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Volume 11 Issue 7
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Original Articles
Empirical Effective Interaction in 22MeV Proton Scattering
AN Zhu*, CHEN Quan, DING Dazhao, SHI Zongren, WAN Shuyang, GAO Keyang
Chin. Phys. Lett. 1994, 11 (7): 401-404 .  
Abstract   PDF(pc) (205KB) ( 366 )
Inelastic differential cross sections of 22 MeV proton scattering for 5 excited states of 28Si have been measured from 10° to 115°. Empirical effective interactions were extracted within the frame of DWBA from the normal parity state data which transition densities were known from electron scattering. The fitting is good except for the forward angle of 4+1 and 0+2 states. The results are discussed.
Hanbury-Brown-Twiss Correlations for Expanding Hadron Matter
ZHAO Weiqin, GAO Chongshou, ZHANG Qinghui
Chin. Phys. Lett. 1994, 11 (7): 405-408 .  
Abstract   PDF(pc) (168KB) ( 417 )
A formula for the two-pion correlation function is derived for a chaotic source when the emission spectrum from each space-time point is known. It is shown that without fully understanding of the evolution process of the source, no real source size can be obtained.
Perturbation-Variational Approach to Hydrogen Atoms in Strong Laser Fields
CHEN Baozhen
Chin. Phys. Lett. 1994, 11 (7): 409-411 .  
Abstract   PDF(pc) (113KB) ( 436 )
In this letter, a perturbation variational approach (PVA) to atomic behavior in strong laser fields is expressed briefly. For the wide range of α0 = 0.1 →50, the ground state energy of H-atom in laser fields is obtained by the present approach. The energy values obtained by PVA agree with the previous values given by Landgraf and Gavrila. In contrast, the advantage of the present method is to give both the energy eigenvalue and the wavefunction of the ground state analytically.
Highly-Excited Double Rydberg States of Ytterbium
XU Xiangyuan, HUANG Wen, XU Chengbin, XUE Meng, CHEN Dieyan
Chin. Phys. Lett. 1994, 11 (7): 412-415 .  
Abstract   PDF(pc) (220KB) ( 513 )
By using five-laser resonance excitation in combination with a new detection method, the highly-excited double Rydberg states NLn’l (N ≥ 40, N/n’≥ 0.5 and L, 1 < 4) of Yb have been observed. The relative excitation strengths between the Δl allowed and forbidden core transitions can be quantitatively measured. Analysis of the spectra has revealed the strong electronic correlation in such highly excited states.

Deducing Plasma Density Profile From Stimulated Raman Scattering Spectrum
ZHANG Jiatai, WANG Weixing, CHANG Tieqiang
Chin. Phys. Lett. 1994, 11 (7): 416-418 .  
Abstract   PDF(pc) (208KB) ( 496 )
A new feasible approach for diagnosing plasma density profile is given in this paper. Plasma density profiles of some hohlraum targets are obtained by comparing theoretical and experimental results of the stimulated Raman scattering (SRS) spectrum. The theoretical model of SRS is three-wave coupling equations.
Transparency Induced by Two-Photon Coherence in the V-Shaped Three-Level System
XU Gu, WANG Yuzhu, YE Chao, ZHOU Shanyu, ZHAO Jiaming, LIU Yashu
Chin. Phys. Lett. 1994, 11 (7): 420-423 .  
Abstract   PDF(pc) (192KB) ( 414 )
We have investigated th steady-state behavior of a V-shape three-level system submitted to the radiative field and to the relaxation process. The coherence induced by simultaneous two-photon transition leads to a strong decrease of medium absorption. In this case, the peak of transparent spectrum is 7 times higher than that of saturant spectrum.
Squeezing Properties of Even Coherent States in a Finite-Dimensional Hilbert Space
ZHU Jiuyun, KUANG Leman
Chin. Phys. Lett. 1994, 11 (7): 424-427 .  
Abstract   PDF(pc) (154KB) ( 574 )
Even coherent states (ECSs) of a finite-dimensional Hilbert space harmonic oscillator (FDHSHO) are constructed explicitly. Some properties of them are discussed. The quadrature squeezing and the amplituded-squared squeezing of these states are investigated in detail. It is found that ECSs of the FDHSHO exhibit not only the quadrature squeezing but also the amplituded-squeezing.
Nonlinear Two-Dimensional Debye Screening in Plasmas
LIN Chang
Chin. Phys. Lett. 1994, 11 (7): 428-430 .  
Abstract   PDF(pc) (99KB) ( 401 )
A general analytical solution for the two-dimensional Poisson equation has been obtained for the nonlinear Debye screening in plasmas. We derive an exact analytical expression for Te = Ti and an approximate expression for Te ≠ Ti for the two-dimensional nonlinear Debye potential.
Formation of the Bicrystal Structure of KTiOPO4 Crystals
SHI Luping, WANG Jiyang, LIU Yaogang, SHAO Zongshu, JIANG Minhua, LIU Xiangyang*
Chin. Phys. Lett. 1994, 11 (7): 431-434 .  
Abstract   PDF(pc) (231KB) ( 496 )
In this paper, by comparing the three possible combinations of the basic structure unit TiO6 octahedra, a simple model is proposed to explain the cause of the formation of the bicrystal structure in KTiOPO4 (KTP) crystals. The theoretical morphology of KTP crystal is studied and the rate of the appearance possibilities of different faces are obtained. The relationships between bicrystal structure and crystal properties are discussed.
Improved Method of Behavior Type Analysis
WANG Yingzong
Chin. Phys. Lett. 1994, 11 (7): 435-438 .  
Abstract   PDF(pc) (157KB) ( 479 )
Zhou-Goovaerts-Schoemaker’s behavior type method for determining the representative mode of defect vibration in cubic crystal is improved in this paper. In the optimum method the combination of the random operator T with the orienting operator C2 [100] plays a central role. The relations between the representative modes and the distribution of the measurable polarized Raman intensities in normal Raman experiment are derived and listed as a table which can make the experiment design and analysis become easier.
Interaction Hamiltonian Between an Electron and Interface Optical Phonons in a Four-Layer Heterostructure
SHI Junjie*, PAN Shaohua
Chin. Phys. Lett. 1994, 11 (7): 439-442 .  
Abstract   PDF(pc) (179KB) ( 523 )
The interaction Fröhlich-like Hamiltonian between an electron and interface optical phonons in a four-layer heterostructure (FLHS) is obtained by means of the orthonormal eigenmodes of interface optical phonons given recently. The electron-phonon coupling functions and their plots for a FLHS and its special cases, an asymmetric trilayer heterostructure (asymmetric single quantum well) and a step quantum well, are given and discussed. We find that the three branches of higher-frequencies are more important for the electron-phonon interaction than the other three in the six branches of interface modes in a FLHS. Moreover, we also find that the situation in an asymmetric trilayer heterostructure is similar to that of a FLHS.

Instantaneous Electron Concentration in Crystalline Insulator Foils Being Irradiated by Charge-Neutral Rays
XIE Xishun, GUAN Xiaosheng, HUANG Xiaoqin
Chin. Phys. Lett. 1994, 11 (7): 443-446 .  
Abstract   PDF(pc) (166KB) ( 446 )
In this paper, we present an analytical solution of the steady and transient electron concentration in a crystalline insulator film exposed to a charge-neutral radiation. If a single, deep electron trap level is supposed, the steady conductivity is found to coincide with the power law. An asymptotic exponential solution of transient electron concentration has also been got when the irradiation-time is very large.
Solitary Magnon Localization in Antiferromagnet Ni( C2H8N2)2NO2C1O4
LIU Wuming, ZHOU Benlian
Chin. Phys. Lett. 1994, 11 (7): 447-450 .  
Abstract   PDF(pc) (168KB) ( 479 )
Employing the Holstein-Primakoff transformation and the coherent state ansatz, we obtain two partial differential equations of motion from Hamiltonian. Using the method of multiple scalar, we reduce these equations into a nonlinear Schrodinger equation and get the single soliton solution. These results show that solitary magnon localization in antiferromagnet Ni(C2H8N2)2NO2C1O4is possible.
Fluorescence Properties of Nd : CeF3 Crystals
GAO Ming, FENG Xiqi, HU Guanqin, YIN Zhiwen
Chin. Phys. Lett. 1994, 11 (7): 451-453 .  
Abstract   PDF(pc) (155KB) ( 519 )
Four Nd : CeF3 crystals doped with 0.1, 0.5, 1.0 and 2.0 wt.% Nd3+ are grown, their absorption and fluorescence spectra are measured. The absorption bands of Nd : CeF3 are much wider than that of Nd: YAG. The absorption peak at 353nm does not depend on Nd3+ concentration linearly and there exists no concentration quenching effect while Nd3+ concentration is less than 2.0wt.%. The fluorescence lifetime and the effective stimulated cross section are measured, respectively, as Tr = 300μs and σc = 2.4 x 10-20 cm2.
Blue-Green Electroluminescent Diodes Utilizing Tris (8-Quinolinolato)-Aluminum Doped Poly (Vinylcarbazole)
MA Yuguang, TANG Jianguo, LIU Shiyong, ZHANG Ruifeng*, SHEN Jiacong*
Chin. Phys. Lett. 1994, 11 (7): 454-456 .  
Abstract   PDF(pc) (164KB) ( 470 )
Blue-green electroluminescent diodes utilizing tris (8-Quinolino1ato)-aluminum doped poly (vinylcarbazole) have been demonstrated. A Schottky-type electroluminescent diode of the polymer film is driven at 20V and has a peak emission wavelength of 490nm at room temperature with lifetime up to 4 h.
Ultrafast Time-Resolved Optical Kerr Effect in Phthalocyanine Langmuir-Blodegett Film
YUAN Ping, XIA Zongju, ZOU Yinghua, QIU Ling*, SHEN Jifeng*, SHEN Yuquan*, XU Huijun*
Chin. Phys. Lett. 1994, 11 (7): 457-460 .  
Abstract   PDF(pc) (204KB) ( 395 )
The resonant optical Kerr effect in the Langmuir-Blodegett film of 2, 9, 16, 23-tetra heptadecylamido substituted vanadyl phthalocyanine was measured with femtosecond laser pulses to determine the relaxation time, and meanwhile slow decay components were observed. The ultrafast nonlinearity of the molecule was also measured.
CNx Films Deposited by Laser Ablation of Graphite Under Low Energy Nitrogen-Ion Beam Bombardment
REN Zhongmin, XIONG Xiaxing, DU Yuancheng, WU Jiada, YING Zhifeng, QIU Yuanxun, LI Fuming
Chin. Phys. Lett. 1994, 11 (7): 461-464 .  
Abstract   PDF(pc) (240KB) ( 481 )
Deposition of CNx thin films on Si(111) has been performed by laser ablation of graphite under a low-energy nitrogen ion beam bombardment. Films with a maximum N-concentration of 34% are obtained. The N species is found to be relatively constant along the depth of films. X-ray spectroscopy data confirm the existence of covalent C - N bonds. Nanocrystallites structure has been detected in the amorphous matrix of the films. Qualitative hardness tests indicate that the films are relatively hard and adhesive.

17 articles