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Volume 12 Issue 11
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Original Articles
Torsion Pendulum Method in Viscosity Measurement of Melts
HONG Xinguo, LU Kunquan
Chin. Phys. Lett. 1995, 12 (11): 641-644 .  
Abstract   PDF(pc) (0KB) ( 190 )
In this paper we present the results of our preliminary study on the improvements of torsion pendulum in order to make it suitable for the viscosity measurement of melt at high temperature. The amplitude features of conventional torsion pendulum and our method have been compared at room temperature and at high temperature, respectively. The relationship between the damping factor and the kinematical viscosity is derived and discussed. The viscous properties of molten KNbO3 and molten Li2B8O13 at high temperatures in air are measured with this method.

Pseudoscalar Meson Production of γ Resonance in e+e- Annihilation
LIU Ximing, Tian Lili
Chin. Phys. Lett. 1995, 12 (11): 645-648 .  
Abstract   PDF(pc) (181KB) ( 410 )
In this letter, we try to analyze the effects on final pseudoscalar meson η,η' production rates of γ decay produced by pseudoscalar mixing angle, “mass effect” and L = 1 mesons production. If L = 1 mesons production is taken into account, the calculated production rates of η' and η and the ratio between them agree well with ARGUS data at certain mixing angles, otherwise, the data cannot be explained completely. Hence we come to the conclusion that L = 1 mesons production cannot be neglected.
Verification of the Orbital Character of Low-Lying M1 Excitation Mode in 160Gd by 22MeV Proton Inelastic Scattering at a Forward Angle
AN Zhu*, SHI Zongren, CHEN Quan, DING Dazhao
Chin. Phys. Lett. 1995, 12 (11): 649-652 .  
Abstract   PDF(pc) (199KB) ( 455 )
By 22MeV proton inelastic scattering at the forward angle of 10°, the orbital character of new low-lying M1 excitation states in 160Gd has been verified. At the same time, several new energy levels of 160Gd are observed, and values of spin, parity and deformation length for two new energy levels with excitation energies of 2.558 and 2.607 MeV are given via collective distorted wave Born approximation calculations.
Fission Before K Statistical Equilibration
LIU Zuhua
Chin. Phys. Lett. 1995, 12 (11): 653-656 .  
Abstract   PDF(pc) (213KB) ( 457 )
For the reaction systems with α < αBG, the fissioning nucleus goes through saddle-point to fission with some memories of the entrance-channel plane. In these cases, by taking the relaxation process of K degree of freedom into account, the varience of K distribution, σ2k is obtained. It is shown that σ2k exponentially depends on the square of the angular momentum, J2 for the reaction systems with α < αBG.Therefore, we have put forward a new version of preequilibrium fission model, and shown the experimental evidence for this new fission mechanism.
Dilepton Production in the Central Rapidity Region
HE Zejun
Chin. Phys. Lett. 1995, 12 (11): 657-660 .  
Abstract   PDF(pc) (231KB) ( 358 )
Generalized Boltzmann approximation of the phase-space distribution function of quarks in the quark phase and of pions in the hadron phase, adopted by previous authors, to a complete expression, the dilepton production in Bjorken's (1+1) dimensional scaling expansion system is studied. We find that the dilepton production is heightened, and the shape of the characteristic dilepton dietribution for the quark matter formation in ultrarelativistic nucleus-nucleus collisions is significantly changed.
Mass Dependence of Cross Section Fluctuation in Dissipative Reaction 19F+51V
LU Jun, WANG Qi, XU Hushan, LI Songlin, ZHU Yongtai, YIN Xu, FAN Enjie, ZHANG Yuhu, LI Zhichang, ZHAO Kui, LU Xiuqin, HU Xiaoqing
Chin. Phys. Lett. 1995, 12 (11): 661-664 .  
Abstract   PDF(pc) (207KB) ( 472 )
Excitation functions for projectile-like fragments from 19F+51V reaction have been measured at 102.25 to 109.50MeV in 250keV steps. A TOF+(Δ E - E) telescope at θL = 21.7° is used to identify atomic number Z and mass number A of ejectiles simultaneously. Fluctuations of the dissipative cross section for a series of isotopes are observed. Their coherence energy widths are extracted by generalized statistical fluctuation analysis and the dependence on mass number and on N/Z values are observed for the first time.
Self-Trapping Process of Exciton in C60
ZHANG Guoping, MAO Yongsheng, ZONG Xiangfu, SUN Xin, LU Jicun, Kee Hag Lee, Tae Young Park, FU Rouli, CHU Junhao
Chin. Phys. Lett. 1995, 12 (11): 665-668 .  
Abstract   PDF(pc) (232KB) ( 467 )
A dynamical scheme is employed to simulate the self-trapping of the exciton in C60. During the self-trapping process, due to the bond distortion, two gap states A1u and A2u are separated from the highest occupied molecular orbital and the lowest unoccupied molecular orbital respectively. From the evolutions of the bond distortion and these two levels the relaxation time of the self-trapping exciton is about 90 fs. It is noticed that the relaxation of the exciton is much quicker than that of the charge transfer in C60.
Polarization Beats in a Cascade Three-Level System
MI Xin, YU Zuhe, JIANG Qian, ZHANG Yanpeng, LI Xiaofeng, FU Panming
Chin. Phys. Lett. 1995, 12 (11): 669-672 .  
Abstract   PDF(pc) (241KB) ( 446 )
Based on the interference between one-photon and two-photon processes, we report polarization beats in a cascade three-level system (PBCTS). We performed PBCTS experiments in Na vapor, which showed a modulation of the four-wave mixing signal intensity with period 55fs, corresponding to the beating between the resonant frequencies of the transitions from 3S1/2 to 3P3/2 and from 3P3/2 to 4D3/2,5/2.
Intersubband Third-Order Nonlinearities in a GaAs/AIGaAs Step Quantum Well Structure by Phase Conjugation Method
MA Jianwei, CHEN Zhenghao. CUI Dafu, LÜ, Huibin, HE Meng, YANG Guozhen
Chin. Phys. Lett. 1995, 12 (11): 673-576 .  
Abstract   PDF(pc) (219KB) ( 429 )
In this letter, we present the observation of phase conjugation at 9.27μm in a GaAs/AlGaAs multiple step quantum well structure. The response is caused by the nearly resonant intersubband transition. The magnitude of x(3) determined by this phase conjugation method is about 8 x 10-5 esu and the phase conjugate reflectivity η is about 6 x 10-3 uncorrected for Fresnel reflections.
Chaotic Behavior of Solitary Wave in Liquid
CHEN Weizhong*, WEI Rongjue, WANG Benren
Chin. Phys. Lett. 1995, 12 (11): 677-680 .  
Abstract   PDF(pc) (230KB) ( 477 )
The chaotic behaviors of the time series of the breather (soliton) amplitude have been observed experimentally in the shallow water in the trough subjected to parametric exciting vertically. The results predict that the water solitary waves should be described by some chaotic equations in the higher order approximations as well as by the nonlinear Schördinger equation in the first order.
Biexcitons in Conjugated Polymers
YU Zhigang, LANG Caiyi, LIN Duliang, SUN Xin
Chin. Phys. Lett. 1995, 12 (11): 681-684 .  
Abstract   PDF(pc) (182KB) ( 452 )
The biexciton in conjugated polymers is studied in the Su-Schrieffer-Heeger model appended by a long-range Coulomb interaction. The wave function of the biexciton is constructed in the Heitler-London approach and, for the first time, the binding energy and radius of the biexciton in conjugated polymers is calculated.
Reduction of Interference Oscillations in Observing Intersubband Transitions in AlSb/GaSb Superlattices by Fourier Transform Infrared Spectroscopy
RU Guoping, LI Aizhen
Chin. Phys. Lett. 1995, 12 (11): 685-688 .  
Abstract   PDF(pc) (204KB) ( 447 )
Intersubband transitions from L1 to L2 subbands in AISb/GaSb superlattices in the 8-18 μm wavelength range are observed by employing normal- and oblique-incident Fourier transform infrared (FTIR) spectroscopic techniques. Using AlSb rather than GaSb as the buffer layer, interference oscillations in normal-incident FTlR spectra are significantly reduced, which facilitates one to distinguish intersubband transition features. In the oblique-incident mode where a 45° thallium hexahedron is used for internal reflection, interference oscillations are eliminated, making it possible to observe weak intersubband transitions that cannot be distinguished in normal-incident absorption spectra.
Femtosecond Optical Pump Induced Enhancement of Terahertz Radiation from GaAs Surface
WANG Li, HE Wenguang, YANG Guozheu, ZHANG Xicheng*
Chin. Phys. Lett. 1995, 12 (11): 689-692 .  
Abstract   PDF(pc) (239KB) ( 484 )
Terahertz (THz) far infrared radiation with a subpicosecond pulse duration is generated from GaAs(100) surface illuminated by femtosecond laser pulses. By illuminating the sample with another pump pulse, we observe an enhancement of THz emission. A mechanism of photocarriers trapping by impurities and defects in the depletion layer is proposed.
Quantum Confinement Effect of Fullerenes in Silica Aerogel
SHEN Jun, ZHU Lei, WANG Jue, LI Yufen, WU Xiang
Chin. Phys. Lett. 1995, 12 (11): 693-696 .  
Abstract   PDF(pc) (212KB) ( 444 )
Fullerenes (C60/C70) were encased in silica aerogel by sol-gel process followed by supercriticd drying technique. Visible light emission was observed from the composite under Ar+ laser (488nm) excitation at room temperature. The luminescent intensity was found to decrease whilst being red shift with the increase of the fullerene content in the composite (from 0.05 up to 2.5mol%). This can be interpreted with quantum confinement effect of fullerenes confined in networks of the nanoporous silica aerogel.
Photoluminescence Studies of Single Submonolayer InAs Structures Grown on GaAs (001) Matrix
LI Wei, WANG Zhanguo, LIANG Jiben, XU Bo, ZHU Zhanping, YUAN Zhiliang, LI Jian
Chin. Phys. Lett. 1995, 12 (11): 697-700 .  
Abstract   PDF(pc) (266KB) ( 608 )
We report a detailed analysis of optical properties of single submonolayer InAs structures grown on GaAs (001) matrix. It is shown that the formation of InAs dots with 1 monolayer (ML) height leads to localization of exciton under certain submonolayer InAs coverage, which play a key role in the highly improved luminescence efficiency of the submonolayer InAs/GaAs structures.
Amplification of the Magnetic Fields in Astrophysical Jets- Screw Dynamo of a Nonneutral Beam-Plasma System
MA Chunyu, HUANG Guangli
Chin. Phys. Lett. 1995, 12 (11): 701-704 .  
Abstract   PDF(pc) (200KB) ( 438 )
When the relativistic electrons produced by in situ acceleration propagate through the plasma of jets, they will drive the fluid components to rotate around the cylindinal axis. The shear of rotation veiocity will amplify the magnetic fields through kinematic screw dynamo mechanism.
16 articles