Vol. 41, No. 11 (1992)
1992, 41 (11): 1737-1744. doi: 10.7498/aps.41.1737
Chen Mobius inverse formula is further generalized. This generalized formula is applied to solve the inverse problem of pairwise interaction in 3D lattice. After discussing structural characters of several typical perfect crystals, we give an algorithm based upon iterative methed with numerical examples. Stability and error of this algorithm are analyzed.
1992, 41 (11): 1745-1752. doi: 10.7498/aps.41.1745
The phenomenon observed by Wu et al., which takes place in the interation of two nonpropagating solitary waves in a trough resonator, is analytically analyed by the perturba-tive variational analysis. The coalescence period and the first-coalescence-time for in-phase solitary waves as well as the interaction forces and the interaction potential existing between two solitons are given, providing a partical description for the interaction between two non-propagating solitary waves.
1992, 41 (11): 1753-1758. doi: 10.7498/aps.41.1753
The Pd77.5Au6Si16.5 alloy was studied by means of a drop tube processing. Pd solid solution phase was found in smaller droplets (diameter D3Si was observed. The difference of free energy between underco-oled liquid and solid state, the activation energy for the formation of postcritical nuclei, tie nucleation rate and the speed of crystal growth were calculated as a function of temperature for Pd solid solution and PdsSi phases, these calculations led to time-temperature-transforma-tion curves which may be used to describe the experimental findings oa the kinetics of solidification of this alloy.
ATOMIC AND MOLECULAR PHYSICS
1992, 41 (11): 1759-1764. doi: 10.7498/aps.41.1759
In this article, the B spline technique is employeed to construct finite basis sets for the radial HF equation. MBPT calculation is performed on the radial hyperfine interaction parameters of 11B ground state with such basis sets. The results for the megnetic dipole parametrs are al = 0.7776850, asd = 0.8462827 and asd/al = 1.0882, which is in good agreement with experimental values of 0.778 (2), 0.844 (3) and 1.085. The electric quadrupole parameter is aq = 0.7462691,showing a discrepancy of 6% from the experiment.
CLASSICAL AREA OF PHENOMENOLOGY
BACKSCATTERING OF ELECTROMAGNETIC MISSILES BY A PERFECTLY CONDUCTING CYLINDER WITH ARBITRARY CROSS SECTION
1992, 41 (11): 1765-1770. doi: 10.7498/aps.41.1765
In this paper, we present a general study on backscattering of electromagnetic (EM) missile by a perfectly conducting cylinder of arbitrary cross section. We find that, when an EM missile with energy decreasing as r-ε(0 -εR/(2r + R), where R is the radii of curvature at tie specular point of the target.
1992, 41 (11): 1771-1781. doi: 10.7498/aps.41.1771
The long-time behavior of squeezing of intense coherent light is studied with off-resonance Jaynes-Cummings model. The interaction between field and atom includes both one-photon transition type and two-photon transition type. The analytical formulae for quadrature variances are obtained. In one-photon transition case, small detuning only has small effect on squeezing. For two-photon transition, however, the situation is quite different. No squeezing will occur in resonance case. Only detuning can cause squeezing. Then a series of minimum appear in the suppressed quadrature variance during time evolution. In Urge N limit this se-ries tends to zero.
Both Λ-type system and V-type one can show lasing without inyersion and inversion without lasing due to atomic coherence. Spontaneous emission noise of Λ-type laser is reduced due to coherent substraction but that of V-type laser is reduced due to coherent addition
1992, 41 (11): 1789-1795. doi: 10.7498/aps.41.1789
The theoretical analysis of photoacoustic Raman spectroscopy (PARS) is prese-nted The general expressions of PARS signal in solid and liquid samples are derived and the theoretical estimation is given.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
1992, 41 (11): 1796-1805. doi: 10.7498/aps.41.1796
Unification of the frequency shift and pulse compression of an ultrashort laser pulse propagating in a background plasma wave is realized by employing the concept of phase modulation of the laser pulse by the plasma wave. The equation for the evolution of the pulse width is obtained, which is analogues to the "energy conservation equation" for a classical particle moving in a potential well. The threshold amplitude of plasma wave for the pulse compression is estimated. Numerical calculation is performed to confirm these results. The possibitity of laser pulse compression by plasma wave in practice is suggested finally.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1992, 41 (11): 1806-1812. doi: 10.7498/aps.41.1806
By using low energy electron diffraction (LEED), the atomic structures on Si (113) surfaces were studied. These surfaces were prepared by both ion bombardment followed by annealing (IBA) and epitaxial growth. When tbeannealing temperature was higher than 750℃, a 1 × 1 unreconstructed structure was observed above 600℃ for both kinds of surfaces. Cooling the specimen from the annealing temperature at a rate of 5℃/min, we found that the surface structure converted from the 1×1 through 3×1 (beteen 600℃ and 400℃) to the final 3×2 superstructure. A lower annealing temperature (～600℃) results in a 3×1 superstructure only. Both 3×2 and 3×1 structures are very stable at room temperature. The influence of surface impurities on the Si(113) surface structure was discussed. The clear 3×1 superstructure was also appeared on the initial Si(113) surface of about 20 monolayers thick epitaxial film grown by evaporation method.
1992, 41 (11): 1813-1819. doi: 10.7498/aps.41.1813
Based on the embedded-atom-method, the st ructures of liquid noble metal Au and Ag have been investigated using Molecular Dynamics computer simubation. Results show that, near the melting point, there exists local cubic symmertry, and long-range correlations among these symmertries, are very weak.
1992, 41 (11): 1820-1824. doi: 10.7498/aps.41.1820
Based on Biersack's angular diffusion model, an effective method was established for calculating the mean project range of MeV heavy ions in solid targets. The calculated values are compared with recent experimental data on the mean project range for 1.0 MeV In+, Xe+, Ta+ and 1.0-2.0 MeV Pb+ The maximum difference-between present calculated values and experimental data is less than 8%, but the maximum differences between experimental data and calculated values by TRIM 86 and PRAL are 23% and 22%, respectively- The results show that the present calculation procedure is sucsessful for predicting the mean projected range on 1.0-2.0 MeV such heavy ions as In+, Xe+, Ta+ and Pb+ implanted in solid target (Si).
1992, 41 (11): 1825-1829. doi: 10.7498/aps.41.1825
In the paper, the sine-squared potential and the parabola approximations of a bent crystal with a varying curvature have been introduced to discribe the dechan-neling effects of charged particles moving in such a crystal Furthermore, we show the possibilities of detlecting charged particles by a bent crystal, derive rhe dechan-nelling fraction of such a crystal and discuss the possible applications.
1992, 41 (11): 1830-1836. doi: 10.7498/aps.41.1830
Two low frequency internal friction peaks, one induced by oxygen jumping in the Cu(l)-O basal planes in the orthorhombic phase and the orther in the tetragonal phase, were systematically studied. The order of orthorhombic-tetragonal phase transition was analysed based upon the internal friction data. It was inferred that the transition, generally considered as second order, may actually be first order, at least near 200℃.
1992, 41 (11): 1837-1841. doi: 10.7498/aps.41.1837
It is shown that, for a realistic problem, how to construct the Cellular Automata rules and what can be done once these rules are given We have constituted the model of nonequilibrium phase by the Cellular Automata approach. A mean-field-like approximation is discussed and its predictions are compared with the exact numerical results for the model.
1992, 41 (11): 1842-1848. doi: 10.7498/aps.41.1842
The crystal habit and size of the Fe nano-particles prepared by an inert gas evaporation method have been observed with transmission electron microscope. The composition, structure and thickness of the surface oxide film on the Fe nano-particles have been analysed in detail by means of several techniques, such as, X-ray diffraction, electron diffraction, X-ray photo-electron spectrum and Auger electron energy spectrum. A model of the composition and structure for these particles has been given. The results show that the crystalline structure of the Fe nano-particles is consistent with the general α-Fe, i.e. bcc structure. On the surface of these particles, there are double layers of the oxide film with about 3 nm thickness, in which the outside is γ-Fe2O3 of about Inm thickness and the inside is Fe3O4 of about 2 nm thickness. The crystal structure of the two kinds of oxide are of cubic spinel-type. The results also indicate that the Fe nano-particles prepared by the gas evaporation method are very stable in dry air. Though the oxide film is thin, it is quite compact and give good protective effect on the particles.
1992, 41 (11): 1849-1855. doi: 10.7498/aps.41.1849
The Pd/W/Si(lll) interface reaction has been investigated by XRD, XPS and AES. As the annealing temperature was low, no reaction among Pd, W and Si can be detected, but W started to diffuse into Pd and Si started to diffuse into. W. When the annealing temperature was raised, Pd and W were mixed and Pd diffused into Si substrate. When the annealing temperature was raised further, the interface reaction leads to a redistribution of the two metals with accumulation of the refractory metal at the outer layer, such a layer can be used as a diffusion barrier to protect the inner shallow contact layer.
1992, 41 (11): 1856-1861. doi: 10.7498/aps.41.1856
ZnSe (100) single crystal films are grown by hot wall beam epitaxy on GaAs (100) substrate. The quality of films are examined by LEED and AES in situ. The films show sharp C(2×2) LEED pattern. When sample are prepared with high growth rate, the Raman spectra show that there are TO modes which are usually forbidden in ZnSe (100) films. ZnSe(100) films with twin can be explained by the TO modes in the Raman spectra. This interpretation is supported by the result of XRD.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
EFFECTS OF HUBBARD INTERACTION AND SITE-TYPE IMPURITY POTENTIAL ON ELECTRONIC STATES IN TRANS-POLYACETYLENE
1992, 41 (11): 1862-1869. doi: 10.7498/aps.41.1862
In this paper, the SSH mode] has been extended to include the site-type impurity potential and the Hubbard interaction. The energy spectra and the electronic states of soliton in transpolyacetylene have been studied by the self-consistent iterative approach. Our numerical calculations have shown that the important differences in the effects of impurity potential and Hubbard interaction on electronic states of soliton. Namely, the site-type impurity potential is to shift the midgap states of the charged solitons in the opposite direction with Hubbafd interaction. Our conclusion are coincident with experimental results
DEEP LEVEL IN BOTH Si/SiO2 INTERFACE AND ITS NEIGH-BOURHOOD AND Si/SiO2 INTERFACE STATES IN p TYPE SILICON MOS STRUCTURE
1992, 41 (11): 1870-1879. doi: 10.7498/aps.41.1870
The deep level in both Si/SiO2 interface and its neighbourhood and Si/SiO2 interface states have been studied systematically with Deep Level Transient Spectroscopy (DLTS). Experimental results show that a dominant deep level, H (0.494), exits in both Si/SiO2 interface and its neighborhood in MOS structure formed by thermal oxidation. The deep level possesses some interesting properties, for example, its DLTS peak height depends strongly on temperature, and when the gate voltage reduces the interval between. Fermi-level and Si valence band to a value less than that between the deep level and Si valence band, its sharp DLTS peak is still observable. The hole capture cross section of the interface states at Si/SiO2 interface has been found to depend on temperature, measured with a new method. The energy distribution of the interface states measured with DLTS contradicts to the distribution obtained by quasistatic C-V technique. A new physical model of Si/SiO2 interface was proposed, with this model the above stated experimental results can be successfully expounded.
1992, 41 (11): 1880-1883. doi: 10.7498/aps.41.1880
We have prepared (YHo) Ba2Cu3O7-y superconductors with hige Jc value by powder melting process (PMP) method. The DTA result shows that the melting temperature of Y-system superconductor can be reduced by Ho addition. The Jc value can be improved and the size of 211 phase can be reduced by Ho substitution. Microstructures and X-ray diffraction pattern indicate that the 123 grains are preferentaially aligned with mutually parallel a-b conductive planes. There are a number of twins and fine 211 particles in the sample. It is also found that many crystal defects exist around the 211 phase. These defects may act as pinning centers.
1992, 41 (11): 1884-1890. doi: 10.7498/aps.41.1884
The magnetization curves of neutron irradiated bulk YBa2Cu3Oy prepared by melt-textured growth method were measured from 1.5 to 85 K. Flux jumps were observed for H∥c at 6K. The anisotropies of critical current are analysed in detail- The pinning mechanism and physical model for flux jumps are discussed.
1992, 41 (11): 1891-1897. doi: 10.7498/aps.41.1891
In this paper, we establish a Ising model of antiferromagnetic spin glass and give its phase diagram.
Using a special lock-in amplifier, the surface and volume conductivities of three kinds of high insulators are measured from -20℃ to 180℃. Hopping and band conductions of conductive polarons are observed in LiNbO3, the transition temperature between the two- conductive states is about 38℃. A conductive polaron can be captured by a trap and becomes a bound polaron. The bound polaron is not an electric carrier, but under the action of external field, its position may be changed to give an ultralow frequency polarization effect. There are many ferroelectric screenning charges on the surface of LiNbO3 and LiTaO3, however, their conductive currents are not so large as those of glass. But the screenning charges supply very large displacement currents. The fact shows that these screenning charges are in bound polaron state. The phenomenon of that the displacement current shows anomalous at about 45, 75, and 130℃ is observed in LiNbO3.
1992, 41 (11): 1906-1912. doi: 10.7498/aps.41.1906
The internal stress in diamond thin films deposited by DC plasma CVD was studied as a function of methane concentration and deposited temperature. Experimental results have shown that total stress in diamond thin films is sensitive to the deposition conditions. The results also indicate that the compressive stress can be explained in terms of amorphous state carbon and hydrogen, and tensile stress is ascribed to the grain boundary relaxation model due to high internal surface area and micristructure with voids.