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Volume 14 Issue 5
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Original Articles
Quasielastic Electron Scattering from 12C
LU Pao, B. P. Nigam
Chin. Phys. Lett. 1997, 14 (5): 321-324 .  
Abstract   PDF(pc) (149KB) ( 395 )
Transverse electron scattering response function ST(q, ω ) has been calculated by using a hard core common harmonic oscillator potential. Good agreement is obtained with the experimental date at q = 400 MeV/c.
Thermodynamics and Time-Like Singularity
ZHAO Zheng
Chin. Phys. Lett. 1997, 14 (5): 325-327 .  
Abstract   PDF(pc) (108KB) ( 374 )
In a stationary space-time, no time-like curve of finite acceleration can reach arbitrarily small neighbourhood of a time-like singular region where goo goes to -∞. The proper temperature of an observer approaching the singular region will go to infinity. The generalized third law of thermodynamics will keep observers away from the time-like singular region.
Reaction Effect of Gravitational Radiation of Rotating Ellipsoid as Central Body upon the Variation of Celestial Orbital Plane
LI Lin-sen
Chin. Phys. Lett. 1997, 14 (5): 328-331 .  
Abstract   PDF(pc) (183KB) ( 358 )
The Reaction effect of gravitational radiation emitted from central body with quadrupole moment on the variation of celestial orbital plane was studied in detail. We derive the formulas for the relation between the variation of the inclination of the orbital plane and contraction of the orbital radius with time. The expressions deduced were applied to the estimation for the evolution of the systems of planet-satellite (Jupiter-2 and Neptune-1).
Biased Brownian Motion Driven by Fluctuating Temperature
LI Yu-xiao
Chin. Phys. Lett. 1997, 14 (5): 332-335 .  
Abstract   PDF(pc) (205KB) ( 530 )
Biased Brownian motion in a periodic potential with fluctuating temperature of thermal bath is studied. The general expression of stationary probability current is obtained. The necessary condition for biased Brownian motion is the combination of fluctuating temperature and a periodic ratchet potential.
Conjecture on the Time Scales of Intramolecular Dynamics and Lyapunov Relaxation
XIE Xi-shun, HUANG Xiao-qin, ZHAO Mei-shan
Chin. Phys. Lett. 1997, 14 (5): 336-339 .  
Abstract   PDF(pc) (213KB) ( 469 )
A dynamical study of intramolecular energy transfer in a realistic polyatomic model molecular system is reported. From the present study and dynamical information established in the previous research we make the conjecture that the Lyapunov rate is always an upper bound on the relaxation rate.
B(E2) Saturation in the Rare-Earth Region
LONG Gui-lu
Chin. Phys. Lett. 1997, 14 (5): 340-343 .  
Abstract   PDF(pc) (207KB) ( 451 )
The quadrupole interactions between neutrons and protons are calculated using Nilsson +BCS model for the neutron-rich even-even rare-earth nuclei. This is used to study the saturation of B(E2)'s in this mass region. The neutron numbers at which saturation of B(E2) occurs are calculated for each isotopic chain. In particular, the calculation suggests that B( E2) saturation may occur in the 2nd half of the 82-126 major shell in erbium and ytterbium.
(EC+β+) Decay of 129Ce
XIE Yuan-xiang, XU Shu-wei, MA Rui-chang, LI Zhan-kui, GUO Ying-xiang, ZHANG Tian-mei, GE Yuan-xiu, WANG Chun-fang, GUO Bin, XING Jian-ping, GUO Tian-rui, WANG Yan-yu, ZHU Shao-fei, XU Wang, DU Jin-zhou
Chin. Phys. Lett. 1997, 14 (5): 344-347 .  
Abstract   PDF(pc) (195KB) ( 379 )
The nuclide 129Ce was produced by a (16O, 4n) reaction on an enriched 117Sn target. Reaction products were transported to a shielded location by using a helium-jet tape transport system. An activity of 4.1 min in chemically separated cerium sample was identified as 129Ce. Based on x-γ-t and γ-γ-t coincidence measurements, the (EC+β+) decay scheme of 129Ce was proposed, and takes accounts of 50 observed γ-lines.
Positron Impact Ionization of Hydrogen, Sodium, and Potassium
ZHOU Ya-jun, PAN Shou-pu
Chin. Phys. Lett. 1997, 14 (5): 348-351 .  
Abstract   PDF(pc) (189KB) ( 309 )
The total ionization cross sections for positron scattering by hydrogen, sodium, and potassium are calculated by applying an equivalent-local optical potential model from the ionization threshold to 300eV. The total ionization cross sections are in excellent agreement with the recent measurements of Jones et al. The total ionization cross sections for sodium and potassium are compared with other theoretical calculations.
Optical Free-Induction Decay Effect in a Λ-Type Quantum-Beat Three-Level System
CAO Zhuo-liang
Chin. Phys. Lett. 1997, 14 (5): 352-355 .  
Abstract   PDF(pc) (163KB) ( 357 )
With Bloch form, a coherent transient effect-optical free-induction decay is studied semiclassi-cally in the Λ-type three-level system driven by a coherent microwave field. The decay behavior has three contributions: a homogeneous part with transverse relaxation time and two inhomo-geneous parts with different time constants that reflect the velocity bandwidth excited and the action of the driving microwave field.

Enhancement of the Femtosecond Third Harmonic Generation by Charge Transfer Process in Poly (N-Vinylcarbazole) /C60 Film
QIAN Jiang, ZHAO Li, WANG Gong-ming, QIAN Shi-xiong, LIU Xian-nian, ZHENG Qi-ke
Chin. Phys. Lett. 1997, 14 (5): 356-359 .  
Abstract   PDF(pc) (250KB) ( 388 )
The femtosecond third harmonic generaction (THG) output has been measured from a series of poly(N-vinylcarbazole) (PVK), C60, mixed and multilayer PVK/C60 films which were all fabricated by physical jet deposition technique. There is an enhancement of femtosecond THG output from the mixed PVK/ C60 film in comparison with other films. Charge transfer complex in the mixed PVK/ C60 film was considered to be the main reason for this increase of the third-order susceptibility.
Two-Photon Resonant Third Harmonic Generation in Carbon Monoxide
WANG Peng-qian, CAO Chuan-shun, SUN Tao-heng
Chin. Phys. Lett. 1997, 14 (5): 360-363 .  
Abstract   PDF(pc) (250KB) ( 472 )
Tunable coherent extreme ultraviolet radiation has been generated in CO by two-photon resonant third harmonic generation via the A1 II(v' = 4) ←X1 Σ+(v" = 0 ) transition. The third nharmonic spectrum exhibits resolved and improved rotational lines due to the expansion cooling of the molecular beam. The saturation and the phase-matching of the nonlinear process are also discussed.
Criterion of Anisotropic Modes and Rejection Band in a Waveguide Filled with Cold Magnetoactive Plasma
DING Zhen-feng, REN Zhao-xing
Chin. Phys. Lett. 1997, 14 (5): 364-366 .  
Abstract   PDF(pc) (167KB) ( 401 )
The dispersion equation characterizing quasi-static TE mode and the criterion for the existence of the anisotropic mode are derived. The characteristics of the rejection band and its bandwidth are investigated in comparison with the previous conclusion.
Measurements of Film Thickness and Growth Temperature of YBa2Cu3O7-δ Films by Pyrometric Absorption Method
XIONG Xu-ming, ZHOU Yue-liang, WANG Hui-sheng, CUI Da-fu, LU Hui-bin, CHEN Zheng-hao, YANG Guo-zhen
Chin. Phys. Lett. 1997, 14 (5): 367-370 .  
Abstract   PDF(pc) (267KB) ( 480 )
A pyrometric absorption method suitable for strongly absorbing films has been developed to monitor the YBa2Cu3O7-δ film growth. This method makes use of the temperature difference between the heater and the substrate. By deducing the absorption formula of radiation light and fitting it to the radiation intensity data measured, it is possible to monitor the film thickness and the film surface temperature during deposition. Experimental results show that this is a simple and practicable method.
Electronic Structures of T-Shaped Quantum Wires
LI Shu-shen, XIA Jian-bai
Chin. Phys. Lett. 1997, 14 (5): 371-374 .  
Abstract   PDF(pc) (203KB) ( 476 )
In this paper, we propose the periodic boundary condition which can be applied to a variety of semiconductor nanostructures to overcome the difficulty of solving Schrödinger equation under the natural boundary condition. When the barrier width is large enough, the average of the maximum and minimum of energy band under the periodic boundary condition is very close to the energy level obtained under the natural boundary condition. As an example, we take the GaAs/Ga1-xAlxAs system. If the width of the Ga1-xAlxAs barrier is 200Å , the average of the maximum and minimum of energy band of the GaAs/Ga1-xAlxAs superlattices is very close to the energy level of the GaAs/Ga1-xAlxAs quantum wells (QWs). We give the electronic structure effective mass calculation of T-shaped quantum wires (T-QWRs) under the periodic boundary condition. The lateral confinement energies E1D-2D of electrons and holes, the energy difference between T-QWRs and QWs, are precisely determined.
I - V Characteristics of Metal/Polynitrobenzene Junctions
ZHENG Hai-peng, ZHANG Rui-feng, HUANG Jing-song, LIU Shi-yong, SHEN Jia-cong
Chin. Phys. Lett. 1997, 14 (5): 375-378 .  
Abstract   PDF(pc) (264KB) ( 470 )
We used a new polyphenylene derivative-polynitrobenzene (PNB) to construct metal/polymer Schottky devices, and studied the influence of polymer film thickness, thermal treatment and different molar-ratio of dopant on the electrical properties of the junctions. The Al/PNB junction with 100nm in thickness of pure PNB film exhibited a relatively good I - V behavior. But the open voltage and rectification chatacteristics improved greatly when the PNB film was heated or lightly doped with poly-N-vinylcarbazole.
Influence of the Nonmagnetic Impurity on the Spin Density State of High-Tc Cuprate Oxides
SHI Da-ning
Chin. Phys. Lett. 1997, 14 (5): 379-382 .  
Abstract   PDF(pc) (207KB) ( 459 )
This letter deals with the suppressive effect of the nonmagnetic impurity, doped into the parent compound of the high-Tc superconductor, on the spin density wave (SDW) state. Taking into account the van Hove singularity in the Fermi surface of the two-dimensional square lattice, our results indicate that the nonmagnetic impurity can lead to sharp reduction of the SDW order, which is in qualitative agreement with the experimental reports.
Local Magnetism in Nanoscale Metallic Grains
ZOU Liang-jian, ZHENG Qing-qi, GONG Xin-gao,
Chin. Phys. Lett. 1997, 14 (5): 383-386 .  
Abstract   PDF(pc) (245KB) ( 409 )
Quantum effects on local magnetism in nanoscale metallic grain with transition-metal impurity are studied in the ballistic regime. It is shown that in nanoscale system near the zero temperature, besides the size effect of the energy level, the level statistics and multilevel repulsion effect play important roles for the local electronic states and the formation of the local magnetic moments.
Mössbauer Spectroscopy and X-Ray Diffraction Studies of the Phase Composition of Crystallized NdxFe81.5-xB18.5 Alloys with 7 ≤ x ≤15
CHENG Zhao-hua, SHEN Bao-gen, ZHANG Jun-xian, MAO Ming-xi, SUN Ji-jun, YANG Chun-li, LI Fa-shen, ZHANG Yi-de
Chin. Phys. Lett. 1997, 14 (5): 387-390 .  
Abstract   PDF(pc) (237KB) ( 462 )
The phase composition of melt-spun Nd-Fe-B with intermediate and high Nd concentrations has been studied by Mössbauer effect. Based on the knowledge of the 57Fe hyperfine parameters for Nd2Fe14B, Nd2Fe23B3, and Nd1.1Fe4B4, the phases produced during annealing Nd-Fe-B amorphous alloys can be identified. It is found that the NdxFe81.5-xB18.5 samples with 7≤ x ≤ 9 contain the Nd2Fe23B3 metastable phase and the Nd1.1Fe4B4 paramagnetic phase. The body-centered-cubic structure of Nd2Fe23B3 cannot generate the hard magnetic properties. The samples with 12 ≤ x ≤ 15 consist of the Nd2Fe14B hard magnetic phase and the Nd1.1Fe4B4 paramagnetic phase. The large coercivity for the high Nd content Nd-Fe-B originates from the very fine size of Nd2Fe14B grains below the particle size of the single domain, which may contribute to a pinning effect of domain wall.
Evolution of the Magnetic Fields of Isolated Radio Pulsars
WANG Zhong-xiang, LU Tan
Chin. Phys. Lett. 1997, 14 (5): 391-394 .  
Abstract   PDF(pc) (203KB) ( 463 )
With a simple evolution model of the magnetic fields of isolated radio pulsars, the statistical evidence for them is investigated. Monte-Carlo techniques are used to generate sample pulsars of particular distributions of initial periods, period derivatives, magnetic fields, luminosities, and Galactic positions. The period-dependent beaming fraction of pulsars is considered in the simulation. Then the best fits by comparing the synthesized populations with the observed pulsars are made. It is shown that the field decay model may also have some consistency with the current understanding of pulsar statistics.
Compton Telescope Observation of Gamma-Ray Flare from Quasar PKS0528+134
ZHANG Shu, LI Ti-pei, WU Mei
Chin. Phys. Lett. 1997, 14 (5): 395-398 .  
Abstract   PDF(pc) (189KB) ( 408 )
The quasar PKSO528+134 was observed to flare by the energetic gamma-ray experiment (EGR-ET) γ-ray telescope on the Compton gamma-ray observatory during the viewing period 213 (VP213). The Compton telescope data from VP213 have been reanalyzed by using the direct demodulation method. Images of the source are obtained at energies above 3 MeV and the time variability in the energy range 10-30 MeV is consistent with the result of EGRET. There is no spectral break at energies above 3 MeV during the flare.
Comment on “About the Energy of the Universe”
ZHAO Min-guang
Chin. Phys. Lett. 1997, 14 (5): 399-399 .  
Abstract   PDF(pc) (46KB) ( 332 )
Reply to the Comment by ZHAO
FENG Shi-xiang, DUAN Yi-shi
Chin. Phys. Lett. 1997, 14 (5): 400-400 .  
Abstract   PDF(pc) (47KB) ( 362 )

22 articles