Vol. 37, No. 11 (1988)
1988-06-05
CONTENT
1988, 37 (11): 1741-1751.
doi: 10.7498/aps.37.1741
Abstract +
IR, WAXS and EXAFS arn used to study the structure of the non-crystalline io nic conductors in the Li2O-Nb2O5-SiO2 system. From the analysis, it is known that Nb5+ ions exist mainly as (NbO6) in the non-crystalline network. The non-crystalline structure varies with Nb2O5 content, it consists of polycyclics formed by shared side (NbO6) and (SiO4) when Nb2O5 content is. low, and shared of apex (NbO6) when Nb2O5 content is higher. The results of conductivity measurement are used to study the relations of the structure and electrial properties. The non-crystalline material with about Li2O 0.45 and Nb2O5 0.3 has the highest conductivity.
1988, 37 (11): 1752-1759.
doi: 10.7498/aps.37.1752
Abstract +
It is shown that the magnetic flux quanmzation should be consistent with the angular momentum quantization of superelectrons. The fractional angular momentum would lead to the fractional quantization of magnetic flux which does not contradict the theory of superconductivity and the result of previous experiments. We propose and analyse a crucial experiment to test the fractional quantum of magnetic flux as well as any"-on"s.
1988, 37 (11): 1760-1766.
doi: 10.7498/aps.37.1760
Abstract +
We investigate in detail the influence of second-order ionization processes on the photo-electron spectrum etc., which has been ignored previously in the study of intense laser-field induced autoionization. It is found that, in the region of laser intensity currently discussed in literature, many physical features are altered significantly. (1) Under certain conditions, line-narrowing effect disappears. (2) The olignal photoelectron peaks are greatly reduced. (3) In agreement with the most recent experimental findings on multiphoton ionization, high-order photoelectron peaks drastically increase with increasing laser intensity, and they dominate the original peaks for sufficiently high Intensities.
1988, 37 (11): 1767-1774.
doi: 10.7498/aps.37.1767
Abstract +
Generation of squeezing light depends on the nonlinear optical processes. Its intensirv is usually low owing to the limitation of the conversion efficiency. In this paper, the general condition for producing squeezing light is given. According to this condition, the conclusion is obtained that a laser cavity with a nonlinear medium and a gain medium can sime-ltaneously amplify the light intensity and reduce the quantum fluctuation of one quadrature phase component of the light field.
1988, 37 (11): 1775-1784.
doi: 10.7498/aps.37.1775
Abstract +
In this paper, the model that we constructed to simulate the DPRHS of Fe100-xPx(x= 25, 20, 15) is taken as the primary configuration. This configuration is then subjected to relaxation under the quasi-dynamical equilibrim boundary through the tail truncated Morse potential (energy minimization). The total energy, reduced distribution function, coordination number distribution, angular distribution and homogeneity are obtained from the calculated data. The dependent relation of the structure of Fe100-x Px on the composition are discussed.
1988, 37 (11): 1785-1793.
doi: 10.7498/aps.37.1785
Abstract +
The properties of co-adsorption of K with O on the Ag(ll0) surface have been investigated with X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), electron energy loss spectroscopy (EELS) and low energy electron diffraction (LEED). It is shown that, at low potassium coverages, there are two distinct oxygen species on the Ag(ll0) which are determined as the dissolved and chemisorbed atomic oxygen species. With K coverage increasing, the molecular oxygen is developed, which is associated with subsurface K. These oxygen species peaks can be clearly distinguished from UPS as well as XPS. The initial sticking coefficient of the K precovered Ag surface for oxygen adsorption is enhanced. K and O display a mutual enhancement of surface to bulk transport. A monolayer K atoms forms (1×2) LEED pattern on the Ag(ll0) surface, which is consistent with the early results. The surface structure, however, transfers into a (2×1) ordered structure when oxygen is exposed to the surface. A mode] for co-adsorption of K with O on the Ag(ll0) is proposed.
1988, 37 (11): 1794-1799.
doi: 10.7498/aps.37.1794
Abstract +
The piezoresistive properties of boron-doped PECVD microcrystalline Si films (μc-Si) deposited on SiO2 coated Si, covar or quartz substrates have been investigated. The relations between the gauge factor (G. F.) and doping concentrations as well as the film thickness etc, have been obtained experimentally. The maximum longitudinal G. F. of 25 and 20 are measured for Si and covar substrates respectively. An expression for calculating G. F. of p-type μc-Si is derived theoretically by using the spliring model of heavy and light hole band at k = 0 and the thermionic emission theory. The calculated dependences of G. F. on the doping concentrations, grain size and trap state density agree well with the experimental results, which offer a better understanding of the piezoresistive characteristics of μc-Si or poly-Si, and enable to optimize the design and fabrication of the μc-Si or poly-Si strain gauges.
1988, 37 (11): 1800-1806.
doi: 10.7498/aps.37.1800
Abstract +
Based on atomic self-consistent-field theory (i.e, independent electron model), we have performed non-relativistic and relativistic calcllations for photoionization cross sections of various ionized iron atoms. We focus on their dependence on the degree of ionization. Relativistic effect on photoinization of Fe is also discussed.
1988, 37 (11): 1807-1813.
doi: 10.7498/aps.37.1807
Abstract +
The succesive average resistivity criterion for localization has been used to study the Sou-koulis-Economou model of one-dimensional systems with incommensurate potentials. It is found that when wave vector Q = 0.7, all electronic states of the three subbands in the middle are extended and there exist no so-called "local mobility edge".
1988, 37 (11): 1814-1822.
doi: 10.7498/aps.37.1814
Abstract +
A model of a transition metal adatom chemisorption on ionic crystals, which is modelled by a semi-infinite chain of alternating A-B atoms, is studied. The Anderson-News approach is adopted to take account of the Coulomb repulsion between the d-orbital electrons of the adatom. Using self-consistent Green's function method, the chemisorption energies and transfer of adatom charge are calculated for different values of the couplilng constant between d-orbital electrons of adatom and surface of ionic crystal Some interesting qualitative conclusions are obtained by discussing the existence conditions and properties of various self-consistent solutions.
1988, 37 (11): 1823-1828.
doi: 10.7498/aps.37.1823
Abstract +
Introducing a structure factor matrix of random walk, we propose an extended generating function method to treat random walks on complex networks. As an illustration of this method, a random walk on an infinite dimer chain is considered.
1988, 37 (11): 1829-1836.
doi: 10.7498/aps.37.1829
Abstract +
By using the technique of transforming generating function, we have calculated the escape probability of random walk on the Y1Ba2Cu3O7 lattice and have obtained its asymptotic expression in the weak coupling limit. Comparison of the expressions of the escape probability and the dimension in the isotropic model yields a relation between the dimensionality and the layer coupling in Y1Ba2Cu3O7. Theoretical cal ulation indicates that Y1Ba2Cu3O7 is very close to a three-dimensional systems.
1988, 37 (11): 1837-1842.
doi: 10.7498/aps.37.1837
Abstract +
The dielectric, ferroelectric and pyroelectric properties of Li0.025Na0.975NbO3 crystals grown by the Czochralski technique have been investigated in the temperature range of 20 K to 300 K. The anomalies of the dielectric constant, electric polarization and pyroelectric properties indicate the existence of a low temperature phase transition. It occurs at about 180 K on cooling and at about 260 K on heating, wit an extraordinary large thermal hysteresis of about 80 K. The room temperature structure of the crystal has been determined and the possible point groups of the low temperature phes deduced. The time response of the pyrocle-ctric charge has been observed. A peculiar new phenomenon that the pyroelectric charge changes its polarity with time is reported. It is attributed to the coexistence of two phases in the process of phase transition.
BRIEF REPORT
1988, 37 (11): 1843-1848.
doi: 10.7498/aps.37.1843
Abstract +
Changes of the magnetic anisotropy and its correlation with both surface and bulk crystallizations are studied with M?ssbauer spect scopy and X-ray diffraction for amorphous alloy Fe81B13.5Si3.5C2 annealed in the air. It is shown that abnormal changes of the magnetic anisotropy as annealing in the air is correlated with the development of surface crystallization into bulk process.
1988, 37 (11): 1849-1854.
doi: 10.7498/aps.37.1849
Abstract +
In this paper, the model that we constructed to simulate the structure of Fe75P25 is taken as the primary configuration. Then this configuration is subjected to relaxation under the quasi-dynamic equilibium boundary through th tail-truncated Morse potential (energy minimization). The total energy, reduced distribution function coordination number, angular distribution function and homogeneity are obtained from the calculated data. The short lange order in amorphous alloy Fe75P25 is disclssed.
1988, 37 (11): 1855-1858.
doi: 10.7498/aps.37.1855
Abstract +
The dependence of the structural relaxation of the material on the annealing temperature Ta is studied by measuring the difference of thermal elongation △l or that of the electrical resistivity △ρ and that of the thermal expansion coeffcient △α between an as-quenched and an annealed sample. △α/α0 is measured by placing an as-quenched and an annealed sample in juxtaposition and heating them with iodine-tungsten lamps. The samples expand freely and the rsitivity of the as-onerched sample, respeomparator. The experimental results are summarized by three curves, namely △α/α0 vs Ta, △l/l0 vs Ta and △ρ/ρ0 vs Ta, where α0, l0, and ρ0 are the linear expansion coefficient, the length and the resistivity of the as-quenched sample, respec lively. The obtained results are discussed.
1988, 37 (11): 1859-1865.
doi: 10.7498/aps.37.1859
Abstract +
The dominent factors affecting the nuclear spin relaxation of 1H in HfV2·Hx hydrides are dipolar couplings. The important theoretical problem is the calculation of spectral density functions for the fluctuation of the dipolar couplings caused by the diffusive motion of 1H in the host lattice. We extended Torrey's theory, based on the model of random walk to nearest neighbor sites for homonuclear dipolar interaction, to the case that both homo- and heteronuclear interactions are existent. Then we calculated the GHH(k, y) and GHV(k, y) for determining the spectral densities JqHH(ω) and JqHV(ω) (q = 0, 1,2) according to the structure constants and H occupations of HfV2 ·Hx obtained from neutron diffractions. Using our theory and data derived from previous work of others, we analyzed the activation energy and the attempt frequency of 1H on interstitial sites and found that our results are satisfactory as compared with the conclusion derived from the phenomenological theory.
1988, 37 (11): 1866-1869.
doi: 10.7498/aps.37.1866
Abstract +
The vitreous and liquid phase of B2O3 are investigated by the temperature-dependent 11B CW-NMR technique. The results show that there are two processes in the structure changes of B2O3 glass with temperature increasing. Above 430℃, an increasing number of bonds begin to snap off and the number of boroxol rings is reduced accordingly. Above 600℃, a chain-like structure is formed, which is composed of B2O3 bipyramids. Above 930℃, this chain-like structure is broken to give B2O3 molecules.
1988, 37 (11): 1870-1875.
doi: 10.7498/aps.37.1870
Abstract +
The band of charge transfer transition was detected in optical absorbance spectra whenmolecule adsorbed on the silver surface in silver sol and silver mirror The effect of anion(Cl-) on the transition was studied. The relationship between aggregation and charge transfer was discussed and some explanations were given.
1988, 37 (11): 1876-1881.
doi: 10.7498/aps.37.1876
Abstract +
The structure and optical absorption property of TiO2-doped Vycor glasses are studied. The experimental results indicate that the optical absorption of the glasses are determined by anatase microcrystals in the glasses. The absorption edge shifts to long (or short) wavelength with increasing (or decreasing) of the microcrystal size. Anatase microcrystal of diameter about 80 ? shows the same absorption edge as that of bulk crystal.
1988, 37 (11): 1882-1887.
doi: 10.7498/aps.37.1882
Abstract +
In combining with X-ray photoelectron spectroscopy (XPS) measurement, the high resolution electron energy loss spectroscopy (HREELS) is used to investigate the evolution of energy gap width during the formation of Al-GaAs(l00) Interface. It is found that at room temperature, the product of Al-GaAs(100) interface reaction is AlAs. And AlGaAs alloy is formed after an annealing treatment. Low energy electron diffraction (LEED) is used also to study the deposition process of Al on GaAs(100)(4×1) surface. The deposited surface is disordered at the beginning and become ordered with Al deposition amount increasing.
1988, 37 (11): 1888-1892.
doi: 10.7498/aps.37.1888
Abstract +
A total current spectroscopy measurement has been performed on Si(lll)7×7 surface. Four peaks at 2.6, 5.2, 8.6, and 12.9 eV above vacuum level have been observed on clean surface, assigned as A, B, C, D respectively. Among them, the peak A contributed by the surface state is identified by hydrogen adsorption experiment. A preliminary explanation of the experimental result has been made.
1988, 37 (11): 1893-1899.
doi: 10.7498/aps.37.1893
Abstract +
The behaviors of amorphous W/C periodic multilayers after annealing have been studied by precise low-angle X-ray diffraction. Afte refraction correction, the period of multilayers can be calculated more accurately using th low angle peaks. The period increases with increasing annealing temperatures. The intensities of 2nd and 3rd Bragg diffraction also increase with the annealing temperatures. These phenomena can be interpreted by the increase of thickness of the carbon layers.
1988, 37 (11): 1900-1905.
doi: 10.7498/aps.37.1900
Abstract +
The X-ray diffraction patterns of a Fibonacci series consisted of two kinds of atoms have been simulated according to the amplitudes summed up with phases. Peaks appeared at K=(m+nt)/(1+2t)d-1, where d is the average planar distance. Relationship between the anglewidth β of diffraction peaks and the total thickness of atomic layers obeys the Scherrer for-mula: β=(0.88λ)/(Dcosθ), just as that for crystals. The intensities of weak diffraction peaks ch-anged irregularly with the increasing number of atomic layers, which can be illustrated by zigzag path in the amplitude-phase diagram.
1988, 37 (11): 1906-1909.
doi: 10.7498/aps.37.1906
Abstract +
The outstanding permanent magnetic material Nd2Fe14B possesses very high energy product. But its Curie temperature is a little bit too low for practical application. Some elements were added into the material in order to raise the Curie temperature. Reference [9] and our recent experimental results show that the Curie temperature can be made higher by partiy subsituting silicon for iron in the material and in Y2Fe14B. For understanding the effect of silicon on magnetism, the occupancy of Si in Y2Fe14B was studied by neutron diffraction. The neutron diffraction results show that silicon occupies preferentially the sites of c, j1, and k2. The magnetic interaction theory is applied to explain the experimental results.
1988, 37 (11): 1910-1914.
doi: 10.7498/aps.37.1910
Abstract +
Total electrooptic coefficients of KTiOPO4 crystal have been measured by interferometric method. The results obtained are:γ13 = 7.9, γ23= 11.3, γ33= 22.7, γ51=10.6 and γ42= 6.2(×10-10cm/V).
