The hybridization of conduction band is studied for close-packed compounds by means of LMTO method. We emphasize that the heterogeneous coordination would be a necessary condition for intensifying hybridization. In view of the hitherto basic understanding on electron-phonon coupling, a scheme of relation can be outlined as follows: high Tc => high η => significant hybridization=> significant heterogeneous coordination Various experimental results on A15, Bl and other close-packed compouds are in fair agreement with this basic principle.
The rotational relaxation of the GaAs (110) surface is considered. A cluster model is used for simulating the crystal surface, and some quasi atoms are added in order to saturate the dangling bonds in the cluster boundary. The stable relaxation geometry of the GaAs (110) surface is determined by minimizing the total energy of the cluster calculated by the Extended Huckel Method. According to the calculation a value of 18° for the tilted angle of the surface bond is suggested, it is in fairly good agreement with that given by the partial yield photoelectron spectroscopy. The density of states for the cluster is also calculated, it is shown that for this relaxation model there is no empty cation state existing within the band gap.
A simple method has been developed to determine the generation lifetime and surface generation velocity simultaneously. This method is based upon the high frequency C-V characteristics derived in response to a linear voltage sweep. The experimental results are given for the cases in which the present method is applicable.
Chemical etching method was used to measure the velocity of isolated dislocations in silican crystals for temperatures in the range of 400-900℃ and under stresses in the range of 0.35-13kg·mm-2. Dislocation Velocity v(τ, T) as a function of temperature (T) and stress (τ) satisfies the following equation v(τ,T)=Aτme-Q/(KT) where m = 1.02-1.49, Q = 1.96-2.07eV. Finally, the experimental results obtained on the motion of dislocations in silican single crystals were compared with those derived from the kink model of extended dislocation.
In order to solve the problem of multi-solution in Patterson analysis using direct method , a model of pseudo structure having the symmetry of the heavy atoms is introduced and the corresponding phase relationships of the multi-solution type are derived.
The diffraction contrast in the X-ray topographs, taken for the crystal face parallel to the c-axis of the α-LiIO3 single crystals, appears to change remarkably under the action of an applied DC field along the c axis. The contrast in the topographs is restored after the removal of the applied field. After either turning on or turning off the DC voltage, relaxation processes are observed in both the change and the restoration of the diffraction contrast in the X-ray topographs. The change of the contrast depends on the polarity and magnitude of the applied voltage, but appears to be independent of the wave length of the X-ray.The X-ray topographs taken under the condition that a DC field is applied to the crystal displays the macroscopic crystal defects decorated by the space charges. In other words, we can observe the originally undetectable defects, while the space charges accumulate on the crystal defects, the local lattice distortion around the defects is enhanced.
A statistical approach is proposed in order to establish a connection between microscopic process and macroscopic process of brittle fracture, and an attempt is made to base the theory of brittle fracture on the statistical foundation of micro-crack kinetics.The brittle fracture is described as a non-equilibrium process in which micro-cracks nucleate and grow, and the single main crack propagates under very small plastic deformation.A differential-integral equation describing this non-equilibrium process is derived. The micro-crack kinetics is studied from the dislocation mechanism. The statistical distribution function of micro-cracks and the fracture probability of metal sample are obtained, and thus the elongation, brittle strength, ductile work, fracture toughness, critical crack length, ductile-brittle transition temperature and their statistical deviation are all deduced theoretically.
A variety of visible fluorescent processes in pure BC13 gas irradiated with TEA CO2 laser radiation are observed. The space, time and spetrum distribution of visible fluorescence, as well as their dependence on the laser energy, the pressure of BC13 gas and other parameters are measured systematically. The visible fluorescent processes in BCl3 gas are discussed by using a simplified dynamical collision model. The analytical expressions for equivalent vibrational temperature and visible fluorescence intensity, and a simple relation Pτdelay= C/K(Tv) are obtained. The calculated values are in agreement with the experimental results.
Based on our previous work, in this paper, we discuss further the mechanism of maltiphoton dissociation of polyatomic molecules in an intense infrared laser field, and obtain non-linear equations which describe the coupling between molecular vibrational modes. Taking SF6 molecule as an example, we calculate numerically the energy transfer time between modes, the Fermi resonance interaction, and the degree of mode excitation by laser field. Finally, the dissociation rate of polyatomic molecule is discussed based on the uni-molecular reaction model, the theortical results are essentially in agreement with experiments.
The temperature profile and thermal-focusing effect induced by a high-order transverse mode laser beam in an internal element have been analyzed. We calculate the input-output power relationship for ordinary and extraordinary waves in a LiNbO3 crystal inside the resonator. Our calculations are in good agreement with the experimental results of P. G. Konvisar et, al., and, further, revise their calculated result for extraordinary waves. The internal thermo-optic hysteresis and focusing effect are also investigated experimentally.
In this paper, the phenomena observed and characteristic relations deduced from large amount of experimental data accumulated during more than 40000 experimental discharges on CT-6 tokamak are described. They are related to the following aspects of tokamak plasma: conditions for stable tokamak discharge, stages of toroidal discharge formation, impurity behaviour and plasma-wall interactions, etc.
>[2Timi/Teme]1/2), a consistent eigen-equation of drift wave is deduced, which is valid for Sy≥1 as well as for Syi2), it can be shown that there is no unstable mode (i.e. there is no solution with γ>0). But if the correction term is taken into account, no definite conclusion about its stability can be obtained as yet.">In this paper, it is shown that in the practical case of Ti≠ 0, for short wavelength modes (i.e. Sy≡ky2ρi2≥1), the usually adopted eigen-equation of drift wave is theoretically inconsistent, consequently, the inference that "The universal mode in fact, is stable" is also inappropriate. Under the condition of low magnetic field shear (Ls/rn >>[2Timi/Teme]1/2), a consistent eigen-equation of drift wave is deduced, which is valid for Sy≥1 as well as for Syi2), it can be shown that there is no unstable mode (i.e. there is no solution with γ>0). But if the correction term is taken into account, no definite conclusion about its stability can be obtained as yet.
In this paper, the effect of acceleration of runaway electrons on the microscopic instabilities is discussed. The result shows that the mechanism of instabilities is no longer a simple wave-particle resonant effect. When the resonant velocity is far away from the boundaries of the velocity region of runaway electrons, the growth rate is not considerably different from that in the no acceleration case. However, if it is close to the boundaries, the effect of acceleration on the growth rate will be important.
From the point of view of the optical information processing, we consider the spectrogram in which the spectral lines are immersed in the bright continuous background as a low contrast optical picture. By means of the coherent optical processing system and a special high-pass filter, the Fourier spectrum of the continuous background can be reduced and then the final result may appear as a spactrogram without continuous background. This may be considered as a new method for enhancement of the ratio S/N of a spectrogram.
The results of studies on XeBr laser output behaviour are reported; in this laser, HBr, BBr3 and C2F4Br2 are used as bromine donor. The maximum energy obtaind is 6 mJ. Volume energy density and efficiency are 0.4J/L, 0.14% respectively. Filially, we propose a way for improving the lasing output level.
In this article, the symmetry of phonons and the coupling between phonons along different coordinates directions are discussed for molecular crystals in which dipolar coupling exists. Also obtained are the relationships between the Raman tensor components of phonons with k=0 which are of the symmetry of the irreducible representations of the unit cell group and those of groups of atoms which possess some site group in a unit cell.
The rigorous formula of Suzuki for correlation function of classical systems and Ising model is generalized and applied to the rotationally invariant Maier-Saupe Hamil-tonian of liquid crystals.The results show that the microscopic treatment of the correlation function and magnetic Cotton-Mouton coefficient by one of the authors is indeed correct within the approximation stated. The random phase approximation results of Vertogen and van der Meer is improved. A scheme to describe the thermodynamics of liquid crystals beyond the mean field approximation is proposed.