Vol. 31, No. 10 (1982)
1982-05-20
CONTENT
1982, 31 (10): 1289-1299.
doi: 10.7498/aps.31.1289
Abstract +
Our pendulum disk is made of natural marble. The suspended wire is made of isoelastic alloy which has been chosen through repeated testing for it's high quality factor, low internal exhaustion and almost zero thermoelastic coefficisnt. A low-damping free oscillating pendulum is set up instead of the discontinuous pendulum which is electro-magnetically attracted against a stop once every swing. Thus artificial disturbance to the pendulum is reduced. The pendulum is put in a vacuum-tight chamber to avoid environmental disturbance and lengthen the damping time. Besides, a multi-faceted reflective mirror ring is located at the centre of the pendulum disk. As a result, the number of times of measurement is increased from one to four or more within a certain period. This makes it possible to numerically solve the damping oscillating equations θi= A exp(-ti/τ) sin(ωti + φ) (i = 1, 2, 3, 4) by means ofcomputer. Therefore, not only can variations of period be measured directly, the variations of amplitude A, damping time τ and initial phase φ can also be calculated. Some modifications have been made on the system of light-electric accepter. Now, the precision detecting period with our torsional pendulum is one-hundred times higher than that of Dr. Saxl's as reported in his first article concerning pendulum in 1964, and ten times higher than the precision of his pendulum in 1970, which is the result of seventeen years of efforts in making improvements. The effective numbers obtained with our setup have reached six to seven figures, and the relative error of period is 2×10-6, or even 8×10-7 in the best case. Basically, the desired requirements have been satisfied. This will provide the possibility of detecting gravitational abnormal phenomena and making a distinction between the frequency fluctuation during a long period of time and that during a short period of time.
1982, 31 (10): 1300-1307.
doi: 10.7498/aps.31.1300
Abstract +
A quadrupole antenna has been designed and manufactured,Weight of theantenna is 498 kg. Having added the tuning equipment to the antenna,in room tem-perature and in the air,the Q value is 4.4×103.Resonant frequency of the antenna can be tuned continuously from 47.3 Hz to 60.5 Hz.Each quarter of the antenna issimplified by representing it as a cantinever beam with a rigid body in the free end.We calculate the resonant frequency by simple method of material meehanics insteadof the complicated method of elastic mechanics and obtain a satisfactory result.Several possible mechanical means to adjust the frequency are compared.In addition,we investigate the possibility of using this type of antenna to detect gravitationalwave at lower frequencies.
1982, 31 (10): 1308-1316.
doi: 10.7498/aps.31.1308
Abstract +
By means of expressing the equilibrium configurations of high-beta tokamak plasmas analytically, the ideal MHD local stability criterion is derived with emphasis on the exploration of the possibility of existence of low-q, high-beta tokamaks. Results obtained show that a great variety of equilibria with these figures of merit may exist, some of them having great stability margin in the central region of the confined plasma against the local modes. Comparisons are made of results corresponding to configurations with different p′(ψ) and △(ρ) functions (△ being the displacement of the magnetic surface) and the tendency is found that the larger the displacement and the flatter the p′(ψ) profile is, the more stable the equilibrium will be.
1982, 31 (10): 1317-1336.
doi: 10.7498/aps.31.1317
Abstract +
In this paper, retaining high-frequency fields up to fourth order, the kinetic and hydrodynamic equations for the beat frequency interaction between longitudinal, transverse high-frequency fields and particles in low-frequency oscillation were derived from Vlasov-Maxwell equations. The results show that, in the case of one dimension, the large amplitude high order fields in sub-acoustic waves weaken the ponderomotive force which causes solitons. In three dimensions, it possibly makes the formation of cavitons slower.
1982, 31 (10): 1337-1347.
doi: 10.7498/aps.31.1337
Abstract +
In this article, the motion of electrons in free electron lasers with variable parameter wigglers is discussed. It is pointed out that, the more quickly the parameter varies, the more trapped electrons move stochastically. The influences of such stochastic motion on laser efficiency have been analyzed numerically. A statistical method to describe the beam behavior in strong stochastic limit has also been developed.
1982, 31 (10): 1348-1353.
doi: 10.7498/aps.31.1348
Abstract +
Rate constants of electron-attachment to Cl2 in mixtures of Ar/Cl2 have been measured over the mean electron energy range 3-5 eV. The results show that electron-attachment rate constant is (3.2±0.4)×10-10cm3/sec at a mean energy of 3.5eV. The effect of variation of the mean electron energy has also been investigated. The experimental results agree very well with that of Los Alamos investigators.
1982, 31 (10): 1354-1361.
doi: 10.7498/aps.31.1354
Abstract +
Nine vibration-rotational bands of various isotopic species of CO2 have been assigned in the 3657-3708 cm-1 region using a tunable diode laser spectrometer. Two of these bands, i.e. the 10011-00001 of 12C16O17 and the 11111-01101 of 12C16O18 were observed for the first time. The now accepted caleulated value of the 10011-00001 band originated from 12C16O17 is found to deviate from our observed value by 0.287 cm-1 and that of the 11111-01101 band originated frorn 12C16O18 by 0.048 cm-1.
1982, 31 (10): 1362-1368.
doi: 10.7498/aps.31.1362
Abstract +
Using (20-300K) Hall coefficient measurement and (6-300K) IR optical absorption, thermal donor generated in P-CZ Si single crystal after heat treatment at 450℃ over a wide range of time has been studied. It is shown from Hall coefficient measurements that two donor levels in the specimen after 100 hrs. annealing are observed: E1= 56 meV, E2= 110 meV. Low temperature IR optical absorption of specimens after annealing of different duration shows complex structure arising from thermal donor. The intensity and number of the absorption peaks increase with increasing duration of annealing. The results obtained can be phenomenologically explained fairly well by the hydrogen-like effective mass approximation theroy assuming the occurence of different species of doubly charged donor. The oxygen-related thermal donor can also be possibly understood as doubly charged donor. The number of species of thermal donor is closely correlated to the duration of annealing.
1982, 31 (10): 1369-1379.
doi: 10.7498/aps.31.1369
Abstract +
Silicon carbide is a typical layer compound. Up to the present more than 150 polytypes of SiC are known. The author has developed a special Laue method which is very efficient in identifying polytypes of SiC. Using this method, we have found eightyfive new polytypes of SiC. In order to determine the crystal structure of some of these new polytypes, oscillation method and Weissenberg method have been tried but without success, because only diffraction spots of the basic polytypes 6H, 15R and 8H can be found in these photographs. This is possibly due to the smallness of these new polytypes in bulk crystals and also to the fact that these tiny polytypes are imbedded in a large 6H or 8H, 15R polytypes. A modified laue method to determine the crystal structure of SiC polytypes is developed, as well as a method for calculating the diffraction intensity of laue spot. The calculation of structure factor Fhkl in [(33)m32]3, [(33)m34]3, [(22)m23]3 and [(44)m43]3 structure families is simplified. Using this method, the crystal structure of nine new polytypes of silicon carbide have been determined. The crystal structure of these new polytypes can be designate by the Z stacking sequences (Жданов notation) as follows, 231R:[(33)1232]3,249R:[(33)1332]3,321R:[(33)1732]3, 339R:[(33)1832]3,237R:[(33)1234]3,417R:[(33)2234]3, 453R:[(33)2434]3,93R:[(44)343]3,261R:[(44)1043]3.
1982, 31 (10): 1380-1386.
doi: 10.7498/aps.31.1380
Abstract +
The structural changes of Ag-Sn films on carbon film have been observed during heating to about 640℃ by using TEM and HVEM. Raising the temperature to 200-250℃, silver and tin react rapidly to form γ phase Ag3Sn. Raising the temperature above 480℃, the γ phase transforms suddenly into laminar β phase. At about 510℃, the β phase film begins to agglomerate. The morphology of the Ag-Sn films on GaAs substrate after heating has been observed by using SEM. It is shown that when the tin content of Ag-Sn films (20-65wt%Sn) is greater and the alloying temperature is higher, the agglomeration of the film is more severe.
1982, 31 (10): 1387-1394.
doi: 10.7498/aps.31.1387
Abstract +
The high temperature behaviours of evaporated thin films of copper alloys (Cu-Ti, Cu-Sn-Ti, Cu-Si) on carbon substrate have been studied in heating stage of TEM and HVEM and recorded by a video tape recorder. The diffraction contrast of the grains in Cu, Cu-Ti and Cu-Sn-Ti films begins to vary rapidly at about 640, 700 and 750℃ respectively. The vacant areas in these films expand rapidly above about 660, 750 and 800℃. Finally the isolated islands are formed. The balling of these films on graphite and diamond substrate has been observed by SEM after heating to 750-850℃. The different morphology of the balling on the surfaces of diamond (100) and (111) is due to the different wetting abilities. The expansion rates of the vacant areas in these films have been calculated by using the model of surface diffusion under different curvatures. The calculated values agree with experimental results in the order of magnitude.
BRIEF REPORT
1982, 31 (10): 1395-1400.
doi: 10.7498/aps.31.1395
Abstract +
A direct no-standards quantitative analysis method of binary alloy is developed and applied to multicomponent alloys including 7-components and 8-components steel samples in which the contents of some components are about 0.25-1.0%. As compared with the indirect no-standards method (Buss et al.), the accuracy of the present method is generally better and the analytical time shorter. It only needs about 10 seconds in calculating the constituents of a 8-components alloy from their characteristic X-ray intensities using a computer with a speed about 130,000 cps. The analytical results of binary alloys, especially NaCl, using this modified method are better than before.
1982, 31 (10): 1401-1404.
doi: 10.7498/aps.31.1401
Abstract +
The structural changes and the morphology of the evaporated Au-11.4 wt%Ge-4.8 wt%Ni films during heating have been studied by TEM. The structure of the as-evaporated film is a supersaturated Au solid solution and after more than 10 minutes anealling above 300℃ the film decomposes into Au solid solution and NiGe compound. In-situ observations in the heating stage of HVEM have revealed that the NiGe grains with size near 2000 A are dissolved into the Au solid solution in 2 seconds during heating to about 500℃. The remaining NiGe grains in the film prevent the balling process of the Au solid solution films occuring above 500℃.
1982, 31 (10): 1405-1411.
doi: 10.7498/aps.31.1405
Abstract +
The dependence of 7Li NMR spectrum in LiKO4 on temperature and crystal orientation has been studied. It is confirmed that there is a structural phase transition at Tc = 195K below which the crystal symmetry is lower than P31c and its unit cell contains at least six molecular formulae. There is no evidence of the existence of an incommensurate phase. At 181K the quadrupole coupling conatant is 38.9 kHz, the asymmetry parameter η = 0.46, and the principal direction z of the electric field gradient makes an angle of 11.6° with the original c axis.
1982, 31 (10): 1412-1416.
doi: 10.7498/aps.31.1412
Abstract +
By using canonical transformation and Bogoliubov transformation, we treat the magnon spectra of the transparent ferrimagnet RbNiF3 having a hexagonal structure. In the whole Brillouin zone a six-branch dispersion relation is obtained.
1982, 31 (10): 1417-1422.
doi: 10.7498/aps.31.1417
Abstract +
The magnetic properties, infrared absorption spectra and M?ssbauer spectra of dif f irent size magnetite particles were measured before and after coating with organic surfactant. The experimental results show that the nature of coating is chemical absorption between the fine magnetite particle surface and the surfactant. After coating the specific magnetization is reduced under equal magnetic field condition and M?ssbauer spectra become more broadened with the magnetite particle size decreasing. The experimental results may be explained by the surface anisotropy theory.
1982, 31 (10): 1423-1430.
doi: 10.7498/aps.31.1423
Abstract +
By making use of the "ultrasonic pulse echo overlap technique", the second and third oder elastic modulus of fused quartz had been measured. From the series expansion of strain energy, where the coefficients are expressed by the second, third, fourth order elastic modulus etc., the ultrasonic equation of state for isotropic fused quartz is derived. This equation of state fit the P-V data measured by Bridgman quite well.
1982, 31 (10): 1431-1435.
doi: 10.7498/aps.31.1431
Abstract +
The percolation problem for the 2-D triangular lattice of the quenched-correlated system is studied by using real-space renormalization group method. The many-body correlations for the occupied sites are considered by Kirkwood's superposition approximation approach and those for occupied and unoccupied sites by a procedure which holds the conservation of probability. The scheme is applied to the case including 3-body correlation and to that with next nearest neighboring correlations. Our conclusion is that, in either case the universality in critical phenomena of percolation ia unchanged, even some complicated correlations are involved.
1982, 31 (10): 1436-1439.
doi: 10.7498/aps.31.1436
Abstract +
The distribution function of the temperature in the case of static 1+1 dimensions have been obtained by using canonical method of quantum field in curved space-time. We then estimate the upper bound to the temperature of the radiation in 1 + 1 dimensional Schwarzschild space-time by calcuating the fluctuation of black hole's energy.
1982, 31 (10): 1440-1442.
doi: 10.7498/aps.31.1440
Abstract +
In this work, the effect of Earth's gravitational field on a interferometer is calculated in gereral relativity. The result is that an expected fringe shift, about 10-10, will occur when the interferometer is rotated through 90° if the length of arms are 1 meter and wavelength of light is 1 μm.
1982, 31 (10): 1443-1448.
doi: 10.7498/aps.31.1443
Abstract +
It is shown that the statement about the equations of motion for a charged massive particle would be a cohsequence of the field equations in the Kaluza unified theory of gravitation and eleetromagnetism, i.e. the equations of motion for the particle could be deduced from the Kaluza field equations, just as in Einstein's theory of general relativity, the equations of motion for a massive particle would be a consequence of the Einstein equations. Furthermore, the Lorentz equations for a particle moving in the Maxwell electromagnetic field in Minkowskian space-time could also be obtained from the Maxwell equations by using the Kaluza formalism of Maxwell theory.
