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Volume 11 Issue 2
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Original Articles
Mass- Asymmetric Breakup in the Extended Finite-Range Macroscopic Model
LUO Qingzheng, DAI Guangxi
Chin. Phys. Lett. 1994, 11 (2): 65-68 .  
Abstract   PDF(pc) (162KB) ( 526 )
Using the Cassinian ovaloid as fission shape both in symmetry and asymmetry, including Yukawa-plus-exponential finite range interaction and diffused surface, the rotating finite-range Cassinian ovaloid liquid drop model is developed. The dependence of the fission barrier heights on mass-asymmetry and on angular momentum is studied for the compound nuclei 1121n, 159Tb and 209Bi. The predicted asymmetric fission barriers and mass yields are compared with experimental data obtained from the deexcitation of hot composite nuclei by complex fragment emission.
Relativistic Theoretical Calculation of O III: Radiative Transition Rates and the Bowen Mechanism in Planetary Nebulae
TONG Xiaomin, ZOU Yu, LI Jiaming, LIU Xiaowei
Chin. Phys. Lett. 1994, 11 (2): 69-72 .  
Abstract   PDF(pc) (204KB) ( 444 )
A full relativistic configuration interaction (RCI) calculation of transition energies and radiative transition rates involved in O III Bowen fluorescence mechanism is presented. The calculated ratios of transition line intensities are in good agreement with the observed ratios. The discrepancies between the RCI calculation and prediction based on LS coupling scheme show that a delicate balance between the electron correlations and the spin-orbital interactions should be important even for the low-Z O III ion.
Absolute Cross Sections for Single Ionization of Ar+ and C1+ by Electron Impact
SHI Wei, FANG Dufei, LU Fuquan, GAO Haibin, GU Jian, WU Songmao, WU Weiming, TANG Jiayong, YANG Fujia
Chin. Phys. Lett. 1994, 11 (2): 73-75 .  
Abstract   PDF(pc) (132KB) ( 457 )
A crossed-beam facility for electron impact ionization of ions was constructed. The absolute cross sections for single ionization of Ar+ and C1+ ions at electron energies ranging from 30 to 500eV were measured. The uncertainty is about ±13%.
Broadband Fluorescence Guided-Wave in DANS/PMMA Thin Film Waveguides
WANG Huitian, DONG Fengzhong, ZHANG Zhanxiang, YE Peixian QIU Ling, SHEN Jifeng, FU Xingfa, SHEN Yuquan
Chin. Phys. Lett. 1994, 11 (2): 76-78 .  
Abstract   PDF(pc) (164KB) ( 479 )
The broadband fluorescence guided-waves excited in DANS/PMMA polymer thin film waveguides by an Ar+ laser beam were demonstrated in terms of the observation of mlines with colour array. Considering the high brightness of these m-lines observation, we assert that it is a kind of stimulated amplification of fluorescence guided-wave.
Theoretical Analysis on Self-Defocusing Mode-Locking in a Ring Resonator
ZANG Weiping, TIAN Jianguo, ZHANG Guangyin
Chin. Phys. Lett. 1994, 11 (2): 79-82 .  
Abstract   PDF(pc) (172KB) ( 727 )
A theoretical analysis of passive mode-locking in a thermal-stable ring cavity containing a Kerr medium and an aperture is presented. The analysis employing the beam propagation theory shows that the power dependence of the cavity loss is extremely sensitive to the relative location of the Kerr medium and the aperture, and is different for the counterpropagating modes, so the unidirectional operation is expected. The combination of Kerr medium with an aperture acts as a p sition feedback, which is similar to the effect of a saturable absorber.
Theoretical Interpretation on Ion Heating Experiments in Reverse Field Pinch Devices
QIU Xiaoming (X. M. Qiu), WANG Aike, XUE Minglun (M. L. Xue)
Chin. Phys. Lett. 1994, 11 (2): 83-86 .  
Abstract   PDF(pc) (166KB) ( 500 )
A new set of equations for the energies of the mean magnetic field and the mean plasma velocity is derived taking the dynamo effects into account, by which the anomalous phenomenon, Ti > Te observed in some reversed field pinches (RFP’s) is successfully explained.
Surface Modification of Hexamethylated Disiloxane Plasma Polymerized Medical Polyurethane
LI Dejun, ZHAO Jie
Chin. Phys. Lett. 1994, 11 (2): 87-90 .  
Abstract   PDF(pc) (201KB) ( 480 )
Surface biomedical properties of plasma polymerization on medical polyurethane were studied. Hexamethylated disiloxane (MI) plasma polymerization was performed at a power of 100 W with the polymerization- time ranging from 1 to 15min. The results showed that hexamethylated disiloxane plasma polymerization resulted in an increase from 30.52 to 37.44s in the recalcification time. At the same time, the anticoagulability of polymerized samples for the polymerization time of 2-5min was 2.5 times that of the pristine. Results of x-ray photoelectron spectroscopy, electron spin resonance analysis showed that plasma polymerization decomposed some of CN bonds to form new SiN bonds and to increase the amount of radicals in polyurethane, which were the main reasons for surface modification.
Restoration and Amplification of Images Through Randomly-Moving Suspension Particles Using Photorefractive Two-Wave Mixing
ZHANG Guangyin, XU Jingjun, LIU Simin, MEN Liqiu, LIU Junxnin
Chin. Phys. Lett. 1994, 11 (2): 91-94 .  
Abstract   PDF(pc) (229KB) ( 474 )
Weak images, which pass through two kinds of suspension media with sizes of randomly-moving suspension particles about 0.05-0.1 cm and 0.01-0.001 cm respectively, are deteriorated by light scattering of particles, but restored and amplified effectively by two-wave mixing in photorefractive crystals with different time constants.
Growth, Second Harmonic and Sum Frequency Generation Operations of Potassium Titanyl Arsenate Crystal
WEI Jingqian, WANG Jiyang, LIU Yaogang, SHI Luping, WANG Min, SHAO Zongshu
Chin. Phys. Lett. 1994, 11 (2): 95-98 .  
Abstract   PDF(pc) (0KB) ( 342 )
Potassium titanyl arsenate (KTiOAsO4, KTA) crystals have been grown with flux method. The infrared absorbing edge of KTA crystal is about 5.3 μm. The electric and other properties of KTA were measured. According to the x-ray orientating, KTA crystal samples were prepared to carry on second harmonic generation (SHG) and sum frequency generation (SFG) experiments. The SHG efficiency of KTA for Nd: YAG is 1.7 times larger than that of KTA. At 20°C, the shortest SHG wavelength is 0.5174μm, and the shortest SFG wavelength is 0.4994μm.

Structural Phase Transitions of Iodine at High Pressure
CHEN Liangchen, ZHANG Zhiting, CHE Rongzheng, YU Tingnan, WANG Jifang
Chin. Phys. Lett. 1994, 11 (2): 99-101 .  
Abstract   PDF(pc) (190KB) ( 861 )
The compression and polymorphic phase transitions of iodine have been studied by using x-ray diffraction with a diamond anvil cell at high pressure up to 77GPa. Considering that iodine is reactive with iron in air, a corrosion-resisting and high-strength gasket was put between the diamonds, thus the sample can be mounted at atmospheric pressure and room temperature. Pressure was measured in terms of the ruby fluorescence and the molybdenum diffraction as an internal pressure standard. According to the x-ray diffraction results, the iodine undergoes the following three structural phase transitions with pressure increasing: ( 1 ) At 21 GPa, from base centred orthorhombic phase (phase I) to body centred orthorhombic phase (phase II). A 2% change in volume occurs. (2) At 44 GPa, from phase II to body centred tetragonal phase (phase III). This is a second order phase transition. (3) At 71 GPa, from phase III to fcc phase (phase IV). The volume decreases by 3%. At this time, the volume is 45% of the original one at atmospheric pressure.

Photoacoustic Spectroscopy Measurement of C60 Thin Film
GU Gang, ZANG Wencheng, ZENG Hao, CHEN Geng, DU Youwei, ZHENG Yibin*, ZHANG Shuyi*
Chin. Phys. Lett. 1994, 11 (2): 102-104 .  
Abstract   PDF(pc) (156KB) ( 502 )
Photoacoustic spectroscopy of C60 thin film is presented. The optical band edge of solid C60 and the optical absorption coefficient at absorption edge are determined. A weak absorption shoulder at 1.70eV is observed. While the thickness of C60 thin film is less than 1μm, photoacoustic saturation at band edge is avoided.
Effects of e-e Interaction on the CDW of MX Complex
YU Zhigang, SUN Xin
Chin. Phys. Lett. 1994, 11 (2): 105-108 .  
Abstract   PDF(pc) (171KB) ( 645 )
We have considered the effects of Hubbard repulsion on the charge-density-wave (CDW) state of halogen-bridged mixed-valence transition metal complex (MX complex) within mean field theory (MFT), and taken electron correlation into account by second-order perturbation relative to the mean field state. It is seen correlation reduces the dimerization and narrows the band gap further compared with MFT.
Electronic Structure of Type-II InAs/GaSb Misaligned Superlattice
LONG Fei, LIU Shenzhi*, MEI Fei, MIAO Jingqi, LIANG Jingguo
Chin. Phys. Lett. 1994, 11 (2): 109-112 .  
Abstract   PDF(pc) (206KB) ( 578 )
The Energy band edges of type-II InAs/GaSb (001) misaligned superlattices as functions of InAs and GaSb layer thicknesses are calculated by a pseudopotential method with quick convergency. The results show the trend of deep-shallow transitions of impurities in the superlattices. The regime in which the superlattice changes from semiconductor to semimetal is also showed.

Radiation Induced Variations of Electrical Conductivity in Polyaniline
YAO Qi, LIU Limin, LI Changjiang
Chin. Phys. Lett. 1994, 11 (2): 113-115 .  
Abstract   PDF(pc) (112KB) ( 596 )
Induced variations of electrical conductivity σdc of polyaniline by γ-radiation have been studied, σdcdc increases from 2.2 to 2.7S/cm due to radiation with a dose of 30-40Mrad. EPR results show that spin concentration increases at the same rate as σdc. The characteristics of σdc versus temperature fit to Inσdc∝T-1 before irradiation, before irradiation, but to Inσdc∝T-1/4 after irradiation.
High Hole Mobility Si/Sil-xGex/Si Heterostructure
JIANG Ruolian, LIU Jianlin, ZHENG Youdou*, ZHENG Guozhen*, WEI Yayi*, SHEN Xuechu*
Chin. Phys. Lett. 1994, 11 (2): 116-118 .  
Abstract   PDF(pc) (169KB) ( 586 )
High mobility Si/Sil-xGex/Si p-type modulation-doped double heterostructures have been grown by RRH/VLP-CVD (rapid radiant heating/very low pressure-CVD). Hole Hall mobilities as high as about 300cm2/V.s(293 K) and 7500cm2/V.s(77K) have been obtained for heterostructures with x = 0.3. The variation of hole mobility with temperature and the influence of Ge fraction on hole mobility were investigated.

Electroreflectance Study of Strained Layer GexSil-x/Si Multiple Quantum Wells
PAN Shihong, HUANG Shuo, CHEN Wei, ZHANG Cunzhou, SHENG Chi*, WANG Xun*
Chin. Phys. Lett. 1994, 11 (2): 119-122 .  
Abstract   PDF(pc) (220KB) ( 460 )
A set of strained-layer GexSil-x/Si multiple quantum wells has been investigated by electroreflectance (ER) spectroscopy. In the ER spectra we have observed transitions in the quantum wells associated with the critical points E0, E1, as well as E0¹. The transitions of E0 and E0¹, which are very weak in the bulk material, are apparently enhanced in quantum wells.
Superconductivity in a New (Sr, Y)CuO2 System Synthesized Under High Pressure
ZHOU Xingjiang, YAO Yushu, DONG Cheng, LI Jingwei, JIA Shunlian, ZHAO Zhongxian
Chin. Phys. Lett. 1994, 11 (2): 123-126 .  
Abstract   PDF(pc) (234KB) ( 405 )
Superconductivity has been observed in a new series (Sr1-xYx)CuO2(x =0.00- 0.30) synthesized under high pressure of 3.5GPa and 950ºC. Compared with the previous (Sr1-xYx)CuO2(Ln =Nd, Pr and La) series, this new series shows a broader superconducting composition range of x = 0.05 - 0.30. The onset transition temperature of this series is 36-38K.
Fluorescence Decay Lifetime of Ultrafine CdS and ZnS Particles
LI Xueping, FAN Changyu, ZHANG Zhenzong, XIAO Xurui
Chin. Phys. Lett. 1994, 11 (2): 127-128 .  
Abstract   PDF(pc) (113KB) ( 388 )
The fluorescence decay properties of CdS and ZnS ultrafine particles have been investigated by a single photon counting technique. We have found that the decay is dependent on the particle size, emission wavelength and colloidal sandwich structure. Shorter emission lifetimes were observed for smaller CdS particles and at shorter emission wavelength. The average emission lifetime of ZnS part in the sandwich structure of ZnS and CdS particles clearly decreased.
18 articles