Creation-annihilation process of defects in WD rolls of a nematic liquid crystal was studied experimentally as an electrohydrodynamic instability of a layer within two free lateral side-walls of relatively large aspect ratio. A regular pattern was seen to be formed through creation and annihilation of defects. The defects began to move fast as they approach to the side-walls. Their motion changed from gliding (across roll-axis) one to climbing (along roll-axis) one with time. Finally the defects disappeared through climbing motion.

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For the hard-sphere Yukawa system, the modified mean spherical model is defined and the exact solution of Ornstein-Zernike equation for this model is presented. The result suggests that the effect of background charge on the static structure of the system is significant.

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A method to calculate the equilibrium crystal shape is presented, which is based on the numerical (Monte-Carlo) evaluation of the Andreev’s Legendre-transformed interface free energy. The method is applied to draw the equilibrium shape of the two-dimensional absolute solid-on-solid models.

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Time-of-flight energy spectra of Ar atoms produced through charge transfer reactions in collisions of Ar⁺(metastable Ar^M+) ions with Ne atoms have been measured at a collison energy of 50 eV. Two prominent peaks appear at exoergicities of about 0.35 and 1 .5 eV. The measurement of the appearance energies of these peaks suggests that the 0.35 eV peak is due to metastable 3d′²F_7⁄2 ions and that the 1.5 eV peak is an indication of the existence of an unknown long-lived excited Ar⁺ state.

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An injected-ion drift tube mass spectrometer, whose drift tube can be cooled with liquid nitrogen, was developed for studying the mobilities of ions in low-temperature gases. The mobilities of Kr⁺⁺ in Kr were measured at 88 K with this apparatus as a function of the reduced field E⁄N ranging from 30 to 280 Td. It was found that the Kr⁺⁺ ions have four distinct mobilities in the E⁄N range below about 70 Td. These mobilities were identified as being associated with Kr⁺⁺ ions in the four different electronic states, ³P₂, ³P₁, ³P₀ and ¹D₂.

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Scaling relation of the diagonal and the Hall conductivities is experimentally studied in the (0↓+) Landau level (0 refers to Landau quantum number, ↓ to antiparallel spin to the magnetic field, + to lower valley) of an n-channel inversion layer on a silicon (001) surface in magnetic fields of 13 T and 15 T at temperatures between 1.5 K and 4.2 K.

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The conductance fluctuation in small metallic systems is sensitive to the sample geometry and the size and position of leads. We formulate the fluctuation by taking into account the sample geometry as a four-terminal network. It is shown that the conductance fluctuation increases dramatically as the distance of the voltage terminals decreases. Recent experimental results for metallic wires support our theoretical prediction.

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Anomalous magnetization curves observed under the strong pulsed magnetic fields up to 520 kOe are understood with itinerant electron metamagnetism. From the results of Sc(Co_1−xAl_x)₂ the critical field of the transition and the spontaneous moment after the transition of ScCo₂ can be estimated to be a few megagauss and about 0.4 μ_B/Co, respectively. These are consistent with recent theoretical results.

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The electrical resistivity and the magnetization of CeZn₂ have been measured. Kondo anomaly is found in the electrical resistivity and the magnetization shows a very large magnetic anisotropy and metamagnetic transitions with three steps only for fields along b-axis. The saturation magnetization per Ce is 1.75 μ_B at 1.3 K and 4.2 K. These results are briefly discussed with a recent theory of Kondo effect and a simple thermodynamical model.

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Spin-waves in MnP have been measured by means of neutron inelastic scattering at various temperatures. Dispersion relation along a-axis exhibits anomalous wave vector and temperature dependences, while the quadratic q dependence was observed along both b and c-axis. The characteristic feature of the spin-wave dispersion relations agree qualitatively with those predicted on analogy with rare earth metals.

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Photo-induced depolarization effect of linearly polarized beam in the giant two-photon absorption (GTA) band of excitonic molecules was examined in CuCl with the use of non-linear ellipsometry. After the careful elimination of the instrumental optical anisotropy, no depolarization was observed under the excitation of 1 MW/cm². The stability of the linearly polarized state was also studied by measuring the polarization character for a slightly elliptical beam and a partially polarized beam. Growth of the depolarization was found in both cases and thus the linear polarization is concluded to be an unstable state in the GTA resonance.

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Specific interactions of anticodonic dinucleoside monophosphates and their cognate amino acids have been detected by using a precise ultraviolet difference asbsorbance photometry. The affinity coefficients are of the order of 1 M⁻¹, similar to those in the base-base stacking interactions, suggesting the lock and key relationship for the above interaction. All signals are hyperchromic and may be caused by destacking of the dinucleoside monophosphate due to the above complex formation.

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One and four types of asymmetric discrete envelope soliton solutions are found for semi-discrete sine-Gordon equation and semi-discrete wave equation with cubic nonlinearity. They are found by appropriately transforming the variables of already-known discrete envelope soliton solutions. Some properties of these solutions are discussed.

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The arrival probabilities with directions for a linear biased correlated walk, satisfy coupled linear difference equations. An exact analytic solution to these equations with a periodic boundary and a general initial condition, is obtained. The solution for an inhomogeneous initial condition can be expressed in terms of the Chevyshev polynomials of the second kind, and is quite complicated. For a homogeneous initial condition, the analytic expressions for the arrival probabilities can be written down in single lines. With a finite bias, the system approaches a stationary state in which the ar-rival probabilities are different for different directions, and a finite current exists. As an application of the theory, a dilute solution of CO in liquid Ar under an electric field is discussed.

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Time characteristics of the secondary emission from iodine molecules excited with light pulses from a cavity-dumped, single-frequency Ar⁺ ion laser at 514.5 nm have been compared with existing theories. It has been found that the experimental data are well explained quantitatively by the theories, provided the 21 hyperfine lines as well as collisional effects and Doppler broadening are taken into account. The cross sections for the phase-changing and population-changing collisions have also been determined. The contributions of coherent and incoherent secondary emission processes are discussed.

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The differential cross section (DCS) for elastic electron scattering from Xe has been measured using a crossed beam method. The measurements were carried out in the angular range from 10° to 125° and at incident energies from 5 eV to 200 eV. The absolute values of the DCS have been determined by means of the relative flow method. The integral and momentum-transfer cross sections are derived from the measured DCS. The results are compared with those of previous experimental and theoretical studies.

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Diffusion and reaction of chemically reacting passive scalars in turbulent shear flows are investigated. A binary irreversible reaction with no heat release is considered. The binary and triple correlations such as the scalar fIux, the scalar variance, and the squared-scalar flux are calculated by applying a two-scale direct-interaction formalism. The results are simplified by the use of the inertial-range theory to construct two models for the passive scalars: an ensemble-averaged model of k-ε type, and a LES model.

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Effect of Hall current on the unsteady free convection flow of a viscous incompressible and electrically conducting fluid, in presence of foreign gases (such as H₂, CO₂, H₂O, NH₃), along an infinite vertical porous flat plate subjected to a transpiration velocity inversely proportional to the square-root of time is investigated in the presence of a uniform transverse magnetic field. The results are discussed with the effects of the parameters Gc (the Grashof number for mass transfer), m (the Hall parameter) and Sc (the Schmidt number) for Pr=0.71, which represents air.

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The variation of column calibration factor F_s with respect to temperature change has been attained for a given column (C.J.G. Slieker and A. E. de Vries: J. Chim. Phys. 60 (1963) 172) to estimate the temperature dependence of thermal diffusion factor α_T of trace mixtures of hydrogenic isotopes in helium only to detect the existence of inelastic collision effect in the mixtures as predicted by T. K. Chattopadhyay and S. Acharyya (J. Phys. B 7 (1974) 2277). Attempts have also been made to interpret the α_T’s thus obtained in terms of the available elastic and inelastic collision theories of thermal diffusion to establish the importance of the column calibration factor in column measurements.

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A method to evaluate the transport coefficients of charged particles under an electric field is developed. Two velocity-distribution functions Ψ_s(v₀) and Ψ_c(v′) are introduced in addition to the usual velocity-distribution function f(v). Here, Ψ_s(v₀)dv₀ and Ψ_c(v′)dv are the probabilities of a charged particle starting a new flight with a velocity in the range v₀, dv₀, and making a collision at a velocity in the range v′, dv′, respectively. The velocity-dispersion functions through flight, H(v′, v₀), and through scattering, S(v₀′, v′) are used to determine Ψ_s(v₀). Since H(v′, v₀) includes the full information on the flight of charged particles, the transport coefficients defined in real space have to be expressed directly by Ψ_s(v₀). The velocity-distribution function f(v) and the transport coefficients defined in velocity space are also expressed by Ψ_s(v₀). This method is simple but is applicable to anisotropic systems.

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Formulae of stellarator approximation valid for finite aspect ratio helical tori are derived by using coordinate transformation and method of averaging. The three dimensional problem of MHD equilibrium and stability is reduced to two dimensional one; this makes possible to convert tokamak codes to stellarator codes. Importance of including residual magnetic field to recover the three dimensional magnetic field from averaged equilibrium is pointed out.

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Ion acoustic double layer solutions have been obtained in a plasma in presence of a negative species of ions. It has been shown that the rarefactive double layer solutions exist when the negative ion concentration is less than a limiting value. our theoretical result is in good agreement with the recent observation of rarefactive double layers moving from the ionosphere to the magnetosphpere of the earth.

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Analysis of θ pumping for tokamak current drive is presented. Diffusion of an externally applied oscillating electric field into a tokamak plasma is examined. When the oscillating electric field is in the same direction as the stationary toroidal plasma current and the current density induced by the applied electric field is larger than the average density of the plasma current over the plasma cross section, the radial profile of the safety factor has an extremum near the plasma boundary region and MHD instabilities are excited. It is assumed that anomalous diffusion of the current induced in the plasma boundary region takes place, so that the extremum in the radial profile of the safety factor disappears. The anomalous electric field due to this relaxation process has a net d.c. component, which is estimated, and the condition for tokamak current drive by θ pumping is derived. Some numerical results are presented for the case of a fusion grade plasma.

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The low-frequency electron-density fluctuations in the mirror-cusp device RFC-XX-M were measured using the Fraunhofer-diffraction method. The density fluctuations by the microinstability were identified to be of the drift-wave mode, by the discussions of the dispersion relation, range of the wave-numbers (k_⊥ρ_i\simeq1, where k_⊥ is the wave-number in the plane perpendicular to a magnetic field and ρ_i is the ion Larmor radius), the localization at the density gradient, and the growth rate. Further, effects of the fluctuations on mirror confinement were discussed and the particle confinement time was deduced from the measured fluctuation intensity.

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Amorphous GeTe₂ films with the thickness ∼0.5 μm, prepared by sputtering technique, transform into the crystalline GeTe₂ films with the isomorphic structure to β-cristobalite, cubic SiO₂, at T_a(annealing temperature)=200°C. The cubic phase of GeTe₂ is metastable and decomposes into the mixed crystal of GeTe and Te at T_a=250°C.

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Elastic constants C₁₁, C₃₃, C₄₄, and C₆₆, and dielectric susceptibilities χ₁₁ and χ₃₃ in LiNbO₃, were determined over the temperature range from 300 to above 1030 K. The elastic-constant difference between constant polarization and constant field C_ii^P−C_ii^E, and the inverse-susceptibility difference between constant strain and constant stress (χ_ii^x)⁻¹−(χ_ii^X)⁻¹ are interpreted in terms of both electrostrictive and higher-order interaction between strain and polarization. The results for χ₃₃ indicate that LiNbO₃ undergoes nearly second-order phase transition at T_C=1410 K. Above T_C, χ₃₃ showed dispersion in the frequency range between 1 and 13 MHz. A comparison of these results with soft-mode frequency implies that the soft mode couples with a low frequency relaxation process near T_C.

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Phase transitions of the triangular Ising model in a field with nearest and second nearest neighbor antiferromagnetic interactions with couplings, −J and −J⁄2, respectively, are studied by the interfacial free energy method, by the mean field approximation, by the transfer matrix and phenomenological renormalization methods and by the Monte Carlo simulation. At low temperatures and at fields weaker than the lower critical field h_c1 the system takes the 2×1 structure, and at fields between h_c1 and the upper critical field h_c2 it takes the 2×2 structure. Between the 2×1 and 2×2 phases near the field h_c1, a partial disordered phase, in which a part of the sublattices are in disorder, is found. Specific heat shows no divergence, when the partial disordered phase changes to other phases.

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Electric-field induced phase diagrams are discussed for the group of crystals like NaNO₂ and SC(NH₂)₂ having incommensurate phases, on the basis of a relevant Landau-type thermodynamic potential. Several different phase diagrams derived from it are presented.

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From a microscopic viewpoint on the role of two kinds of hydrogen bonds, antiferroelectric phase transition in NH₄H₂PO₄ is re-examined. The role played by the protons of NH₄ ions is explicitely taken into account, and it is shown that the hydrogen bonding effect of NH₄ ions with neighbouring oxygens may be renormalized into the effective antiferroelectric interaction between protons which form the network of hydrogen bonds connecting PO₄ groups.

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The commensurate (C)-incommensurate (IC) phase transition in Rb₂ZnCl₄ has been investigated through studies of the X-ray diffraction and the P-E hysteresis loop. Simultaneous observation of the P-E hysteresis loop and the misfit parameter reveals that the double hysteresis loop observed in the IC phase corresponds to the field induced C–IC transition. The “triple”-like hysteresis loop observed in the vicinity of the C–IC phase transition temperature corresponds to the coexistence of the IC and the C state near E=0 followed by the field induced C–IC transition at a finite value of E. The effect of pinning on the electric field dependence of the misfit parameter and the polarization is considered on the basis of the Landau type theory. The tendency of the calculated results agrees well with that of the experimental results.

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By using the molecular dynamics method, structural and dynamical properties of a model system of C₈K type compounds are studied. The model consists of one intercalant layer sandwiched by rigid graphite layers. The solid-liquid transition of intercalant ion system is observed, and the static and dynamical properties of the liquid state are investigated. The calculation of the pair distribution function clarifies the characteristic local structure of the “liquid”. The observation of traces of the ionic motions reveals that the motions of ions have a strong correlation. It is not the case that an individual ion jumps from a site to another one independently. The analysis of the activation energy of the calculated self-diffusion constant of the intercalant ions also leads to a conclusion consistent with this.

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The mass density of liquid Se–Te mixtures up to 20 at.% Te was measured by the Archimedean method in the temperature and pressure ranges up to 1350°C and 1200 bar. It was observed that at 20 at.% Te the isochore curves show maxima on the P-T plane. The thermal expansion coefficient α_P derived from the isochore curve data changes sign from positive to negative around 19 at.% Te at 1000°C and 100 bar. The concentration where α_P changes sign moves to Se-rich side by application of pressure. The anomalous behaviour in the isochore curve suggests the occurrence of the structural transition.

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A volume phase transition of poly-N-isopropylacrylamide (NIPA) gel immersed in some pure and mixed solvents has been investigated experimentally. A slightly discontinuous transition of NIPA get in water changed to a more distinctly first-order transition on adding a small amount (<20%) of alcohols to water. As the concentration of alcohols in the mixed solvent increased further, the volume transition blurred and eventually disappeared. Analyzing the experimental results on the basis of the mean field theory of polymer solution, it has been shown that the polymer-solvent interaction parameter χ exhibits a drastic change at the volume transitions. This indicates that the enthalpy and entropy of solution depend strongly on polymer concentration.

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Effects of thermal annealing on gas-evaporated Ge microcrystals as small as 90 Å were investigated by Raman spectroscopy and electron microscopy. It is found that the size of microcrystals abruptly increases when they are annealed at 500°C, presumably due to the surface melting coalescence. The abrupt growth of microcrystals leads to an abrupt increase in the intensity of crystalline Raman signal. The close similarity between the spectral changes presently observed and those previously observed for a-Si and a-Ge films suggests that the crystallization process in so-called amorphous films can be well understood in terms of the growth of microcrystals.

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The quasi-one-dimensional chains of halogen-bridged mixed-valence platinum complexes (HMPC) have characteristic twofold degeneracy similar to the trans isomer of polyacetylene, which strongly suggests the presence of soliton-like excitations in HMPC. It is shown that the microscopic Hamiltonian proposed by Ichinose for HMPC, which naturally is different from the Su-Schrieffer-Heeger model of trans-polyacetylene, leads to the Takayama-Lin-Liu-Maki Hamiltonian when the continuum limit is taken. This theoretical result implies that we can expect various soliton processes found in trans-polyacetylene to take place in HMPC as well, though such experimental evidences are scarce as yet.

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The Madelung energies and the first and second derivatives of the crystal potentials at two unequivalent NH₄⁺ ion sites and one SO₄²⁻ ion site in (NH₄)₂SO₄ crystals have been calculated by the point charge model at various temperatures from 25 to −140°C. The Ewald’s method improved by Honma has been used for lattice sums. This new method has been less influenced by the choice of a type of a unit cell and has given more rapid convergence than the method in which summations are taken only over real space. The temperature dependence of the optical absorption spectra of (NH₄)₂SO₄: Tl is analyzed by using the crystal fields of the host crystal, and fairly good agreements with the experiment are obtained.

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One electron molecular orbital(MO) energy levels of Tl-(SO₄)_n complexes in (NH₄)₂SO₄ have been calculated by using the charge-consistent extended Hückel method at various temperatures from 25 to −140°C. The calculation has been performed both for the ground and excited states, and the result shows that the highest occupied MO in the ground state, s′, mainly consists of the thallous 6s orbital, and the lowest three partially occupied MO’s in the excited state, p_1,2,3′^*, consist of the thallous 6p orbitals. The optical absorption bands of (NH₄)₂SO₄:Tl are attributed to the transitions between MO’s, s′ and p_1,2,3′^*. The temperature dependence of the absorption spectra is explained by that of both the energies of MO’s and the crystal fields of (NH₄)₂SO₄ crystals.

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The absorption spectra of ammonium sulphate, (NH₄)₂SO₄, crystals containing a small amount of thallous ions have been measured in the energy region from 20000 to 60000 cm⁻¹. At 15°C only one broad band is found for all of a, b and c-polarized lights below the fundamental absorption edge of the host crystals. However, at −196°C the band for c-polarized light is split into two, 46450 and 47750 cm⁻¹, and for a-polarized light there appears a shoulder in the higher energy side of the band. These absorption bands are attributed to the superposition of the transitions between the molecular orbitals in the two unequivalent Tl-(SO₄)_n complexes. The temperature dependence of the absorption spectra is explained by that of the molecular orbital energies of the complexes and that of the crystal fields of (NH₄)₂SO₄ crystals.

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The increase in the conductivity, Δσ, and the increase in the paramagnetic susceptibility, Δχ_p, by the addition of noble metal solutes were experimentally studied in liquid Se–Te mixtures. The curve of Δσ versus the square root of the conductivity of solvent σ^1⁄2 has a broad maximum in the intermediate region where metal-nonmetal transitions gradually occur in liquid Se–Te mixtures. The trend of Δχ_p versus σ^1⁄2 has also a broad maximum in the relatively low conductivity region. The broad maxima of Δσ and Δχ_p are suggested to be closely related to the formation of the delocalized threefold site and the dangling bond state which are induced by the addition of noble metal solutes.

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Irreversible resistivities of as-deposited indium films during annealing process were measured. Using Vand’s theory, an activation energy of defect, E, and the initial lattice distortion energy function, F₀(E), were evaluated. The spectrum of F₀(E) showed two peaks, one at the activation energy E_max1=0.30 eV, and the other at E_max2=0.45 eV. The dependence of the activation energies on the film thickness were not observed. But the values of F₀(E_max1) and F₀(E_max2) were dependent on the film thickness. It is suggested that the peak at E_max2 is related to the stress introduced during the annealing process.

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Multilayered Nb/Ti thin films were made by a dual dc- and rf-sputtering technique. The samples with modulation wavelength λ ranging from 2000 Å down to 20 Å were prepared. X-ray diffractometry shows that the as-deposited multilayer modulation is sinusoidal in the shorter wavelength, while nearly square in the longer wavelength. Irrespective of the wavelength λ, the Nb is bcc with stacking of (110) parallel to the substrate, and the Ti is either the stacking of hcp(00.2) or bcc(110). The superconducting transition temperature T_c is close to that for bulk Nb (9.3 K) in the region λ>1000 Å, while T_c decreases to 4 K with decreasing λ in the region 50<λ<1000 Å. Dependence of the transition temperature on the wavelength is in good agreement with that observed by Qian et al. and is explained by the proximity effect according to Werthamer theory.

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The magnetic phase diagram of an fcc alloy AuCr has been constructed by means of magnetic and neutron diffraction measurements. It shows a nature of spin glass at dilute concentration of Cr and a nature of a long range antiferromagnetism at high concentration. At intermediate concentration, about 11 to 13 at.% Cr, it has short range antiferromagnetic clusters. Since the cluster size is almost independent of temperature change below the freezing temperature of spins which is determined by the susceptibility measurement, we can conclude that the intermediate phase is composed of antiferromagnetic clusters frozen in the matrix of spin glass. Near 13 at.%Cr, the system has narrow region which shows the reentrant property.

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Finite size calculation up to 18 spins combined with the extrapolation to the thermodynamic limit is performed to obtain thermodynamic properties of spin 1/2 triangular antiferromagnet. It shows that both of isotropic and Ising-like Heisenberg systems are in quantum spin fluid state at low temperatures with the singlet ground state. In contrast with the classical system, the result is consistent with the picture that the sublattice ordering has no relevance and no phase transition occurs.

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Mössbauer effect measurements of ⁵⁷Fe in SrFe_1−xCo_xO₃(0≤x≤0.5) have been performed at room temperature, 77, 64 and 4.2 K in order to study the electronic structure of Fe⁴⁺ ions. The Mössbauer spectra at 4.2 K were a single set of magnetically split lines, the form of which varied little with x. It is confirmed by the present study that Fe⁴⁺ ions have nearly a high spin electron configuration for 0≤x≤1. Mössbauer spectra at 77 K had a paramagnetic line as well as magnetically split lines in the range of 0.05≤x≤0.15, in which local fluctuation of composition of Co is considered to give rise to a magnetically inhomogeneous structure.

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By parallel pumping experiments antiferromagnetic spin-wave frequencies at the Brillouin-zone-boundary in (C₂H₅NH₃)₂CuCl₄ have been measured as a function of static magnetic fields below the spin-flop critical field. The experimental results are in good agreement with the spin-wave theory which includes the effect of the magnetic dipolar interaction. Measurements have been done at pumping frequencies from 7.7 to 10.8 GHz and in the temperature range from 1.4 to 2.6 K. The instability threshold of the zone-boundary magnons is empirically described as H_1c=0.30×T^2.46 Oe.

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The electrostrictive corrections have been made to a previous theory based on the pseudo one-dimensional Ishing model. The corrected results explain well the dielectric and the heat-capacity data of CsD₂PO₄ (d-CDP) both in the para- and ferroelectric phases even without the proton-tunnelling terms, but they are not so successful in the case of CsH₂PO₄ (CDP). The ratio of the effective dipole moments which indicates the strength of the effect of proton-tunnelling [Levstik et al.: J. Phys. C19 (1986) L25] is evaluated as μ_ε⁄μ_p=1.2 for CDP. This value suggests that, in CDP, the tunnelling-effect cannot be neglected.

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Details of emission and excitation spectra of powder phosphors were obtained at various temperatures between 6 K and room temperature. The emission spectra consist of six groups of emission lines located at about 565, 605, 650, 710, 790 and 900 nm at 300 K. The position of each emission line shifts slightly towards shorter wavelengths in the order, MgS:Sm³⁺, CaS:Sm³⁺, SrS:Sm³⁺ and BaS:Sm³⁺. The first five groups are assigned to the transitions from the ⁴G_5⁄2 state to the ⁶H_J(J=5⁄2, 7/2, 9/2, 11/2, 13/2) states and the last group to the ⁶F_J(J=1⁄2, 3/2, 5/2) states in a Sm³⁺ ion. The excitation processes are explained as being due to three transitions; (i) the transitions within the 4f⁵ configuration in a Sm³⁺ ion, (ii) the electronic 4f⁵→4f⁴·5d transition in a Sm³⁺ ion and (iii) the fundamental absorption in host crystal, followed by the transfer of the excitation energy to an unexcited Sm³⁺ ion.

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Raman scattering spectra of SiC polytypes 27R and 33R have been measured with a back scattering geometry using a (0001) face. The relative Raman intensities of folded modes in transverse acoustic (TA) and transverse optic (TO) branches have been calculated with the aid of a linear chain model. The calculated Raman profile for each branch agrees semi-quantitatively with the observed spectrum. The result indicates that the Raman intensity analysis of the folded modes can be used to identify the polytype of SiC with longer period.

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Photoemission spectra of BaPb_1−xBi_xO₃ are measured for x=0, 0.25, 0.3 and 0.6 by use of synchrotron radiation. A remarkable discrepancy from the results of band calculation is recognized. It is found that the O 2p_⊥ band has a high density of states (DOS) at binding energies (E_B) of 3.0∼3.5 eV. The DOS at the Fermi level (E_F) is found to be negligibly small in all samples. The E_B of the Pb 5d bands for x=0.3 and 0.6 are around 0.3 eV smaller than those for x=0. It is also found that the Ba 5p core levels shift to larger E_B by ∼0.3 eV with increasing x. The Bi 5d core levels have shown no additional structure besides the spin-orbit splitting, whereas the Pb 5d core spectra are remarkably distorted for x=0.3 and 0.6. These effects are discussed in regard to the charge transfer and the hybridization of electronic states.

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Photo-induced reflectivity change in Z₃-exciton region of a CuCl single crystal ∼3.4 μm thick has been studied to monitor the inhomogeneous distribution of high density excitons. A pump and probe technique has been used. The results have been analyzed qualitatively using a model in which the reflection of light from a dielectric composed of a directly photo-modulated thin layer and a moderately modulated remaining region is treated. In a typical case of ∼5 MW/cm² excitation at 3.234 eV at 1.6K, the shift of the Z₃-exciton energy and its damping constant in the directly modulated layer have been estimated to be 3±1 meV and 4±1 meV, respectively. The effective thickness of the layer has been evaluated to be less than 0.2 μm. A fact suggesting the propagation of photo-excitation effects toward the rear surface region which is far apart compared with the penetration depth of the pump beam has been found.

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