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Vol. 36, No. 4 (1987)

1987-02-20
CONTENT
THE LOW FREQUENCY EFFECTS OF TRANSVERSE CONDUCTIVITY OF ELECTRON IN LOCALIZED STATE OF THE TWO DIMENSIONAL ELECTRON GAS IN MOS INVERSION LAYER UNDER THE CONDITION OF QUANTIZED LIMIT
Zhao Leng-zhu
1987, 36 (4): 411-418. doi: 10.7498/aps.36.411
Abstract +
In this article, we analyze the frequency characteristics of electron conductivity in localized states of the 2 dimensional electron gas (2DEG) in MOS inversion layer under the condition of quantized limit. Based on the frequency dependence of Fermi distribution function, we derived the frequency characteristics of the two dominant conduction processes, i.e., the conductivity due to the process of thermally exciting to the mobility edge, σME (ω),and that due to variable range hopping process, σVRH(ω). We found that σME(ω) and σVRH (ω) are both complex functions. The time constant of σME(ω), τn, is longer, corresponding to a low frequency process. And that of σVRH(ω) is much shorter, corresponding to high frequency process. The theoretical curve is compared with experimental data. It is found that in order to fit the theoretical curve to the experimental one, the time constant τn should be approximately 3.6 ×10-6 s.
DETERMINATION OF REAL IONIZATION AND ATTACHMENT COEFFICIENTS IN OXYGEN
Li Zhen-ying
1987, 36 (4): 419-425. doi: 10.7498/aps.36.419
Abstract +
A new method for determining the real ionization and attachment coefficients in oxygen is presented. Add a small amount of CO(H2) or CO2 into O2 measure the variation of the apparent ionization and attachment coefficients with the compositions of the gaseous mixtures, and then the real ionization and attachment coefficients in O2 can be found respectively.
QUANTUM DEFECT THEORY——THEORETICAL MULTIPLE-SCATTERING CALCULATIONS
PAN XIAO-CHUAN, LIANG XIAO-LING, LI JIA-MING
1987, 36 (4): 426-435. doi: 10.7498/aps.36.426
Abstract +
Molecular Rydberg states and their adjoint continuum can be described in an unified manner by a compact set of slightly energy-dependent parameters in quantum defect theory. Here, we present a multiple-scattering method to calculate these physical parameters. As illustrative examples, calculations for H2 and NO are carried out.
NON-EQUILIBRIUM DISTRIBUTION OF THE POPULATION OF ALKALI ATOMS IN THE GROUND STATE INDUCED BY LASER-MW DOUBLE RESONANCES
CHEN XIAO-YUAN, ZHU XI-WEN
1987, 36 (4): 436-443. doi: 10.7498/aps.36.436
Abstract +
We obtained the conditions under which the maximum non-equilibrium distribution of the population of alkali atoms in the ground state in atomic beam pumped by laser-MW double resonance is achieved. These conditions are consistent with recent experiments. We examined the processes which affect the realization of the non-equilibrium distribution of population, and indicated the methods of eliminating the effects of these processes. The features of pumping processes with laser-MW double resonances are discussed, and compared with the two laser pumping process.
MEASUREMENT OF THE (5p3/2ns)1 AND (5p3/2nd)3 AUTOIONIZING LEVELS OF STRONTIUM BY THE MULTI-STEP EXCITATION TECHNIQUE
WU BI-RU, ZHANG SEN, ZHONG JIAN-WEI, QIU JI-ZHEN, HU SU-FEN, LU JIE, SUN JIA-ZHEN
1987, 36 (4): 444-451. doi: 10.7498/aps.36.444
Abstract +
The (5p3/2ns)1 (n = 13-21), (5p3/2nd)3 (n = 13-24) autoionizing levels of strontium have been measured by the laser multi-step excitation method and polarization technique. In the core excitation profiles for the (5p3/2ns)1 states below the 5p1/2 ionization limit, distortions appear at locations corresponding to the (5p1/2ns), and (5p1/2nd)1 levels. Distortions also appear in the (5p3/2nd)3 excitation profiles. These results show that there exist interse-ries interactions between the (5pjns) and (5pjnd) autoionizing series of strontium.
SPONTANEOUS CURRENT GENERATED FROM LASER PLASMA
WANG RUN-WRN, PAN CHENG-MIN, LIN ZHUN-QI, ZHU DA-QING, HE XIN-FA, ZHAN JI-RAN, WANG XIAO-QING, CHENG ZHONG-YU, BAI JIAN-RONG, JIANG MING-HUA
1987, 36 (4): 452-458. doi: 10.7498/aps.36.452
Abstract +
We studied a phenomena of spontaneous current generated from laser plasma, which was produced from several plane target made from Rh, Ag and Cu irradiated with high power laser light. The pulse-width, output energy and wavelength of the laser were 200 ps (FWHM), 0.1-4J and 1.06 μm. respectively. At the focus spot of the target irradiated with laser, a spontaneous current density as high as 107A/cm2 was found in the experiment.
DYNAMICS OF MULTIPHOTON IONIZATION OF ACETALDEHYDE BY UV LASER
HAN JING-CHENG, GUAN YI-FU, LIU HOU-XIANG, LI SHU-AIO, WU CUN-KAI, ZHU RONG
1987, 36 (4): 459-466. doi: 10.7498/aps.36.459
Abstract +
In this article, we present the experimental results of mass spectroscopic study of multi-photon ionized acetaldehyde molecules in gaseous phase excited by XeCl excimer laser under the molecular beam condition. Based on the linear relations between the intensities of fragment ions and the pressure of sample gas, we show that the multiphoton ionization and fragmentation of acetaldehyde is an unimolecular reaction, this result reveals some photochemical be havior of acetaldehyde in the photolysis process by uv laser. According to the MPP mass spectrum of acetaldehyde, the variation of the intensities of the fragment ions in the MPI mass spectrum with laser power and photophysical property of its first excited single state 1(n,π*), we propose a parent dissociation-neutral fragments ionization model of MPI of acetaldehyde, with which the experimental results can be explained.
LASER- INDUCED AUTOIONIZATION AND PHOTOELECTRON SPECTRUM
ZHAO LI-GENG, XU ZHI-ZHAN
1987, 36 (4): 467-472. doi: 10.7498/aps.36.467
Abstract +
In this paper, laser-induced autoionization and the photoelectron spectrum are studied theoretically by using resolvent operator method. Our calculations show that there are four peaks in the photoelectron energy distribution. The widths and positions of these peaks are derived analytically. We also discuss the condition of stabilization of autoionizing state by laser field.
IMPROVEMENT OF QUANTITATIVE EDS ANALYSIS OF THIN FILMS BY MEASURING THE I(L)/I(K) INTENSITY RATIOS
DUAN JIAN-ZHONG, WU ZI-QIN
1987, 36 (4): 473-482. doi: 10.7498/aps.36.473
Abstract +
The intensity ratios I(L)/I(K) of eight kinds of pure element's thin films from Ge to Sn have been measured in a TEM using X-ray EDS at 40, 80, 100, 120,160 and 200 kV. Using these I(L)/I(K) values, the Cliff-Lorimer factor KXSi and their interpolated values for the K lines, the KXSi values for L lines are obtained. In order to determine which Q ionization cross-section formula in literature is the best, the calculated values I(L)/I(K) using nine formulas of Q were compared with expermental data. It has been found that there are large discrepancies between the expermental data and calculated values. After considering the errors by various parameters used in calculation, it becomes evident that the discrepancy is mainly caused by inaccuacy of cross-section and the best formula of Q proposed by Fabre de la Ripelle must also be revised. The quantitative analysis for several specimens with known composition was done using our revised Q and EDAX-9100's progroms. The results snow that by using our revised formula of Q, the errors of analytical results from K-K and K-L lines at 100 and 200 kV could be reduced significantly.
THE EFFECT OF COMPOSITION ON CRYSTALLIZATION TEMPERATURE OF Fe-BASE AMORPHOUS ALLOYS
CHE GUANG-CAN, SHEN BAO-GEN, ZHAO JIAN-GAO, ZHAN WEN-SHAN, LIANG JING-KUI
1987, 36 (4): 483-489. doi: 10.7498/aps.36.483
Abstract +
In this paper, the relationship between composition and crystallization temperature of Fe-base amorphous alloys are investigated systematically. Among 95 Fe-base amorphous alloys, the crystallization temperatures of about 85% of them are in the range of 700-825 K, Tcr/Tm≈1/2 (0.42-0.62), and conform to Sakka's principle The crystallization temperature of Fe1-x Bx-ySiy is greater than that of Fe1-xBx and the later greater than that of Fe1-xBx-yPy in turn. Those mentioned above are discussed with reference to the composition, phase diagrams, machanism of the crystallization, diffusion and the relationship between the crystallization temperature and the average electronic concentration (e/a).
A STUDY OF INCLUSIONS AND DISLOCATIONS IN LiNbO3 CRYSTALS BY X-RAY TOPOGRAPHY
GE CHUAN-ZHENG, JIANG SHU-SHENG, MING NAI-BEN, FENG DUAN
1987, 36 (4): 490-494. doi: 10.7498/aps.36.490
Abstract +
The inclusions and dislocations in LiNbO3 crystals have been studied by means of X-ray topography. The influence of elastic anisotropy on the contrast of inclusions was observed. The Burgers vectors of dislocations in this crystals were found to be of the type of 1/3〈1120〉, the smallest lattice vector, and 1/3〈0111〉, the next smallest lattice vector. The pure twist sub-boundary which consists of two sets of pure screw dislocations with Burgers vectors l/3〈101l〉 was also observed.
THE ADSORPTION 6F WATER ON SODIUM PREDEPOSITED InP(111) SURFACE
DONG GUO-SHENG, DING XUN-MIN, HOU XIAO-YUAN, WANG XUN
1987, 36 (4): 495-500. doi: 10.7498/aps.36.495
Abstract +
The room temperature adsorption of water on clean and sodium predeposited InP(lll) surface has been studied by UPS and HREELS. The sticking coefficient of water on InP(lll) surface increases significantly as the surface is covered with 0.3 moiiolayer of sodium. This sticking coefficient enhancement could be shown to be related to the charge transfer between the sodium atoms and the surface phosphorous atoms. Water species adsorb On the surface mainly in the form of undissociated molecules. The existence of P-H bond related loss energy peak at 282 meV observed in HREELS suggests that a portion of water molecules may interact with sodium atoms predeposited on the surface or possibly decomposed on the surface to release free hydrogen atoms which could make bonding with surface phosphorous atoms.
THE PRESSURE CALIBRATION UP TO MBARS AND THE ACHIEVEMENT OF 5.5 MBARS UNDER HYDROSTATIC AND NONHYDROSTATIC CONDITION
MAO HE-GUANG, PETER BELL, XU JI-AN
1987, 36 (4): 501-510. doi: 10.7498/aps.36.501
Abstract +
Pressure calibrated up to 0.8 Mbar under hydrostatic condition and to 2 Mbars under non-hydrostatic condition. We find the red shift of ruby R fluorescence to 830nm at the highest pressure point in our diamond high pressure cell. The shift correspond to 5.5 Mbars by calibration.
BRIEF REPORT
PERCOLATION MODEL OF Ti-Al2O3 CERMET
CHEN XIN-ZHENG, NAN CE-WEN
1987, 36 (4): 511-513. doi: 10.7498/aps.36.511
Abstract +
The relation between the microstructure and the macroscopic conductivity of Ti-Al2O3 cermet is analysed by using percolation theory. It is found that the result of percolation model is consistent with experimental result. The percolation threshold ω* the critical percent content of Ti-Al2O3 cermet is 0.16, and critical exponents are the same as those of three-dimensional continuous percolation.
STUDY OF FAST IONIC CONDUCTOR BY POSITRON ANNIHILATION
LEI ZHEN-XI, PAN XIAO-LIANG, WANG YUN-YU, YANG JU-HUA
1987, 36 (4): 514-517. doi: 10.7498/aps.36.514
Abstract +
The fast ionic conductor, LiCl-LiF-B2O3, LiF-B2O3 in microcrystalline and non-crystalline forms were studied by positron annihilation. It was found in all cases, the intensity of the mid-lifetime component I2 depends directly on the electrical conductivity σ. Additional measurement of Doppler broadening on the same systems indicated that voids between the microcrystal and network phases provid more transfer path for Li ions, thus lead to higher conductivity in the microcrystalline form of LiCl-LiF-B2O3 system.
STRUCTURAL STUDIES OF AMORPHOUS HYDROGEN STORAGE ZrNi-ALLOYS
WANG GEN-SHI, CAO MING-ZHONG, SHAN HUI, CHEN JI-ZHOU, WANG JUN-QIAO
1987, 36 (4): 518-523. doi: 10.7498/aps.36.518
Abstract +
In this article the effect of hydrogen on structure of amorphous alloys of the form Ni0.243Zr0.757 Hy 0≤y≤0.25 is reported. The results of investigations on the structure of amorphous Ni0.243Zr0.757 and its hydrogenated sample are described. X-ray diffraction data are employed to calculate their radial distribution functions (RDF(r)) structures. The coordination umber of Ni-Zr metallic glass is determined as 10.6 and the hydrogen atoms in the hydrogenated amorphous Ni0.243Zr0.757H0.25 apparently prefer to occupy the tetrahedral hole surrounded mainly by 4 Zr atoms and a few by 3 Zr + 1 Ni atoms.
STATISTICAL TEEORY OF IMPURITIES AND DEFECTS IN a-Si:H
CHEN GUANG-HUA, PENG YING-QUAN, CHEN JI-HONG
1987, 36 (4): 524-528. doi: 10.7498/aps.36.524
Abstract +
This article present a multi-level model on the doping mechanism and defect state in the gap of a-Si:H films, and calcnlate the doping efficiency η using the method of statistical physics. It was found that the results from the model and calculation not only cover all arguments of Street et al., but also make a distinction between heavy and light doping. The η of light doping agrees with usual results, only heavy doping obeys η∝?-1/2low.
APPLICATION OF SIMPLIFIED EXPRESSION OF EMITTED CHARACTERISTIC X-RAY INTENSITY FOR MICROANALYSIS
XUE DE-JUN
1987, 36 (4): 529-532. doi: 10.7498/aps.36.529
Abstract +
Based upon the model of depth distribution of X-ray production and consideration of absorption of X-ray by matrix of the sample, the expression of emitted characteristic X-ray intensity I has been derived I = MCI. G, where M is a constant, C is the concentration of measured element, I. is the X-ray intensity factor and G is the correction factor. By this method the results of quantitative analysis under various accelerating voltage are obtained for stainless steel, aluminium alloy, brass and sulfide. Comparing with chemical analysis, the standard deviation of 376 data is 0.62%.
EXPERIMENTAL STUDIES OF EXCITED STATES IN COLLISIONS BETWEEN He+ AND Ne
LEI ZI-MING, LIU JIA-RUI, PAN GUANG-YAN
1987, 36 (4): 533-539. doi: 10.7498/aps.36.533
Abstract +
In collisions between He+ and Ne, two processes of excitation are found, one is one electron capture into excited states and another is direct excitation of projectile and target by ion impact. Optical method of measurement is performed using Optical Multichannel Analysis System (OMA), and the data of emission cross sections are obtained in the energy range of 70-150 keV.
EXPERIMENTAL STUDIES ON LOW TEMPERATURE MAGNETISM OF THE Gd3Ga5-xAlxO12 SINGLE CRYSTAL
LlU PIN-QING
1987, 36 (4): 540-546. doi: 10.7498/aps.36.540
Abstract +
Gd3Ga5-xAlxO12 single crystal has been grown by the Czochralski rechnique. It was ascertained as garent single phase material by X-ray photography. Experimental studies of the magnetization and susceptibility of Gd3Ga5-xAlxO12 have been carried out along the [111] crystal axis in the temperature range of 1.5 to 77 K, and compared with Gd3Ga5O12 (GGG).The primary results show that the susceptibility of this material obeys the Curie-Weiss law when the magnetic field is below 500(Oe), the ordering temperature is far below 1.5 K. The magnetization of GGAG is about 4% higher than that of GGG for magnetic fields greater than l0000(Oe). When the magnetic field is about 30000 (Oe). The Critical magnetic field of GGAG is about 4000(Oe) higher than that of GGG. It is shown that the substitution technique is efficient in searching after new working substance for magnetic refrigerator.