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Volume 5 Issue 8
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Original Articles
PROBLEMS ON A POSSIBLE FOURTH GENERATION DOWN QUARK OF MASS 23GeV
ZHAO Guangda, QIN Danhua, DING Yihing*, CAI Shenou**
Chin. Phys. Lett. 1988, 5 (8): 337-340 .  
Abstract   PDF(pc) (40KB) ( 368 )
For a possible fourth generation down quark of mass 23GeV we discuss the problems on the energy gap between hidden and open channels for the new flavor and on peculiar fermion mass relations in view of the grand unification. It is unlikely to be the conventionally expected fourth generation down quark.
EFFECTIVE MEDIUM THEORY OF MULTIPHASE MIXTURE AND SELECTIVE ABSORPTION OF ELECTROLYTICALLY COLORED ANODIC ALUMINUM OXIDE
WANG Yiping, WU Zhengsen
Chin. Phys. Lett. 1988, 5 (8): 341-344 .  
Abstract   PDF(pc) (49KB) ( 314 )
The effective medium theory is extended to multiphase mixture, and a corresponding formula of effective complex dielectric permittivity is derived. An electrolytically colored anodic aluminum oxide is regarded as a multilayer absorption composite, and the reflectances of Au-Cu-A12O3 and Ag-Cu- A12O3 coatings have been measured.
ELECTRON CYCLOTRON RESONANCE HEATING ON CT-6B TOKAMAK
LUO Yaoquan, WANG Long, YANG Size, QI Xiazhi, LI Zanliang, WANG Wenshu, LI Wenlai, WU Xiaowen, ZHAO Hua
Chin. Phys. Lett. 1988, 5 (8): 345-348 .  
Abstract   PDF(pc) (44KB) ( 436 )
An electron cyclotron resonance heating experiment has been performed by using a gyrotron system for the fundamental and second harmonic resonance heating on CT-6B tokamak. Obvious changes are observed in soft X-ray radiations, electron cyclotron emission, displacement of plasma column, impurity line radiations, and bremsstrahlung radiation when heating pulse is injected, indicating an increase of the plasma electron temperature.
COHERENT WAVE MIXING PROCESS BY USING METASTABLE ATOMS
ZHANG Jie, CHENG Bingying, ZHANG Daozhong, ZHAO Lizeng, ZHAO Yuying, WANG Tianjuan
Chin. Phys. Lett. 1988, 5 (8): 349-352 .  
Abstract   PDF(pc) (47KB) ( 365 )
In PbCI2 vapor under the mutual interaction of two laser beams with wavelengths at λ1=266nm and λ2=280.2nm ( or 282.3nm), a strong coherent emission at 405.8nm is generated, which corresponds to transition between states 6p7s 3p01 and 6p2 3p2 in atomic Pb. The dependences of its intensity I405.8 on the power and detuning of λ2 are measured. The results show that it is caused by a four-wave mixing process in Pb, in which the initial state is a metastable state, 6p2 3p2.
NN PAIR EMISSION IN GaAs0.15P0.85: N UNDER HYDROSTATIC PRESSURE
ZHANG Yong, YU Qi, ZHENG Jiansheng, YAN Bingzhang, WU Boxi, LI Guohua, WANG Zhaoping, HAN Hexiang
Chin. Phys. Lett. 1988, 5 (8): 353-356 .  
Abstract   PDF(pc) (48KB) ( 426 )
The photoluminescence of GaAs0.15P0.85: N has been studied at 77K under hydrostatic pressure. The NN1 emission is clearly observed when P>l0kbar. This result indicates that pressure enhances the thermally assisted Nx→NN1 exciton transfer. The pressure behaviors of Nx and NN1 levels are analysed.
EXPERIMENTAL STUDY ON STIMULATED RAMAN SCATTERING ORIGINATED FROM METASTABLE POPULATION OF ATOMIC Pb
ZHANG Daozhong, ZHANG Jie, CHENG Bingying, ZHAO Lizeng, ZHAO Yuying, WANG Tianjuan
Chin. Phys. Lett. 1988, 5 (8): 357-360 .  
Abstract   PDF(pc) (54KB) ( 773 )
Under excitation of 355nm or 266nm UV radiation some strong emissions have been observed in PbI2 vapor. Analysis shows that they are 1st, 2nd order Stokes and 1st anti-Stokes components of 355nm laser and 1st order Stokes and enti-Stokes components of 266nm laser. The initial states of Raman transition are 6p2 3p1 and 6p2 3p2 metastable states of atomic Pb, respectively. The population on it is created by photodissociation of PbI2. The dependences of Raman components on pump power, PbI2 density and pressure of buffer gas are investigated experimentally.
THE EFFECTIVE PENETRATION DEPTH OF A HIGH-Tc SUPERCONDUCTOR YBa2Cu3O7
PENG Jinlin*, YAN Shousheng, ZHANG Hang+, SUN Yunxi, LI Guozhong, ZHANG Wenbin, WEN Qingzhe
Chin. Phys. Lett. 1988, 5 (8): 361-364 .  
Abstract   PDF(pc) (53KB) ( 371 )
The dependence of the effective penetration depth λe, on the external magnetic field in a high-Tc superconducter YBa2Cu3O7 has been measured by both dc and ac methods at liquid-nigtrogen temperature. It is found, that λe increases rapidly with increasing external field and is 0.13~0.15mm in macroscopic scale. The Hcl of the specimen, about 800e at 77K here, can be determined more reliably by comparing dc λe with ac λe . The difference between λedc and λeac, and the jumping of λedc may indicate the characters of superconducting glass.

THE MAXIMUM LENGTH SCALE OF OBJECTS WTTH RFGULAR CONFIGURATION IN THE UNIVERSE
FANG Lizhi, YAN Lin*
Chin. Phys. Lett. 1988, 5 (8): 365-368 .  
Abstract   PDF(pc) (52KB) ( 417 )
The maximum length scale of objects with regular configuration, which is the configuration of virialized objects, has been discussed in cosmic string theory. It was shown that this maximum scale is about the same as that of clusters of galaxies. This result can be used to explain why the objects with scale Less than clusters of galaxies often possess symmetrical configuration, while larger objects are always irregular.
A POSSIBLE PICTURE OF HIGH-TC SUPERCONUUCT
FENG Shiping, XING Dingyu*
Chin. Phys. Lett. 1988, 5 (8): 369-372 .  
Abstract   PDF(pc) (43KB) ( 370 )
The extended Hubbard model proposed by Emery for CuO2 basal plane is used to discuss high temperature superconducting oxides. It is shown that oxygen holes may form singlet pairs with neighbouring copper holes and those singlet pairs may lead to super conductivity.
THE MAGNETIZATION PROPERTIES OF HIGH-Tc YBa2Cu3O~7 SUPERCONDUCTING RING
YAN Shousheng, PENG Jin lin, SUN Yunxi, LI Guozhong, ZHANG Wenbin, WEN Qingzhe, ZHANG Hong*
Chin. Phys. Lett. 1988, 5 (8): 373-376 .  
Abstract   PDF(pc) (52KB) ( 355 )
The magnetization properties of an YBa2Cu3O~7 superconducting ring were measured at about 80K. The critical field of most of weak couplings is readily obtained and is 170e for the material used. The current is most likely distributed in the body of the specimen. The magnetization measurement of a ring-shape specimen may be a good method to study the characters of weak couplings in oxides superconductors.
RAMAN SCATTERING IN FIBONACCI METALLIC SUPERLATTICES
ZHANG Xingkui, XIA Hua, HU An, ZHU Shining
Chin. Phys. Lett. 1988, 5 (8): 377-380 .  
Abstract   PDF(pc) (44KB) ( 429 )
Raman scattering experiments from acoustic phonons in Fibonacci metallic Nb-Cu superlattices were performed. The main features of the experimental results show that the Raman spectrum is dominated by triplet peaks which originate from the density of states of longitudinal - acoustic (LA) phonons in the subbands of phonon dispersion. The expected rich structure of gaps in the phonon spectrum has been labeled by strongest diffraction wave vector factor nτP.
η-ξ VACUUM AND THERMAL GREENS FUNCTIONS
XU Feng, GUI Yuanxing*
Chin. Phys. Lett. 1988, 5 (8): 381-383 .  
Abstract   PDF(pc) (28KB) ( 370 )
In the previous paper, a new vacuum state was defined. As claimed in that paper, this vacuum state is a thermal state in the ordinary sense. In this paper, we derive the Greens function of this vacuum and prove that it is exactly the ordinary finite temperature thermal Green function. So we demonstrate that this state is exactly the thermally equilibrium state.
12 articles