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Volume 10 Issue 12
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Original Articles
Interactions Between Higgs Field and Gravitation
CHEN Fangpei
Chin. Phys. Lett. 1993, 10 (12): 705-708 .  
Abstract   PDF(pc) (152KB) ( 474 )
The invariant properties of the Lagrangian densities for a physical system comprising fermion fields, Higgs fields, internal gauge fields and gravitational fields under gauge group transformations are studied. Utilizing these invariant properties and after Eggs mechanism, three fundamental and general equations concerning the interaction between Higgs bosons and gravitation are derived.
Brown-Rho Conjecture and Quantum Hadrodynamics
ZHANG Yijun, SU Rukeng
Chin. Phys. Lett. 1993, 10 (12): 709-711 .  
Abstract   PDF(pc) (111KB) ( 476 )
The Brown-Rho conjecture about the effective mass of nucleon at finite-temperature and finite-density is checked from the quantum hadrodynamics (QHD)-II model. We find that under mean field approximation, the effective mass of nucleon given by QHD-II model has a best fit with Brown-Rho conjecture, but transition temperature is a function of density.
New Feature of Long-Range Correlations in Hadron-nucleus Interactions
FENG Shengqin, ZHOU Daicui*
Chin. Phys. Lett. 1993, 10 (12): 712-715 .  
Abstract   PDF(pc) (215KB) ( 329 )
A new characteristic phenomenon of the dependence of long-range correlations among produced particles on the number of recoiled protons, Np, in hadron-nucleus collisions at high energy is found in our investigation by using the data of the NA5 experiments at CERN/SPS, which shows an obvious stepwise structure in the correlation strength as a function of the upper limit of Np. A model based on the concept of effective target is proposed to explain this phenomenon.

Photon Production : a Signature of Quark-Gluon Plasma Formation in Relativistic Nuclear Collisions
ZHOU Baosen, AI Xiaobai(Ai Hsia-bai)
Chin. Phys. Lett. 1993, 10 (12): 716-719 .  
Abstract   PDF(pc) (236KB) ( 395 )
Considering the influence of latent heat, the photon spectra from the quark-gluon plasma (QGP) and from the hadronic background are calculated. A “full stopping scenario” which assumes a spherical nuclear fireball expanding in a 3+1 dimensional flamework is addressed to solve the relativistic hydrodynamic equations. Our results show that at large transverse momenta, say pr≥ 4 - 5 GeV/c, one may probably expect to distinguish the photons originating in QGP from in the hadronic background. According to the measured total spectrum authors pose a graphical method to diagnose if QGP exists.
A Molecular Dynamics Simulation of C60-C60 Collision
LIU Lei, CHEN Kaitai, LI Yufen
Chin. Phys. Lett. 1993, 10 (12): 720-723 .  
Abstract   PDF(pc) (196KB) ( 545 )
The formation process of C120-complex in C60- C60 collision has been dearly demonstrated by a molecular dynamics simulation. The complex, with a peanut-shell-like structure, is in a quite stable dynamical state. The results are consistent with recent observations.
Generation of Sub-Poissonian Light in an Open-Loop LED System by the Quantum Correlation
YIN Jianping*, WANG Yuzhu
Chin. Phys. Lett. 1993, 10 (12): 724-727 .  
Abstract   PDF(pc) (221KB) ( 569 )
This paper describes the generation and observation of sub-Poissonian light in an open-loop system with low quantum efficiency at room temperature. The experimental results show that the photocurrent fluctuation spectrum density can be reduced below the shot noise Emit by 72% (-5.5dB) in an open-loop light-emitting diode (LED) system at the frequency of 2MHz. The noise reduction is not limited by quantum efficiency of the LED, or the current transfer efficiency.
Tuning Curves of 70 MHz Frequency Differences for HeNe Standing-Wave Lasers
ZHANG Shulian, HAN Yanmei
Chin. Phys. Lett. 1993, 10 (12): 728-730 .  
Abstract   PDF(pc) (148KB) ( 619 )
Two experiments are reported on measuring the variation of the frequency differences for the standing wave lasers with tuning the cavity length. The frequency difference is caused by an intracavity quartz crystal plate (laser mode splitting technology,). The relative variation of the frequency difference during the tuning are about 10-3 order from the edge to the centre of lasing bandwidth. The difference between the largest and the smallest frequency differences is two orders as large as that of ring lasers.
Direct Imaging of Excimer Laser Induced Plasma Near the Surface of YBa2Cu3O7-xTarget
LIU Darning, LU Dongsheng, LI Zaiguang, LU Ling, LEI Zhiliang
Chin. Phys. Lett. 1993, 10 (12): 731-733 .  
Abstract   PDF(pc) (137KB) ( 435 )
Using an optical spectroscopy analyzer, the axial and radial distributions of emission spectra intensities of XeCl excimer laser induced plasma near the surface of YBa2Cu3O7-x target were measured. The angular distributions of excited species in the laser plasma plume were obtained by curve fitting. They followed cosnθ when the incident laser power density was 2.24x108 W/cm2 and the background oxygen pressure was 2x10-1 Torr, where the value of n was between 3.66 and 5.56.
Photoelastic Visualization of Ultrasound Generated by Pulsed Laser
ZHANG Shouyu, ZHANG Pengzhi, SHEN Jianzhong, DENG Jingjun, YING Chongfu
Chin. Phys. Lett. 1993, 10 (12): 734-736 .  
Abstract   PDF(pc) (142KB) ( 459 )
We applied the dynamic photoelastic technique to visualize the ultrasound generated in a glass sample by an Nd: YAG pulsed laser. When a laser pulse was incident on the surface of the glass sample covered by thin layer of black ink, narrow pulses of longitudinal, shear, and surface acoustic waves were seen in the sample. The photoelastic picture also showed that the directivity patterns of ultrasound generated in the present case qualitatively agree with the theoretical prediction for the case of a normal surface-acting force.
Exact Solution of Soliton Model in Deformable Two-Dimensional Electron-Phonon System
WANG Yi, HUANG Xiaowu, DU Yijin
Chin. Phys. Lett. 1993, 10 (12): 737-740 .  
Abstract   PDF(pc) (161KB) ( 396 )
The total Hamiltonian is generalized to the case of a polaron moving in deformable two-dimensional electron-phonon system. A nonlinear Schrödinger equation for 2D deformable medium is derived, and an exact solitary-wave solution is obtained by the method of series of functions.
Electronic Structure of Beta Silicon Nitride
WANG Renzhi, CHEN Chuanhong
Chin. Phys. Lett. 1993, 10 (12): 741-743 .  
Abstract   PDF(pc) (168KB) ( 438 )
Electron structure of silicon nitride β-Si3N4 was calculated by LMTO-ASA method cooperated with the use of Löwdin perturbation technique that saved computation time considerably. The results are in good agreement with that of ab initio pseudopotential method and indicate that appropriate setting of empty spheres is especially important for a crystal with a widely open structure.
LMTO Study on Band Structure of β-SiC/β-GaN (100) Interface
LU Wenchang, ZHANG Kaiming, XIE Xide
Chin. Phys. Lett. 1993, 10 (12): 744-747 .  
Abstract   PDF(pc) (232KB) ( 524 )
The linear muffin-tin orbital method and the supercell approach are used to study the band structures of the β-SiC/β-GaN (100) interface within the atomic sphere approximation. It is found that the Si-N, C-Ga bonding configuration is favorable. The band alignment is of type-I with the band gap of the β-GaN completely endosing the band gap of the β-Sic. The localized interface state strongly related to the interface C atoms exists in the original band gap.
Electronic Structures of Wurtzite Compounds GaN, AlN and Strained-Layer Superlattice (Ga2N2)1(A12N2)1(001)
KE Sanhuang, HUANG Meichun, WANG Renzhi
Chin. Phys. Lett. 1993, 10 (12): 748-751 .  
Abstract   PDF(pc) (215KB) ( 990 )
The electronic structures of wurtzite compounds GaN, AlN and strained-layer superlattice (SLS) (Ga2N2)1(A12N2)1 (001) constituted by straining GaN-layer to match the lattice constant of AlN according to the elastic theory are studied with the first-principles Linearized-Muffin-Tin-Orbitals band-structure method. The band offsets at the SLS are determined by the frozen potential approach. The resutls of the bulk materials are in good agreement with available experimental data.
Photoabsorption Spectra of Nano-Crystalline Silicon Films
LIU Xiangna, HE Yuliang, F. Wang*, R. Schwarz*
Chin. Phys. Lett. 1993, 10 (12): 752-755 .  
Abstract   PDF(pc) (177KB) ( 553 )
The photoabsorption spectra of nano-crystalline silicon (nc-Si :H) films were measured by means of constant photoconductivity method. We investigated the changes of absorption spectra with the increasing of crystallinity as the deposited films are amorphous, microcrystalline and nano-crystalline. We found that in nc-Si : H the transition processes in the interfacial region between the grains predominate the whole range of the absorption spectra. We related the phenomenon to the structural changes in the material.
Femtosecond Spectroscopy Studies on YBa2Cu3O7-x and PrBa2Cu3O7-x Epitaxial Thin Films
ZENG Wensheng*, LIN Weizhu*, ZHU Derui*, PI Feipeng*, XU Geng*, MO Dang*, XIA Zongju, ZOU Yinghua, WANG Jingjing, YUAN Ping, XIONG Guangcheng, GAN Zizhao
Chin. Phys. Lett. 1993, 10 (12): 756-758 .  
Abstract   PDF(pc) (186KB) ( 413 )
We report the results of femtosecond spectroscopy studies on YBa2Cu3O7-x (x=0.1, 0.4, 0.8) and PrBa2Cu3O7-x (x=0.l) epitaxial thin films at room temperature. The transient reflectivity signals ΔR(t) in the samples are consistent with a band filling model. The relaxation times of ΔR(t) in YBa2Cu3O7-x increase from less than 100 fs to more than 1ps with increasing x and with substitution of Pr for Y. These results reveal that in high Tc superconductors decrease of carrier concentration slows down the carrier-phonon coupling.

15 articles