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Vol. 36, No. 9 (1987)

1987-05-05
CONTENT
THE COMPRESSION OF AND THE FLUX TRAPPED IN A FIELD-REVERSED PINCH PLASMA
WU CHENG, YE MAO-FU, ZHANG BAO-ZHEN, LI YIN-AN
1987, 36 (9): 1105-1111. doi: 10.7498/aps.36.1105
Abstract +
The compressional process is analysed for a field-reversed pinch plasma on our FRP-1 device. A description is quantitatively given for the oscillation of the flux trapped lnside the neutral sheet and the calculated results are found to be in good agreement with the experimental data.
DISSIPATIVE DRIFT INSTABILITIES IN A HOT ELECTRON PLASMA
HUANG CHAO-SONG, REN ZHAO-XING, QIU LI-JIAN
1987, 36 (9): 1112-1121. doi: 10.7498/aps.36.1112
Abstract +
Density-gradient-driven dissipative drift instabilities in a hot electron plasma are studied. Dispersion relation (including that of resistivity and viscosity) is derived. Hot electron ring can reduce growth rate of the instability and anomalous transport flux. Stability condition for the drift wave is βh>4ξ/(l + 2ξ). The fluctuation levels and the exciting region of drift mode are measured, and the stabilizing effects of hot electron ring observed. It is found that the experimental results are consistent with the theoretical predictions.
MIGRATION OF VACANCIES IN BCC METALS
ZHU HUI-LONG, HUANG ZU-QIA
1987, 36 (9): 1122-1132. doi: 10.7498/aps.36.1122
Abstract +
The vacancy-concentration effect on the vacancy-migration-energy and the behaviour of divacancies were considered Using a formula derived for the vacancy current in bcc metals. It turns out that the vacancies will migrate in the direction of increasing concentration, if the concentration is over some critical value which we have determined.This method can also be used for other metals.
THE ELECTRON CORRELATION FUNCTION OF QUASI ONE-DIMENSIONAL SYSTEM
FENG WEI-GUO, SUN XIN
1987, 36 (9): 1133-1140. doi: 10.7498/aps.36.1133
Abstract +
For the quasi one-dimensional electron systems with coulomb interaction, the many-body wave function is obtained on the basis of the correlation oscillation behavior of the electron gas, and the electron correlation function g (|z12|) for quasi one-dimensional systems has been calculated in this paper.
THE LOCALIZATION OF THE VIBRATIONAL MODES AROUND THE SOLITON
SUN XIN, XIE SHI-JIE, LI ZHONG-YI
1987, 36 (9): 1141-1147. doi: 10.7498/aps.36.1141
Abstract +
In order to figure out the localizations of the five localized modes around the soliton in polyacetylene, the dependences of their configurations on the length of the chain have been studied in both the open chain and the close ring cases. For the open chain, it is found that the localized mode g4 has some different behavior from the localized modes g1, g2, g3 and g5, namely, when the length of chain is increasing, the configurations of g1, g2, g3 and g5 do not change, whereas the wings of g4 become broader, this means that the localization of g4 is not so complete as the other localized modes.
A POSSIBLE SURFACE ATOMIC STRUCTURE MODEL OF InP (100) (4×2) RECONSTRUCTION
HOU XIAO-YUAN, DONG GUO-SHENG, DING XUN-MIN, WANG XUN
1987, 36 (9): 1148-1153. doi: 10.7498/aps.36.1148
Abstract +
The InP(l00) (4×2) reconstructed surface prepared by argon ion bombardment and post annealing under phosphorus pressure has been investigated by LEED, HREELS and UPS. It was found by HREELS that the forming of surface In-H and P-H bonds during hydrogen exposure happened almost simultaneously. By measuring the UP spectra using polarized light sources, it can be verified that the dangling bond states of surface P atoms do not possess the symmetrical characteristic with respect to the two basis vector directions of surface unit mesh. It could be deduced from the above evidences that there must exist some In vacancies on the In-rich InP (100) surface, and the dangling bonds of those P atoms which are located next to the In vacancies orientate off their normal directions. We propose here a missing row-dimer model for the atomic arrangement of InP (100) (4×2) stucture, which could explain the observed experimental qualitatively and might be used as a working model for seeking a precise surface structural model.
THE STUDY OF RADIATIVE LIFETIME OF THE METASTABLE ATOMIC LEVEL IN MERCURY DISCHARGES BY OPTOGALVANIC SPECTROSCOPY
ZHANG YU-YING, LI GUI-TANG, SUN TAO-HENG
1987, 36 (9): 1154-1160. doi: 10.7498/aps.36.1154
Abstract +
An optogalvanic spectroscopy method for study of atomic mercury metastable level is reported. The experiments are described in which the mercury discharge was irradiated with a dye laser at 577 nm and 579 nm, thus exciting the atoms from the 61P1 level to 63D level, which decays to the 63P levels. By measuring the time dependence of the optogalvanic and fluore-sence signals, the effective lifetime and the ambipolar diffusion coefficients were obtained. The theoretical explanation for the experiments is presented.
PHOTOREFLECTANCE SPECTRA FOR CONDUCTING POLYMER P3MT
M. TOMKIEWICZ, D. S. GINLEY, YUAN REN-KUAN, SHEN XUE-CHU
1987, 36 (9): 1161-1168. doi: 10.7498/aps.36.1161
Abstract +
We report here the photoreflectance spectra of the conducting polymer. The interband transition and the transition associated with bipolaron have been observed for the poly (3-mythyl thiophene)-P3MT with different doping densities and under different temperatures, different intensities of modulation light. It was also demonstrated experimentally that the bipolaron may be induced by light with photon energy larger than the band gap Eg of the material, the bipolaron is the intrinsic elementary excitation state which is independent on the way of inducement ( photoinduced or doping-induced); bipolaron may be pinned by ionized impurity and then the confinement parameter will be increased.
EVALUATION OF 121Sb M?SSBAUER ISOMER SHIFTS
GU BING-LIN, HU MIN, HE YAN-CAI
1987, 36 (9): 1169-1176. doi: 10.7498/aps.36.1169
Abstract +
The M?ssbauer isomer shifts of 121Sb have been evaluated in the present paper, in which the electronic structure of the atoms bonded together was considered by using band-structure calculations. The finite size of atoms in the solid was also taken into account. Based on the above considerations the calibration constants for 121Sb M?ssbauer isomer shifts have been calculated.
BRIEF REPORT
CRYSTAL STRUCTURES AND MAGNETIC PROPERTIES OF R13Fe74Si13 ALLOYS
HU BO-PING, ZHANG SHOU-GONG
1987, 36 (9): 1177-1181. doi: 10.7498/aps.36.1177
Abstract +
Crystal structures and magnetic properties of R13Fe74Si13 (R = Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Y) alloys are investigated in this paper. The results show that R13Fe74Si13 alloys have pseudobinary intermetallic compound R2(Fe0.85Si0.15)17 as the main phase instead of forming a ternary compound of the type R2Fe14B. The Si atoms probably substitute for Fe atoms in R2Fe17 (9d site in Th2Zn17 or 6g site in Th2Ni17). Curie temperatures of R13Fe74Si13 alloys are comparably higher than that of R2Fe17. Saturation magnetization and magnetic anisotropy at room temperature were measured. Based on the results of extracting sample measurement at low temperatures the variation of the magnetization of R13Fe74 Si13 with temperature was discussed.
COHERENT-POTENTIAL APPROXIMATION FOR AMORPHOUS FERROMAGNETIC Fe-TM-B ALLOYS
SHI SHUANG-HE, CHEN JIN-CHANG, ZHAO JIAN-GAO, ZHAN WEN-SHAN, SHEN BAO-GEN
1987, 36 (9): 1182-1186. doi: 10.7498/aps.36.1182
Abstract +
A concentration-dependent Curie temperature for amorphous (Fe1-xTMx)1-yBy alloys is given as a solution of a cubic equation using the coherent-potential approximation; and a conclusion has been reached for the exchange inreraction, that JFe-Fe is positive, JTM-TM and JFe-TM are negative. The present conclusion is different from Onodera's result for Fe-Mn-B alloys.
THE DISPERSION OF THE INTERFACE IMPEDANCE BETWEEN THE IONIC CONDUCTOR AND METAL ELETRODE
CUI WAN-QIU, YIN JIAN
1987, 36 (9): 1187-1193. doi: 10.7498/aps.36.1187
Abstract +
The impedance spectra of amorphous Lithium ionic conductor 29.6P2O5-44.4Li2O-26.0LiCl and 36.3P3O5-44.4Li2O-15.1LiCl-4.2Al2O3 were studied. The equivalent circuit of the measuring box system and the dispersion relation of the interface impedance were given. Under a certain condition, this interface impendance can be transferred to the constant phase angle (CPA) impedance.
ULTRAFINE POWDERS PRODUCED BY U-V LASER PHOTOLYS OF IRON PENTACARBONYL
LIN JIN-GU, SU YANG, SHAN JUN, YANG JUN-HUI, FU KE-JIAN
1987, 36 (9): 1194-1198. doi: 10.7498/aps.36.1194
Abstract +
Photodissociation of Fe(CO)5 have been achieved using U-V laser as the photolysis source, A middle- energy U-V laser pulse (~20 mJ/pulse) is directed into a specially designed gas cell which typically contains 10-20 Torr of Fe(CO)5. We have obtained some ultrafine powders from U-V laser photolys of lron-pentacarbonyl in gas cell. Through the analysis of products by using modern physical instruments, we identify that the resulting powders are iron oxide, ironcarbide; they also contain a little crystalline state of iron or carbon and oxygen. The particles in the powders are uniform in size (300-400 ?) and have catalytical activity. At appropriate laser power densities, U-V laser photodecomposition of Fe(CO)5 has also-achieved to produce Fe film on the window of the gas cell. The film composition was examined by X-ray fluorescence.
DIRECT DISPLAY OF THE ACCUMULATION OF SPACE CHARGES IN ONE-DIMENSIONAL IONIC CONDUCTOR α-LiIO3
LIU JIAN, XIE JU-SHAN, FENG SHANG-TING, ZHANG GUANG-YIN, WU ZHONG-KANG
1987, 36 (9): 1199-1202. doi: 10.7498/aps.36.1199
Abstract +
The optical and electric properties of α-LiIO3 and its quasi one-dimensional ionic transportation are closely correlated. A great deal of information of the ionic transportation can be obtained by studying the optical and electric phenomena. Here two experiments have been designed and carried out. We have proved that the accumulational lines of space charges are produced by the interstitial Lithium ions and cation vacancies also the bright lines of grating which we recently reported are charge carriers. The whole growth layer are rich of positive charges. It can be sure that the ionic tube transportation is identi cal with the accumulation of space charges.
OPTICALLY INDUCED LIGHT DIFFRACTION IN LiNbO3: Fe
XU YU-HENG, WU ZHONG-KANG, WAN JIN-XIONG, ZHANG GUANG-YIN, LIU SI-MIN, MOU ZONG-YING, LU YONG-BIN
1987, 36 (9): 1203-1208. doi: 10.7498/aps.36.1203
Abstract +
In This paper, Diffraction cones are studied in LiNbO3:Fe. These diffracted cones are shown to result from the degenerate four wave mixing among the incident reflected and scattered beams induced by imperfections in the crystals. The angles of the cones are determined by phase matching condition △k = 0, which can be achieved by Ewald sphere construction from diffraction theory, while diffraction cones induced by degenerate four wave mixing of time-resolution are also discussed.
THE METASTABLE PHASES FORMED IN AN AMORPHOUS Pd80Si20 ALLOY DURING CRYSTALLIZATION
WU LI-JUN, GUO YONG-XIANG, WU YU-KUN, GUO KE-XIN
1987, 36 (9): 1209-1212. doi: 10.7498/aps.36.1209
Abstract +
By tilting the crystals formed in an amorphous Pd80Si20 alloy during crystallization in a transmission electron microscope, three phases have been determined. The metastable phase P1 has a primitive orthorhombic unit cell (a = 0.46, b = 1.37, c = 1.69nm) and its possible space group is Pnmm or P(nm21). Using the data of crystal P1 the EDP of MSII and Pd9Si2 phases reported by Masumoto et al and Duhaj at el respectively can be explained. The metastable phase F has a face-centred orthorhombic unit cell with the same values of a and b as the P1 phase but c = 1.46 nm. The phase P2 crystallized at high temperature has a primitive orthorhombic unit cell (a = 0.39, b = 0.76, c = 0.54nm).
AN INVESTIGATION ON POLYCRYSTALLINE BORON AND BORON-CONTAINING METALLIC GLASSES BY SEELFS
FEI LU, ZHENG YU, ZHANG QIANG-JI, HUANG JIN-LIN, HUA ZHONG-YI
1987, 36 (9): 1213-1218. doi: 10.7498/aps.36.1213
Abstract +
The slow electron energy-loss spectra in a reflection mode recorded above a core-level, known as the surface extended energy-loss fine structure (SEELFS), can give detailed local surface structural information of solids. This work reports for the first time the investigation of the role the boron atoms play in polycrystalline boron, Fe80B20 and Fe78.5 Si5B16.5 samples by using this technique. The oscillating structures were up to 300 eV above the boron K-edge. With the program daveloped in this laboratory, the radial distribution functions around the excited site were obtained by analyzing the SEELFS data. After phase-shift correction, the nearest-neighbor bondlengths of surface atoms were found: 1.57 ? for polycrystalline boron, 2.14 ? for Fe80B20 and 2.12 ? for Fe78.5Si5B16.5
THERMAL EXPANSION COEFFICIENTS OF POLYBIS-(P-TOLUENE SULFONATE) OF 2,4-HEXADIYNE-l,6-DIAL SINGLE CRYSTAL AT LOW TEMPERATURE
RUAN YAO-ZHONG, LI LI-PING, WU ZHI-QIANG, HE PING-SHENG
1987, 36 (9): 1219-1223. doi: 10.7498/aps.36.1219
Abstract +
The thermal expansion coefficients (along and normal to the chain direction) of PTS have been measured by differential parallel-plate capacitances from 77 K to 273 K. A sudden change near the phase transition temperature 195 K and a negative expansion coefficient near 200 K along the chain direction have been observed. The causes of these result are discussed qualitati-vly.
NON-THEPMAL DISTRIBUTION AND TOTAL ENTROPY INCREASE OF SCALAR PARTICLE GAS IN THE MULTI-DIMENSIONAL UNIVERSE
ZHOU MIN-YAO
1987, 36 (9): 1224-1229. doi: 10.7498/aps.36.1224
Abstract +
In this paper, we discuss the non-thermal distribution, the energy density and entropy increase of a massless particle gas in the Multi-dimensional phase of universe. Starting from the assumption that the distribution of particle number be invariant during the inflation, and in the approximate condition that the initial temperature T0 = β0-1 1/2a20-1 (D is the dimension of the extra space and a20 is the scale of the extra space befor inflation), we calculate the ratio of the total entropy St at the ending of the Multi-dimensional phase to the corresponding quantity S0 in the initial stage, which has the same order of magnitude as the ratio of T0a20 to Tfa2f (Tf is the temperature just as the universe enters the ordinary phase and a2f is the stable scale of the extra space. Planck unit, h =c = kB=G= 1, is used throughout ).
ELECTRONIC STRUCTURE IN ONE-DIMENSIONAL INCOMMENSURATELY MODULATED CHAINS WITH DISORDER
TAN MING-QIU, XIONG SHI-JIE
1987, 36 (9): 1230-1234. doi: 10.7498/aps.36.1230
Abstract +
The influence of the substitution disorder and the period disorder on electronic structures of one-dimensional, nearly periodic systems is studied in terms of numerical method. The results show that the Cantor set structure of electronic spectra in the almost periodic systems is destroyed in both the disordered cases, but Ihe former may -create new impurity levels in the forbidden band, and the latter mainly broadens the original energy bands.
ENERGIES OF A FINITE 2D COULOMB INTERACTING ELECTRON GAS IN A STRONG MAGNETIC FIELD
XIONG XIAO-MING, ZHOU SHI-XUN
1987, 36 (9): 1235-1240. doi: 10.7498/aps.36.1235
Abstract +
A method for calculating the energies of a finite interacting electrons system in a strong magnetic field is presented. The numerical results have been obtained both for the first and the second Landau levels.