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Vol. 36, No. 3 (1987)

1987-02-05
CONTENT
APPLICATION OF RANDOM TRANSFORMATION TO NON-CIRCULAR CROSS-SECTION PLASMA DIAGONOSTICS
LI DING, HUO YU-PING
1987, 36 (3): 275-283. doi: 10.7498/aps.36.275
Abstract +
In this article, a new way is explored, which uses the method of image reconstruction from the projection based on the theory of random transformation, to determine simultaneously the magnetic configuration and 2-D distribution of physical quantities of non-circular cross-section plasma from the diagonostic results. Assuming that the distributions of the physical quantities only depends on the magnetic surface function and all the surfaces are similarly concentric, we have proposed three methods of treatment. For D-shaped plasma, the analytical treatment and numerical simulation have been discussed in detail. An example of determination of magnetic configuration and electron temperature and density from soft X-ray and microwave interference measurements has been demonstrated.
THE KINETIC THEORY ON rf WAVE CURRENT DRIVING IN NON-UNIFORM PLASMAS
PAN CHUAN-HONG
1987, 36 (3): 284-292. doi: 10.7498/aps.36.284
Abstract +
We used the Green's function method to solve the quasilinear Fokker-Planck equation and obtained the rf wave current-driving effeciency in non-uniform plasmas. It is shown that the current-driving effeciency increases considerably if the non-uniformity is taken into account, and the effeciency decreases with increasing β.
SILICON FILM DEPOSITED BY LASER-PLASMA
FU GUANG-SHENG, HAN LI, LI XIAO-WEI, ZHANG LIAN-SHUI, DONG LI-FANG, LU FU-RUN, XUE CHUN-YIN
1987, 36 (3): 293-300. doi: 10.7498/aps.36.293
Abstract +
In this work, the laser diposition process of Si thin film at low temperature and under low pressure is studied. We obtain both poly-crystalline and non-crystalline films, the sizes of them are about a few cm2, and they are satisfactorily homogeneous. The optimum condition of diposition process is determined care-fully. When the pedestal temperature is 380°, poly-crystalline films are formed. Based on the model of photo-breakdown of SiH4 through resonant absorption of laser and energetic Si-atom formation induced by the shock waves produced thereafter, the laser plasma CDV dynamic process is analysed. We find that the photo-breakdown of SiH4 by TEA CO2 laser and the induced shock waves have important influuences on the growth of Si films. The sizes and crystalline structure of Si films as calculated theore tically agree qualitatively with experimental results.
EXPERIMENTAL STUDIES OF EXCITED STATES IN COLLISIONS BETWEEN He+ AND Ar
PAN GUANG-YAN, LEI ZI-MING, LIU JIA-RUI
1987, 36 (3): 301-307. doi: 10.7498/aps.36.301
Abstract +
One electron capture process and direct exciting process both occured in collision between-He+ and Ar in energy range 70-150 keV. From the comparison of experimental results between He++Ar and He++Ne collision systems, we see that the emission cross sections of the triplet Hel of the former are much larger than those of the latter, when the velocity of incident ion He+ is small. The latter become larger than the former, when the velocity of He+ is greater than 1.0 a.u (2.2×108 cm/s). Therefore, the potential energy defect and the velocity of projectile are very important factors in the electron capture process and there is a competition between them-in collisions.
THE HIGH PRESSURE MODIFICATION OF LITHIUM POTASSIUM SULPHATE (LiKSO4) AND ITS P-T PHASE DIAGRAM ABOVE ROOM TEMPERATURE
SHEN ZHONG-YI, HU JING-ZHU, ZHANG YUN, YIN XIU-JUN
1987, 36 (3): 308-314. doi: 10.7498/aps.36.308
Abstract +
The high pressure transition and phase equilibrium beheviour of lithium potassium sulphate (LiKSO4) were studied by an improved high pressure DTA method and X-ray diffraction in a diamond anvil cell at elevated temperatures. The P-T phase diagram was accurately determined up to 3GPa and 800℃. A high pressure modification of LiKSO4 was observed beyond 1.65 GPa. The structure was determined to be orthorhombic with a = 7.933 ?, b = 9.493 ? and c= 9.679 ?, and its thermal expansion at high pressure and the stability of the quenched sample at normal pressure were also examined.
THE CONDUCTION PROPERTIES OF ELECTRONS IN CeBi UNDER PRESSURE
ZHONG FAN, JIN BIAN-JUN, HUANG TONG-KAI, MENG RU-LING
1987, 36 (3): 315-321. doi: 10.7498/aps.36.315
Abstract +
The electrical resistivity of CeBi single crystal has been measured in the temperature range 4.2-273 K and under pressure up to 18 kbar. The experimental results show that the Neel temperature increases with pressure and the magnetic resistivity ρs varies proportionally to InT at T>TN. By using Anderson model and taking into account p-f mixing mechanism, we calculated the pressure dependence of CeBi magnetic resistivity. The present results are compared with the experimental data. It is shown that the distance between the 4f level and the Fermi level decreases with rising pressure and pressure enhances the p-f interaction.
STUDY ON THE ELECTRICAL PROPERTIES AND MAGNETIC RESONANCE OF NONCRYSTALLINE MATERIALS IN THE Li2O-P2O5-V2O5 SYSTEM
CHUI WAN-QIU, RUAN LI-JIAN
1987, 36 (3): 322-331. doi: 10.7498/aps.36.322
Abstract +
The conductivity, NMR and ESR spectra of the specimens in the Li2O-P2O5-V2O5 system are measured. Conductivity measurements on these materials reveal a sharp break in the slope of the curve of log conductivity vs reciprocal temperature in the vicinity of transformation temperature. And the conductivity shows abnormal increasemant during pre-crystallization process above the break point, this is caused by the increase of degree of ordering during that process. Valency state analysis of vanadium ions by ESR show that only V4+ and V5+ ions exist in these materials. When P2O5/V2O5 mote ratio is fixed, the 7Li-NMR and V4+-ESR line width narrow clown continonsly with increasing lithia content, this indicates that ionic conductivity increases and electronic conductivity decreases continously in these materials. At first, conductivity de-creases with the increasement of lthia content, but it increases when lithia content exceeds 30 mol%. The conduction mechanism of these materials was also discussed.
PHASE RELATIONSHIP AND ELECTRICAL CONDUCTIVITY OF Li1+xGe2-xAlxP3O12 SYSTEM
LI SHI-CHUN, CAI JIAN-YI, LIN ZU-XIANG
1987, 36 (3): 332-338. doi: 10.7498/aps.36.332
Abstract +
Phase relationship and electrical conductivity of the system Li1+xGe2-xAlxP3O12 were studied.A good host compound LiGe2P3O12 was found. Solid solution with R3c structure can be formed in the range 04+ with Al3+ in LiGe2P3O12, and then an unknown phase appeared at x>0.6. The conductivity increased rapidly when Ge4+ was substituted by a small amount of Al3+(x=0.1). The conductivity increased with the increase of content of A13+ and reached a maximum at x = 0.5. The conductivities of Li1.5Ge1.5Al0.5P3O12 equal to 3.5×10-5, 1×l0-2 and 3.1×10-2 S cm-1 at room temperature, 300℃ and 450℃ respectivily. Activation energy of conduction is 0.33 eV, electron transfer number is about 10-5.
EXCITON-PHONON INTERACTION IN ALKALI HALIDE CRYSTALS
ZHENG HANG, FANG JUN-XIN
1987, 36 (3): 339-349. doi: 10.7498/aps.36.339
Abstract +
This article deals with the exciton-phonon interaction which has important effects on the properties of the charge transfer excitons (CTE) in alkali halide crystals. An interaction mechanism: the modulation of the Hamiltonian of the CTE system by the vibrations of the constituent ions, which may play an important role, is studied. The CTE-phonon interaction Hamiltonian is derived. From this interaction Hamiltonian, we have discussed the lifetime of the CTE. The linewidths calculated self-consistently under proper approximations agree semiquantitatively with the data measured by experiments in the literature. So we consider that this interaction Hamiltonian may present the important exciton-phonon interaction in alkali halide crystals.
ON GRAVITATIONAL SOLITONS
TAO FU-ZHEN
1987, 36 (3): 350-356. doi: 10.7498/aps.36.350
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A system of exact gravitational soliton solutions of Einstein's equations in vacuum is obtained. It is shown that gravitational solitons exist, which are regular everywhere, nondispersive and stable, popagating with constant velocity. Finally, The singularity and energy density of these gravitational solitons are also discussed.
BRIEF REPORT
A NEW CRITERION FOR SUPERCONDUCTIVITY OF ELEMENTS
WANG RONG-YAO, LUO QI-GUANG
1987, 36 (3): 357-362. doi: 10.7498/aps.36.357
Abstract +
This article gives a new criterion for superconductivity. It can be applied to all the ele-ments in periodic table. The criterion shows that the values of electronegativity of all superconducting elements concentrate in a narrow range from 1.3 to 1.9 and that the elements with values outside this region would be non-superconductive.Deepgoing studying the relation between electronegativity and superconductivity of elements will contribute to revealing the connection between electrostatic inter action of electron with crystal lattice and superconductivity, which is able to benefit further inquiries about the mechanism of superconductivity.
THE EFFECT OF PARALLEL CONDUCTANCE IN AlGaAs/GaAs HETEROJUNCTION
SHI CHANG-XIN, XIN SHANG-HENS, WU DING-FEN
1987, 36 (3): 363-367. doi: 10.7498/aps.36.363
Abstract +
The relationship between the gate voltage and charges in the parallel conducting layer has been calculated for AlGaAs/GaAs heterojunction, which is at large gate voltage and has the effect of parallel conductance. Then, the transconductance characteristics of the high electron mobility transistor (HEMT) is obtained. The comparison of theory and experiments are also made, and we find that they are in good agreement.
PRECURSOR STATES AND HIGH MOBILE PROPERTY OF H2O ON Pt(100) SURFACE
SHI DAN-HUA, CAO PEI-LIN
1987, 36 (3): 368-371. doi: 10.7498/aps.36.368
Abstract +
Using ASED-MO method, the binding energies for different adsorption orientations and positions of H2O molecule on Pt(l00), and the activation energies and coefficient of surface diffusion are calculated. It is found that there are precursor states for H2O chemisorption, through which the equilibrium geometry via O atom toward substrate on top position is reached. When H2O molecule is in the precursor states, the potential surface is very flat, the diffusion coefficient is large and the mobility is high.
ELECTRONIC STRUCTURE OF CMS SURFACES ——CPA METHOD
PANG GEN-DI, XIONG SHI-JIE, CAI JIAN-HUA
1987, 36 (3): 372-376. doi: 10.7498/aps.36.372
Abstract +
Based on tight-binding approximation, the electronic structure of CMS surfaces is discussed with the CPA method, combined with the infinite order perturbation theory. Both substitute disorder model and Anderson disorder model are included in numerical calculations.
ON THE EXACT PROOF OF THE METHOD OF INVERSE SCATTERING FOR SOLVING THE EQUATION OF A FERROMAGNETIC CHAIN AND ITS VERIFICATION
SHUAI ZHI-GANG, CHEN ZONG-YUN, HUANG NIAN-NING
1987, 36 (3): 377-381. doi: 10.7498/aps.36.377
Abstract +
In current deductions of the inverse scattering method for solving the equation of a ferromagnetic chain, the factor λ-1 brings about difficulties. In this note, we show that this factor should be dropped and an equivalent result to the Takhtajan's equation can be obtained, except for some expected corrections at point λ = 0. It is also verified that the solutions given by the ISM satisfy the equation of a ferromagnetic chain.
THE TWO MODE CONVERSION IN AN INHOMOGENEOUS MAGNETIZED PLASMA
YU WEI, XU ZHI-ZHAN, CHEN ZE-ZUN
1987, 36 (3): 382-385. doi: 10.7498/aps.36.382
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The field structures in the overdense region above the resonant paint of an inhomogeneous magnetized plasma are studied. Our work indicates that owing to the mutual conversion be-tween the extraordinary electromagnetic wave and the longitudinal plasma wave, the electromagnetic wave will grow again in the overdense plasma.
THE DAMAGE PHENOMENA ON INFRARED MATERIALS IRRADIATED BY INTENSE PULSED CO2 LASER
LI HUI-NING, WU ZHAN-LIN, LIU SHU-YING, MEI HUA, WANG CHUN-KUI, FANG HUI-YING, FU YU-SHOU, LI SHU-YING
1987, 36 (3): 386-390. doi: 10.7498/aps.36.386
Abstract +
Experiments show that the materials damage effects irradiated by intense CO2 laser can be divided into two types: the ablation and shock wave damage. The ablation is dominant when laser power density is lower than air breakdown threshold. When laser power density is higher than berakdown threshold, the shock wave damage becomes prime. Under our experimental condition, when strong laser beam irradiates on brittle targets such as infrared window materials MgF2, KCl, Ge, etc., small cracks or broken pieces are formed very easily. The damage effects are related to pulse energy, power density, pulse width and irradiated area on the target. The photographs of radiation damage are also given.
MECHANISM OF FORMATION OF C2* d3Пg STATE FROM CHCIF2 BY IRRADIATION WITH INTENSE IR LASER
WANG ZHENG-MIN, YANG LI-SHU, LIU ZONG-CAI, WU CHUAN-XIU, GE LI-HE
1987, 36 (3): 391-394. doi: 10.7498/aps.36.391
Abstract +
Electronically excited radicals C2* were formed from CHC1F2 molecules by irradiation with a TEA CO2 laser. Six bands of Swan system have been observed. The mechanism of the formation of C2*d3Πg state in the infrared multiphoton dissociation of CHC1F2 is presented based on the potential energy curves of the C2 molecule. C2 is a somewhat unnsual molecule, the state b3∑g- crosses the first excited state a3Πu at an internuclear distance of about 1.80?, and lies below it for greater nuclear separations. At first, the state b3∑g- is formed in the elementary step C + CF2 + M→C2* + F2 + M of the reactionsof the photoproducts of CHC1F2 in preference to the low-lying X1∑g+ and a3Πu states, and then undergoes a radiationless transition into the d3Πg state through crossing with the d3Πg,ν′= 6 level.
THE INFRARED REFLECTION SPECTRA OF THE CRYSTALS OF BARIUM MATEBORATE IN THE LOW TEMPRETURE PHASE
YANG YAN-YONG, ZHANG GUANG-YIN, WU BO-CHANG
1987, 36 (3): 395-400. doi: 10.7498/aps.36.395
Abstract +
The infrared reflection spectra (100-4000 cm-1) of the two different polarized components for the single crystals of barium mateborate in the lowe tempreture phase, a new type of nonlinear optical material, at room tempreture are reported in this paper. The transverse and longitudinal frequencies of the fundamental vibration modes in the frequency range above 200 cm-1 are given, and the spectra are analysed in terms of the ‘layermolecular structure' model with reference to the Raman spectra. As a result, the assignment of the inner fundemental vibration modes of the crystals is achieved.
THE EFFECTS OF (OH)- ON STABILIZATION OF F2+- CENTERS
ZHANG TAO, WAN LIANG-FENG, RUAN YONG-FENG, GUO SHAO-ZANG
1987, 36 (3): 401-407. doi: 10.7498/aps.36.401
Abstract +
Based on our experiments, the effects of (OH)- on stabilizing F2+-centers in LiF crystals are discussed. We obtained the absorption peaks of the F2+-centers in irradiated LiF crystals which had been kept at room temperature for nine months. And the number of the F2+-center was sufficient for use in color center lasers.
STUDY ON A PLANE-LIKE PRECIPITATE IN SILICON SINGLE CRYSTAL BY X-RAY TOPOGRAPHIC METHOD
CHU XI, MAI ZHEN-HONG, DAI DAO-YANG, CUI SHU-FAN, GE PEI-WEN
1987, 36 (3): 408-410. doi: 10.7498/aps.36.408
Abstract +
A plan-like precipitate in silicon single crystal was investigated by means of X-ray section topography. limited topography, dilatation topography and SEM. The configuration and position of the defect in matrix were determined. And a breief analysis about its formation is also presented.