Vol. 38, No. 1 (1989)
1989-01-05
CONTENT
1989, 38 (1): 1-8.
doi: 10.7498/aps.38.1
Abstract +
By the method of symbolic dynamics, the Farey sequences, the * products of Farey sequences and M. S. S. sequences, the binary trees and the new trajectories for varied Farey; numbers of the circle map are studied.
1989, 38 (1): 9-15.
doi: 10.7498/aps.38.9
Abstract +
We studied the effects of electron-electron interaction on the electronic states of the-polaron in polyacetylene, based on the SSH and Hubbard models. The results show: 1. There emerges a new bound state in the gap caused by the e-e interation, that is a shallow discrete level near the top of the valence band. 2. The bound state below the bottom of the valence band disappears, and meanwhile, two bound states appear above the top of the conduction band.
1989, 38 (1): 16-23.
doi: 10.7498/aps.38.16
Abstract +
Using the "self-reproducing profile model", we derive a basic equation for synchronously pumped-passive mode-locked dye lasers and an analytical expression for duration of the light pulses emitting from this lasers system. Based on these results, some characteristics of such a hybrid mode-locked lasers system are interpreted theoretically.
1989, 38 (1): 24-30.
doi: 10.7498/aps.38.24
Abstract +
Electric quadrupole transition enhanced tthree-wave difference-frequency generation in isotropic medium is investigated. Taking account of the contribution of electric quadrupole interaction, we derive the second-order nonlinear susceptibility. We also discuss the possibility of observation of collision induced second-order nonlinear optical processes. The experiments are performed with 3s→4d electric quadrupole transition in sodium vapor. The experimental results agree with theoretical predictions.
1989, 38 (1): 31-34.
doi: 10.7498/aps.38.31
Abstract +
By using multi-frame optical probing photography, we have discovered and investigated the large-scale "Horn Tip" plasma jet structures in the coronal region of line-focused laser-produced plasmas. These plasma jets always appear at the boundary between the hot plasma and the cold target material, or between two plasmas with different Z-numbers.
1989, 38 (1): 35-43.
doi: 10.7498/aps.38.35
Abstract +
In this paper, the interference phenomenon in an optical system with three gratings in series arrangement is proposed and analysed in terms of the partial coherence theory and the ambiguity function. As a result, the fringe intensity distribution is derived as a joint convolution-correlation integral of three equivalent functions of gratings. The conditions on the distances and the period ratios between gratings are studied. With the change of the slit width, the Talbot effect, the partially coherent effect and the Lau effect can be observed in sequence. The profile of partially coherent fringes varies with the relative shift of any grating. Finally, experimental verifications for theoretical predictions are given.
1989, 38 (1): 44-52.
doi: 10.7498/aps.38.44
Abstract +
The model of the crystal surface developed by Allan was used to derive the Green's function of the fcc (100) surface for tight binding solids. The Green's function method is employed to study the general feature of an adsorbate, and to analyse the interaction energy between an adatom and the substitutional impurity atom at metal surface. Finally, the trends in the influence of substitutional impurity atom along transition series on the heat of adsorpotion for oxygen and hydrogen on the fcc (100) surface of Ni, Pd and Pt metal is predicted qualitatively.
1989, 38 (1): 53-59.
doi: 10.7498/aps.38.53
Abstract +
The modified Eliashberg equations and Tc formula are obtained by incorporating the effect of many phonons into the theory of superconductivity. The result of our analysis is that the high frequency phonon plays an important role in raising Tc, and the large number of degenerate degree contributes greatly to superconductivity as well.
1989, 38 (1): 60-67.
doi: 10.7498/aps.38.60
Abstract +
The measurements of X-ray diffraction, d.c. resistance versus temperature and Hall coefficients at low temperature have been performed for YBa2Cu3-xMxOy systems. (x = 0.00, 0.025,0.05,0.075,0.10,0.125,0.15,0.20,0.25,0.275,0.30,0.325,0.35,0.375,0.40 for M = Co; x=0.025,0.05,0.075,0.10,0.15,0.20,0.30 for M = Zn)The crystallographic data show that an orthorhombic-tetragonal phase transition takes place as Co content increases,while the crystal structure exhibit drastic changes with Zn content. The measurement of resistances indicates that a metal-semiconductor transition occurs at certain x for Co dopant hut not found for Zn dopant. The hole carrier concentration raduces with Co content monotoneous-iy but varies nonmonotoneously with Zn content, giving a maximum at about x= 0.15 The concepts of localization and acceptor are used to explain these phenomena. The suppression of Tc for both systems is discussed with various possible suppression mechanisms.
1989, 38 (1): 68-75.
doi: 10.7498/aps.38.68
Abstract +
The breakdown characteristics of very thin nitrided silicon oxide film have teen exammed. The breakdown mechanism of this film and the factors affecting the breakdown characteristics have been explored. It has been found that the improvement of breakdown properties of this nitrided oxide depended greatly on the changes of the microstructure of the film and interface, as well as the composition of the film. The narrowing of the band gap width of the film after nitridation makes the electric field for intrinsic breakdown decrease, but the occurrence of breadown may be greatly postponed by the dense material, the smoothed interface and the effect of traps. Experimental evidences confirmed that the im-pact-ionization exists in the intrinsic type of breakdown, but the permanent breakdown is caused by the heat transfer for all cases.
1989, 38 (1): 76-82.
doi: 10.7498/aps.38.76
Abstract +
Photoluminescence (PL) spectra of annealed a-SixC1-x:H films were studied. The-widths of the exponential bandtails were determined by means of the temperature dependences of PL peak energy positions. The experimental results shows that PL peak energy positions shift towards the lower energy with annealing temperature increasing. The bandtail widths have been calculated according to the exponential bandtail model, the calculation shows that the bandtails contract with increase of annealing temperature. A discussion about the results has been given.
1989, 38 (1): 83-90.
doi: 10.7498/aps.38.83
Abstract +
The 5.8, 3.0 and 1.2 MeV Li ions were used to study the MBEIn0.25Ga0.75As/GaAs (100) sample. Ion channeling angular scans about[100] and [110] axes were carried out in the (100) plane.It is found that in the case of 5.8 MeV, the critical angle of the epilayer is almost the same as that of the substrate and the angle misalignment between them is 0.90° for axis [110] , corresponding to the misfit of sample being 1.62%, in good agreement with theoretical calculation. In the 3.0 MeV case, serious asymmetry have been observed in RBS/Channeling angular scan; in the 1.2 MeV case, the angular misalignment is reduced to 0.50° and the critical channeling angle of substrate is increased significantly. We have studied and discussed the physical mechanism of these anomalous phenomena in detail, and present a good interpretation of the experimental results.
1989, 38 (1): 91-97.
doi: 10.7498/aps.38.91
Abstract +
The mechanism of high temperature creep associated with the climb of extended dislocations is investigated. Based on the model for the contraction of extended jogs [1], the time needed for the contraction under the action of applied stress and the climb velocity of extended dislocations are derived. And consequently, an expression of the steady state creep rate is obtained. According to this expression, the creep rate is shown to be proportional to the third power of the stacking fault energy. This is consistent with the majority of experimental results. The possible reason for the deviation from the third power relation in some cases is also discussed.
1989, 38 (1): 98-104.
doi: 10.7498/aps.38.98
Abstract +
This paper studies the interaction of a four-lever cascade atom with two-mode cavity fields in which the lower mode is initially empty. It is shown that there exist long time dipper squeezing and alternate squeezing, as well as strong antibunching and superbunching. The relation between the squeezing and superbunching is disclosed, the nonclassical squeezing and antibunching may occur at the same time. This nonlinear properties originate from the effect of complicated superposition states.
1989, 38 (1): 105-110.
doi: 10.7498/aps.38.105
Abstract +
Space-time resolved X-ray photograms of carbon (4671? thick with substrate) and gold (15μm in thickness) planar targets were obtained using a pinhole coupled to a soft X-ray streak camera. The planar targets were irradiated with laser (λ = 1.06 μm) pulses of about 100 ps duration from a LF-12 Nd: glass laser. The spectral response of the soft X-ray camera is defined to be 0.1-10 keV. Average plasma expansion velocities on the C and Au traget surface measured at a laser power density of about 1014 w/cm2 for were 5.l×107cm/s and 6.1×107 cm/s respectively.
1989, 38 (1): 111-117.
doi: 10.7498/aps.38.111
Abstract +
A method for determining the orientation of thin crystal layer has been proposed, namely the Raman scattering extrems technique. The intensity of Raman scattered light from the diamond structure thin layer as a function of both the normal of the thin layer and the polarization direction of incident light is derived. The orientation of the thin layer is then determined by means of four extrema of this function. The results obtained by this method, for silicon wafers are compared with that dettermined by the X-ray method.
1989, 38 (1): 118-123.
doi: 10.7498/aps.38.118
Abstract +
The probabilities α′,α″ and β of intrinsic, extrinsic and twin stacking faults were measured respectively based on previous determination of Deff, ρ, M, Re and of samples A, B, C. The stacking fault energy γ and true subgrain size D0 were also obtained.
1989, 38 (1): 124-127.
doi: 10.7498/aps.38.124
Abstract +
The piezoelectric coefficients of NH04IO3 crystal have been measured by interfe-rometric method. The results are d31=35.2, d32=23.4, d33=55.9, d24=-2.4, d15=-9.5×10-8 CGSE/dyn.
1989, 38 (1): 128-133.
doi: 10.7498/aps.38.128
Abstract +
In this paper, the microhardness of LnP5O14 (Ln = La→Lu) crystals have been measured and discussed. The anisotropy of microhardness and the influence of temperature on microhardness have also been studied. These results indicate that the microhardness of crystals depends not only on the crystal structure and lattice energy but also on temperature.
1989, 38 (1): 134-139.
doi: 10.7498/aps.38.134
Abstract +
Based on the characteristic of superionic glasses and the infrared divergence response theory, we studied the anelastic relaxation of amorphous superionic conductors. We consider that the ultrasonic attenuation of superionic glasses is due to the thermal active relaxation process of mobile superions bonded weakly to the glassy network and the accompanishing low energy excitation dissipation.The theory can explain the experimental characteristics which failed to be interpreted by previous theory with distributed relaxation times. Our predictions agree well with available experimental data.
1989, 38 (1): 140-144.
doi: 10.7498/aps.38.140
Abstract +
The change in electrical resistance of Pd-, Cu-, Ni- and Fe-base metallic glasses in tensile process and the effect of composition, cold deformation and heat treatment on the strain coefficient of resistance k, have been investigated. The results show that the resistivity increases with the increase of strain and K is positive. K of all the alloys are always less than those of pure metals; k of cold deformed state and annealed state samples are greater than that of rapidly quenched state samrte. The physical nature of K and its factors of influence on metallic glasses are discussedpl in virtue of generalized Ziman theory.
1989, 38 (1): 145-148.
doi: 10.7498/aps.38.145
Abstract +
The optical properties of YBa2Cu3O7-δ are studied by electroreflectance spctra. In the visiblr range, two peaks at 1.78 eV and 2.43 eV are obtained. Analysis of the features show the utility of the modulated reflectance techniques for studying the band structure of superconducting system. Hence a new means to study the optical properties of superconducting system is suggested.
1989, 38 (1): 149-153.
doi: 10.7498/aps.38.149
Abstract +
The temperature dependence of the dielectric constant of monomer single crystal TS has been determined for the range 77-300 K, two anomalies have been observed near 160 K and 203 K. The variation of the dielectric constant of TS during thermal solid state polymerization is obtained. It the initial stage of polymerization, the dielectric constant decreases slowly; when sample conversion to polymer exceeds 30%, the dielectric constant increases rapidly. We suggest that this behavior may be related to side-group and π-electron and hend explain the results qualitativly.
1989, 38 (1): 154-158.
doi: 10.7498/aps.38.154
Abstract +
A general approach for analysing the effect of electron-many phonon interaction on electron life time and the corresponding expressions are present for the case of temperature T》 Debye Temperatule TD. It is pointed out that the electron-many phonon interaction may be important for 90 K superconductivyty in Y1Ba2Cu3O7-δ.
1989, 38 (1): 159-162.
doi: 10.7498/aps.38.159
Abstract +
The basic assumptions of a recent model of the rapid initial oxidation of silicon put for-wara by Schafer and Lyon are examined. It is found that some of their hypothesis is inconsistent with existing experimental data. Instead, our previous model on initial oxidation can be used to explain the experimental data satisfactorily. The charge density at the interface and the equilibrium concentration of oxygen in the oxide are estimated based on this model, they agree well with measured results. These comparisons suggest that our previous model of oxidation give an overall satisfactory picture of the rapid initial thermal oxidation process of silicon.
1989, 38 (1): 163-169.
doi: 10.7498/aps.38.163
Abstract +
Calculations of electronic structures for Si29 and Si47 clusters, which are cut from continuous random networks of a-Si, and those of simple ones Si8H18,Si17, have been performed by using CNDO LCAO MO method. The origin and nature of the gap states due to intrinsic defects such as weak bond, bent bond and charged configurations are examined in a-Si:H. The results show that two weak bond states situated in both sides of band gap have been contracted and shifted to the center of the gap as the weak bond is stretched. These weak bond levels have been shifted to some location near the top of valence band or near the bottom of conduction band due to extra charges. The bent bond states mainly appear near the top of valence band. When the bond is bent severely,the bond level shifted upwards, close to the center of band gap from below. The structural lopological disorder may induce the gap states at any position within the band gap. It is suggested that all the weak bond and bent bond as well as charged configuration are the principal forms of intrinsic defects in a-Si:H. Various experimental results of gap states are explained according to these theoretical calculations.
1989, 38 (1): 170-174.
doi: 10.7498/aps.38.170
Abstract +
In this papel, the property of variance of period of the torsional pendulum with appto-ximate linear elastic coefficient in damped vibration is analysed theoretically. The results corresponding to experiment are obteined. Several methods used to reduce variance of the period and to improve measurement precision are developed, such as method of eliminating background variance and method of double suspension wires, on which prestressing force is added.
