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Volume 14 Issue 4
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Original Articles
Exact Expressions of Energy Spectrum and Partition Function for Quantum Quadratic Systems
PAN Jian-wei, ZHANG Yong-de, G. G. Siu
Chin. Phys. Lett. 1997, 14 (4): 241-244 .  
Abstract   PDF(pc) (184KB) ( 629 )
Based on the linear quantum transformation theory, we present a new approach to obtain the explicit expressions of energy spectrum and simplify the derivations of partition functions for general multi-mode boson and fermion quadratic systems.
A Novel Phase Transition Phenomenon in Bistable System
JIA Ya, , LI Jia-rong, CHEN Yi-cheng
Chin. Phys. Lett. 1997, 14 (4): 245-247 .  
Abstract   PDF(pc) (156KB) ( 444 )
A bistable system driven by additive noise and multiplicative noise is studied, when the correlation time of the correlations between two noises is nonzero. It is found that the system undergoes a succession of two phase transitions as the strength of the correlations between two noises increases.
Statistical Properties of Type V intermittent Diffusion
WU Shun-guang, ZHAO Shao-you, QU Shi-xian, GAO Zhan-hai, HE Da-ren,
Chin. Phys. Lett. 1997, 14 (4): 248-251 .  
Abstract   PDF(pc) (169KB) ( 309 )
In an unbounded system type V intermittency turns into an intermittent diffusion. The velocity autocorrelation function, its power spectrum S(ω), and the mean-square displacements σ2 ( t ) for the iterations inside channel are calculated both analytically and numerically. The diffusion as contrast with the conventional types of intermittent diffusion, is similar to a normal type.
Pion-Nucleon Sigma Term and Strangeness in Nucleon
Chin. Phys. Lett. 1997, 14 (4): 252-254 .  
Abstract   PDF(pc) (137KB) ( 415 )
It is shown that the meson exchange interaction between dynamical quarks generated by the chiral symmetry breaking is of crucial importance to explain the empirical value of the pion-nucleon σ-term. The large contribution of ss and gluon to a nucleon mass is predicted by using the QCD energy-momentum trace anomaly from the pion-nucleon σ-term.
Low-Spin Identical Bands in Non-adjacent Odd-A and Even-Even Nuclei
MA Ying-jun, LIU Yun-zuo
Chin. Phys. Lett. 1997, 14 (4): 255-258 .  
Abstract   PDF(pc) (261KB) ( 393 )
A great number of low-spin identical bands in pairs of odd-A and their non-adjacent even-even nuclei in a region of A = 150 - 190 are found, this fact seems to support the idea that the occurrence of identical bands in neighboring odd-A and even-even nuclei is caused by the cancellation of various factors which influence the moments of inertia of nuclei.

Ground State Properties of Z = 114 Isotopes in the Relativistic Mean-Field Theory
REN Zhong-zhou, ZHU Zhi-yuan, CAI Yan-huang, SHEN Yao-song, ZHAN Wen-long, XU Gong-ou
Chin. Phys. Lett. 1997, 14 (4): 259-262 .  
Abstract   PDF(pc) (240KB) ( 383 )
The ground state properties of even-even Z = 114 nuclei have been investigated in the relativistic mean-field theory with inclusion of deformations. The calculated binding energies agree well with values from macroscopic mass models. Calculations show that there exists a spherical shell. at N = 184, because the quadrupole deformation at N = 184 is zero. For nuclei near N = 162, there are small prolate deformations.
Gamma Decay of the Lowly Excited States of 229AC
YUAN Shuang-gui, YANG Wei-fan, SHEN Shui-fa, FANG Ke-ming, MOU Wan-tong, ZHANG Xue-qian, LI Zong-wei
Chin. Phys. Lett. 1997, 14 (4): 263-265 .  
Abstract   PDF(pc) (165KB) ( 414 )
By bombarding the natural thorium targets with 14 MeVneutrons, 229Ra was produced through the reaction 232Th(n,α) 229Ra. The radium activities were separated from the irradiated targets by coprecipitation with BaC12. A total of 18 weak γ rays with energies of 14.5, 15.6, 18.8, 21.8, 22.5, 44.0, 47.5, 55.0, 63.0, 69.6, 93.6, 94.1, 98.5, 102.2, 104.5, 106.1, 161.1, and 171.5keV, which could be assigned to the decay of 229Ra, has been observed in the isolated radium fractions employing high-resolution HPGe detectors and γ (x)- γ coincidence methods. A decay scheme of 229Ra based on these observations has been proposed.
Properties of Very Hot Nuclei from Heavy-Ion Reactions at Intermediate Energies
ZHENG Yu-ming, SA Ben-hao, WANG Hui
Chin. Phys. Lett. 1997, 14 (4): 266-269 .  
Abstract   PDF(pc) (226KB) ( 384 )
The liquid-gas phase transition from heavy-ion reactions at intermediate energies has been studied in the incomplete-fusion-fragmentation model. The relative yields of decay modes of the projectile remnant are also analyzed and compared with the experimental ones. The experimental results are nicely described by the incomplete-fusion-fragmentation model.
Production and Assignment of a New Transuranium Neutron-Deficient Isotope 235Am
SHI Li-jun, GUO Jun-sheng, LIU Hong-ye, GAN Zai-guo, YANG Wei-fan, MOU Wan-tong, GUO Tian-rui, SHEN Shui-fa, FANG Ke-ming, YUAN Shuang-gui, QIN Zhi, ZHANG Xue-qian, MA Rui-chang, ZHONG Ji-quan, WANG Shu-hong, KONG Deng-ming, QIAO Ji-min
Chin. Phys. Lett. 1997, 14 (4): 270-272 .  
Abstract   PDF(pc) (170KB) ( 492 )
A new transuranium neutron-deficient isotope 235Am was produced via the reaction of 238Pu ( p , 4n) 235Am by using a 35 MeV proton beam. The recoiled products were collected by a helium-jet and long-capillary system. Americium isotopes were separated out by a rapid radiochemical method. X-ray, γ-ray, and x-γ coincidence measurements were taken in the study. According to 235Pu decay γ-ray and Np K x-ray growth-decay property, 235Am was definitely identified and its half life is determined as 15 ± 5 min.

Generation of Superpositions of Squeezed Coherent States
ZHENG Shi-biao, GUO Guang-can
Chin. Phys. Lett. 1997, 14 (4): 273-276 .  
Abstract   PDF(pc) (149KB) ( 886 )
A scheme to prepare superpositions of squeezed coherent states is presented. It involves an appropriately prepared atom crossing a high-Q cavity initially filled with a squeezed coherent field. After the nonresonant interaction with the cavity field the detection of the atomic state leaves the cavity field in a superposition of two squeezed coherent states.
Effects of Field-Correlation on Raman-Enhanced Nondegenerate Four-Wave Mixing Spectra
MI Xin, YU Zu-he, JIANG Qian, LI Xiao-feng, FU Pan-ming
Chin. Phys. Lett. 1997, 14 (4): 277-280 .  
Abstract   PDF(pc) (238KB) ( 481 )
The effects of field correlation on Raman-enhanced nondegenerate four-wave mixing (REN-FWM) have been investigated by examining the RENFWM spectra as a function of time delay between two beams. An enhancement of the ratio between the resonant and nonresonant REN-FWM signal intensities was found as the time delay was increased when the laser had broadband linewidth.
Mutual Interactions of Stimulated Raman Scattering and Stimulated Four-Photon Mixing in an Er3+-Doped Fiber
YU Zhong-qiu, XU Yue-e, LIANG Er-jun, XU Yong-an, LI Xin-min, YUAN Bin, SHEN Shu-po
Chin. Phys. Lett. 1997, 14 (4): 281-283 .  
Abstract   PDF(pc) (190KB) ( 466 )
The mutual interactions of stimulated Raman scattering (SRS) and stimulated four-photon mixing (SFPM) in an Er3+-doped optical fiber have been studied with a tunable pulsed dye laser. Besides normal SRS and SFPM signals, we have observed some new spectral lines. Some of the new lines are attributed to three photon mixing (one from the pump, one from the first-order Stokes and one from SFPM) while the others are assigned to new SRS produced by one of the SFPM signals. The mechanisms of the generation of these new spectral lines are discussed.
Optical Information Storage in Poly [3-Methyl-4-Bis( N,N- Oxyethylene)Imino-4-Nitro-Azobenzene Sebacoyl] Film by Degenerate Four-Wave Mixing
BI Dong-ying, ZHANG Ling-zhi, LIANG Zhao-xi, XIE Zhong-hui, LIN Wei-zhu, LIAO Chang-jun, LIU Song-hao
Chin. Phys. Lett. 1997, 14 (4): 284-286 .  
Abstract   PDF(pc) (137KB) ( 705 )
Optical storage caused by photo-induced anisotropy in poly[3-methyl-4- bis(N, N-oxyethylene) imino-4-nitro-azobenzene sebacoyl] film is studied by degenerate four-wave mixing. Molecule orientation gratings which are stable for three months are produced. The grating in the sample can be “erased” by using circular polarized light. So an azobenzene polymer thin film can be used many times to restore optical information.

Modulation Instability of Low Frequency Whistler Waves
WANG De-yu*, M. Raadu, N. Brenning
Chin. Phys. Lett. 1997, 14 (4): 287-290 .  
Abstract   PDF(pc) (172KB) ( 492 )
A self-focusing modulation instability of whistler wave has been investigated in the frequency region of ωci < ω << ωce. It is found that the ion term contribution should be taken into account. The results show that the necessary condition of instability depends on the pitch angle of perturbation wave.
Renormalization Group Approach on Nanostructured Systems
YAN Xiao-hong, ZHANG Li-de, DUAN Zhu-ping, YANG Qi-bin
Chin. Phys. Lett. 1997, 14 (4): 291-294 .  
Abstract   PDF(pc) (236KB) ( 422 )
The electronic spectra of one-dimensional nanostructured systems are calculated within the pure hopping model on the tight-binding Hamiltonian. By means of the renormalization group Green's function method, the dependence of the density of states on the distributions of nanoscaled grains and the changes of values of hopping integrals in nanostructured systems are studied. It is found that the frequency shifts are dependent rather on the changes of the hopping integrals at nanoscaled grains than the distribution of nanoscaled grains.
Theoretical Examination on Optical and Magnetic Behaviors of Cu2+ Ions in Cs2CuCI4
SUN Wei-li, ZHAO Min-guang
Chin. Phys. Lett. 1997, 14 (4): 295-297 .  
Abstract   PDF(pc) (170KB) ( 360 )
A set of formulas on the energies of d - d transition, the EPR g-factors, and the magnetic susceptibilities has been deduced for d9 ions. The results calculated by using these formulas are in good agreement with the experimental findings of the Cs2CuCI4 crystal. This shows that the optical and magnetic properties can be explained by using both the approximate parame-terized d-orbital and the diagonalization procedure of the complete energy matrix. Moreover, for obtaining more pieces of information, the lower symmetry and spin-orbit coupling need to be considered in the theoretical calculation.

Higher-Order Dispersion and Soliton Pulse Compression in the Dispersion-Decreasing Fibers
XU Wen-cheng, GUO Qi, LIU Song-hao
Chin. Phys. Lett. 1997, 14 (4): 298-301 .  
Abstract   PDF(pc) (177KB) ( 690 )
The compression results of picosecond and femtosecond soliton pulses in the dispersion-decreasing fibers are reported in this paper. We found that the high-order dispersion has a great influence on the soliton compression. The expressions of optimum compression factor and optimum fiber length are obtained numerically.
Improving Stability of Organic Electroluminescent Diode by Inserting Copper Phthalocyanine Between the Anode and Hole Transport Layer
ZHANG Zhi-lin, JIANG Xue-yin, XU Shao-hong, T. Nagatomo, O. Omoto
Chin. Phys. Lett. 1997, 14 (4): 302-305 .  
Abstract   PDF(pc) (198KB) ( 505 )
Copper phthalocyanine(CuPc) thin film layer was inserted between the anode indium tin oxide and the hole transport layer TPD of an organic thin film electroluminescent device with a double-layered structure. It is found that the CuPc layer greatly improves the device stability. The durability of the device with CuPc layer increases about 8 times. The fact that at a constant current density the driving voltage remains unchanged with operation time for the device with CuPc layer means that the barriers of the carriers injection are stable due to the inserted CuPc layer.
Structure and Raman Spectroscopy of Nanocrystalline TiO2 Powder Derived by Sol-Gel Process
ZHOU Qi-fa, WU Shang-hua, ZHANG Qing-qi, ZHANG Jin-xiu, CHEN Jian, ZHANG Wei-hong
Chin. Phys. Lett. 1997, 14 (4): 306-309 .  
Abstract   PDF(pc) (200KB) ( 773 )
Nanocrystalline TiO2 powder was prepared by sol-gel process. The structures of the as-prepared and the TiO2 powder heat-treated at different temperatures were studied by thermogravimetric analyzer, differential thermal analysis, x-ray diffraction, and Raman spectra. As the powder was heat-treated at 350°C, it turned into tetragonal anatase structure. A structural transformation from anatase to rutile type occurred and the grains of the powder grew drastically when the powder was heat-treated at above 550°C. The structural transformation from anatase to rutile type completed at 750°C. The Raman spectra of TiO2 nanocrystalline powder were also studied.
Magneto-Impedance in Fe73.5Cu1Mo3Si13.5B9 Alloy Ribbons
KU Wan-jun, GE Fu-ding, YAN Ge, ZHU Jing,
Chin. Phys. Lett. 1997, 14 (4): 310-313 .  
Abstract   PDF(pc) (218KB) ( 493 )
Giant magneto-impedance (GMI) effects in Fe73.5Cu1Mo3Si13.5B9 alloy ribbons have been measured under different external magnetic fields and different ac driving current frequencies. The results show that the longitudinal and the transverse GMI change with the annealing temperature. Based on the classical electromagnetic theory, the difference between the longitudinal and the transverse GMI (R,X,Z) has been discussed in this letter.
On the Crust of a Strange Star
HUANG Yong-feng, LU Tan
Chin. Phys. Lett. 1997, 14 (4): 314-316 .  
Abstract   PDF(pc) (184KB) ( 556 )
The strong electric field near the surface of a strange star is discussed, and its supporting interaction to the normal nuclear crust is calculated by using a self-consistent method. It is proved that the crust would begin not to be supported by this electric field at a quite low density at the crust base, much lower than the previously assumed neutron drip density.
Quantum Creation of a Schwarzschild-de Sitter Black Hole
WU Zhong-chao
Chin. Phys. Lett. 1997, 14 (4): 317-320 .  
Abstract   PDF(pc) (185KB) ( 409 )
Using the Hartle-Hawking no-boundary proposal for the wave function of the universe, we can study the wave function and probability of a single Schwarzschild-de Sitter black hole created at the birth of the universe. The black hole originates from a gravitational instanton with conical singularities. The probability of a black hole creation is the exponential of one quarter of the sum of areas of the black hole and cosmological horizons. One quarter of this sum is the total entropy of the universe.
22 articles