Vol. 33, No. 6 (1984)
1984-03-20
CONTENT
1984, 33 (6): 729-737.
doi: 10.7498/aps.33.729
Abstract +
The far infrared absorption spectra measurements were performed on the CdxHg1-x Te samples with x=0.18 to 0.45 in the wavenumber region of 15-500 cm-1 at the temperatures from 4.5 to 300 K. In addition to the absorption structures of two phonon combination on both sides of the reststrahlen band of the material, a low frequency absorption band has been observed for the first time between 20-50 cm-1 in all the measured samples. By comparison with the phonon spectra of the mixed crystals CdxHg1-x Te which have been estimated by means of the ab initio density functional calculations of planar force constants, we have attributed the low frequency absorption band to the TA band modes induced by the disorder and "doping" effects resulting from by the crystalline mixing in the material.
1984, 33 (6): 738-746.
doi: 10.7498/aps.33.738
Abstract +
The behavior of deep level wavefunctions induced by short range defect potential is investigated when the energy difference ε between the defect state and the band edge is very small. When ε→0, the wavefunctions tend to expand in real space and concentrate in k space when some symmetric matching condition is satisfied. A specific scheme is developed for efficient and reliable numerical calculations of the deep level wavefunctions when ε is very small. For the case of A1 symmetric defect states near the bottom of the conduction band, for Si, when ε1 defect states near the top of the valance band, no concentration in k space occur since the A1 defect states mismatch to the Block states at valance band maxima.
1984, 33 (6): 747-754.
doi: 10.7498/aps.33.747
Abstract +
The thermal desorption spectra of hydrogen chemisorpted on Si(100) clean surface have been measured by means of flash heating the sample under ultra high vacuum. The result shows that with the low hydrogen exposure at room temperature there is only one desorption peak A, while a second desorption peak B with lower peak temperature appears after increasing the exposure time. If the hydrogen exposures are carried out at elevated temperatures, the peak B does not appear in the desorption spectra at the temperature higher than 230℃, and no peak A appeared at the temperature above 530℃. With heat annealing the sample after room temperature exposure, the peak B will not existed if the annea- ling tempersture is higher than 350℃, and the peak A will also disappeared at 530℃ annealing. From all these features of thermal desorption, we believe that the peak A and B are related to the desorptions of monohydride and dihydride phase on Si (100) surface respectively. The measured activation energies of desorption of these two phases are 52.9 kcal/mol and 14.5 kcal/mol. It could be deduced from the peak asymmetry and the invariance of peak temperature with the initial hydrogen coverage that the desorption of peak A is happened as a first order desorption process. This has been futhur confirmed by the order plot. But the mechanism of hydrogen desorption on Si (100) surface is different from both the ordinary first order and second order desorption.
1984, 33 (6): 755-761.
doi: 10.7498/aps.33.755
Abstract +
The dislocation distribution function in the plastic zone at a crack tip is calculated with the help of a modified BCS-type crack model. It is found that opposite sign dislocations appear on the slip plane immediately ahead of the crack tip. These negative dislocations seem to enter the crack tip and blunt it, resulting in a dislocation-free zone at the crack tip. The image force theory of the formation of dislocation-free zone is discussed.
1984, 33 (6): 762-769.
doi: 10.7498/aps.33.762
Abstract +
Russ's method is usually used in the no-standards quantitative analysis of X-ray EDS. Recently Wu et al. put forward a direct no-standards quantitative analysis method. The direct no-standards quantitative analysis method is also used in this article. However we utilized the advantages of Russ's method in which the physical model in normal ZAF correction is used. The method developed by us is easy for calculation. The analytical value of the NaCl, NaI, KCl, ZnS, AgI, GaAs are better than that of Russ's method. Especially the values of the samples which contain the elements of lower atomic number are more apparent.
1984, 33 (6): 770-778.
doi: 10.7498/aps.33.770
Abstract +
The phase diagrams of pseudo-binary systems LaNi5-NdNi5 and LaNi5-CeNi5, the aniso-tropy of grain sizes of actived LaNi5-NdNi5 samples, hydrogen absorption capacity and hydrogen desorption isotherms at 29℃ and influence of other phase on hydrogen absorption characteristics of LaNi5 have been investigated by means of X-ray diffraction and DTA, X-ray diffraction line broadening method, and second ways respectively.The variations of lattice parameters, unit cell volumes and atomic distances of actived and unactived samples were determined.The anisotropy of grain sizes of actived LaNi5-NdNi5 system, the difference of hydrogen absorption capacity and hydrogen absorption plateau pressures of RmNi5(Rm = misch-metal) were explained from structure viewpoint and our experimental results.
1984, 33 (6): 779-785.
doi: 10.7498/aps.33.779
Abstract +
The true dc measurement of electrical field effect on the resistivity of orthorhombic TaS3 in the CDW state was performed for the first time with extremely short distances between the contacting leads. Very weak nonlinear effect was observed up to 1300 V/cm. A distinct resistivity-increasing effect was found, which can not be understood within the framework of any currently available theories. We propose a transverse tunneling model to account for this anomaly.
1984, 33 (6): 786-796.
doi: 10.7498/aps.33.786
Abstract +
The traditional approach of treating kinetic problem of plasma is solving kinetic equation for f (v, r,t), then calculating the wanted macroscopic quantities by integration. It is shown that this is not a convenient and direct way. If transforming f (v, r, t) in to the Fourier space K, with respect to v, getting f(K, r, t) and corresponding equation of it, then only the value of f (K, r, f) near K≈0 is need for practical interest Two examples, one is the derivation of dispersion equations of electro-magnetic modes in a inhomogenius low β plasma, the other is the effect of collision on the temperal echo, show the main procedures of this approach and its advantage over the traditional one.
1984, 33 (6): 797-804.
doi: 10.7498/aps.33.797
Abstract +
By means of the quasi two dimensional motion picture of adsorbed 4He monolayer or second layer, an effective pair potential of helium atoms has been derived. The second virial coefficients and its second derivatives calculated from this effective potential agree with the experimental data much better than that calculated from the ideal 2-dimension model.
1984, 33 (6): 805-813.
doi: 10.7498/aps.33.805
Abstract +
A set of coupled equations for a quantum statistical system that determine self-consis-tently the order parameter, the energy spectrum, the dissipation and the distribution for both fermion field and collective excitation is suggested with a loop expansion formalism. They are applicable to non-equilibrium as well as equilibrium systems.
1984, 33 (6): 814-825.
doi: 10.7498/aps.33.814
Abstract +
Starting from the transformation properties of constrained system which is a general transformation results of action and constrained equations, we obtain generalized killing's equations of constrained system. The transformation generated by the solution of generalized killing's equations, may yield classical Noether's conservation quantities. We have considered the time-space and internal transformation of continuous constrained system which leave constrained equations invariant and give a necessary and sufficient condition that transformations may yield conservation current. The application to incompressible continuous media are presented. The application to generalized and classical mechanics are discussed and some illustrations for the solution of generalized killing's equations are also given. The Poincare's invariant is generalized to constrained generalized mechanical system.
1984, 33 (6): 826-832.
doi: 10.7498/aps.33.826
Abstract +
The solution of Euler's equation in the theory of harmonic mapping and the relationship between them have been studied in general. The Ernst equation and its solution are discussed from this point of view.
BRIEF REPORT
1984, 33 (6): 833-839.
doi: 10.7498/aps.33.833
Abstract +
The photoluminescent behavior of N+ and Zn+ implanted GaAs1-xPx has been investigated at 4.2 K. The experimental results show that the alloy composition x, at which N-Zn transition completely becomes N bound excitonic recombination, depends on the nitrogen and zinc impurity concentration.Using Campbell localized model, we calculated the probability ratio of N-Zn transition to N bound excitonic recombination as a function of composition and N, Zn impurity concentration.At 1.8 K, we have clearly observed the typical spectra of N-Zn transition and N bound excitonic recombination in the same sample.
1984, 33 (6): 840-844.
doi: 10.7498/aps.33.840
Abstract +
In this paper, oxygen precipitates and induced defects in annealed dislocation-free CZ-Si with high oxygen content have been investigated by HVEM. The oxygen precipitates are spherical crystobalite at 750-1050℃. In addition to spherical precipitates, there are some square plate-like oxygen precipitates with {001} habit plane. Punching prismatic dislocation loops are emitted from oxygen precipitates along 〈110〉 directions above 950℃.The loops are interstitial loops with Burgers vector α/2〈110〉 and axis 〈110〉.The loops are generated by a square plate-like precipitate or by a cluster of spherical precipitates. When dislocation loop encounters obstacle, the complex dislocation configuration may be produced. A stage in a stacking fault has been observed, it is formed by climb of the stacking fault. If treatment temperature is below 850℃, no bulk stacking fault results.
1984, 33 (6): 845-849.
doi: 10.7498/aps.33.845
Abstract +
The data of electron scattering factor for all neutral atoms, given in International Tables for X-Ray Crystallography in the range of sinθ/λ from 0.0 to 2.0 have been fitted by use of the damping least square method to an analytical formula with nine parameters as f(s)=sumfrom i=1to4 (aie-bis))+c. A relative deviation factor R=sumfrom k=1toN (|fok-fok|)/sumfrom k=1toN (fok) is served as the criterion of the relative deviation between the calculated and the observed values of the atomic scattering factor. The calculation shows that the relative deviation factors R for all atomic factors are approximately equal to 10-3. All parameters and corresponding relative deviation factors are tabulated. The maximun errors, the mean error, the mean square error and the summation square deviation are also given.
1984, 33 (6): 850-853.
doi: 10.7498/aps.33.850
Abstract +
On the basis of determining the ordering of Co and Mn atoms in the Y(Mn1-xCox)12 alloys, we went on to carry out the neutron diffraction measurement of these compounds at liquid nitrogen temperture to investigate their magnetic structure. Some magnetic superstructure peaks were observed, which can be indexed as h+k+l=2n+1 based on the YMn12-type unit cell. The experimental data were analysed using various possible magnetic structure models. From the best fit between the calculated and observed intensities, it is concluded that: (A) Y(Mn1-xCox)12 are antiferromagnetic structure of noncollinear type for x = 0, 0.3 and 0.4; The arrangement of partial magnetic moments on 8f and 8j sites change into parallel to each other for x = 0.5, 0.6 and 0.67. Whereas the magnetic moments on 8i sites still remain in antiparallel configuration. Moreover, the ratio of ferromagnetic composition increases with the increase of Co concentration x; All magnetic moments on 8i, 8j and 8f sites are parallel to each other in the basal plane of the tetragonal structure for x = 0.8. The sample exhibits ferromagnetism in such a case. (B) As compared with the YMn12, the substitution of Mn with Co leads to an increase of the mean magnetic moment on 8i, 8j and 8f atoms.
1984, 33 (6): 854-860.
doi: 10.7498/aps.33.854
Abstract +
The conductivities of three PEO-NaSCN samples whose molecular weight are 6000, 12000 and 20000 respectively have been studied as a function of temperature during two thermal cycles. It was found that the completeness of complex reaction in the samples had a obvious effect on the electrical behaviours. The complex reaction in molecular weight 12000 sample was complete, therefore the electrical property was not influenced by thermal history. While this reaction in the other two samples did not fully complete and can occure in certain temperature range during the first heating process, thus rather complicated log σ versus 1/T curves were observed. It was noted that the extra PEO content in the samples had a remarkable influence on the electrical property. Molecular weight 12000 sample contains more extra PEO content than the others. Therefore it has the highest conductivity and the logσ versus 1/T curve consists of two straight lines with a discontinuity at temperature near the melting point of pure PEO. While the extra PEO content in molecular weight 6000 sample is much less, it is responsible for the lowest conductivity and continual change of conductivity with temperature.
1984, 33 (6): 861-866.
doi: 10.7498/aps.33.861
Abstract +
The nonlinear evolution equation of the resistive m≥2 tearing modes near their linear thresholds is derived as ?-Q2A+K/2A2à-Q2(δ△1e)/(△1e)A3=0 where the quasilinear approximation has been used; A is the mode amplitude; Q and K are the dimensionless linear growth rate and wave vector; △e and δ△1e are the linear and nonlinear discontinuities of the logarithmic derivatives. The nonlinear time evolutions of the modes are discussed in detail. No bifurcation solution exists for a symmetrical sheet pinch model.
1984, 33 (6): 867-873.
doi: 10.7498/aps.33.867
Abstract +
Starting with the equations of phase equilibrium curve for the Collins model of two-dimensional alternative binary system, we obtained the conditions which must be satisfied by the attractive interactions between the atoms to get the phase diagram with a minimum (or maximum) point. The obtained results show that, this point is unique, and the position of the point (zf, tf) changes with the percent age of 4-atom obviously.
1984, 33 (6): 874-880.
doi: 10.7498/aps.33.874
Abstract +
By using the Judd-Ofelt theory, the Q2 parameters of the oscillator strength, were obtained in PrP5O14 crystals. The calculated oscillator strengths were compared with the experimental data. The radiative transition probabilities of electric dipole and magnetic dipole from 3P1,3P0,1D2 and 1G4 energy levels and the multipolar coupling transfer probabilities be tween the 1D2- 1G4 and 3H4- 3F4 energy level pairs were calculated. The concentration effect of 1D2 emission intensities and the diagrams which show the dependence of intensities on concentrations and the excited light were also given.
1984, 33 (6): 881-886.
doi: 10.7498/aps.33.881
Abstract +
In this paper, the superradiant beats of cooperative decay for a simple system of two detuned sources is systematically investigated. The superradiant beat characterics of modulation in the emitted intensity by the detuning are obtained through numerical solutions of equations describing the time-dependence of this system.
LETTERS
1984, 33 (6): 887-890.
doi: 10.7498/aps.33.887
Abstract +
Initial flow stresses and coercivities during and after tension and tension plus compression in ferrite-martensite dual phase steels have been measured. It was found that both parameters for tension plus compression are smaller than those for tension only. For the flow stress, this phenomenon is called Bauschinger effect. The relative decrease of coercivity is larger than that of flow stress.
1984, 33 (6): 891-896.
doi: 10.7498/aps.33.891
Abstract +
We have discussed the backward scattering in the γ+e→H+e processes with circular polarized photons and polarized electrons. Using the extremely sharp peak of the differential cross sections in the backward direction, one could hopefully search the Higgs particles in Weinberg-Salam model.
