Vol. 38, No. 7 (1989)
1989-04-05
CONTENT
1989, 38 (7): 1041-1047.
doi: 10.7498/aps.38.1041
Abstract +
In the paper, applying the stochastic statistical methods, we obtain the resonant radiation spectrum of a two-level atom ensemble driven by multimode squeezed light. Co-responding to different squeezing degrees of the quantum fluctuations of the driving field, the central peak of radiation spectrum exhibits subnatural-and supernatural-linewidth phenomenon, and in all cases the side peaks are broadened. The positions of the side peaks and the character of symmetry of radiation spectrum depend upon the coherent excitation direction and the squeezing direction of the driving field.
1989, 38 (7): 1048-1055.
doi: 10.7498/aps.38.1048
Abstract +
A beam of gold atoms was produced by heating the gold containing material by electrothermal method. Two UV laser beams then orthogonally irradiated the atomic beam, exciting the Au atoms to very high Rydberg states from their ground states (6S1/2). A high voltage pulsed electric field was applied to the interaction region approximately 200 ns after the laser pulse, it ionized the Au atoms into Rydberg states. By scanning the wavelength of laser in a certain range, the positions of 38 energy levels of Au atoms in n2D3/2 (n = 18-38) and n2S1/2 (n = 21-34; 36-38) series have been determined. the ionization limits of the n2D3/2 and n2S1/2 series were found to be ED = 74409.8 (3)cm-1 and Es = 74410.0(2) cm-1, respectively, by parametric fitting. The quantum defects of all these levels were also calculated.
1989, 38 (7): 1056-1061.
doi: 10.7498/aps.38.1056
Abstract +
Based on the Hartree-Slater self-consistent field theory, we considere the residual interaction which is omitted in obtaining the Hartree-Slater self-consistent field in previous calculation. We calculate the near threshold photoionization cross sections of K-shell of atomic Ne-and Ne+ ion and the cross section ratios as examples. We discuss the effects of residual interaction and compare our results with experiments.
1989, 38 (7): 1062-1068.
doi: 10.7498/aps.38.1062
Abstract +
We use the mean field renormalization group method to treat the semi-infinite Ising ferromagnetic system with the amorphization of the surface. The critical behavior of the surface with a surface random field, including critical temperature, the possibility of tricritical and reentrant phenomena, are investigated in detail.
1989, 38 (7): 1069-1076.
doi: 10.7498/aps.38.1069
Abstract +
In this papar,a new atomic structure model of the Si{001}2×1 surface determined from band theory calcution of low-energy-electron diffraction are prensented.The new structure model involves a dimer band length ld = 2.387? and thee atomic layer distances d1 = 0.50±0.01?, d2= 0.96±0.01?, d3 = 1.17±0.01? and two asymmetric displacements of dimer atoms.
1989, 38 (7): 1077-1085.
doi: 10.7498/aps.38.1077
Abstract +
In this paper, a scalene triangle-dimer-adatom model of the Si(lll)7×7 surface determined from band theory calculation of Low-Energ electron diffraction is prensented. We found the first-layer spacing distance d1 = 0.95±0.02?(expanded 21.3%±0.02?), the second-layer spacing distance d2=0.83±0.02?(expanded 5.9%±0.02?), the third-layer spacing distance d3 = 0.69±0.05?(contracted 10.9%±0.05?) and the fourth-layer spacing distance d4 = 2.38±0.08? (expanded 3.8%±0.08?).
1989, 38 (7): 1086-1092.
doi: 10.7498/aps.38.1086
Abstract +
In this article we report the results of photoluminescence studies on In0.25Ga0.75 As-GaAs straiaed quantum wells grown by molecular beam epitaxy under pressure at 77 K. The applied hydrostatic pressure ranges from 0 to 50 kbar. The pressure coefficients of T valley of (InGa)As-GaAs strained quantum wells are presented. We have observed the crossover between the energy level in the well and X valley in the barrier GaAs. With the analysis of its behavior under pressure, the ratio of conduction band offset to valence band offset in In0.25 Ga0.75 As-GaAs heterojunction is determined as Qc =△Ec:△Ev = 0.68:0.32. The theoretical studies on (InGa) AsGaAs strained quantum wells under normal pressure fit the experimental results very well. Some discussions about (AlGa)As-GaAs quantum wells are also included in this paper.
1989, 38 (7): 1093-1102.
doi: 10.7498/aps.38.1093
Abstract +
Using a novel variational wave function for the ground state of the shallow donor in a narrow GaAs/Ga1-xAlxAs quantum-well, we have calculated the wave function and the binding energy for impurity ground state. The numerical results shown that it is important to describe the coupling between the narrow quantum-well and the impurity potential correctly.
1989, 38 (7): 1103-1110.
doi: 10.7498/aps.38.1103
Abstract +
In this paper, an analytical energy band easy to calculate for GaAs, AlAs and AlGaAs is proposed. The transfer eigenvalue and energy effective mass are obtained by asing the LCAO transfer matrix model. By studing the transfer eigenrunction for two energy valleys, the transformation between different energy valleys is derived, from which new concepts about symmetry transformer and symmetry filter are suggested. Using the energy effective masses and the transformation coefficients between energy valleys at the interface, we derive the equations of envelope function and their boundary conditions for this single band-double valley model. Applying this theory to GaAs/AlGaAs/AlAs system, the confined energy level and wavefunc-tion are calculated. Finally, the significance of this generalized effective mass theory is discussed.
1989, 38 (7): 1111-1121.
doi: 10.7498/aps.38.1111
Abstract +
In this paper, we present a new method for calculation of depth profiles of implanted ions in multilayer materials. It combines the Monte Carlo simulation method with the method of numerical solution of the LSS transport equation. Taking into account the reflection of the ions at the interfaces of the layers the analytical expression of the range distribution in the multilayer materials is obtained. The comparison between the theoretical and the experimental results is made and good agreement is shown.
1989, 38 (7): 1122-1126.
doi: 10.7498/aps.38.1122
Abstract +
The HR-1 austenic steel have been irradiated with 70 keV 4He ions to the dose of 5×1016—1018cm2 at room temperature. Isochronal post-annealing has been carried out at temperatures up to 1273 K. 2.5 MeV proton elastic scattering,TEM and SEM are used to investigate the trap-ping, migration and release of He.
1989, 38 (7): 1127-1133.
doi: 10.7498/aps.38.1127
Abstract +
In this paper, the strain and stress fields produced by the dislocation are analysed by means of continuous dislocation distribution. The dislocation distribution inside the core is expressed by the dislocation gauge fields which are calculated under certain gauge condition. The stresses inside and outside the core of a screw dislocation are obtained. Outside the core, the stresses are the same as that of Volterra dislocation, but inside the core, the stresses of the screw dislocation approach zero when ρ goes to zero. Finally, the energy of the screw dislocation is calculated.
1989, 38 (7): 1134-1139.
doi: 10.7498/aps.38.1134
Abstract +
X-ray topographic contrast of inclusions in the crystal of potassium acid phthalate (KAP) has been studied experimentally and theoretically. The nature of inclusion formation was determined in view of their black and white contrast. An "Inclusion Decoration Method" for use in determining the nature of the strained regions in the crystal with very large areas has been proposed. The results together with such an analysis technique are presented in this paper. It has provided a practical way to identify the structural weakness in single crystals.
1989, 38 (7): 1140-1045.
doi: 10.7498/aps.38.1140
Abstract +
Using an exact real-space renormalization-group technique, we show that self-avoiding trails (SAT) and self-avoiding walks (SAW) on the Sierpinski gasket enjoy the same critical exponent ν for the ‘correlation length' and therefore belong to the same universcllily class. On the other hand, it is shown that SAT on branching Koch curves with maximum ramification number Rmax>3 belongs to another universality class different from that of SAW.
1989, 38 (7): 1146-1153.
doi: 10.7498/aps.38.1146
Abstract +
The behavior of velocity of ultrasound in glasses below 3 K is analysed by combining the tunneling model and the infrared divergence theory. The variation of sound velocity is regarded as consisting of two parts, i.e., non-relaxation process and relaxation process. The former is analysed by the Bose elementary excitation theory and the latter by the theory of tun neling relaxation with infrared divergence. The theoretical curve of sound velocity vs temperature is consistent with the experimental data. The observed In T rule of sound velocity for normal frequency (107Hz) at 0.3-1K, and the phenomenon of appearance of sound velocity minimum for ultrahigh frequency (2GHz) belowe 0.1 K are also explained.
1989, 38 (7): 1154-1161.
doi: 10.7498/aps.38.1154
Abstract +
The chemisorption of CO on Fe(ll0) surface has been investigated using angle resolved ultraviolet photoemission spectroscopy (ARUPS)The experimental results, compared with the calculation, show that the molecular axis of Co is nearly perpendicular to the iron surface at 150K and low coverage of CO. The angle between CO axis and the surface normal is less than 10 degrees.
1989, 38 (7): 1162-1166.
doi: 10.7498/aps.38.1162
Abstract +
A method of measuring micro-vibration amplitude with laser is presented. By using the optical resonant characteristic of Fabry-Perot etalon and intensity-comparison lock-in technique of laser, we have completed a measurement with the minimum amplitude of vibration at the order of 10-12 cm under the condition of an ordinary laboratory.
1989, 38 (7): 1167-1171.
doi: 10.7498/aps.38.1167
Abstract +
Arccording the general covariant equation of motion and Maxwell equations, we derive the analytical expressions for various quantities of electron plasma wave. It is pointed out that the plasma wave with △ω = 2ωp is completely harmonic. The condition of complete resonance is given by △ω= 2ω(p0) [1+(e2(A2((1)2)+(A2((2)2))/(2m2c4)+(3e2A2(1)A2(2))/(m2c4)]-1/2.
1989, 38 (7): 1172-1176.
doi: 10.7498/aps.38.1172
Abstract +
Photoionization spectra of Ca and Sr atoms above the classical field-ionization threshold are observed by using two-photon excitation method. The relation between the resonances and the applied electric field as well as polarization, of laser beam are discussed.
1989, 38 (7): 1177-1181.
doi: 10.7498/aps.38.1177
Abstract +
This paper presents an investigation of dipole spin modes in an anisotropic medium with uniaxial anisotropy and a weak exchange effect. The critical angle between surface wave and volume wave is given according to the new circumstance and the real ω vs k figure in space is analysed. The experimental results of single crystal YIG FMR spectra agree well with our calculation.
1989, 38 (7): 1182-1186.
doi: 10.7498/aps.38.1182
Abstract +
Some previous experimental results about the concentration dependence of magnetic ani-sotropy for metalmetal amorphous alloys were analyzed. By introducing a new parameter, a model of tetrahedral directional order was proposed. The comparison with some experimental data shows good agreement.
1989, 38 (7): 1187-1190.
doi: 10.7498/aps.38.1187
Abstract +
In this paper, we apply the decoration and decimation transformation to the square-lattice spin-1 model and show that it is equivalent toa checkerboard Ising model with cross and four-spin interactions. Then, the approximate critical condition is obtained for the model and it reduces to Onsager's exact solution in the Ising-model limit.
1989, 38 (7): 1191-1195.
doi: 10.7498/aps.38.1191
Abstract +
In this paper, we consider a Kagome-lattise mixed-spin model and show that it is equivalent to an eight-vertex model via decimation and duality transformation. According to the free-fermion approximate solution of the eight-vertex model, the approximate expressions are given for the free energy and critical condition of the model.
1989, 38 (7): 1196-1198.
doi: 10.7498/aps.38.1196
Abstract +
The critical behavior of Ising model with three-spin interactions on three-node hierarchical lattices is investigated by using an exact renormalization group transformation. As in the case of Bravais lattices, the model with two-spin interactions and the one with three-spin interactions belong to different universality classes.
1989, 38 (7): 1199-1204.
doi: 10.7498/aps.38.1199
Abstract +
Starting from the quasi-two dimensional Bose condensation, we studied the influence of layer-thickness and ox gen-vacancy on the critical temperature Tc in real high-Tc, superconductors. The results are consistent with known experiments qualitatively.
1989, 38 (7): 1205-1209.
doi: 10.7498/aps.38.1205
Abstract +
Incomplete poling of ferroelectric crystals has significant effect on their diffraction intensities. In the crystal structure determination, this effect must be taken into account. For lead hydrogen phosphate, appropriate equations are derived to correct this effect. Incorporating this correction in the structure determination of this crystal, a better fit is obtained.
INVESTIGATION OF THE ANOMALOUS HALL EFFECT IN n-Ge AT ROOM TEMPERATURE BY THE INVERSION LAYERS MODEL
1989, 38 (7): 1210-1214.
doi: 10.7498/aps.38.1210
Abstract +
In this paper, we make quantitative rheor ncal calculation for the anomalous Hall effect in n-Ge semiconductor at room teperature by use of the inversion layers model. The results are in agreement with the experiments.
