The interaction between a weak probe laser pulse and a two-level system strongly driven by a near-resonant laser pulse is studied by dressed model. The probe pulse exhibits absorption or. amplification when its frequency ω_{2} tuned to the resonance frequency ω_{2}=ω_{1}±<Ω_{21}^{D}>. The transient behavior of nonlinear wave-mixing effect, where the resonant enhancement exists, is also obtained.

We have discussed the polarization rotation of degenerate four-wave mixing in the external magnetic field. The third-order nonlinear susceptibility X_{yxx}^{(3)} is calculated in the J_{g}=0→J_{e}=1 transition. It consists of two components. The first component is due to the saturation effect of the population difference. The second component is due to the Zeeman coherence induced in the interaction between atom and field.

By means of X-ray diffraction method, we determined the lattice parameters and phase transition temperatures of specimen of K_{0.5}Bi_{0.5}TiO_{3}—Na_{0.5}Bi_{0.5}TiO_{3} system with varions components, as well as the component of the boundary between tetragonal and rhombohedral forms. The X-ray powder diffraction data of K_{0.5}Bi_{0.5}TiO_{3}—Na_{0.5}Bi_{0.5}TiO_{3} polycrystals are also given.

The analysis of the present letter shows that the negative magneto-resistance effect, observed by Guan Wei-yan et al. in rapidly cooled Al-Si alloys, is nothing but the longitudinal peak effect in films of type II superconductors displayed in the form of R-H_{3} curves. Based on the flux-line-cutting model, a possible explanation for this ef-fect is proposed.

It is found that there is an empirical correlation between phonon spectrum parameters λ, 〈ω〉,〈ω^{2}〉 and the Hall coefficients R_{H} in a variety of nontransition metals and alloys; there is a maximum of λ,〈ω〉 and 〈ω^{2}〉 as RH =-3.5--4.0×10^{-11}m^{3}/As. There is also a similar empirical correlation between λ, 〈ω〉, 〈ω^{2}〉 and Hall coefficients R_{HL} of responding liquid metals. Finally, the question of raising T_{c} of amorphous superconductors is discussed.

Computer simulation calculation shows that if there were no rigid translation of adjacent grains, the shortest distance between lattice points at all the incoherent twin boundaries would be 0.408a, where a is the lattice parameter, except for coherent ones. This distance is smaller than atomic diameter 0.707a, therefore atomic overlap occurs. The interface energy can be greatly reduced by a rigid, translation of these two crystals. The displacement vectors of four interfaces (111), (122), (121) and (765) were determined experimentally, they are 0.254a, 0.300a, 0.204a and 0.126a respectively.

Stimulated scattering of electromagnetic wave from low-frequency modes is discussed. The starting point is Braginskij's equations which include energy equation. The thresholds and growth rates are obtained. Beside that there is a scattering from thermal mode, we also find that the Brillouin scattering is different from the previous results.

We have discussed the effect of the split of the energy levels between spin-up and spin-down electrons caused by magnetization on the magnon-induced resistivity in ferromagnetic metals at low temperatures. As a result of such an energy split, the low-temperature magnetic resistivity always declines exponentially with decreasing temperature in the single-hand model, while it may probably be enhanced in certain conditions in the two-band model. The comparison between the low-temperature expression of magnetic resistivity deduced from the single-band model considering the energy-gap in the spin-wave spectrum and the experimental data of Tb and Dy shows agreement not only on temperature dependence of resistivity at low temperatures but on the magnitude of high-temperature magnetic resistivity as well.

Based on the viewpoint of Fourier optics, we have analysed systematically the (monochromatic) point spread function and transfer function of rainbow holographic imaging limited by an arbitrary aperture, revealed the essential relation between the function and the aperture, then established a unified theory which is analogous to that of conventional imaging system. Thus we provided a simple and clear mathematical basis for calculation of the limited resolution and the cut-off frequency.

The excitonic superconductor proposed by Allender, Bray and Bardeen is a kind of Layered Ultrathin Coherent Structure (LUCS) composed of metal and semiconductor layers. In a previous work, we have studied the electronic structure of a metalme-tal LUCS in the tight binding approximation. We present here the result of a similar study of a metal-semiconductor LUCS, with the hope that it may be helpful to more detailed further investigations of the ABB model of superconductivity.

The effects of CW CO_{2}-laser irradiation on semiconductors are studied with primary emphasis on the physics of the process. Experimental results and theoretical considerations show that semiconductor sample can be heated to desired temperatures by CW CO_{2}-laser irradiation. The CW CO_{2}-laser irradiation with wavelength of 10.6 μm is different from the other short wavelength lasers in the following features: light absorption of laser radiation through free carrier absorption, uniform temperature distribution throughout the thickness of the wafer, enhancement of annealing efficiency by laser irradiation from back surface. The temperature profile produced by stationary CW CO_{2}-laser irradiation is capable of annealing As^{+} ion implantation damage in Si with a solid-state regrowth mechanism. During the regrowth process the implanted As^{+} ions are incorporated into substitutional lattice sites and can be made electrically active to a high degree without redistribution of the original profile. Using CO_{2}-laser irradiation from the back surface we have produced ohmic contacts with excellent electrical properties for GaAsFET without damaging the device structure on the front surface.

The calculation of SHG coefficients for crystals with zinc blende and wurtzite structures (AB-type crystals) has been carried out by using the equivalent orbital method. Upon neglect of the electron-phonon interactions, the possibility of adopting the energy bands functions for calculation of these coefficients has been considered. The equivalent orbital method, originally an approximate one in the calculation of the band structures of AB-type crystals, is then used to calculate SHG coefficients for those crystals at K = 0. With some modifications of the band width, the SHG coefficients at K = 0 can be represented approximately as the average of the SHG coefficients for various K vectors. Multiplied by the total number of K vactors in the first Brillouin zone, this gives the macroscopic SHG coefficients for these crystals.Attempts have been made to calculate SHG coefficients for 17 species of crystals with zinc blende and wurtzite structures systematically. It is interesting to note that the values thus obtained agree satisfactorily with the experimental data. Hence the following conclusions can be drawn:1. The one-gap model has been found to be appropriate to zinc blende structures, but it is not the case for wurtzite. 2. It is shown that the coefficients x_{533}^{(2ω)} for the wurtzite structure are the sum of two terms, i.e., contributions from the single state (Γ_{1},Γ_{3}) as well as from the doublet state (Γ_{5},Γ_{6}). The former is found to be negative, whereas the latter is positive.3. It is appropriate to use Pauling ionicity as a measure of the ionicity of the A-B bond.

When MULTAN-78 or MULTAN-80 is empoyed to solve a crystal structure, usually only partial structure can be found at first. The remaining atoms are then located by the weighted Fourier synthesis. In this paper, however, two examples are given to show that, when most of the atomic positions are already known, especially when the known part contains heavy atoms, the unweighted Fourier synthesis can give better results than that from the weighted Fourier synthesis.MULTAN-80 has been modified to calculate also the unweighted Fourier synthesis.

Acetyl pieriafeltarragenin compound is an acetyl compound of picriafeltarra-genin which is one of effective component of plant Picria Fel-Tarrae Lour. The mole-cular formula is C_{34}H_{48}O_{7}. Space group is D_{2}^{4}-P2_{1} 2_{1} 2_{1}. The cell dimensions are a=22.357(10)?,b=15.277(8)?,c=9.089(4)?. Four molecules are contained in a cell (z=4).The intensity data were collected on a PW-1100 four circle diffractometer. The total number of independent reflections amounts to 2234. The crystal structure has been determined by direct method (MULTAN-78),and the structure parameters have been refined by means of full matrix Least.squares method to R=0.1099. The difference Fourier Syntheses gives out all the hydrogen positions.

In this paper, we have verified that the KLiSO_{4} single crystal is a Li ionic conductor. It was determined that carriers in KLiSO_{4} single crystal are interstitial Li ions and Li vacancies by measuring the voltage distribution in the specimen. After turning off the applied dc voltage, the decrease of current follows a negative power law of time in a certain time domain. Correspondingly, the dielectric dispersion which has a negative power relationship with frequency has also been found in a certain frequency domain. The background current, the dc electric conductivity and the apparent dielectric constant of KLiSO_{4} single crystal exhibit sharp peaks besides jump nearby the transition temperature. These peaks were observed only when the rate of temperature change is low, thus it is shown that the phase transition includes a relaxation process.

A deformable permanent magnetic alloy, with composition of 62Pe-23Cr-15Co (in wt %), has been studied by high-temperature X-ray diffraction method. Debye-Scher-rer photographs of samples treated with aging in magnetic field and also of those treated without magnetic field were taken. It has been observed that the transformation process with rising temperature up to 800℃ is different in the two classes of samples. The lattice parameters of the samples without a treatment in magnetic field have been measured at various temperatures; and it has been found that in these samples a transitional phase unknown before appeared at 610℃, which was unstable at other temperatures.

The structural unit CCMCC, being of general significance, is regarded as a basic object of research. We suggest a microscopic model of the structure transformation of graphite-to-diamond, that is, the puckered dimers of diamond as crystallized units would be formed by the connections of the outer electrons between atoms of the transition metal and aetplanes of graphite, similar to the σ-π coordinate bonding.

Based on the colloid aspects and the model of the structure transformations in diamond synthesis under the action of a solvent-catalyst, it is suggested that the coalescence of the puckered dimers of diamond as crystallized units is the main way of diamond nucleation. From experiments, a curve representing the qualitative relationship between the number of diamond nuclei and the temperature as well as the relationship between the diamond nucleation and the pressure are obtained. The roles of the above mentioned nucleation mechanism on directing the practice of diamond synthesis are discussed.

In this paper, we advanced and designed a mechanical resonant antenna, which is a tuning fork with collective mass, for detecting gravitational radiation from Vela pulsar. And showed that the sensitivity of antenna can be increased by the method of accumulation signal because the gravitational radiation signal from Vela pulsar is a continuous and monochromatic signal. Last, the parameters of antenna are given, the sensitivity of which can come up to gravitational radiation intensity from Vela pulsar which is estimated by the present theory.