form.

Relativistic Density-Dependent Hartree Approach for Nuclear Matter in the Chiral-Symmetry-Breaking Model
JIANG Wei-zhou, ZHU Zhi-yuan, QIU Xi-jun
Chin. Phys. Lett. 1996, 13 (6): 416-419 .  
Abstract   PDF(pc) (210KB) ( 456 )
A relativistic density-dependent Hartree approach in the chiral-symmetry-breaking field model has been developed for nuclear matter. The coupling constants of the relativistic Hartree-Lagrangian are made density dependence and obtained from the relativistic Brueckner-Bethe-Goldstone results of nuclear matter. The calculated saturation nuclear density, binding-energy and compressibility for nuclear matter are close to the empirical ones.
In-Medium Nucleon-Nucleon Cross Section
CAI Yan-huang, SONG Hong-qiu, U. Lombardo
Chin. Phys. Lett. 1996, 13 (6): 420-423 .  
Abstract   PDF(pc) (193KB) ( 338 )
Within the framework of Brueckner-Hartree-Fock method, the in-medium nucleonnucleon (NN) cross section is calculated. We base our investigation on a separable Paris potential for the NN interaction and a continuous choice for the single particle spectrum. It is found that the in-medium cross section is strongly modified by medium effect. In particular, with increasing of nuclear density, the cross sections decrease. This indicates a proper treatment of the density dependence of the in-medium NN cross sections is important.
Intensity Dependence of Cesium D2-Line Saturation Spectra
LI Yi-min, CHEN Xu-zong, GAN Jian-hua, JI Wang-xi, HUA Jing-shan, YANG Dong-hai, WANG Yi-qiu
Chin. Phys. Lett. 1996, 13 (6): 424-427 .  
Abstract   PDF(pc) (196KB) ( 381 )
The intensity dependence of the cesium D2-line saturation absorption spectra in a nearly zero magnetic field was investigated theoretically and experimentally. By using rate equations the D2-line saturation absorption spectra were calculated, which agree reasonably well with the experimental results. The variation of the spectra with different cell lengths was also reported and explained with theoretical calculation.
Double Ionization of Helium by Partially Stripped Oxygen Ions
CAI Xiao-hong, SHEN Zi-yong, CHEN Xi-meng, LIU Zhao-yuan, LIU Hui-ping, MA Xin-wen, HOU Ming-dong
Chin. Phys. Lett. 1996, 13 (6): 428-431 .  
Abstract   PDF(pc) (230KB) ( 477 )
New measurement of the ratio of the double ionization cross section to that of the single ionization of helium induced by 2.0-7.5 MeV partially stripped Oq+ ion (q = 1,2,3,4) is presented. Combining the measured data with the Olson-Schlachter scaling, the double ionization cross section of helium by partially stripped oxygen ion is obtained. It is found that the v/qeff dependence of the obtained double ionization cross section agrees well with the (v/qeff)-4 law.
Squeezing in the Thermal Jaynes-Cummings Model
XIE Rui-hua, , ZOU You-tao, LIU Dun-huan
Chin. Phys. Lett. 1996, 13 (6): 432-435 .  
Abstract   PDF(pc) (204KB) ( 367 )
We have studied the influence of thermal photons on the symmetry between the field and atomic squeezing (SFAS) exposed in the resonant vacuum-field Jaynes-Cummings model with an initially coherent atom. We have shown that when the number of thermal photons (Nav) is less than 0.01, the SFAS is not sensitive to the presence of thermal photons; when Nav≥ 0.01, the broken SFAS can be seen; when Nav≥ 0.1, the squeezed atom cannot radiate a squeezed field any longer. Also, we have discussed the possibility of detection of the boken symmetry in superconducting maser cavity.
Discovery of the Induced Superslow Optical Relaxation Processes in I2
JIANG Hong-Jie, Zhang Yong, ZHU Jia-hua, FANG Shao-wu, DING Liang-en, XIA Hui-rong
Chin. Phys. Lett. 1996, 13 (6): 436-439 .  
Abstract   PDF(pc) (237KB) ( 395 )
We discover superslow optical processes with relaxation time as long as 250ms in I2. The demonstration is performed by a series of experiments with novel considerations for I2 interacting with phase modulated laser fields, monitored by both coherent and noncoherent detection with digital frequency scale and time scale simultaneously for comparison.

Observation of Optical Bistability in Two-Dimensional Volume Refractive Index Grating Thermally Fixed in LiNbO3:Fe Crystal
WANG Zhen-lin, WU Jun, YANG Zhen-ju, ZHU Yong-yuan, Min Nai-ben
Chin. Phys. Lett. 1996, 13 (6): 440-443 .  
Abstract   PDF(pc) (208KB) ( 430 )
Experimental observation of optical bistability in a nonlinear two-dimensional volume refractive index grating is reported. The index grating in LiNbO3:0.1 wt.% Fe photorefractive single crystal was fabricated by using hologram recording and subsequent thermal fixing techniques. Due to the thermal fixing, the stored 2D volume index grating shows no optical erasure during readout. An explanation of the nonlinear phenomena is also given in terms of the intensity-enhanced bulk photovoltaic effects in LiNbO3:Fe material.
Preparation and Microstructure of Nanosized GaN Crystals
YU San, LI Hong-dong, YANG Hai-bin, LI Dong-mei, SUN Hai-ping, ZOU Guang-tian
Chin. Phys. Lett. 1996, 13 (6): 444-446 .  
Abstract   PDF(pc) (168KB) ( 467 )
Gallium nitride crystals in nano-scale have been fabricated by dc arc plasma method using gallium and N2 +NH3 as starting materials. Transmission electron microscope, selected area diffraction and x-ray diffraction investigation of the as-grown GaN crystals show that the well faceted crystals are single crystalline GaN in wurtzite structure having lattice constants a0 = 3.18 Å and c0 = 5.18 Å.
Self-Consistent Kinetic Modeling of Electron Distribution Function in a Low-Pressure Inductively Coupled Plasma
YANG Yun, WU Han-ming
Chin. Phys. Lett. 1996, 13 (6): 447-450 .  
Abstract   PDF(pc) (238KB) ( 368 )
Based upon the spatially inhomogeneous Boltzmann equation in two-term approximation coupled with electromagnetic and fluid model analysis for the recently developed inductively coupled plasma sources, a self-consistent electron kinetic model is developed. The electron distribution function, spatial distributions of the electron density and ionization rate are calculated and discussed.
Surface Growth Kinetics and Directed Percolation in a Ballistic Deposition-Reaction Model
Chin. Phys. Lett. 1996, 13 (6): 451-454 .  
Abstract   PDF(pc) (305KB) ( 395 )
The surface growth kinetics and directed percolation processes in a ( 2 + 1)-dimensional ballistic deposition-reaction model are studied in this paper. As the probability P increases a transition of the morphologic structure is found, which results from the diffusion and the directed percolating processes of the particles.
Electroluminescence of Boron Doped Diamond Thin Films
ZHANG Bing-lin, WANG Xiao-ping, HE Jin-tian, Liu Da-jun, WANG Jian-en, Howard R. Shanks
Chin. Phys. Lett. 1996, 13 (6): 455-457 .  
Abstract   PDF(pc) (144KB) ( 443 )
Blue electroluminescence of boron doped diamond thin film is reported. The boron doped diamond thin films were deposited by microwave plasma assisted chemical vapor deposition on silicon substrate. The electroluminescence device was driven by a frequency-modulated power supply. The optimum frequency is near 3 kHz. The dependence of electroluminescence intensity on boron impurity has been investigated. The intensity increases with increasing boron impurity. This is expected result according to “Band A ”electroluminescence mechanism of donor-accepter pairs recombination.

Band Offset and Optical Property of (ZnS)n/(Si2)n (110) Superlattice
LI Kai-hang, HUANG Mei-chun, WANG Ren-zhi
Chin. Phys. Lett. 1996, 13 (6): 458-460 .  
Abstract   PDF(pc) (162KB) ( 479 )
Supercell self-consistent calculation of band structures of (ZnS)n/(Si2)n (110) (n = 2,3,4,5) has been performed by means of linear muffin-tin orbitals method. The valence-band offset of such systems is calculated by frozen optential method and their Joint density of states has been computed by tetrahedron method. Our results show that the (ZnS)n/(Si2)n (110) superlattices have a large valence-band offset and their optical properties integrate exellent optical properties of bulk ZnS and that of Si.

Bound Phonons and Bistability of Donors in Gal-xA1xAs: Te
LIAN Shi-yang
Chin. Phys. Lett. 1996, 13 (6): 461-464 .  
Abstract   PDF(pc) (191KB) ( 363 )
Bound phonons in Te-doped Gal-xA1xAs were first observed in Raman scattering experiments at low temperature. They are assigned to electrons trapped at an effective-mass-like level. At higher temperatures, this level disappears to the benefit of a stable DX-like deep level. These results reveal a shallow-deep bistable characters of donors in Gal-xA1xAs: Te under some conditions.
Surface State at K Point of Surface Brillouin Zone on Cu{111} Surface
YANG Yi, LIU Feng-qin, JIA Jin-feng, DONG Yu-hui, IBRAHIM Kurash, QIAN Hai-jie, WU Si-cheng*, LÜ, Si-hua*
Chin. Phys. Lett. 1996, 13 (6): 465-468 .  
Abstract   PDF(pc) (216KB) ( 435 )
Electronic structure of Cu {111} surface dong Γ-K line of surface Brillouin zone (SBZ) was studied using synchrotron radiation angle-resolved photoemission. A surface state located at 3.0eV below Fermi level, near K point of SBZ was observed for the first time. It is described by localized d-electron Tamm surface state.
Micromagnetics and Signal Analysis of Shielded Spin-Valve Multilayer
ZHANG Huai-wu, YANG Shi-qing, LIU Ying-li, WANG Hao-cai, H. J . Kim*
Chin. Phys. Lett. 1996, 13 (6): 469-472 .  
Abstract   PDF(pc) (213KB) ( 474 )
In order to linearize a spin-valve giant magnetoresistance head, the exchanges layer sputtered at fringe area or a permanent magnet layer longitudinal biasing for domain stabilization based on a physical calculated model may be considered. The correlations between the head performance characteristic and head geometric parameters have been simulated by putting the head on a suitable front-end electric circuit. The simulative results show that the optimal sensing current is from 10 to 40mA and the linear geometric parameteres for gap width are at the range of G1 + G2 ≤ 0.5 μm.

Effect of Pressure on the Nucleation of Diamond with Addition of Oxygen in the Microwave Plasma Chemical Vapor Deposition System
WANG Jian-jun, LÜ, Fan-xiu
Chin. Phys. Lett. 1996, 13 (6): 473-476 .  
Abstract   PDF(pc) (232KB) ( 406 )
Effect of oxygen addition on diamond film deposition at higher pressure was studied. It was found that addition of oxygen suppressed diamond nucleation, and the effect of suppression increased with increasing pressure, and at certain pressure level diamond deposition was completely prohibited. Etching effect due to oxygen addition dominated at the very early stage (nucleation stage), therefore it is still possible to take the advantage of oxygen addition on quality improvement of diamond films by introducing oxygen after the nucleation stage.

Influence of Mass-Loss on the Orbit of Comet Shoemaker-Levy 9
YU Li-zhong, ZHENG Xue-tang
Chin. Phys. Lett. 1996, 13 (6): 477-480 .  
Abstract   PDF(pc) (171KB) ( 370 )
Using the Jeans problem and the Fermi problem of two bodies with variable masses, the influence of solar and cometary mass-loss on the orbit of comet Shoemaker-Levy 9 (SL9) is discussed in this paper. It is shown that solar and cometary mass-loss both will cause the secular and periodic terms in the semimajor axis a of comet SL9. The influence of solar mass-loss on the orbit of comet SL9 is very small and it may be omitted. But the influence of mass-loss of comet SL9 itself on its orbit is large and it may cause the secular variation in a to be about l04 km every year. The cometary mass-loss will obviously influence the time and place of the comet SL9 crashing into Jupiter.

21 articles