Vol. 34, No. 7 (1985)
1985, 34 (7): 849-859. doi: 10.7498/aps.34.849
Infrared absorption spectra of neutron irradiated FZ-Si grown in hydrogen atmosphere have been measured in wavenumber ranges 1800—300 em-1 and 400—200cm-1 by FTIR. The annealing behaviour of stronger absorption bands has been shown. By comparing with spectral results of proton implanted silicon measured by IR and neutron irradiated FZ-Si grown in hydrogen atmosphere measured by DLTS, the possible constructions of H-related centers are discussed.
The band structure and the density of states of CoSi2 were calculated by means of the self-consistent LMTO method. The peak positions of the calculated DOS were in reasonable agreement with the corresponding peak positions of the synchrotron radiation photoemission studies. Our calculated results showed that the main characteristic of the electronic structure of the silicides CoSi2 and NiSi2 were dominated by the hybridization between the transition metal-3d orbitals and the silieon-3p orbitals. The bonding in CoSi2 and NiSi2 was different from that of bulk Si, where the bonding was due to the sp3 hybridization of Si atom orbitals.
The integral equation for the inhomogeneous electron correlation function is established on the basis of the many-body wave function of metal surface, and the divergent terms in this equation caused by the long-range correlation are eliminated. Then we get the numerical results of the correlation function for Al surface in the first iteration.
1985, 34 (7): 873-881. doi: 10.7498/aps.34.873
In this paper, the Kubo-Anderson process has been adopted to discribe the random frequency modulation of driven field. Its suppression effect on inhomogeneous cold plasma wavebreaking has been analysed. The expressions of wavebreaking time, fast electron energy and the average square of maximum localized electric field have been derived, which can be applied in any band width of the frequency modulation while the Bogoliubov's nonlinear frequency shift is not taken into account. The agreement between the theoretical predictions and the experimental results is fair. Thus we show that the random frequency modulation is an effective method to suppress the wavebreaking and fast electron energy.
THE SCHWINGER-DYSON EQUATIONS OF THE WILSON LOOP VARIABLE IN THE LATXTICE GAUGEX FIELD THEORY AND THE PROBLEM OF UNIVERSALITY
1985, 34 (7): 882-891. doi: 10.7498/aps.34.882
Some categories of generalized Wilson actions are introduced and the Schwinger-Dyson equations corresponding to these actions are derived. It is shown that these equations have the same form as those in the continuum limit, thus showing that these generalized Wilson actions are equivalent.
1985, 34 (7): 892-900. doi: 10.7498/aps.34.892
In the core of some massive neutron star there may appear pion condensate. The weak processes such as μ(p1)→μ(p2) + e- + ve and μ(p1) + e→μ(p2) + ve (i. e. equation (9) and (10) of this paper), in pion condenate,have been proved to be essential in damping the radial vibrations in the neutron star. The time scale of this damping effect is model depen dent and may be several days.Considering processes (9) and (10), the equilibrium condition in the pion condensate is μπ=μe. However, only irreversible processes could damp the vibration, so the key parameter here should be ξ=(μπ,-μe)/kT describing the deviation from equilibrium. In this paper, we have derived the reaction rates of processes (9) and (10), and the related neutrino luminosities, and done numerical calculations. Results obtained are the relations of W-t and T-t, as shown in Fig. 2 and 3, using Wv and T to denote the vibrational energy and the temperature of the neutron star respectively.
1985, 34 (7): 901-907. doi: 10.7498/aps.34.901
Single ion anisotropy of Fe3+ ions at each site of the 7 sublattices (2d, 4e 4fⅣ,4fⅥ, 6g, 12k and 4f) in the hexagonal ferrite Zn2-W has been calculated by crystal field theory using point charge model. As expected, the results show that the contributions of diffrent sites are different and may be either positive or negative, thus the experimental results of substituted W-type ferrites can be explained.
1985, 34 (7): 908-918. doi: 10.7498/aps.34.908
BaF2-BiF3 system has been studied by means of solid state reaction, X-ray powder diffraction technique and complex impedance measurement.We found two kinc's of Ba1xBixF2+x solid solution: fluorite-type (0s≈0.5(141/2)aF,cs≈2(31/2)aF). The crystallographic and electrical properties of the two solid solutions have been investigated and discussed.New F- ionic conductors Bi1-yBayF3-y (0.05≤r≤0.17) (y = 1-x) with tysonite-type structure have good electrical performances. This may be due to the higher polarizability.
1985, 34 (7): 919-924. doi: 10.7498/aps.34.919
A fluorite-type solid solution Ba1-xInxF2+x(03(InF6)2 and BaInF5 have been obtained in the BaF2-InF3 system.The transport properties of these phases were measured and compared with those in BaF2-BiF3 system. The influence of the cationic polarizability and of the covalent character of the host-lattice on the electrical properties has been discussed.
1985, 34 (7): 925-932. doi: 10.7498/aps.34.925
The con ducting behavior of an amorphous Li+ conductor B2O3-0.7Li2O-0.7LiCl-0.1Al2O3 has been measured continuously and automatically by using the a.c. Volt-Ampere method in the isothermal treatment process at a certain temperature below its transition temperature. It was found that the conductivities of specimens increased at the initial stage and decreased monotonically after passing a maximum, and then two flat steps appeared. Comparing these results with that obtained by DSC and XRD analysis, we confirmed that the presence of the maximum of the conductivities is principally due to the amorphous phase separation, and the flat steps on the diagram of the conductivities are due to the amorphous crystallization. These results were discussed preliminarily in the view of the interface effects between different phases.
1985, 34 (7): 933-940. doi: 10.7498/aps.34.933
Based on a Hartree-Slater self-consistent theory, we calculate two-photon ionization cross-sections of Cs and Xe as illustrative examples. Our theoretical method can easily be applied to calculate other types of two-photon transitions and can also be extended to calculate higherorder multiphoton ionization processes. Comparing our theoretical results with available experimental data and other theoretical results, we can discuss the validity of our theoretical method. For two-photon ionization processes of alkali atoms (e.g. Cs), our results are in good agreement with recent accurate experimental measurements.
PRELIMINARY EXPERIMENTAL RESULTS OF THE β-PARTICLE DETECTION WITH SUPERCONDUCTING TUNNEL JUNCTION USING D. C. JOSEPHSON EFFECT
1985, 34 (7): 941-945. doi: 10.7498/aps.34.941
The detection of nuclear particles with superconducting tunnel junctions using D. C. Josephson effect is expected to have the merits of good energy resolution and fast time response. It was the first time to perform such an experiment to detect Sr90-Y90 β-particles by the Nb-NbOx-Pb superconducting tunnel junctions. The results showed that, under the β-particle irradiation, not only the critical current and energy gap voltage of the superconducting tunuel junctions decreased, but also voltage pulse signals at both ends of the superconducting tunnel junction were produced. In this paper we report some phenomena observed about β-particle detection with superconducting tunnel junctions using D. C. Josephson effect.
Crystal of PbBi2Nb2O9 belongs to orthorhombic system with space group D2h23 - Fmmm, z = 4 and cell parameters a = 5.4806(7) ?, b = 5.4791(7)?, c = 25.416(3) ?, V = 763.2(2) ?3, Dobs = 7.91g/cm3, Dx = 8.26g/cm3, μ(Mo,Kα) = 678.38cm-1, F(000) = 1608. The crystal structure was determined by the direct method (Multan-78) and Fourier-technique. The coordinations of atoms, isotropic and anisotropic thermal parameters were refined to R = 0.107 for 396 independent reflections by block-diagonal least-squares refinement technique. The Nb-O octahedra are deformed from Oh to C4v and the atoms Nb deviate 0.225 ? from the center along the directions of the 4-fold axes. The deformation of the Nb-O octahedra and the position deviation of metal ions Nb may be the structual reasons resulting in the ferroelectric properties of PbBi2Nb2O9.
The structure defects were observed by HREM in α-Si3N4, which was made by hot-pressing method with MgO and LiF as the additives. The observations indicate that the phenomenon of phase seperation occured in the grain boundaries of three grains junction, showing inhomogeneous chemical composition in glassy phase of grain boundaries. In the grains, the stress areas caused by lattice distortion and displacement of (100) planes were found. The distortions of the lattices are so serious in some regions that the hexagonal symmetry in the unit-cell gets lost. The distortion of the lattices could be measured by the deviation of the spacings of (100) planes from the normal value, 6.771?. With HREM we have found electron radiation damage of α-Si3N4 grains at lattice level caused probably by the distortion of the unit-cells of α-Si3N4. As compared with β-Si3N4, α-Si3N4 is less stable thermodynamically. According to our observations of both α-Si3N4 and β-Si3N4 made by hot-pressing method, the defects of the structure in α-Si3N4 are much more than that in β-Si3N4. This indicates that the phenomenon probably arises from easier distortion of the α-Si3N4 lattices than that in β-Si3N4.
1985, 34 (7): 956-959. doi: 10.7498/aps.34.956
The theorem of minimum entropy production and its implication to stability of no-nequilibrium stationary states are examined. It is found that, apart from the assumption of linear phenomenological relations and weak amplitudes, the validity of this theorem depends on the degree of deviation of states discussed from critical stability of local equilibrium. The possibility of oceurence of ordered structures in linear nonequ-ilibrium region is also discussed.
1985, 34 (7): 960-963. doi: 10.7498/aps.34.960
We analysed the pulse avalanche discharge processes of XeCl laser at high gas pressure up to 10 atm. The influences of delay effect on the discharge formation time were discussed. By comparing the calaulated results with experimental data observed in the XeCl laser pulse avalanche discharge, the critical avalanche track length was obtained as ξ≌1 mm.
1985, 34 (7): 964-967. doi: 10.7498/aps.34.964
The structures of Ga atoms deposited on Ni(lll) surface was studied. When the coverage is less than one monolayer, two superstructures. (3(1/2)×3(1/2)) R30°and (2×2), have been observed, by means of LEED and AES.A quasi-equilibrium phase diagram has been drafted, and thus the rangs of coverage and temperature while these superstructures appear can be estimated.
1985, 34 (7): 968-972. doi: 10.7498/aps.34.968
Based on published experimental data of Rp, a proposed relative correction method combining with numerical solution program of LSS equation was used to calculate the electronic stopping power of B+ implantation in GaAs, as follows NSe(E) = 12.4E0.605,Using this expression, the range statistic parameters Rp,△Rp and R⊥for B+ implanted GaAs were calculated.
OBSERVATIONS ON HIGH TEMPERATURE CREEP PROCESSES OF A NICKEL BASE ALLOY BY TRANSMISSION ELECTRON MICROSCOPY
1985, 34 (7): 973-977. doi: 10.7498/aps.34.973
On the basis of the previous paper , dislocation structures in the primary and secondary stages of high temperature creep of a nickel base alloy (Ni80Cr20Ti) have been studied by transmission electron microscopy. The observations and analyses have been emphasized on the primary stage. It is shown that, in the primary stage of high temperature creep, a large number of individual dislocations are formed. They generally do not lie on the slip planes. The majority of them are shown to be mixed type dislocations. It is concluded that such kind of dislocations is a product of the combination of climbring of edge dislotions and cross slipping of screw dislocations.
OPTICAL PROPERTIES AND LINEAR ELECTRO-OPTIC EFFECT IN FERROELECTRIC SINGLE CRYSTAL (KxNa1-x)0.4(SryBa1-y)0.8Nb2O6
1985, 34 (7): 978-982. doi: 10.7498/aps.34.978
This paper describes the measurements of optical properties and linear electro-optic effect in ferroelectric single crystal (KxNa1-x)0.4(SryBa1-y)0.8 Nb2O6. This crystal exhibits a large birefringence, and has a transparency range from 4000 ? to 5.6μm. The low halfwave voltage of (KxNa1-x)0.4 (Sry,Ba1-y)0.8 Nb2O6 gives a high value n03·rc of 730×10-12m/V, which is the figure of merit for EO modulator materials. The threshold energy of 600MW/cm2 (4pps) for laser damage makes (KxNa1-x)0.4 (SryBa1-y)0.8Nb2O6 attractive for large power laser modulation.