Vol. 36, No. 1 (1987)
1987-01-05
CONTENT
1987, 36 (1): 1-9.
doi: 10.7498/aps.36.1
Abstract +
In the present paper, by using optical mixing and self-focusing theory, the resonant self-focusing effect of two parallelly propagating laser beams with frequency difference equal to the plasma oscillation frequency in a homogeneous plasma is studied theoretically. The nonlinear dielectric constant and the threshold power for resonant self-focusing are derived analytically. The scaling laws of the threshold power with respect to laser-plasma parameters are discussed and compared with that of usual ponderomotive self-focusing. Finally, the effect of the deviation from frequency matching condition on the threshold power is also studied.
1987, 36 (1): 10-16.
doi: 10.7498/aps.36.10
Abstract +
In this paper, the five arrangements of optical system are briefly compared with each other, by which the experiments of electron interference and holography have been carried out up to now. Using a Mollenstedt electron static bi-prism as the beam splitter, two operation modes making the experiment successfully in JEM-200CX type electron microscope are presented. Some parameters of the experimental and calculated results are given. Finally, on the basis of our own experience, we propose some points for attention in operating.
1987, 36 (1): 17-23.
doi: 10.7498/aps.36.17
Abstract +
In this paper, we report the observed conditions of condensation and growth of a-Si on different kinds of substrate materials surfaces studied with the SEM technology. Explanations about the phenomena are given.
1987, 36 (1): 24-28.
doi: 10.7498/aps.36.24
Abstract +
We have investigated the surface damage induced by visible laser in LiNbO3:Fe. The laser damage tracks (glide lines and microcracks) and microdomains are produced at +c side of the periphery of light-illuminated regions. These microdomains arise at laser damage tracks and at cylindrical grooves on the surface of sample. We also found that these damage defects in LN:Fe can be decorated by space-charges due to photovoltaic effect and they are directly observable between crossed polarizers. Role of the cavity field, the electrostatic repulsive force at the doma-in boundary and self-enhanced diffraction light induced by physical imperfection on laser-induced surface damage are discussed.
1987, 36 (1): 29-36.
doi: 10.7498/aps.36.29
Abstract +
The morphological change of salol crystals with respect to supercooling is studied by in situ observation method and the Kyropoulos technique. The relation between morphology and structure of salol crystals is analysed based on Hartman-Perdok's concept of periodic bond chains (PBC). Kihara's core potential model is used to extend PBC concept. The theoretical morphology derived by extended PBC method gives better fitting to observed morphology obtained by in situ observation method.
1987, 36 (1): 37-46.
doi: 10.7498/aps.36.37
Abstract +
It has been found that the forces on the domain walls (DWs) in ferromagnetic material for measuring internal friction (IF) when the magnetic field (H) is increased at constant rate (a) are: (1) main driving force caused by the H, namely A00+A10at; (2) harmonic perturbation force A30sinωt; (3) interaction force which is proportional to A10at, A30sinωt and a resistant force depending on the internal stress field and anisotropy field A20sinωt. The equation of motion of DWs can be written as ρ(d2 x)/(dt2) + r(dx)/(dt)+κx = A00 + A10at + A20t sinωt + A30 sin ωt where A00,A10,A20,A30 are constants depending on material chosen and test condition; ρ is the mass density, γ is the viscous damping parameter and κ is the coefficient of restoring force. The IF caused by DWs motion can be obtained from the solution of the equation of motion as follows Qm-1=B1 (Eλsδ)/(Ms2Hm) (dM)/(dH)·α/ω (If for α≠0) Q0-1=B2 (γωE)/(κ2) (If for α=0) where E is the modulus, λs is the saturation magnetostriction,Ms is the saturation magnetization, Hm is a critical field at whichthe reversible motion of DWs becomes irreversible B1, B2 are dimensionless positive numbers. When α≠0, the visco-elastic IF may be initiated and the IF varies with α/ω; when α= 0, the low-frequency micro-eddy current IF may be initiated and the IF varies with ω. The calculated results are compared with experimental data and interface dynamics.
1987, 36 (1): 47-53.
doi: 10.7498/aps.36.47
Abstract +
As self-consistent LDF-DVM method is used to study the chemisorption of I/Si(lll) and I/Ge(lll). Two cluster models are adopted to simulate the top site and 3-fold site respectively. The optimum geometry is determined by minimizing the total energy. Chemisorption of iodine on top site is found to be more stable than that on 3-fold site. The results are in good agreement with the of SEXAFS. A series of DOS are calculated for the chemisorption of column VII elements F, Cl, Br, I on the top site of Si(lll) surface. The results are analysed and compared with experiments and other theories. In addition, the applicability and limitations of semi-empirical method EHT are discussed.
1987, 36 (1): 54-59.
doi: 10.7498/aps.36.54
Abstract +
The 〈0001〉axial channeling parameters, axial half-angle ψ1/2 and minimum yield xmin, of α-LiIO3 crystal have been measured by collimated MeV proton beam at different beam energies. Under the action of an electrostatic field along the c-direction of the crystal, the increase of channeling-backscattering yield from the surface I atoms, proportional to the duration of electrostatic field action, has been observed. The time-dependence of the amount of the random surface I atoms has been calculated quantitatively for different durations of electrostatic field action. The increase of the α-particle yield from proton induced 7Li(P,a)4He reaction-channeling with the duration of electrostatic field action has been observed as well.
1987, 36 (1): 60-66.
doi: 10.7498/aps.36.60
Abstract +
The ionic conductivities of some PECH-and PECH-PEO-alkaline salt complexes have been determined. The effect of some factors such as polar group concentration, cation size and anion size as well as procedure of thin film preparation on conductivity of polymer ionic conductor has been studied. For lithium salt complex the polar group reduces the conductivity, while for sodium salt complex the polar group enhances the conductivity. This phenomenon was explained by a model involving the existence of two kinds of potential well in the polymers. It has been found that the cation size has strong influence on conductivity. For both small Li+ and large K+ , the conductivity is low but for mediun size Na+, the conductivity is high. An ion transport picture in amorphous PECH has been proposed to illustrate this behaviour. In addition, it was shown that the larger the anion size is, the lower the conductivity will be. Finally, the re-sults suggested that the procedure of thin film preparation influenced the film conductivity.
1987, 36 (1): 67-73.
doi: 10.7498/aps.36.67
Abstract +
The condition for the existence and the stability of solitons in the coupled system of Lang-muir waves and transverse waves are investigated. The method is completely nonlinear and makes use of Liapunov theory. The condition for the existence of the solitons and the criterion for the stability are found. The results we obtained recover the previous ones in the uncoupled case.
BRIEF REPORT
1987, 36 (1): 74-77.
doi: 10.7498/aps.36.74
Abstract +
During Ar+ laser scanning at low speeds, four kinds of crystallization zone appear on a-Si:H films deposited on quartz substrates. They are microcrystalline phase zone, solid phase zone, supercooled liquid phase zone and liquid phase laser zone, grown by liquid phase transverse epitaxies. The temperature field control model of laser crystallization of hydrogenated amorphous silicon has been proposed, by which the crystallization processes and their features can be explained.
1987, 36 (1): 78-88.
doi: 10.7498/aps.36.78
Abstract +
We have studied the high-order nonlinear frequency-mixing effect in transverse Zeeman La-ser medium by using Lamb's semiclassical theory and vector field model, and obtained the analytical expressions of dielectrical polarization and light intensity. The results could explain the phenomena of high-order harmonic in σ-π light and σ, π light, and give the physical interpretation of beat wave deformation.
1987, 36 (1): 89-94.
doi: 10.7498/aps.36.89
Abstract +
In this paper, we report the behavior in various cases of ultrashort light pulse with about 10 ps duration (1.06 μm) passing the nonlinear medium, coloured LiF crystals. The interval of pulse trains becomes shorter than before. Pulse durations become shorter when crystal is thiner and become longer when crystal is thicker. These phenomena are related to the characteristics of the coloured LiF crystals.
1987, 36 (1): 95-100.
doi: 10.7498/aps.36.95
Abstract +
The substitution effect of a few percent of V and Nb for boron in the cobalt base amorphous alloys on the induced magnetic anisotropy has been investigated. Disk shape samples have been subjected to isothermal magnetic annealing in the temperature range 260-320℃. The kinetic curves of formation of induced anisotrpy have been measured with a sensitive torque-magnetometer and the kinetic parameters have been calculated by assuming that the distribution of re-lexation time obeys a log-normal law. These results show that subtitution of vanadium or neobi-um for boron in the cobalt amorphous alloys can reduce the Ku∞ (T) effectively but only have-a very slight effect on the kinetic parameters. The problems of the influences of transition metal additions on the induced magneto anisotropy and stability are discussed.
1987, 36 (1): 101-107.
doi: 10.7498/aps.36.101
Abstract +
Optical constants and dielectric constants of normal cesium oxide thin films are related to wavelength of incident light and cesium impurity contained. In this paper, three curves for index of refraction n and extinction coefficient k and complex dielectric constants of cesium oxide with different Cs impurity contents are shown with respect 10 wavelength in visible and infrared lights. The relations between the colors of scattering and reflection lights and these curves are discussed.
1987, 36 (1): 108-113.
doi: 10.7498/aps.36.108
Abstract +
The barium yttrium fluoride, BaYF5, can be simultaneously doped with divalent europium and some trivalent rare earth ions. The purpose of this paper is to enhance the understanding of some fluorescence properties of this optical materials which are rare earth-activated BaYF5 fluorides with potential pactical applications. The emission and excitation spectra, fluorescence lifetime of the Eu2+ and Ho3+ ions, and supersensitivity of Ho3+ absorption band (5I8→5G6) in the system BaYF5 have been investigated under excitation of nitrogen laser pulse. The emission Corresponding to the 5S2→5I8 transition dominates the Ho3+ spectrum. Energy tramsfer from Eu2+ to Ho3+ ion occurs. The experimental and theoretical results fit the Inokuti and Hirayama's equation. The mechanism of radia-tionless energy transfer is found to be dipole-dipole interaction. The critical transfer distance R0 is approximately 6?. Probabities and efficiencies of energy transfer have also been calculated.
1987, 36 (1): 114-119.
doi: 10.7498/aps.36.114
Abstract +
An experimental investigation was made about SdH effect in n-Hg1-x CdxTe at various-temperatures in the range 2.3-24 K. The longitudinal and transverse magnetoresistance oscillations were measured and the spin split peaks (N>3) were clearly observed. The effect of non-parabolic conduction band and the shift of Fermi level with magnetic field on the experimental results have been discussed.
1987, 36 (1): 120-124.
doi: 10.7498/aps.36.120
Abstract +
Assuming the BCS mechanism, we use Anderson model Hamiltonian to analyse the problem of coexistent ferromagnetic and superconducting state for Kondo type heavy fermion superconductors. Results show that the coexistent state is unstable.
1987, 36 (1): 125-129.
doi: 10.7498/aps.36.125
Abstract +
The relationships between the optimum cut direction and various parameters have been analysed. The dielectric constant, pyroelectric coefficient and figure of merit were measured with temperature change on different directions of ADTGSP crystal. The results show that the pyroelectric voltage response is significantly improved by using cuts at oblique angles to the pyroelectric axis.
