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Volume 10 Issue 4
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Original Articles
Angular Momentum in Super-space
ZENG Gaojian
Chin. Phys. Lett. 1993, 10 (4): 193-196 .  
Abstract   PDF(pc) (209KB) ( 528 )
In this paper, we use two Grassmann variables to construct an angular momentum operator, which may be used to describe a system of angular momentum 0 and 1/2.
Rederivation of AB Scattering Cross Section by the Method of Path Integration
GU Zhiyu, XIE Yuan, HUANG Bowen, QIAN Shangwu*
Chin. Phys. Lett. 1993, 10 (4): 197-200 .  
Abstract   PDF(pc) (130KB) ( 434 )
Taking advantage of the calculation based on the original fundamental ideas of Aharonov and Bohm (AB) on the one hand, and making some necessary revisions on the other hand, this paper rederives the famous AB scattering cross section from the known propagator by the path integral method.
On Representation Transformation in Einstein Quantum Cosmology
DING Haogang, HUANG Chaoguang, ZHANG Yuan Zhong
Chin. Phys. Lett. 1993, 10 (4): 201-204 .  
Abstract   PDF(pc) (149KB) ( 375 )
We consider invertibility and consistency conditions in representation transformation in quantum cosmology, which is regarded as a necessary condition to pick up physical states of the Universe.
Stopping Power of Au and Ag for He Ions
HUANG Xiaojing, LU Xiting, JIN Changwen, ZHOU Chengfang, YE Yanlin, XIA Zonghuang, LIU Hongtao, JIANG Dongxing
Chin. Phys. Lett. 1993, 10 (4): 205-208 .  
Abstract   PDF(pc) (186KB) ( 389 )
Energy loss of 0.45-5.0 MeV 4He ions in Au and Ag films were measured with the Rutherford backscattering method, and the stopping powers at lower energy range were extracted by comparing with that determined by Anderson et al. at higher energy range. Significant deviation between the experimental data and the semiempirical calculations by TRIM-90 appears around the stopping maximum. The accuracy of our results was expected to be ±l%.

A Nuclear Detector Using Scanning Tunneling Microscopy
TANG Xiaowei
Chin. Phys. Lett. 1993, 10 (4): 209-210 .  
Abstract   PDF(pc) (123KB) ( 385 )
A new principle of nuclear detector is proposed that primary latent tracks of incident nuclei are directly measured using scanning tunneling microscopy. The new detector has a super-high spatial resolution about 30-50 Å.
Separation of Fullerence Molecules in an Eletric-Magnetic Isotope Separator
LIN Fucheng, WU Zhengliang, XIE Yanyan, ZHANG Guilin*, CHEN Miao*, ZHANG Yingji*
Chin. Phys. Lett. 1993, 10 (4): 211-212 .  
Abstract   PDF(pc) (102KB) ( 341 )
An electric-magnetic isotope separator was used to separate fullerence molecules C60 and C70 produced by dc contact arc vaporization then extracting method. The potential for the analysis of huge fullerence molecules and the producing of macroscopic quantity of any fullerence molecules was revealed. It also showed that the secondly ionized molecules might be produced in the sample preparing process.

Observation of Collimated Atoms by Light Pressure Force in Absorption Cell
WANG Yuzhu*, YE Chao WU Yongsheng, WANG Xiaojuan, ZHOU Shanyu CHENG Yudan, MA Longsheng, DING Liangen
Chin. Phys. Lett. 1993, 10 (4): 213-216 .  
Abstract   PDF(pc) (257KB) ( 418 )
Experimental observation of laser cooling and collimation of moving atoms in an absorption cell by light pressure force of an intense standing light wave field is reported. The hyper fine structure of atomic sodium has been observed due to the cooled and collimated atoms. The mechanism of laser cooling and collimation of atoms is discussed.
Absolute Measurement of the Photoionization Cross Section of the Excited 7p State of Potassium
FENG Baohua, ZHANG Zuren
Chin. Phys. Lett. 1993, 10 (4): 217-219 .  
Abstract   PDF(pc) (152KB) ( 529 )
The absolute photoionization cross section for the excited 7p state of K has been measured using the method of ionization saturation. The measured cross sections σ7p (321.8nm) and σ7p (643.6nm) are (0.9±0.6) Mb and (1.9±0.9)Mb, respectively. The results are in good agreement with the calculated values.

Phase Conjugation of Squeezed Light
LI Shiqun, WU Ling-An*
Chin. Phys. Lett. 1993, 10 (4): 220-222 .  
Abstract   PDF(pc) (144KB) ( 438 )
Phase conjugation in degenerate four-wave mixing with a squeezed input beam is investigated. We show that the phase conjugate mode is always super-Poissonian and never squeezed, but the combination mode may be squeezed to an extent even greater than the input probe wave.
Higher Harmonics in Free Electron Laser with a Two-Wavenumber Plane Wiggler Magnetic Field
LU Bo, YANG Zhonghai, LIU Shenggang, YU Junsheng*
Chin. Phys. Lett. 1993, 10 (4): 223-226 .  
Abstract   PDF(pc) (157KB) ( 377 )
The higher harmonics of the free electron laser (FEL) with a two-wavenumber plane wiggler magnetic field, which may induce a lot of higher harmonics, are investigated. Using a two-wavenumber wiggler comprised of two separate periodicities, kω and kω + Δk, numerical simulations show that the higher harmonic may be amplified and the first harmonic may be suppressed in this kind of FEL with an optimized parameter Δk. The coupling coefficient and gain coefficient in low-gain regime of the harmonic are also obtained.
Very High Photorefractive Gain in Two-Beam Coupling with Thin Iron-Doped LiNbO3 Crystal
ZHANG Jingwen, SUN Wanjun, BIAN Shaoping, XU Kebin, SUN Guangyao, LI Minghua*, XU Yuheng*
Chin. Phys. Lett. 1993, 10 (4): 227-230 .  
Abstract   PDF(pc) (246KB) ( 546 )
The largest exponential gain coefficient ( Γ=250 cm-1), to our knowledge, is obtained in thin (d=0.20mm) iron-doped LiNbO3 crystal. The dependence of two-beam coupling coefficients on beam crossing angle are measured and compared in two samples fabricated from the same material with different values of thickness. The explanation based on light climbing effect is given.

CW Self-Frequency-Doubling Laser Operating on Nd : MgO : LiNbO3 High-Gain Polarization
LI Ruining, WANG Junmin, LIANG Xiaoyan, XIE Changde, PENG Kunchi, XU Guanfeng*
Chin. Phys. Lett. 1993, 10 (4): 231-234 .  
Abstract   PDF(pc) (207KB) ( 508 )
The CW second-harmonic wave of high-gain polarization at λ=l.085μm was demonstrated with Nd : MgO : LiNbO3 self-frequency-doubling laser cavity inserted with a quarter wave-plate of the fundamental wavelength. The pump power threshold for the second-harmonic generation as low as 9.9mW was achieved. The maximum second-harmonic output was 11.4 m W, the conversion efficiency for the total second-harmonic output was 11.3% per Watt.
Diffraction from the Second-Order Photorefractive Grating in Paraelectric KTa1-xNbxO3 Crystals
LIAN Yingwu, YANG Changxi, YE Peixian, GUAN Qingcai, WANG Jiyang
Chin. Phys. Lett. 1993, 10 (4): 235-238 .  
Abstract   PDF(pc) (172KB) ( 486 )
Diffraction from the second-order photorefractive grating written in KTa1-xNbxO3 (x=0.32) crystal with cubic phase has been observed for the first time. The behaviors of this diffraction have been investigated experimentally. Some qualitative explanations have been proposed.

Variation of Defective Structure During the Grain Growth of Nanocrystallites
LIU Xuedong, ZHU Jie*, WANG Jingtang
Chin. Phys. Lett. 1993, 10 (4): 238-241 .  
Abstract   PDF(pc) (351KB) ( 459 )
In this paper, we report the variation of defective structure of nanocrystalline Fe-Mo-Si-B alloys with the increase of grain size. Results suggest that for the average grain size D=55 nm, microvoid-sized defects exhibit maximum volume and minimum concentration.

Multi-photon Up-conversion Luminescence of ErP5O14 Noncrystalline
CHEN Xiaobo, ZHANG Guangyin, WANG Hong, LIU Yanbin, LI Jiaji CHEN Jinkai, ZHANG Wanlin, SHANG Meiru
Chin. Phys. Lett. 1993, 10 (4): 242-244 .  
Abstract   PDF(pc) (167KB) ( 555 )
In this paper we report the observation of multi-photon up-conversion luminescence phenomenon of ErP5O14 noncrystalline induced by pulse DCM dye laser and clarify that the mechanism of up-conversion is the step by step absorption of single Er3+ ion.
Green’s Function and Density of States of Fibonacci Quasicrystal
ZHONG Jianxin, YAN Jiaren
Chin. Phys. Lett. 1993, 10 (4): 245-248 .  
Abstract   PDF(pc) (183KB) ( 908 )
We present a new real-space decimation approach to calculate the electronic average Green’s function and density of states of Fibonacci lattice. The approach only concerns with the deflation rule of the lattice. The average Green’s function and the density of states can be calculated in a simple manner to any degree of accuracy.
Photoexcitation and Decay of Higher Order Bands in Neutron Irradiated Silicon
SHI Yi, WU Fengmei, ZHENG Youdou, KOji SUMINO*
Chin. Phys. Lett. 1993, 10 (4): 249-252 .  
Abstract   PDF(pc) (266KB) ( 450 )
The optically induced excitation and decay processes of the higher order bands in fast neutron irradiated silicon have been investigated in detail using Fourier transform infrared spectrometer at low temperatures with a variety of illumination intensity. It is found that the excitation process follows an exponential time dependence and the decay follows a logarithmic. The present results suggest that the characteristic of the optically active of the higher order bands is associated with the slow relaxation of photoexcited carriers.
Dynamics of Spacing Selection for Lamellar Eutectics in Directional Solidification
LIU Junming, LIU Zhiguo, WU Zhuangchun
Chin. Phys. Lett. 1993, 10 (4): 253-256 .  
Abstract   PDF(pc) (214KB) ( 518 )
Profile and its splitting features of solidifying interface of lamellar eutectic in directional solidification have been investigated by solving numerically the nonlinear coupling equation of solidification. It is argued that critical splitting point of the solidifying interface Is marginally stable, and therefore is the possible operating point of spacing selection dynamics. Three modes of the dynamics are proposed, and a new scaling law of the lamellar array is derived, which has a more general form than the classic one.
18 articles