We compute the dynamic structure factors S(q, ω) for large-scale percolating networks with site numbers of the order of 10⁵, by applying a novel numerical method suitable for an array-processing supercomputer. It is confirmed that the dynamic structure factors are scaled by a single characteristic length Λ(ω). The scaling function h(x), where x=qΛ(ω), behaves as x^3.2 for x>>1, and x^−2.4 for x<<1. These results are argued in terms of a scaling theory for S(q, ω).

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The self-field method (J. Phys. Soc. Jpn., Vol. 59 (1990)) is applied to the electron scattered by the δ-function potential. It is found that an electron interacting with others has an effective size based on its self-field although the electron is in fact treated as a point particle without structure.

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Light amplification by a relativistic electron beam traveling in a laser light and an electrostatic (ES) wave propagating in the direction antiparallel to the beam direction (“electric wiggler”) through an emission whose transverse source current is produced by the laser light is calculated by relativistic quantum kinetics. From the viewpoint of quantum kinematics, this emission is exactly the same as the free-electron two-quantum Stark emission in which the transversely oscillating source current needed for the axial emission is due to the intrinsic electron spin angular momentum. These two emissions are different in dynamics since the former is an one-quantum process while the latter is a two-quantum process. It is suggested that the experimentally-observed plasma-maser emission is due to both.

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The Lagrangian for the linearized, ideal and resistive magnetohydrodynamic (MHD) equations is discussed by introducing the perturbation of the total pressure. In the resistive MHD equations, the Lagrangian is expressed in terms of the electric displacement vector (time integral of the electric current) as well as the plasma displacement. The NOVA and NOVA-R formulations can be derived by using the obtained Lagrangian.

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Incoherent inelastic neutron scattering and neutron Compton scattering measurements were performed on KH₂PO₄ (KDP). No drastic changes in either measurements were observed through the ferroelectric phase-transition temperature (T_c). These results suggest that the hydrogen wave functions in KDP are unchanged through T_c and the tunneling state of hydrogen is not realized above T_c.

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The thermal expansion coefficient α_i(T) of CeCu₂ single crystal has been measured up to 20 kbar in the temperature range from 4.2 K to 260 K in order to study the anisotropic behavior of the α_i(T) at high pressure. It is found that the contribution of the 4f electron to the α_i(T) shows an anisotropic behavior; i.e., α_a(T) and α_b(T) of CeCu₂ become similar to those of YCu₂ with the application of pressure, but α_c(T) of CeCu₂ differs greatly from that of YCu₂ at high pressure. A decrease in the density of states at the Fermi level is observed at high pressure. The result suggests a pressure-induced crossover from the concentrated Kondo state to the intermediate valence state.

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A new model of the electron-hole pair magnetic polaron lattice formation in magnetic semimetals is proposed and the stability condition is studied on a simple model. It is shown that in Ce-monopnictides the conduction electrons form either neutral electron-hole pair magnetic polaron or extended band states loosely coupling with hole induces magnetic polaron. Various anomalous properties in CeSb under high pressure are explained well by this model.

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The magnetoresistance of the heavy fermion compound CeInCu₂ has been measured at both ambient and hydrostatic pressures up to 2 GPa. It is found that the high pressure induces positive magnetoresistance, which is characteristic of the Kondo coherent state, associated with the enhancement of the Kondo temperature. The result is discussed briefly on the basis of the theoretical model by Kawakami and Okiji.

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We discuss the electronic state of Ni atoms in Ni metal and of Ni impurity in Cu and Au metals from the viewpoint of 3d configuration interaction (CI) using the Anderson impurity model including atomic multiplets. On the basis of the discussion, we give an interpretation for the Ni 2p-core X-ray photoemission spectrum (2p XPS) in Ni metal and Ni impurity systems and 3d photoemission spectra in Ni metal. The interpretation is, furthermore, shown to be consistent with the previous one for the 2p→3d circularly polarized X-ray absorption in ferromagnetic Ni using the CI approach.

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Superconducting properties of Tl₂Ba₂CaCu₂O₈ are investigated taking into consideration the inter- and intralayer pairings. Two kinds of pair potentials are determined self-consistently based on a microscopic energy band calculation. The obtained local tunneling conductance is influenced by the coexistence of two kinds of pairing.

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A simple derivation is presented of the Diophantine equation which is valid for any two-dimensional periodic system with noninteracting electrons in a magnetic field. It relates the quantized Hall conductance, the flux per unit area, and the location of a gap containing the Fermi level. Several comments are given.

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Quantum transport is studied for open billiards with a pair of conducting leads. Boundaries of the billiards are of squared-cosine shape and the electric conductance as a function of the Fermi wave number is computed by tuning the degree of opening. A quantized plateau accompanied by a sequence of intermittent sharp dips in a ‘strongly opened’ case changes into anomalously noisy fluctuations in a ‘weakly opened’ case. In the latter case, however, the smoothed conductance shows regular oscillations around some plateau values. The failure of the adiabatic approximation is also discussed.

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The conductance in superlattices is studied using the Landauer formula with a transfer-matrix technique. The characteristics of the superlattice, i.e., the layer structure and roughness at interfaces, are treated in a tight-binding model on a two-dimensional long-strip lattice. In this context the magnetoresistance of a magnetic Fe/Cr superlattice, which is known to show giant magnetoresistance, is discussed.

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Superconductor-insulator (S-I) transitions tuned by normal tunneling resistance or magnetic field in two-dimensional granular films of tin are investigated, with emphasis on the effect of grain size. We found that for 280 Å grains, the sheet resistance at the S-I boundary in a magnetic field-tunneling resistance plane is close to R_Q(≡h⁄4e²), while that for 1200 Å grains is much higher.

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The magnetic and superconducting properties of the new heavy fermion superconductors (HFS), UNi₂Al₃ and UPd₂Al₃ have been investigated by ²⁷Al NMR. The magnetic ordering is unambiguously identified by a significant increase of ²⁷Al linewidth below T_N=4.6 K and an enhancement of the nuclear-spin-lattice relaxation rate ²⁷(1⁄T₁) around T_N in UNi₂Al₃ and by a gradual increase of the linewidth and a distinct drop of ²⁷(1⁄T₁) below T_N=14 K in UPd₂Al₃. Below T_c=0.9 K in a magnetic field of 2.8 kOe, no anomalies of 1⁄T₁ and Knight shift have been observed in UNi₂Al₃, whereas the superconductivity in UPd₂Al₃ is well evidenced by a significant decrease of both 1⁄T₁ and Knight shift below T_c=1.8 K in 4.9 kOe. The behavior of 1⁄T₁ in UPd₂Al₃, with no coherence peak just below T_c, is well described down to 0.65 K by a model of gap zeros on lines at the Fermi surface, being quite similar to the behavior in HFS reported thus far.

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The possibility of a superconducting double transition in the recently discovered heavy Fermion materials UX₂Al₃ (X=Pd, Ni) is examined theoretically. It is found that the preexisting antiferromagnetic order breaks the symmetry to lift the degeneracy of the pairing function for UPd₂Al₃, leading to a double transition, while it does not break for UNi₂Al₃ when the spin-orbit coupling is strong. Thus no double transition is induced. We point out that the pressure or stress experiment may serve to control the split transition temperatures.

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We report the calculation of the 3d X-ray photoemission spectrum (3d XPS) in ferromagnetic Ni at the Ni 2p threshold energy with circularly polarized light on the basis of an extended Anderson model, which includes intraatomic multipole electron-electron interactions. Our study predicts that a strong resonance and a magnetic circular dichroism (MCD) pattern characteristic of the resonant photoemission 3d⁸+ω→2p⁵3d⁹→3d⁷+ε appear with increasing incident photon energy across the satellite region of the Ni 2p_3⁄2 absorption. We consequently propose a new critical check of the existence of 3d⁸ (“two-hole bound state”) in the initial state, which has been discussed to explain the Ni 2p X-ray absorption and its MCD, and 3d⁷ (“three-hole bound state”) in the final state of 3d XPS.

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Gravitational forces are calculated for a planet moving with the sun in the Milky Way galaxy, using the linearized Einstein theory. Two terms are found to be anisotropic: one may be called a “gravitomagnetic force”, and the other is expressed as an anisotropic effective mass of a planet experiencing the Newtonian gravitational force exerted by the sun. In the direction of constellation Cygnus the effective mass of a planet of intrinsic mass m is m(1+(1⁄2)P), and it is m(1−(1⁄2)P) in the other directions. The polarization P is the anisotropy of space and has magnitude of 1.0×10⁻¹² (M. Mizushima: J. Phys. Soc. Jpn. 61 (1992) 1125). Because of this “anisotropic-mass effect” the equilibrium orientation of planetary orbits is in the plane perpendicular to the direction of Cygnus. The gravitomagnetic force shifts the equilibrium orientation of the planetary orbital plane to the direction perpendicular to constellation Lyra. Thus, the present orientation of the planetary orbital plane is understood as the equilibrium orientation due to these two anisotropic effects.

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Based on the commutation relations of spin operators, the second quantization operators derived by Holstein-Primakoff and Dyson and its Hermitean conjugate operators are obtained. The matrix representations for a scalar product of two spins by the Dyson’s operators are not in agreement with the rigorous one except for the case of spin 1/2, although their eigenvalues are correct.

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Zimm and Bragg theory of (Remark: Graphics omitted.) transition has been modified to explain (Remark: Graphics omitted.) transition in polynucleotides, in particular (Remark: Graphics omitted.) transitions in poly (dG-dC) and poly (dG-me⁵ dC). Lambda anomaly in specific heat measurements around the transition point have also been explained by a further modification of the same theory. Theoretical results are found to be in good agreement with the experimental data. The Nucleation parameter which determines the sharpness of transition and depends on the extent and strength of cooperativity, is consistent with the stabilization/destabilization of the ordered states under various environmental conditions, e.g. methylation of cytosine residue at C5 position or change in the cationic concentration of the solvent.

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The techniques proposed in I of this series are applied to the calculation of the sum of the correlation functions of one fixed spin on one surface and spins on the opposite surface of the Ising model on a two-dimensional lattice of finite width and infinite length. Some arguments are given to claim that the present method provides a simple method of calculating the correlation length in the paramagnetic phase; the transition temperature being obtained at the same time.

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It is shown in the 3-rd virial approximation that the smectic A-crystalline phase transition occurs in perfectly aligned identical rigid cylinders (or discs) with diameter D and length L, by using the method of symmetry breaking potential. The smectic A phase and a hexagonal crystalline phase are shown to co-exist for 0.39<η<0.53, where η denotes the packing fraction. In the co-existence region, the crystalline lattice constants a\doteqdot1.35D in the hexagonal plane and c\doteqdot1.26L along the normal to the plane and the smectic layer spacing l\doteqdot1.35L are obtained. The hexagonal columnar phase is shown to be more stable than the smectic A phase at higher density than η_SmA-Col\doteqdot0.78 but always less stable than the crystalline phase. These results are in dependent of the ratio D⁄L due to the assumption of perfectly parallel alignment of molecules.

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Microscopic studies on the band structures of ^76,78Se and ⁸²Kr are performed. The method is based on the angular momentum and the particle number conserved Hartree-Fock-Bogoliubov approach. For the effective interaction slightly renormalized G-matrix which is derived from the Bonn OBEP is employed. Two quasiparticle excitations in the intrinsic configurations are shown to have crucial role in determining the γ-band moment of inertia in these nuclei. The observed features of the γ-band in ⁷⁶Se are well reproduced in our framework. The quality of our resulting wavefunctions are analyzed by calculating both one nucleon transfer spectroscopic amplitudes and the energy levels belonging to the several bands in the neighboring odd mass nuclei. The calculated quantities well reproduce the experimental data.

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Introducing effective masses of mesons and nucleons in the framework of the cloudy bag model, we calculated the bound nucleon form factors, magnetic moments, rms radii and axial coupling constant. These form factors have been applied to evaluate the dynamical charge longitudinal structure factors and the sum rules of nuclear response functions.

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For the single and double icosahedral group, the matrix representations and the basis functions of the irreducible representations have been calculated. The basis functions are sought in real spherical harmonics (l≤9) for the single group, and in spinors—composed of orbital angular momentum l and one-half spin (total momentum j≤9⁄2 and l≤4)—for the double group.

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Single and double electron loss and capture cross sections have been measured for He⁰, He¹⁺ and He²⁺ ions passing through a Zn vapor target at energies ranging from 0.8 to 2.0 MeV. Uncertainties of the cross sections were improved by applying the Rutherford scattering method for the determination of the target thickness. When combined with other previous experimental data, obtained cross sections support the oscillatory dependence on target atomic number. In addition, the equilibrium mean charges of He ions were compared for solid and gas phases of the Zn element, but no density effect has been observed.

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Crossed transport phenomena of heat and matter are thermodynamically discussed by using transported enthalpy and entropy, and those of transport, without using linear kinetic equations. The steady-state thermodynamics developed here is effective in dealing with thermo-osmosis, thermal diffusion and thermoelectricity. It is important to distinguish between transported thermal quantities and those of transport in any case. All of the results obtained agree exactly with corresponding expressions of linear nonequilibrium thermodynamics based on the Onsager theorem of reciprocity. Quasithermodynamic ambiguities are consistently eliminated by introducing entropy generated internally, d_iS, in harmony with the second law of thermodynamics. At the same time, a few points confused by many authors are corrected.

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Dynamic light scattering from dilute aqueous suspensions of polystyrene-latex particles subjected to steady simple shear flow was examined. The diffusion and the convection motions of the particles in shear flow were found to be detected from the measured homodyne correlation function if the intensity profile of the incident laser beam was assumed to be the superposition of the Gaussian- and the box-type of distributions. In addition, it was detected that there are some dynamical motions which might be due to oscillatory fluctuation of the shear gradient or to shear-induced aggregates of the latex-particles.

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For the relative diffusion of a pair particles in turbulent flow, the mechanism in leading to Richardson’s four-third law is studied analytically and numerically by using the effective Hamiltonian method. With this analysis, in connection with the Kolmogorov’s spectrum and the scaling law, it is shown that the main contribution to the Richardson’s law comes from a relatively small region of the inertial range, and there is a considerably large contribution from the vortexes whose diameters are larger than the relative distance between a pair of particles. It is also reported that the range of Richardson’s law in the smaller scales in the turbulence with a multi-range spectrum is extended toward large scales beyond a typical length in the smaller scales.

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The relaxation process of the velocity distribution of neutral atoms injected into dilute atomic gases with Maxwellian and non-Maxwellian velocity distributions has been analysed by numerically solving the Boltzmann equation using the transient FTI method. Here, only isotropic scattering in the center of mass frame and the collision characteristics of constant collision frequency and of constant collision cross section are assumed. Numerical analysis for the relaxation of the velocity distribution of the entire gas with a non-Maxwell initial distribution was also carried out by linearizing the Boltzmann equation sequentially in time. The results obtained are very simple and suggestive. The mechanism driving the neutrals toward the Maxwell distribution is discussed.

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A solution with cylindrical symmetry for the time-independent two-dimensional Vlasov equation is given numerically. It is demonstrated that, by adding appropriate numbers of particles trapped in potential-energy troughs, which are created by beam particles with definite angular momenta, varieties of localized vortical solutions can be constructed. There are an electron density hole and an ion density hole in the central region. Around these holes, electrons and ions are distributed on rings in the configuration space.

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A neutron diffraction study on the liquid Tl–Se system has been carried out over the whole concentration range. Profiles of the total structure factors or the pair distribution functions are essentially similar to those of pure liquid Tl up to 66.7 at.% Tl content, suggesting that there forms a certain short range order in the liquid state which is not far from the structure in the sense of short range scale of the pure liquid Tl. The existence of covalent-type Se polymeric structure is confirmed in Se-rich composition range. We have also derived the partial structure factors, using three different total structure factors in a small concentration range, where the partial structure factors were assumed to be constant.

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An X-ray diffraction study has been carried out for characterizing the structure of the amorphous germanium-sulphur system. An essential feature of the total structural functions, structure factors and pair distribution functions is unchanged in the region between 40 and 15 at.% Ge. It is also found that their number densities are linearly increased on going from 40 to 15 at.% Ge and the number density of crystalline GeS₂ is considerably larger than that of amorphous GeS₂ in which there involve many vacant sites. The partial structural functions of a_ij(q) and g_ij(r) have also been estimated from measured total structural data using an assumption of their concentration independence. A possible model was proposed for explaining the short range ordering in amorphous Ge–S.

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A theory of stationary anharmonic localized modes in solids with the cubic and hard quartic lattice anharmonicity is formulated. The theory using the lattice-Green’s function method is, in principle, applicable to any type of solids, ordered or disordered, of any dimension. Nonlinear eigenvalue problems for a fundamental mode and its higher harmonics are solved in a successive manner. The obtained result is illustrated for a d-dimensional version of the simple cubic lattice with nearest neighbor interactions to obtain concrete results for the localized-mode frequency, its profile functions, lattice distortions, and so on. For extreme localization, the stationary anharmonic localized mode is well described by a generalized anharmonic Einstein oscillator model.

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The Pbnm→P2₁/n ferroelastic phase transition in phenothiazine is studied using a 6-exp atom-atom potential energy function. Important couplings between the shear strain e₅ and molecular reorientation and between e₅ and the totally symmetric e₃ strain have been found in agreement with experiments. The first-order transition character is discussed in terms of the phenomenological Landau theory.

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Dielectric properties of tris-sarcosine bromide ((CH₃NHCH₂COOH)₃CaBr₂) which is isomorphous to the ferroelectric crystal tris-sarcosine calcium chloride ((CH₃NHCH₂COOH)₃CaCl₂, TSCC) have been investigated under high pressure down to 4.2 K. The hydrostatic pressure of excellent quality has been generated using helium gas as a pressure transmitting medium. The ferroelectric activity has been confirmed by the dielectric hysteresis loops. The pressure-temperature phase diagram of the ferroelectric phase transition is determined from the peak of the dielectric constant of the b-plate in various isobaric measurements. The transition temperature is well represented by an equation T_C∝(p−p_C)^1⁄2 which is a well known relationship for quantum ferroelectrics.

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The structure and dynamical properties of oxygen conductor yttria stabilized zirconia, (ZrO₂)_1−x(Y₂O₃)_x, are investigated for three dopant concentrations of 4.85, 10.2 and 22.7 mol%Y₂O₃ using a method of molecular dynamics simulation. It is shown that a Y–O nearest neighbor distance is longer than that for Zr–O, and an oxygen coordination number for Y ion is a little larger than that for Zr ion in all dopant concentrations. The self-diffusion constant of O ions, D, shows a maximum at 10.2 mol%Y₂O₃ with increasing the dopant concentration. These results are in agreement with experimental measurements. It is shown that dopant Y ions play an important role in such notable behavior of oxygen diffusion.

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The conductance and its fluctuations in mesoscopic NS (N is a normal metal and S is a superconductor) wires are studied numerically. It is shown that the conductance fluctuations in the NS wire is enhanced as compared with an ordinary normal metal wire (N wire) by about a factor two. For the conductance itself, an enhancement which has been expected is found to vanish when the length of the normal segment is longer than the mean free path.

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For the superconducting superlattices whose diffusion constant changes continuously, we study the upper critical field H_c2 and its angular derivative dH_c2(θ)⁄dθ at θ=0, where θ is the angle between the layer plane and the applied magnetic field. The latter quantity shows whether the order parameter has a preferential position relative to the sample. From H_c2 and dH_c2(θ=0)⁄dθ, we discuss the difference of this model from the model whose diffusion constant changes discontinuously at the interfaces and the Josephson coupling model.

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Superconducting properties of La_2−xSr_xCuO₄ are investigated theoretically within the framework of the phonon mediated pairing mechanism by solving the linearized Eliashberg equation, based on the electronic structure derived by Kamimura and Eto, in which holes are mainly accommodated in the Cu dz² and O-p hybridized upper Hubbard band in a superconducting phase. Effective electron-phonon coupling constant λ is estimated as 0.46 by fitting the calculated T-dependence of resistivity to the experimental data by Takagi et al. Then T_c is calculated by using the energy dispersion of the dz² upper Hubbard band. The calculated x-dependence of T_c agrees well with the experimental result by Torrance et al. The x-dependences of an isotope effect, the energy gap parameter, the heat capacity jump at T_c and the penetration depth are also calculated. The origin of a high T_c value is due to the occurrence of a sharp peak in the density of states of the dz² upper Hubbard band.

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Ground-state properties are studied for the one-dimensional isotropic spin-1 Heisenberg magnet with antiferromagnetic nearest-neighbor (nn) and next-nearest-neighbor (nnn) interactions. The energy, the singlet-triplet energy gap, the two-spin correlation function, and the den Nijs and Rommelse string correlation function in the ground states of finite-size systems of up to 16 spins are calculated exactly. By extrapolating these results, the ground-state properties at the infinite-size limit are discussed. It is found, in particular, that as the ratio of the nnn interaction constant to the nn one increases, the string order parameter (the limiting value of the longest-distance string correlation function) as well as the Haldane gap (the limiting value of the singlet-triplet energy gap) divided by the sum of both interaction constants increases. This result implies that the competition between the antiferromagnetic nn and nnn interactions stabilizes the Haldane phase.

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A modified mean field theory is applied to the axial next nearest-neighbor Ising (ANNNI) model, where the model is treated exactly along the direction of competing axial interactions while the mean field approximation is made within the ferromagnetic layer. Particular attention is paid to the partially disordered states and the asymmetric states, which are predicted to be stabilized by the mean field theory if the intralayer interaction is weak. Both numerical and analytical calculations are made to find that neither the partially disordered states nor the asymmetric states are stabilized but only the conventional ordered states are stable.

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On the basis of the method of equation of motion, the ground states of the quantum spin systems with a long-range order are studied. The equations of motion for the spin operators are linearized by introduction of the effective field, which is the order parameter itself. The linearized equations of motion and the use of approximate commutation relations for spin operators lead to the boson representation of the systems. It is emphasized that in the ground state with the long-range order along the x-axis, the relationship (S_j^y)²+(S_j^z)²=1⁄2 should be retained in the average. By use of the above constraint for spin fluctuations, the values of the long-range order and ground-state energy are calculated within the boson approximation. The results agree well with ones obtained by different methods.

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Pressure dependence of magnetic susceptibilities of YFe₂O₄ and ErFe₂O₄ has been measured up to 6 kbar above about 100 K. Two magnetic phase transitions are observed in the temperature region of 200–250 K at ambient pressure for both compounds. The transitions of YFe₂O₄ are depressed with increasing pressure. Especially the lower transition rapidly decreases in temperature and then disappears at 6 kbar. The transitions of ErFe₂O₄ show different pressure dependence, that is, the higher transition temperature increases and the lower one decreases with increasing pressure. The depression of the transition temperatures is explained as the volume effect on the first order phase transition, while the pressure dependence of the higher transition in ErFe₂O₄ is interpreted as the 10/3 law for the volume dependence of superexchange interaction.

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Paramagnetic and antiferromagnetic resonance have been observed in single crystals of Bi₂CuO₄ in submillimeter wave region using pulsed magnetic fields at temperatures from 4.2 K to 265 K. At the paramagnetic state, g-values have been determined to be g_⁄⁄=2.26±0.01 and g_⊥=2.04±0.01. The angular independent line-widths are 0.37±0.03 T which is quantitatively explained by the dipole interaction and anisotropic exchange interaction. An antiferromagnetic resonance mode of planer type antiferromagnet has been observed below the Néel temperature and explained by the conventional antiferromagnetic theory.

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Electron-nuclear double resonance (ENDOR) and electron-nuclear-nuclear triple resonance (TRIPLE) spectra of pristine cis-rich (CH)_x at low temperatures are consistent with the spin density distribution of the soliton predicted for a finite electron correlation. The ratio of the peak value of the negative spin density ρ(1) to that of the positive spin density ρ(0) is determined to be ρ(1)⁄ρ(0)∼−0.44 with the aid of ENDOR-induced ESR measurements. On the other hand, intrinsic ENDOR spectra due to the soliton spin density is not observable in ¹³C-enriched samples because of the line shape distortion caused by the overlapping second-harmonic signal of ¹³C nuclear frequency and other structures at frequencies related to ¹H and ¹³C nuclear Larmor frequencies.

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The absorption spectra are reported for HgI₂, PbI₂ and BiI₃ clusters and molecules incorporated into supercages of zeolite LTA at various loading densities. The spectra exhibit bands originating from a molecule to five molecular clusters of HgI₂ and PbI₂, and from a monomer and a dimer of BiI₃. The excitation energies are largely shifted to the higher energy side compared with the respective bulk exciton energies, and shift with decreasing the number of molecules, indicating the quantum size effect on the excitation energy. The blue shift decreases in the order of HgI₂, PbI₂ and BiI₃. The blue shift can be interpreted qualitatively in terms of the effective mass approximation, but quantitative analysis is beyond the framework of the effective mass approximation. The quantum size effect on the oscillator strength is also observed.

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The reflectivity spectrum of Y₂O₃ single crystals at 297 K has been measured from 6 eV to 110 eV, and optical functions are derived by the Kramers-Kronig transformation. The plasma loss peaks are found at 14.2₃ eV and 38.40 eV. The spectrum of ε₂(E) is tentatively interpreted in terms of the energy levels of Y²⁺, Y³⁺ and O²⁻ free ions. The spectral dependence of ε₂ suggests that interband transitions will be exhausted in the neighbourhood of 50 eV. In the energy region of E\gtrsim50 eV occurs the spectrum due to the free electron-like absorption alone. The accuracy of the data is discussed by the effective optical dielectric constant. The spectral dependence of the free electron-like absorption is compared with that predicted by the Drude formula. The origin of the loss peak at 38.40 eV is discussed.

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The picosecond spectroscopy with the time delayed double excitation technique has revealed that the F-H center pair ([F-H]) is converted from the self-trapped exciton (STE_L) at the a_1g state within 20 ps in KCl, NaCl and RbCl at 14 K. Conversion efficiencies from the STE_L to the [F-H] and to unknown X states were estimated by assuming two possible candidates of the hole π_g state or the higher electronic state in the STE as the precursor for [F-H] formation. Percentages of branching from the precursor to the [F-H] were 49, 86 and 20% in KCl, NaCl and RbCl, respectively. Rest of the STE were converted to unknown X states. By making use of these results, we criticized the state acceptable as the precursor, i.e., the hole π_g state or the electronic states.

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Time delayed double excitation spectroscopy in the picosecond range has revealed transient F bands due to the F center perturbed by an H center at the next nearest site, [F-H]_nnn, in RbCl, KCl and NaCl single crystals after excitation of the self-trapped exciton (STE) from the lowest triplet state to higher excited states. The F band consists of a doublet peaking at 1.99 and 2.11 eV (RbCl), at 2.25 and 2.38 eV (KCl) and at 2.70 and 2.86 eV (NaCl) with the ratio of 2:1 in height in every crystal at 108 ps after the excitation. The peak positions and relative height of the doublets are understood qualitatively by the theory for the off-center type STE. No dichroism of the doublet observed by the light polarized in the [100] or [010] direction suggests rotation of the [F-H] axis during relaxation from the electronic b_1u state, but not necessarily from the hole excited π_g state.

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