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Tatsuyuki Kawakubo, Tsuneo Murata, Yoshimi Tsuchiya
1983 Volume 52 Issue 2 Pages
355-356
Published: February 15, 1983
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The flow velocity fluctuation generated behind a circular cylinder which is placed in a unidirectional stream has been measured by means of laser velocimetry. The variance of the fluctuation is proportional to the square of the mean flow rate and is found to reduce with going down the stream.
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Nazakat Ullah
1983 Volume 52 Issue 2 Pages
357-358
Published: February 15, 1983
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An expression for the energy spectra in the rotation-vibration region is given using a coupling term in Bohr-Mottelson’s Collective Hamiltonian. It is shown that for certain strength of the coupling term it reduces to the well-known Ejiri’s expression for the energies of the collective states.
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Choji Nakaya
1983 Volume 52 Issue 2 Pages
359-360
Published: February 15, 1983
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A new type of solution is found for a nonlinear equation which describes the free surface of a viscous fluid film flowing down a vertical plane wall. A strongly nonlinear corrugation of the film surface concentrates in a small portion, and propagates downward with a constant velocity. Single waves observed experimentally can be considered as a train of such solitary waves.
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Tatsuya Ito, Yoshimi Tsuchiya, Tatsuyuki Kawakubo
1983 Volume 52 Issue 2 Pages
361-363
Published: February 15, 1983
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Intermittent behavior in the transition to turbulence in Bénard convection has been examined. The flatness which is a measure of the intermittency is found to enhance anomalously at the onset of the turbulence and decrease with the Rayleigh number.
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Shunjiro Shinohara, Isao Ochiai, Shunji Tsuji, Hiroshi Toyama, Kenro M ...
1983 Volume 52 Issue 2 Pages
364-367
Published: February 15, 1983
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In the non-circular tokamak TNT-A, we have tried to elongate plasma column by the combined operation of rapid rise of plasma current and rapid decrease in the decay index
n (=−(
R⁄
Bz)·(∂
Bz⁄∂
R)) with gas puffing after the current establishment. The increase in elongation ratio is obtained without deleterious effects on MHD instabilities. Dependence of elongation ratio on plasma parameters is calculated and compared with measurements. The growth rate of positional instabilities in the vertical direction is measured as a function of the decay index, and has good agreement with a calculation.
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Fumio Komori, Shun-ichi Kobayashi, Wataru Sasaki
1983 Volume 52 Issue 2 Pages
368-371
Published: February 15, 1983
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Temperature and magnetic field dependence of conductivity in Bi thin films is measured and compared with theories of the localization and the Coulomb interaction between electrons. The anti-localization effect in the case of strong spin-orbit interaction—logarithmic increase of conductivity with decreasing temperature—is found together with the other ln
T term due to the interaction effect. From the analysis of the magnetic field dependence the inelastic scattering time is determined to vary as
T−1 below 1.5 K and as
T−2 above 4 K being consistent with the temperature dependence of conductivity.
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Koji Kajita
1983 Volume 52 Issue 2 Pages
372-375
Published: February 15, 1983
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Stability of surface electrons on thin helium films adsorbed on solid neon is discussed both theoretically and experimentally. A new type of “bubble” electron which is formed at the interface of liquid helium film and solid neon is examined together with the surface electron. It is shown that the surface electron is definitely stable in pressing electric fields below a critical value which depends on the helium film thickness. An experiment demonstrating the recovery of surface electrons from the bubble states is given.
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Kazuhiro Fukushima
1983 Volume 52 Issue 2 Pages
376-379
Published: February 15, 1983
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Modulated wave train solution of a modified nonlinear Schrödinger equation,
iψ
t−
aψ
xx−
b|ψ|
1⁄2ψ=0, is investigated using a nonlinear transmission line. Good agreement between experiment and result of the numerical calculation is obtained.
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Akira Nakamura
1983 Volume 52 Issue 2 Pages
380-387
Published: February 15, 1983
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We have found new type exact solutions (ripplon solutions) of the 2-dimensional Toda lattice equation. The new solution reflects the effect of the essential multi-dimensionality of the system. We have shown that the general superposition of ordinary solitons and the various ripplons is possible.
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Etsuro Date, Michio Jimbo, Tetsuji Miwa
1983 Volume 52 Issue 2 Pages
388-393
Published: February 15, 1983
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A method is given for generating hierarchies of soliton equations on which infinite dimensional subalgebras of gl (∞) act infinitesimally. Various choices of subalgebras and discrete or continuous time evolutions lead to a variety of difference or differential equations. As examples it is shown that i) the discretizations of the KdV equations, the Boussinesq equation, the sine-Gordon equation and the Toda lattice, and ii) the two dimensional generalized Toda lattice of types
Al(1),
Dl(2),
A2l(2) and
Cl(1) are reductions of the single component KP hierarchy.
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Miki Wadati, Kiyoshi Sogo
1983 Volume 52 Issue 2 Pages
394-398
Published: February 15, 1983
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The concept of gauge transformation in soliton theory is introduced. It is shown that three different eigenvalue problems in 2×2 matrix form are connected by the gauge transformations. As an application of the theory, the interrelations among the nonlinear Schrödinger equation, the derivative nonlinear Schrödinger equation, isotropic Heisenberg equation and a new integrable equation are studied.
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Masahiro Nakagawa, Tadashi Akahane
1983 Volume 52 Issue 2 Pages
399-406
Published: February 15, 1983
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The intermolecular repulsions are approximately introduced into the molecular field theory of multi-component system of nematogens developed by Humphries-James-Luckhurst (H–J–L), and its effects on nematic-isotropic transition temperatures are investigated in binary mixtures of nematogens. From the comparison of the theoretical and experimental results, one can conclude that the intermolecular repulsions are also important to treat the nematic-isotropic phase transition in binary mixtures in addition to the intermolecular attractions. It is found that the effects of the intermolecular repulsions tend to lower the nematic-isotropic transition temperatures in binary mixtures.
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Riichiro Saito, Hiroshi Kamimura
1983 Volume 52 Issue 2 Pages
407-416
Published: February 15, 1983
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Electronic states of π-electrons coupled with lattice vibrations in a linear conjugated carbon chain, are calculated with a particular purpose of clarifiing the vibronic structure of bond alternation defect. First the vibronic Hamiltonian is derived from a general Hamiltonian. It is shown in the adiabatic approximation that the ground state of an odd number of carbon atoms corresponds to the bond alternation defect with an unpaired electron. Then taking account of the kinetic energy of lattice vibrations, the vibronic states of the defect is obtained. It is shown that the unpaired electron moves relatively freely. Finally a method to calculate self-consistently the electronic states and the lattice deformation in the presence of Coulomb interaction is presented. It is shown within the Hartree-Fock approximation that the ground state changes from CDW state to SDW state with increase of on-site Coulomb interaction.
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Junichi Yoshida, Kiyosi O-Ohata
1983 Volume 52 Issue 2 Pages
417-423
Published: February 15, 1983
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The total charge transfer cross-sections have been computed for the collision of O
3++H in the energy range of 2–240 keV. The PSS method with the classical trajectory is employed to obtain the cross-sections. The reaction channels which have the avoided crossing with the incoming channel at the internuclear distance less than 20 a.u. have been included into the calculation. The computed cross-section is found to be relatively constant as a function of the collision energy. The computed cross-sections are considerably large in comparsion with the experimental data by Phaneuf, but are of the same order of magnitude as the experimental result given by Gardner.
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Hirofumi Hanaki, Toshio Kusakabe, Nobuo Nagai, Masakatsu Sakisaka
1983 Volume 52 Issue 2 Pages
424-430
Published: February 15, 1983
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The single- and double-electron capture cross sections of He
2+ have been measured for targets of Ne, Ar, Kr, Xe and N
2 in the energy range from 0.7 to 4.5 keV. The cross section curves obtained are almost flat except the double-electron capture cross section for the He
2+–Ne case, which increases rapidly in the energy range studied. A simplified model of statistical electron transfer is introduced with the concept of interaction range and electron transfer probability to consider the collision mechanism. The He
2+–Ar, –Kr and –N
2 collisions show that single-electron capture proceeds within the interaction range of 2×10
−8 cm, mostly accompanying ionization. In the He
2+–Xe interaction, single-electron capture is considered to be quite predominant and double-electron capture with ionization also a major process. These transfers occur with the interaction range of 4∼6×10
−8 cm.
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Akihiko Ohsaki
1983 Volume 52 Issue 2 Pages
431-441
Published: February 15, 1983
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The potential scattering of charged particles in a strong magnetic field is formulated. The collision cross section is defined in such a way that the rate of scattering agrees with the field-free rate in the weak-field limit. A threshold law for the Landau-state excitation is derived. The higher-order Born series are calculated to obtain the approximate cross section formula. It is shown that in the low-energy collision the forward elastic scattering is observable. A relation between the elastic scattering cross sections for attractive and repulsive potentials is discussed.
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Akihiko Ohsaki
1983 Volume 52 Issue 2 Pages
442-448
Published: February 15, 1983
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The potential scattering of charged particles in a strong magnetic field is studied. A new exact formulation without utilizing the Green’s function is presented by removing the defect of the Green’s function formalism. The method is applied to a study of the cyclotron resonance. At the threshold of the Landau-state excitation the scattering cross section is finite in contradiction to the previous theories. For an attractive potential at least one Feshbach resonance occurs below the threshold.
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Moon-Uhn Kim
1983 Volume 52 Issue 2 Pages
449-455
Published: February 15, 1983
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Axisymmetric slow viscous flow due to a stokeslet situated along the axis of a circular disk is examined. The problem is formulated as a mixed boundary value problem, and a formal expression for the stream function is obtained. By evaluating the formal expression, it is found that a finite toroidal eddy always exists on the opposite side from the stokeslet and that an additional eddy adjacent to the stokeslet appears for values of the radius of the disk larger than a critical value.
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Norihiko Nakauchi, Yoshio Saito
1983 Volume 52 Issue 2 Pages
456-465
Published: February 15, 1983
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Dynamical equations governing the energy, temperature and heat-flux spectra in homogeneous axisymmetric Boussinesq turbulence are formulated by applying the modified zero-fourth-cumulant approximation. For nearly-isotropic turbulence with a weak buoyancy force, it is shown that they are reduced to the equations of turbulent field convecting a passive scalar. For this case, numerical calculations are performed to determine the spectra at the Reynolds number 32, Rayleigh number 100 and Plandtl number unity. The results show that the approach to isotropy seems rather slow. The temperature and heat-flux spectra indicate that there are several subranges of the wavenumbers governed by different similarity laws. Also the heat-flux spectrum is found to have a sharp peak which shifts toward the low-wavenumber range.
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Osamu Sano
1983 Volume 52 Issue 2 Pages
466-469
Published: February 15, 1983
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The Lorenz model of convective instabilities is reduced to a one-dimensional motion of a mass point in a potential well. Under suitable conditions, characteristic forms of chaotic oscillations as well as quasi-periodic ones are represented analytically by the use of the Jacobian elliptic functions.
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G. Mandal, K. K. Mandal
1983 Volume 52 Issue 2 Pages
470-477
Published: February 15, 1983
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In this paper the effects of Hall current on Couette flow of an electrically conducting fluid between two parallel plates in the presence of a uniform transverse magnetic field for a rotating system has been discussed. Here, we have taken the plates to be of arbitrary conductivity and arbitrary thickness. Analytic solution has been obtained exactly and influence of different parameters viz., Hartmann number, rotation parameter, wall conductivity parameters, Hall parameters for the liquid as well as the plates, and the thickness parameters on the primary and secondary velocity profiles, and induced magnetic field components, magnetic and viscous stresses as well as flux ratio has been examined numerically.
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J. L. Navarro, J. A. Madariaga, J. M. Saviron
1983 Volume 52 Issue 2 Pages
478-484
Published: February 15, 1983
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Starting from the Furry, Jones and Onsager basic equations and following a method of successive approximation, a formulation suitable to determine thermal diffusion factors from column steady measurements both in gaseous and liquid mixtures is derived. In the gas case, a proportionality relation, valid for any column type, between the logarithm of the maximum separation factor and the thermal diffusion factor evaluated at an adequate average temperature is obtained. It is shown that this temperature and the proportionality constant are independent of the nature of the gas mixture. For liquid mixtures, the so-called forgotten effect is carefully analysed.
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Mitsuhiro Shigeta
1983 Volume 52 Issue 2 Pages
485-491
Published: February 15, 1983
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The electron diffusion rate due to electrostatic high n ballooning modes in a sheared magnetic field is investigated. The electron motion in a fluctuation having many wave numbers with the same frequency is described by a map. An analytic theory based on a scaling hypothesis for the map is proposed to calculate the diffusion coefficient. The resultant exponent of the diffusion rate is three-halves with respect to the wave amplitude. The result is compared with numerical calculations.
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Alexander J. Anastassiades, Constantine L. Xaplanteris
1983 Volume 52 Issue 2 Pages
492-500
Published: February 15, 1983
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A drift wave instability of a magnetized plasma has been studied in the presence of an rf-field. Radial dc potential, density and rf-field gradients exist in a coaxial plasma cavity. Strong waves were observed in the plasma, propagating azimuthally with their frequency specified mainly by an ion drift motion. A theoretical model developed in this paper justified the existence of these waves whose growth rates depend strongly on the electron drift velocities due to the radial density and rf-field gradients, respectively. All the features of the wave instability appeared in our experimental data were satisfactory explained by the theoretical model.
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Shigeru Hayashi
1983 Volume 52 Issue 2 Pages
501-504
Published: February 15, 1983
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In order to measure the number density of charged particles in a high speed flow on slightly ionized argon, the hollow electric collector probe has been shown to be useful. This work is to investigate effects of the dimension of hollow probes and the strength of applied electric field on capture of charged particles. The experimental results show that the lower aspect ratio (=the ratio of the distance between electrodes to the electrode length) and the higher applied electric field are effective for capturing all charged particles entering into the probe. Even when an ion number density is relatively high (≤10
13 cm
−3), the hollow probe can be used for measurement of plasma density in a flowing plasma, though there are restrictions on minimum dimensions of probes and maximum strength of applied electric field.
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M. Bashir Chaudhry, Tsuguhiro Watanabe, Kyoji Nishikawa
1983 Volume 52 Issue 2 Pages
505-510
Published: February 15, 1983
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Electrostatic drift waves driven by a Gaussian density profile in a sheet plasma of thickness of the order of the ion Larmor radius ρ
i have been studied numerically. The frequency range considered is less than the ion cyclotron frequency ω
ci. The method is based on an integral equation in wavenumber space derived from the Vlasov-Poisson system of equations and on the direct computation of the integral equation. Eigenfrequencies and eigenfunctions are studied systematically by varying the plasma thickness, the transverse wavenumber and the parallel wavenumber. Unique features for the case of the ideal sheet plasma, whose thickness is equal to ρ
i, are disclosed, whereas the usual drift waves have been found for the case when the plasma thickness is as large as 100ρ
i.
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Heiji Sanuki
1983 Volume 52 Issue 2 Pages
511-519
Published: February 15, 1983
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The effect of an ambipolar field on the stability of electrostatic flute modes for a bumpy torus has been studied for both the positive and negative ambipolar fields using a relatively simple model of a bumpiless cylinder with an artificial gravity. It has been shown that the flute modes are stabilized effectively by the hot electron ring togehter with the rf electric field. The large
m number modes (
m denotes the azimuthal mode number) are stabilized by the finite Larmor radius effect and the small
m number modes are also stabilized by the reduction of gravitational force due to both the hot electron ring and the rf electric field.
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Kenji Yamamoto, Hajime Narumi
1983 Volume 52 Issue 2 Pages
520-527
Published: February 15, 1983
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A practical scheme for the diagnostics of an ultra-dense plasma with inclination of strong-coupling is presented. The complex level shift induced by various plasma perturbations is calculated for the low-lying states of a hydrogen-like moderate-
Z ion immersed in the DT plasma. The plasma perturbations are taken into acount on the basis of an ion-sphere model along with the Stark broadening theory. The result for the width of a spectral line such as Ne X Lyman-γ is found to be in good agreement with the recent experiment at the electron number density
Ne∼10
22 cm
−3 and the electron temperature
kBTe∼500 eV. The free-bound edge-shift at much higher density of
Ne∼10
24 cm
−3 is estimated from the complex level shift and is discussed in relation to the ionization-potential lowering of the emitter due to the screening effect in the plasma.
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Hidetoshi Suemitsu, Koichi Wani, Kuniya Fukuda
1983 Volume 52 Issue 2 Pages
528-535
Published: February 15, 1983
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Helium plasma containing a small amount of O-ions was produced by the linear Z-pinch discharges in He–O
2 (0.5 mol%) mixture, and the temporal changes of emission intensities of the OII to VI-ion lines as well as of the HeII 304 Å resonance line were measured in the extreme ultraviolet λ100 to 550 Å. At the same time the temporal change of the electron density
Ne was measured with a laser interferometer and the temporal change of the electron temperature
Te was determined from that of the Hell free-bound intensity distribution. Under the measured
Ne and
Te changes, the simultaneous rate equations for the ionization of O-ions have been calculated to give the temporal changes of the OII to VI-ion line intensities. The result falls far from the observation, especially the calculated intensities of OV- and VI-ion lines are much smaller than the observed intensities. The ionization processes of impurity O-ion in the He plasma are discussed.
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Toshihiko Dote, Masatoshi Shimada
1983 Volume 52 Issue 2 Pages
536-541
Published: February 15, 1983
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As against that a quasi-neutral theory of the positive column developed on the basis of swarm analysis by using transport equations was basically described in a collision-dominated fluid model, a fluid description of the collisionless positive column has been made and relation of its description with the above collision-dominated positive column theory has been discussed. The electron temperature characteristics calculated by means of the collisionless theory also have been drawn in comparison with those for the collision-dominated theory. According to these results, it is afresh concluded that the above theory for a collision-dominated model corresponds to a general theory valid all over the range from higher to lower pressure.
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Yasunari Kurihara
1983 Volume 52 Issue 2 Pages
542-548
Published: February 15, 1983
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In the coexistent state of the charge (spin) density wave and superconductivity, mixed collective modes are formulated on the basis of a diagram method which corresponds to the random phase approximation. This theory gives the basis of the collective modes assigned to new Raman peaks in 2H-NbSe
2. Our theory starts with a more fundamental Hamiltonian in which the direct coupling between two modes is not assumed in contrast with the theory of Littlewood and Varma.
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Masashi Iizumi
1983 Volume 52 Issue 2 Pages
549-555
Published: February 15, 1983
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Neutron-scattering measurement of the phonon dispersion relations has been carried out for the body-centered cubic phase of thallium existing above 230°C. The
T1 mode propagating in the [110] direction with the [1\bar10] polarization has been found to have extremely low energy. The low-lying mode at the zone boundary is related to the atomic displacements taking place in the bcc-to-hcp martensitic phase transformation in this crystal. The lattice instability relevant to the transformation is discussed on the basis of the interplaner force-constant analysis of the
T1 mode dispersion relation.
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Kuon Inoue, Yoshihiro Ishibashi
1983 Volume 52 Issue 2 Pages
556-561
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Raman scattering experiment has been performed with high sensitivity for K
2SeO
4 over a temperature range from 5 K to 135 K with special emphasis put on the observation of the phase mode in the incommensurate phase. The result has revealed that the phase mode in the commensurate phase becomes to exhibit gradually an over damped spectral profile as the commensurate-incommesurate phase transition temperature (
Tc=93 K) is approached from below and that the overdamped mode persists even in the incommensurate phase. An analysis based on a damped oscillator model shows that the frequency ω
0 of the phase mode decreases as
Tc is approached from below according to ω
0=
A(
T0−
T) with
T0=121 K, while it increases slightly in the incommensurate phase with further increasing temperature from
Tc. Discussion is presented in comparison with the existing theories.
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Shigeru Shindo
1983 Volume 52 Issue 2 Pages
562-571
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The classical mechanical theory of gas-surface inelastic collisions of Zwanzig is developed to include the thermal motion of lattice atoms. The fluctuation-dissipation theorem is verified between the thermal motion of struck atoms and response functions. The energy exchange between impinging gas atoms and lattice vibration is calculated, which is compared to the result from the distorted wave Born approximation. The trapping (sticking) conditions of impinging atoms are obtained in the form of the critical trapping energy. It is shown that the equation of motion of the impinging atoms approximately coincides with the generalized Langevin equation. The effective potential and the friction coefficient,which appear in the Langevin equation, are calculated.
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Hiroshi Tanaka, Koichi Shindo
1983 Volume 52 Issue 2 Pages
572-577
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It is shown that the Littlewood ionicity parameter
rσ′ characterizes 〈IV〉 compounds under pressure which have the metallic β-Sn structure or the NaCl structure with either metallic or nonmetallic nature. A calculation based on the nearly free electron approximation at the
X point indicates that whether the compounds with the NaCl structure are metallic or nonmetallic is determined by only the magnitude of the largest antisymmetric potential
v3. It is found that
rσ′ is proportional to
v3·
a02 where
a0 is the lattice constant. The important role of the potential
v3 in the NaCl structure is also investigated by a simple band calculation.
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Nobuyuki Shima
1983 Volume 52 Issue 2 Pages
578-586
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The electronic band structure of NbSe
3 is calculated by the relativistic LCAO–Xα–SCF method. The electronic structure near the Fermi level is found to be crucially influenced by the presence of the two kinds of prismatic chains in the unit cell. The calculated density of states explains qualitatively the observed XPS spectrum. There are five conduction bands whose main orbital component are
dz2 orbitals of Nb atoms. About 0.6∼0.7 electrons transfer from each Nb atom to Se atoms. The partial densities of state of orbital components are also calculated to understand the character of each band.
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Atsushi Oshiyama
1983 Volume 52 Issue 2 Pages
587-596
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A first-principles selfconsistent non-relativistic calculation of the energy-band structures of quasi-one-dimensional transition metal chalcogenides Nb
3S
4, Nb
3Se
4 and Nb
3Te
4 has been performed by using the numerical-basis-set LCAO method. The resulting Fermi surfaces of these three chalcogenides consist of warped or undulating plane-like sheets. The calculated Fermi-level density of states agrees well with the experimental value obtained from the specific heat measurement. The characteristic features of the observed optical reflectivity spectra of Nb
3S
4 are explained by the calculated energy-band structure. Moreover, a mechanism of electron-electron Umklapp scattering processes associated with the calculated Fermi surfaces is proposed as an origin of the unusual
T3 form of the temperature dependence of the electrical resistivity of Nb
3S
4 and Nb
3Se
4.
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Yoji Koike, Masami Okamura, Takashi Nakanomyo, Tetsuo Fukase
1983 Volume 52 Issue 2 Pages
597-604
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Resistivity measurements of TiTe
2 have been made. Above 10 K, a typical metallic behavior has been observed, while at low temperatures an increase of resistivity with a log
T dependence has been found. From measurements of magnetoresistance, this anomaly has been concluded to be due to not the Kondo effect but the two-dimensional Anderson localization in the weakly localized regime. Negative magnetoresistance observed for
J⊥
H⁄⁄
c-axis is proportional to
H2 in low fields and to log
H in intermediate fields and saturates about 40 kOe. This field dependence is in good agreement with Hikami
et al.’s theory based on the two-dimensional localization. Moreover, TiTe
2 seems to be a new system, where two carriers (three-dimensional and two-dimensional) exist and the two-dimensional carriers are considered to be localized at low temperatures.
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Y\={o}ichi Takaoka, Tôru Moriya
1983 Volume 52 Issue 2 Pages
605-616
Published: February 15, 1983
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A possible explanation is given for the anomalous electrical resistivities of Pu and PuAl
2 which show maxima at low temperatures where the susceptibilities show no remarkable temperature dependence. We study a mechanism in which the s-wave conduction electrons mixed with the f electrons by the s-f hybridization are scattered by the spin fluctuations of the f electrons via the f-f Coulomb interaction. The decrease in the resistivity at higher temperatures is due to the breakdown of the s-f hybridization (dehybridization) owing to the thermally enhanced spin fluctuations. The dehybridization effect and the temperature dependence of the resistivity strongly depend on the width and the structure of the f band. For favorable structure of the f band the calculated resistivity shows a maximum.
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Seizo Morita, Syozo Imai, Isao Fukushi, Satoru Takaki, Yosihisa Takeut ...
1983 Volume 52 Issue 2 Pages
617-621
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The Riedel peak in the Josephson current in bridge-type point-contact Josephson junctions has been studied by measuring the frequency dependence of the maximum height of the fundamental (
n=1) Shapiro-step in the energy range near hω∼4
Δ0 with a submillimeter-wave laser, where
Δ0 is the real part of the energy gap. The imaginary part of the energy gap,
Δ2, has been estimated from the observed rounding of the Riedel singularity. As a result, the damping factor δ=
Δ2⁄
Δ0\gtrsim0.05 has been obtained. The value of δ∼0.05 seems to be the lowest value which is intrinsic to bridge-type junctions. It has been also found that the value of δ is large in the junctions which show strong heating effects.
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Yasunori Kubo, Shoji Ishida
1983 Volume 52 Issue 2 Pages
622-628
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The transverse dynamical spin susceptibility χ
−+(
q, ω) of Ni
2MnSn is calculated within RPA with use of the energy values and the wave functions determined by the T.B.-OPW method and the spin wave spectra are evaluated. The effective exchange interaction
Ueffd-d is introduced as only one parameter. The correspondence between theoretical results and experimental ones is fairly good. It is evaluated how the correlation between the spin density of d-electrons of Mn and that of conduction electrons changes with increasing
q in comparison to the cases of Cu
2MnAl and Pd
2MnSn obtained before. The spin wave excitations of Ni
2MnSn are investigated by examining the relation between spin wave excitations and Stoner ones.
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Yoshikazu Makihara, Yoshikazu Andoh, Yuzo Hashimoto, Hironobu Fujii, M ...
1983 Volume 52 Issue 2 Pages
629-636
Published: February 15, 1983
Released on J-STAGE: June 01, 2007
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Measurements of magnetization, susceptibility, thermal expansion and electrical resistivity have been carried out on the RMn
2 compounds with R=Gd, Tb, Dy, Ho and Er. Magnetization measurements were made on the single crystals for all the compounds. A simple ferrimagnetic structure is observed at 4.2 K for GdMn
2, HoMn
2 and ErMn
2, and an antiferromagnetic one in TbMn
2. While, a canted ferrimagnetic structure appears at 4.2 K in DyMn
2. The Mn moment deduced from saturation magnetization decreases rapidly from 1.6 μ
B for GdMn
2 to 0.2 μ
B for HoMn
2 with increasing the atomic number of rare earth in the C15 compounds. While, the Mn moment is almost zero in ErMn
2 with the C14 structure. Anomalous discontinuities in the thermal expansion and resistivity for GdMn
2 and TbMn
2 are observed at the magnetic transition temperature where Mn moments lose a long range ordering. It seems likely that the discontinuity is associated with the onset of the Mn moment.
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Yoshiro Kakehashi
1983 Volume 52 Issue 2 Pages
637-647
Published: February 15, 1983
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The molecular-field-type theory of the local environment effect proposed previously is extended up to the Bethe approximation, and the magnetism of NiMn alloys is further investigated by using both the Bethe theory and the molecular-field theory. The susceptibility, the phase diagram and the magnetization-temperature curves are obtained as functions of the concentration and the atomic short range order (ASRO). It is found that they strongly change with the ASRO. A reasonable explanation of the experimental susceptibilities is obtained by taking the ASRO into account. Experimental
Tc and the magnetization curves with the change of the ASRO are also well explained by the theory. Present theory shows that the spin-glass temperatures
Tg are largely reduced with the atomic ordering and that the inflections of the susceptibility at
Tg are rather small in NiMn alloys.
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Kazuyoshi Takeda, Kuniyuki Koyama
1983 Volume 52 Issue 2 Pages
648-655
Published: February 15, 1983
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The fully mapped
T-
H (temperature-magnetic field) phase diagram of a quasi-two-dimensional (2d) antiferromagnet Mn(HCOO)
2·2H
2O (
TN=3.69 K) has been determined by the measurements of magnetic heat capacity and susceptibility. The critical field has been estimated to be 105±5 kOe at
T=0 K, which gives the intra-layer exchange constant |
J|⁄
kB=0.35±0.02 K. By applying external field, an anomalous increase of the Néel temperature
TN(
H) has been found (
TN(
H)≈1.10
TN(0) at
H=35 kOe) for the first time in this 2d compound as in the case of quasi-1d compounds.
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Kazuyoshi Takeda, Kuniyuki Koyama
1983 Volume 52 Issue 2 Pages
656-663
Published: February 15, 1983
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Two-dimensional (2d) XY behaviours have been revealed in a quasi-2d isotropic antiferromagnet Mn(HCOO)
2·2H
2O (
TN=3.69 K) in the external magnetic field of appropriate strength. The anomalous increase of the observed Néel temperature
TN(
H) in the field has been explained to be attributed to a crossover of spin symmetry from the Heisenberg type to the XY type induced by the field. The absolute values of magnetic heat capacity of this 2d XY system induced by the field of
H=20 kOe have been compared with the theoretical values expected for the 2d plane rotator model. A quantitative agreement has been found between them in the temperature region higher than
TN(
H). Discussion has been given of the heat capacity peak near the critical region.
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Kazuyuki Itoh, Akinori Hinasada, Hironori Matsunaga, Eiji Nakamura
1983 Volume 52 Issue 2 Pages
664-670
Published: February 15, 1983
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The crystal structure of Rb
2ZnCl
4 was determined at several temperatures in the normal phase by using X-ray reflection data collected by an automatic four-circle diffractometer. The β-K
2SO
4 type structure with large thermal amplitudes was obtained. The split-atom method reveals that the ZnCl
4 group lies with equal probability in two equilibrium arrangements. In addition to the disordered motion, softening of a rotational motion of the ZnCl
4 group is suggested from the temperature variation of thermal vibrations. The magnitude of the thermal amplitude gives an information about the mechanism of the phase transition in the β-K
2SO
4 type ferroelectrics.
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Izumi Hirabayashi, Kazuo Morigaki, Shoji Yamanaka
1983 Volume 52 Issue 2 Pages
671-676
Published: February 15, 1983
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Luminescence of disordered silicide layer compound, i.e., siloxene (Si
6H
3(OH)
3) is investigated at low temperatures. Fatigue in the luminescence is observed at 4.2 K and 77 K by prolonged irradiation of UV light. This fatigue is recovered by heating the sample at higher temperature. Inverse Arrhenius-type temperature dependence is also observed in the luminescence of siloxene. These results suggest that the electronic and structural properties of this material have a resemblance to some amorphous materials.
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Shosaku Tanaka, Takaaki Kuwata, Takehiro Hokimoto, Hiroshi Kobayashi, ...
1983 Volume 52 Issue 2 Pages
677-685
Published: February 15, 1983
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The picosecond time dependence of the optical gain due to high density electron-hole plasma (EHP) in GaAs is studied by means of time-resolved luminescence spectroscopy. The carrier temperature
Te and the concentration
Ne-h of the EHP are determined from the spectral shape analysis of the optical gain. Our result shows that in 160 ps,
Te decreases from 60 to 34 K, and
Ne-h decreases from 1.5×10
17 to 0.7×10
17 cm
−3. The decrease in
Te results from the energy loss process of hot carriers due to the polar LO-phonon scattering, and the decrease of
Ne-h is mainly dominated by the bimolecular recombination process. Time variation of the optical gain spectra and time response of its maximum value are clearly ascribed to the time change of
Te and
Ne-h in the EHP.
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Kenichi Takarabe, Kunio Wakamura, Tsutomu Ogawa
1983 Volume 52 Issue 2 Pages
686-693
Published: February 15, 1983
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Infrared reflection spectra of InS single crystals are observed in the wavenumber range between 50 and 900 cm
−1 for each polarization in
c-plane. The vibrational frequencies of longitudinal (ω
L) and transverse (ω
T) modes are determined by the Kramers-Kronig analyses as follows: ω
L=309 and ω
T=217 cm
−1 for
E⁄⁄
a, and ω
L=110, 236, 322, and ω
T=104, 196, 296 cm
−1 for
E⁄⁄
b polarizations. Almost the same frequencies are obtained from the fitting procedure by using the classical oscillator model. It is confirmed that the obtained dispersion parameters are more explicit values than those of previous works for twin crystals. The difference in crystal structures between InS and other layer semiconductors,
e.g. GaS, GaSe, InSe, is explainable qualitatively in terms of effective charges or ionicities.
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Michio Shimotomai, Tadao Iwata, Tohru Takahashi, Masao Doyama
1983 Volume 52 Issue 2 Pages
694-702
Published: February 15, 1983
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The positron techniques of lifetime and Doppler-broadening were applied to vacancies in graphite. Vacancies were introduced into highly-oriented pyrolytic graphite by irradiation with 2 MeV electrons and fission reactor neutrons. The lifetime of positrons trapped at the vacancies was determined as 245±5 ps. Lifetime studies revealed two distinct vacancy annealing stages at 600–900°C and at 1300–1500°C. The Doppler-broadened lineshapes of the annihilation gamma-ray were taken in the directions perpendicular and parallel to the
c-axis of the graphite lattice. Momentum distribution for an electron-positron pair at a vacancy was deduced and compared with the results of calculation based on the defect molecule model in the framework of LCAO–MO theory.
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