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Mitsugu Matsushita, Shunji Ouchi
1989 Volume 58 Issue 5 Pages
1489-1492
Published: May 15, 1989
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A numerical method proposed here enables us to scale-independently analyze the self-affinity of various curves such as noise and real topographical curves. The length
N and variances for two appropriately chosen coordinates,
X2 and
Z2, of a curve are measured between two arbitrary points on the curve by using the smallest fixed scale. The self-affinity is confirmed by testing whether
X and
Z are scaled as
X∼
Nνx and
Z∼
Nνz. The method is applied to transect profiles of real mountain topography, which is found to be self-affine with ν
x=1 for the horizontal and ν
z<1 for the vertical coordinate variations. The consistency of a scaling relation (
D=2−
H) between a self-affine profile with
H=ν
z and a self-similar contour with the fractal dimension
D in the same area is also discussed.
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Shoichi Kai, Nobuyuki Chizumi, Mitsuhiro Kohono
1989 Volume 58 Issue 5 Pages
1493-1496
Published: May 15, 1989
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A detailed investigation of defect motions has been carried out near the onset of the fluctuating Williams domains (FWD) in the electrohydrodynamic instability using a cell with intermediate aspect ratio. The number of defects in the cell changes nonperiodically in time with the 1⁄
f-type power spectrum. The threshold for the onset of the FWD shows a large hysteresis in the present aspect ratio. We conclude that the FWD is the defect chaos with rather low dimensionality.
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Takashi Karasudani, Mitsuaki Funakoshi, Masayuki Oikawa
1989 Volume 58 Issue 5 Pages
1497-1500
Published: May 15, 1989
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Breakdown and rearrangement of regular vortex streets in the wake of a circular cylinder are examined experimentally. The evolution of vorticity field is obtained using digital image processing for visualized flow fields. For 100<
R<140 (
R is the Reynolds number based on the velocity
U0 and diameter of the cylinder) a primary vortex street evolves to a parallel shear flow of Gaussian profile due to anisotropic extension of the vortex regions. Subsequently a secondary vortex street of larger scale appears. Its wavelength is within the instability region in the linear stability theory for the above velocity profile. The wavelength is, however, considerably smaller than that of the most unstable mode. Finally it is shown that the vortex regions in the primary and secondary vortex streets move at the speeds 0.15
U0∼0.19
U0 and 0.05
U0∼0.10
U0, respectively, relative to the fluid at infinity.
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Kenro Miyamoto
1989 Volume 58 Issue 5 Pages
1501-1503
Published: May 15, 1989
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MHD fluctuation level in RFP plasma is deduced from a model that supposes that MHD relaxation and sustainment of reversed field pinch (RFP) configuration are caused by the reconnection of lines of magnetic field driven by (
m=0,
n=1) mode nonlinearly excited by
m=1 (poloidal mode number) internal kink modes with the different toroidal mode numbers
n and
n+1. Thus the lines of magnetic forces become stochastic by the MHD fluctuations and the transport of RFP plasma in the braided magnetic field is clarified.
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Kousuke Yakubo, Tsuneyoshi Nakayama
1989 Volume 58 Issue 5 Pages
1504-1507
Published: May 15, 1989
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We have performed supercomputer simulations in order to gain insight into the nature of localized fractons excited on percolation nets. It is found that fracton modes possess a quite unique character, i.e., the core of fracton excitations falls off sharply at their edges. This is in contrast with the case of homogeneously extended modes (phonons), in which the change in their amplitudes is correlated smoothly over a long distance. In this connection, ensemble averaging over as many as one hundred fractons yields evidence of the strong localization of these modes which are quite different from the usual localized excitations.
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Shunsuke Hirotsu, Akira Onuki
1989 Volume 58 Issue 5 Pages
1508-1511
Published: May 15, 1989
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We present the first experimental evidence of the effect of uniaxial tension on a volume phase transition (or gel-gel transition) of polymer gels. With an increase in the magnitude of tension, the first-order transition temperature
T0 of poly-N-isopropylacrylamide/water gel increases and the size discontinuity at the transition becomes larger. These results are consistent with a phenomenological theory of volume phase transition of gels under anisotropic stress. The magnitude of the shift of
T0 with tension can be correctly predicted using empirical parameters determined in previous studies.
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Yoshifumi Sakamoto, Junjiro Kanamori
1989 Volume 58 Issue 5 Pages
1512-1515
Published: May 15, 1989
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It is shown on the basis of a Monte Carlo simulation calculation that the lattice gas model with infinitely repulsive nearest neighbor, repulsive second, third and sixth neighbor interactions on a triangular net can describe well the surface reconstruction of Ge(111) below and above the phase transition. The (1×1) state immediately above the transition is found to be divided into domains of irregular polygons of the (2×2) arrangement, which can reproduce the diffuse patterns of RHEED and LEED. A plausible explanation of the underlying mechanism of this characteristic short-range order is proposed. The (1×1) state of Si(111) is also discussed.
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Daijiro Yoshioka
1989 Volume 58 Issue 5 Pages
1516-1519
Published: May 15, 1989
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A two-dimensional square-lattice Hubbard model is investigated. A slave-fermion formulation, in which the electron operator is expressed by a combination of
bose operators for the spin freedom, and
fermi operators for the charge freedom, is used. The phase diagram for the resonating valence bond (RVB) state is obtained. The RVB state shows long-range antiferromagnetic order at
T=0, the period of which deviates from that of the commensurate Néel order as the system deviates from the half-filled case.
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Kunihiko Yamaji
1989 Volume 58 Issue 5 Pages
1520-1523
Published: May 15, 1989
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The dependence of the title is shown to originate in a singular angle dependence of the distribution width of the area of the semiclassical closed orbits under the magnetic field in the reciprocal space. In quasi-two-dimensional metals with a cylindrical Fermi surface, the distribution width of the area of the orbits on the Fermi surface vanishes at certain inclination angles of the magnetic field, entailing the appearance of remarkable effects. The observed peaks of the coarse-grained magnetoresistance are found to correspond to these special angles.
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Minoru Takahashi
1989 Volume 58 Issue 5 Pages
1524-1527
Published: May 15, 1989
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A two-dimensional square lattice antiferromagnet (
Remark: Graphics omitted.) is treated by the modified spin-wave theory. A set of self-consistent equations is obtained. This theory is consistent with the usual spin-wave theory and one-loop order renormalization group theory. For La
2CuO
4 we obtain
J\simeq900 K from analysis of the neutron scattering experiment.
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Takashi Imai, Hiroshi Yasuoka, Tadashi Shimizu, Yutaka Ueda, Koji Kosu ...
1989 Volume 58 Issue 5 Pages
1528-1531
Published: May 15, 1989
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Copper nuclear quadrupole/magnetic resonance (NQR/NMR) has been observed for the pyramidal copper sites in a metallic but nonsuperconducting copper oxide with mixed valence, La
4BaCu
5O
13+x. The electric quadrupole interaction, as well as the NMR shifts, was found to be quite similar to that observed for YBa
2Cu
3O
7, while the nuclear spin-lattice relaxation rate was found to be much lower (1⁄
T1=190 sec
−1 at 100 K) compared with that in the normal state of YBa
2Cu
3O
7 (1⁄
T1=2300 sec
−1 at 100 K). These observations indicate that the behaviors of antiferromagnetic copper spin fluctuations of nonsuperconducting and superconducting oxides are very different.
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Kazuo Gesi
1989 Volume 58 Issue 5 Pages
1532-1534
Published: May 15, 1989
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The effect of hydrostatic pressure on the successive phase transitions of {N(CH
3)
4}
2ZnI
4 has been studied by dielectric measurement up to about 320 MPa. Both the I–II transition temperature (
TcI–II, 254 K at 1 atm) and the II–III transition temperature (
TcII–III, 210 K at 1 atm) increase linearly with increasing pressure at the rates of d
TcI–II⁄d
p=120 K/GPa and d
TcII–III⁄d
p=350 K/GPa. The intermediate II phase disappears at 176 MPa.
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Takao Nanba, Makoto Watanabe
1989 Volume 58 Issue 5 Pages
1535-1538
Published: May 15, 1989
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The change in the phonon spectrum of KI due to the pressure-induced phase transition from the B1 phase (rock salt) to the B2 phase (cesium chloride) was observed at room temperature by the absorption measurement using a diamond anvil cell. The synchrotron radiation was used as the light source in the far infrared region. From the energy shift of the transverse optic (TO) phonon with pressure, the mode Gruneisen parameters were found to be 1.70 in the B1 phase and 2.70 in the B2 phase. The TO phonon energy of KI in the B2 phase was found to be 106 cm
−1.
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Katsufumi Nagahama, Nobuo Yajima
1989 Volume 58 Issue 5 Pages
1539-1549
Published: May 15, 1989
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Impurity localized modes of nonlinear lattice systems are studied by applying the method of multiple scales. The solutions of the localized modes of both infinite and semi-infinite nonlinear lattice systems are obtained up to the third order of the amplitude. According to the sign of the parameter specifying the second order nonlinearity, nonlinear lattice systems expand or shrink in the vicinity of impurity. Moreover, the frequencies of the localized modes are shown to decrease or increase with their amplitude, depending on the magnitude of the parameters specifying the second and the third order nonlinearities. As an example, numerical experiments for the Toda lattice with an impurity and the semi-infinite Toda lattice with an impurity are performed, and the results are in good agreement with those obtained by the perturbation method.
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Takahiro Yamaguchi, Yoshitaka Yamamoto, Kuninosuke Imaeda
1989 Volume 58 Issue 5 Pages
1550-1558
Published: May 15, 1989
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We have investigated the response of a nonlinear chemical reaction system: the Oregonator with an external periodic force. The mode diagram obtained by changing both the amplitude and the frequency of the external force shows a band structure which consists of several simple periodic modes π(
m) appearing with increasing order of multiplicity
m, but has intervening π(
m,
m+1) bands. For small values of the amplitude, the band structure becomes more complex by the appearance of such modes as π(
m,
m+1,
m+2) modes (
m=2, 3, 4). The order of appearance of the modes becomes irregular and chaotic modes also appear so that prediction using the strange attractor is not easy.
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Shigeo Homma
1989 Volume 58 Issue 5 Pages
1559-1569
Published: May 15, 1989
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A simple method, which we call
n-site approximation, is proposed for calculating the thermodynamic functions of the one-dimensional plane rotator model in an external field. On the basis of this method, these functions are expressed in the form of a series expansion in terms of the modified Bessel function of integer order. We have derived the free energy and the pair correlation function up to
n=7 and
n=2 approximations, respectively. A general procedure for obtaining each term associated with a series expansion of the free energy is discussed.
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Takenori Kobayashi, Kunikazu Takeshita, Akira Kagaya, Hiroaki Tsubota, ...
1989 Volume 58 Issue 5 Pages
1570-1580
Published: May 15, 1989
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The angular distribution of the
15N(γ, π
−)
15O(g.s.) reaction at
Eγ=170 MeV was measured using a liquid ammonia target at pion emission angles of θ
π=70°, 90°, 110° and 130°. The result is compared with the DWIA calculations and other experimental data. A large discrepancy is observed between the experimental result and the theory. In contrast with the
13C case, the E0 suppression is not clearly confirmed from the present analysis.
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Il-Tong Cheon, Sung Dahm Oh
1989 Volume 58 Issue 5 Pages
1581-1584
Published: May 15, 1989
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New energy shifts have been calculated for the
nS1⁄2 states of the atom placed at the center between two parallel, perfectly conducting plates. They are inversely proportional to the distance,
b, from two plates. Our numerical calculations with
b=1 μm give the energy shifts, −1.478×10
−8 eV (−3.574 MHz) and −1.189×10
−8 eV (−2.876 MHz), to the 2
S1⁄2 and 4
S1⁄2 states of He
+. The shifts in the 1
S ground states of the hydrogen atom and He
+ have also been estimated as 1.455×10
−8 eV (3.518 MHz) and 5.841×10
−8 eV (14.124 MHz) for
b=1 μm.
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Ichihiro Yamada, Atsunori Danjo, Takato Hirayama, Atsushi Matsumoto, S ...
1989 Volume 58 Issue 5 Pages
1585-1589
Published: May 15, 1989
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Absolute cross sections for electron impact ionization of C
+, N
+ and P
+ ions have been measured for electron energies from threshold up to 1000 eV, using the crossed beam technique. The measured cross sections for both C
+ and N
+ ions are in good agreement with the semiempirical Lotz formula over the whole energy range investigated, and also with those previously reported except for near threshold. The results for P
+ ions show a more rapid rise from the threshold and larger values around the peak than those calculated with the Lotz formula.
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Kazuhiko Okuno, Atsushi Fukuroda, Nobuo Kobayashi, Yozaburo Kaneko
1989 Volume 58 Issue 5 Pages
1590-1594
Published: May 15, 1989
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By means of the translational energy spectroscopy, one-electron capture processes by Ne
2+ ions from N
2 molecules have been studied at several collision energies from 400 eV to 1600 eV at zero scattering angle. All Ne
+ ions produced in Ne
2+–N
2 collision are resulted from only the exothermic reaction channels with the exothermicities ranging from 3.2 eV to 9.4 eV. Two groups of sharp peaks are observed, and they are assigned as
(
Remark: Graphics omitted.)
A broad peak which corresponds to capture of an inner-valence-shell (2σ
g) electron of N
2 is observed. The reaction mechanism is discussed on the basis of the reaction window.
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Hiroyuki Mizutani, Tohru Nakano
1989 Volume 58 Issue 5 Pages
1595-1603
Published: May 15, 1989
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Simulated two-dimensional Navier-Stokes turbulence with the
k−4 energy spectrum is considered from a multifractal point of view. The calculations cover the range of Reynolds numbers 55<
RL<850. Turbulence has an inertial range in almost one decade of wave number. The generalized dimensions
Dq are computed for the enstrophy dissipation rate as well as the energy dissipation rate. For the former
D∞=1.2∼1.3, implying that the intense enstrophy dissipation occurs nearly on a line. For the latter
Dq is close to two, the geometrical dimension, for positive values of
q, which means that the energy dissipation occurs uniformly in space. We do not observe that both
Dq depend appreciablly on Reynolds number as well as the pattern of the initial large-scale fields. The pictures obtained from the multifractal considerations are consistent with what is known already in two-dimensional turbulence, implying that the multifractal analysis is a good tool for studying turbulence structure.
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Satoshi Takeuchi
1989 Volume 58 Issue 5 Pages
1604-1610
Published: May 15, 1989
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Coherent interaction between charged particles and an elliptically polarized electromagnetic wave propagating across a static magnetic field
B0 is investigated analytically and numerically. The particle can be unlimitedly accelerated along the wave front on a plane across the field
B0. The trapping condition is obtained that depends on the polarization angle θ of the wave, the ratio
E1⁄
B0 and the phase velocity
Vp where
E1 is the magnitude of the electric field of the wave. Once an L-polarized wave with θ is found to satisfy the condition, an R-polarized wave with π−θ automatically satisfies it provided
E1⁄
B0 and
Vp are common to the both cases. Some features of an extraordinary wave which is a plausible candidate of the driving waves in a magnetized plasma are also discussed.
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Reiji Sugaya
1989 Volume 58 Issue 5 Pages
1611-1623
Published: May 15, 1989
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Electron heating due to nonlinear Landau damping of electrostatic waves in an electron beam-plasma system is studied theoretically. The fast and slow space charge waves of an electron beam and the Trivelpiece-Gould modes interact nonlinearly with plasma or beam electrons and cause an effective electron heating and a beam relaxation which leads to a saturation of electron heating. For nonlinear interaction with plasma electrons, the virtual (beat) wave produced by the two electrostatic waves can heat plasma electrons by its electron cyclotron damping. On the other hand, for nonlinear interaction with beam electrons, the Trivelpiece-Gould mode enhanced by nonlinear Landau damping can heat plasma electrons by its electron Landau damping. For both cases, the conservation of total energy flux and the existence of the energy transport are proved quantitatively.
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Masatoshi Yagi, Masahiro Wakatani
1989 Volume 58 Issue 5 Pages
1624-1630
Published: May 15, 1989
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The effect of parallel heat conductivity κ
⁄⁄ on
g mode is studied analytically. Under electrostatic approximation, growth rate γ is reduced according to κ
⁄⁄−2⁄5 for large κ
⁄⁄ case. Small κ
⁄⁄ limit is also discussed. For electromagnetic case, the stabilizing effect remains; however, its degree decreases, when beta value increases. These results are confirmed numerically.
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Kunihito Nagayama
1989 Volume 58 Issue 5 Pages
1631-1638
Published: May 15, 1989
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An analytical solution of the high-pressure Riemann problem for solids which satisfy the Grüneisen type equation of state has been obtained. Square of acoustic impedance along an isentrope passing through any thermodynamic states is written as a polynomial of the homogeneous solution,
X of the differential equation for the isentropic pressure change. The form of equation of state,
p(
v, ε) were calculated based on this assumption. Furthermore, elastic effects are included into the equation of state, and the von Mises yielding condition is assumed to be valid up to very high pressures. As a typical example, the elastic-plastic Riemann problem for the case of aluminum are solved after rather simple calculation.
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Shozo Takeno
1989 Volume 58 Issue 5 Pages
1639-1643
Published: May 15, 1989
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Dynamical self-trapping of vibrons in quasi-one-dimensional (1d) lattice space caused by their nonlinear interactions with 1d acoustic lattice phonons is studied with particular attention paid to the lattice discreteness effect. For coupled model field equations satisfied by vibrons and phonons, an elimination of phonon field variables can be achieved rigorously, leading to nonlinear-Klein-Gordon-type generalized Langevin equations with memory kernels written in terms of the Bessel functions. Within the framework of a rotating-wave approximation and neglecting friction terms with memory effects and random-force terms, an exact Green’s function method is developed to describe the dynamical self-trapping of vibrons as intrinsic, movable localized modes.
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Yasuhiro Shinnaka, Iwao Sasaki, Seishi Yamamoto, Toshiki Kaneda
1989 Volume 58 Issue 5 Pages
1644-1647
Published: May 15, 1989
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Crystallographical and group-theoretical analysis of the metastable phase transitions II–V
*–V in NH
4NO
3 is performed. The phase transitions are explained as a sequence
D4h5(II)–
D2h13(V
*)–
D2h10(V). The order parameter of the
D4h5→
D2h13 phase transition transforms as the irreducible representation τ
3+τ
3* at the
M-point of the Brillouin-zone boundary. The representation responsible for the transition
D2h13→
D2h10 is τ
7 at the
Z-point. It follows that II→V
* is driven by an ordering of NO
3− ions and V
*→V is driven by an ordering of NH
4+ ions. With X-ray diffraction method, it is also found that the occurrence of the metastable transitions is facilitated by pressure. The temperature dependence of the intensity of superlattice reflection shows that the transition II→V
* is of second order type and the critical temperature is 51°C at 0.15 GPa.
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Yorihiko Tsunoda
1989 Volume 58 Issue 5 Pages
1648-1654
Published: May 15, 1989
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With the help of data published by previous authors, it is demonstrated that the low temperature structure of γ-Fe precipitates in Cu, which was revealed recently by the present author and his colleagues, is regarded as a transitional state of fcc-bcc (γ−α) martensitic transformation in Fe. Several questions which may arise from this argument are also discussed.
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Fujio Kakinuma, Kenji Suzuki
1989 Volume 58 Issue 5 Pages
1655-1661
Published: May 15, 1989
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The heat capacity for liquid Te-I mixtures has a marked concentration dependence. Large heat capacities are observed around the stoichiometric composition TeI
4. Liquid Te
0.8I
0.2 mixture shows a broad maximum in the temperature dependence of heat capacity. The magnetic susceptibilities for liquid Te
1−xI
x mixtures with
x≥0.8 are nearly independent of temperature. In the intermediate concentration region, linear behaviour is observed in the plots of logχ
p·
T versus
T−1. Large excess heat capacities for I-rich mixtures can be attributed to the dissociation of polymeric complexes. For Te-rich mixtures, excess heat capacities are closely related to the change in the density of states near the Fermi level
EF caused by the bonding rearrangement.
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Kohji Fukuda, Tsutomu Kasuga, Takao Mizusaki, Akira Hirai, Kiyohisa Eg ...
1989 Volume 58 Issue 5 Pages
1662-1666
Published: May 15, 1989
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The self-diffusion process of water molecules through high-silica porous glass has been studied for three samples with different pore diameters using a stimulated echo method with pulsed field gradients. It was found that the diffusion process over a large distance can be described as a Gaussian diffusion process and that the effective diffusion constant is proportional to the porosity of the high-silica glass sample.
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Seiji Tasaki, Fukuo Yoshida
1989 Volume 58 Issue 5 Pages
1667-1675
Published: May 15, 1989
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Collective density excitations are studied in Fermi liquids, with particular attention to the role of the Landau parameter of the second order
F2. The density response function χ(
k,
z) including
F2 is obtained by solving the Landau transport equation in the collisionless regime. From comparison of it with an formal expression in the small wavenumber limit, a relation is pointed out between
F2 and a pair correlation function. It is also found that there exists a critical value of
F2 above which χ(
k,
z) exhibits two poles outside the continuum region. Zero-sound modes and their intensities, as well as the dynamical structure factor
S(
k, ω), are evaluated below and above the critical value. Discussion is also given on the
F2-dependence of
S(
k, ω) at non-zero wavenumbers.
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Masato Seimiya, Yositaka Onodera
1989 Volume 58 Issue 5 Pages
1676-1684
Published: May 15, 1989
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When an impurity is placed between chains in quasi-one-dimensional solids, it can cause transfer of electrons between chains through itself. The effects of this impurity induced interchain coupling on polarons are studied by means of the continuum version of the Holstein model. It is found that when the coupling strength exceeds a certain critical value, the polaron wave function extends itself over plural chains surrounding the impurity, rather than being localized on a single chain. Higher conductivity in directions perpendicular to the chains than in the parallel direction observed quite recently in doped halogen-bridged mixed-valence platinum complexes lends support to the above-mentioned picture.
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Taizo Sasaki, Hiroshi Katayama-Yoshida
1989 Volume 58 Issue 5 Pages
1685-1693
Published: May 15, 1989
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The atomic configurations and the electronic structures of the isolated hydrogen and the hydrogen-boron complex in crystalline silicon are determined using a normconserving pseudopotential and the supercell method within the local-density approximation. It is found that the isolated hydrogen is stable at the anti-bonding site. On the other hand, the bond-center site model has been found to be favorable for the hydrogen-boron complex. The site assignment of the muonium is also discussed on the basis of the calculated electronic structure. Moreover, it is found that the mechanism of the hydrogen passivation should be understood in terms of the three-centered bond rather than the classical two-centered bond model.
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Akira Morita, Taizo Sasaki
1989 Volume 58 Issue 5 Pages
1694-1704
Published: May 15, 1989
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A theoretical study of the electron-phonon interaction and anisotropic carrier mobilities in black phosphorus is presented. It is shown that the electron-phonon interaction is expressed in a deformation potential form in the rigid ion model and the long wave phonon approach. The deformation potential constants are calculated using the pseudopotential band theory and the lattice dynamical theory. The pressure coefficient of the energy gap estimated with the deformation potential constants is found to be in good agreement with experiment. The electron and hole mobilities are obtained by solving the Boltzmann equation. The results can explain the peculiar anisotropy of the hole and electron mobilities. Calculated mobilities at 100 K are μ
xh=10.0, μ
yh=3.2, μ
zh=2.7, μ
xe=5.8, μ
ye=3.1, and μ
ze=2.6×10
3 cm
2/V·s and the corresponding observed values are 10.0, 4.0, 1.5, 6.5, 1.3, and 1.1×10
3 cm
2/V·s, respectively.
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Yoshiyuki Ono, Tomi Ohtsuki, Bernhard Kramer
1989 Volume 58 Issue 5 Pages
1705-1716
Published: May 15, 1989
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We study the system size dependence of the inverse participation number (IPN) of the electronic eigenstates of a two-dimensional disordered system subject to a strong perpendicular magnetic field with periodic boundary condition in one direction, and Dirichlet boundary conditions in the other. Two types of random potentials are considered, random arrays of δ-function potentials, and of Gaussian potentials with a finite range of the order of the magnetic length. The fractal dimensionality
d* of the most extended states is estimated to be 1.39 for the δ-potential case and 1.56 for the finite-ranged impurity model. The edge states have
d*=1. Their insensitivity to the impurity potential is explicitly demonstrated. Through the analysis of the energy dependence of
d*, it is found that there is a continuous change of states from the edge states to the bulk extended states with lowering energy.
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Hiroshi Shimada, Taizo Masumi
1989 Volume 58 Issue 5 Pages
1717-1724
Published: May 15, 1989
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Hall mobility of photoexcited holes in the
Γ7+ valence band of Cu
2O has been measured at low temperatures. On the basis of the theory of carrier-lattice interactions in
polyatomic crystals the intrinsic scattering mechanisms of this substance have been clarified, for the first time, in a wide temperature range up to 400 K. From 40 K to 100 K scattering is dominated by the low-frequency LO phonon, ω
1. Above 100 K, the effect of the high-frequency LO phonon, ω
2, becomes remarkable. Here, ω
1=153 cm
−1 and ω
2=660 cm
−1 at 4.2 K. Mobility quenching due to the metastable self-trapping of holes possibly underlies the phenomena above 200 K. Below 40 K, the temperature dependence of mobility can be explained in terms of a combination of the effects of optical, acoustical and neutral impurity scatterings. The magnitude of the deformation potential of the
Γ7+ valence band is estimated to be as small as 0.7±0.3 eV.
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Masanori Ushida, Kazuhide Tanaka, Kenji Sumiyama, Yoji Nakamura
1989 Volume 58 Issue 5 Pages
1725-1734
Published: May 15, 1989
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Valence band and core-level characteristics of sputter-deposited Fe–Cu, Fe–Ag and Fe–Cu–Ag alloy films have been studied by X-ray photoelectron spectroscopy using monochromatized Al Kα radiation. These films are composed of metastable bcc, fcc and amorphous phases depending on the alloy composition. Their valence band spectra consist of well-resolved peaks representative of Fe-, Cu- and Ag-derived
d bands in the respective alloy systems, whose spectral features are similar to those of Ni–Cu and Pd–Ag alloys reported by Hüfner
et al. The spectral component of the Fe-derived
d band near the Fermi level tends to shrink rapidly in Cu- and Ag-rich fcc alloys. This feature is discussed in relation to the variation of the Curie temperature with the Cu or Ag concentration in these alloys. The core-level spectra of Fe 2
p, Cu 2
p and Ag 3
d states reveal that charge transfer among constituent elements is not appreciable. The effects of thermal annealing and the attendant phase separation upon these XPS spectra are also studied.
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Hiroshi Shimahara
1989 Volume 58 Issue 5 Pages
1735-1747
Published: May 15, 1989
Released on J-STAGE: June 01, 2007
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The superconductivity mediated by antiferromagnetic spin-fluctuations (AFSF) is studied in the quasi-one-dimensional Hubbard model. The superconducting transition temperature and the momentum dependence of the order parameter are calculated numerically. An effect of the long-range (>>the lattice constant) AFSF is examined. The obtained phase diagram is compared with that of the organic superconductors (TMTSF)
2X and (DMET)
2X, and some qualitative agreements between the theory and experiments are obtained.
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Yoshikazu Suzumura, Thierry Giamarchi
1989 Volume 58 Issue 5 Pages
1748-1754
Published: May 15, 1989
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The effects of non-magnetic impurities on quasi-one dimensional superconductors are investigated by use of the bosonized hamiltonian which consists of phase variables of charge density wave (CDW) and superconductivity. Applying a renormalisation-group method and a mean-field treatment of the interchain coupling, we calculate the superconducting (SC) transition temperature as a function of the disorder. We find that, contrary to the one-dimensional case, the SC phase is completely destroyed by the impurity pinning of the CDW, only for a finite concentration
Dc of the impurities.
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Takahito Kaneyoshi
1989 Volume 58 Issue 5 Pages
1755-1766
Published: May 15, 1989
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Magnetic properties of a semi-infinite two-sublattice Ising ferromagnet consisting of spin-1/2 and spin-1 are investigated in terms of the effective-field theory with correlations. The effects of bulk and surface single-ion anisotropies on the surface magnetization are examined. We find a number of characteristic behaviors of the surface magnetism due to the single-ion anisotropies.
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Takahito Kaneyoshi
1989 Volume 58 Issue 5 Pages
1767-1774
Published: May 15, 1989
Released on J-STAGE: May 29, 2007
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Magnetic properties of a free ferrimagnetic or a ferromagnetic surface on a semi-infinite ferrimagnetic Ising alloy consisting of two different spins are investigated within the framework of the preceding paper. A compensation point in the surface magnetization is found when the value of surface single-ion anisotropy takes a certain negative value, although it never appears in the bulk. This may be a very important phenomenon for technological applications.
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Nobuyoshi Hosoito, Kenichi Yoden, Ko Mibu, Teruya Shinjo, Yasuo Endoh
1989 Volume 58 Issue 5 Pages
1775-1786
Published: May 15, 1989
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Neutron diffraction technique is applied to the study of magnetic/magnetic artificial superstructured films (ASF’s) composed of alternate stackings of Fe and Dy layers. Neutron and conventional magnetization experiments are combined, and the contributions of the Fe and Dy layer to the magnetizations are separately estimated. Based on temperature and magnetic field dependences of the magnetizations, magnetic properties of Fe/Dy ASF’s are discussed. It is indicated that, besides a strong magnetic anisotropy of Dy atoms, an antiferromagnetic coupling of Fe and Dy moments at the interface plays an important role on the magnetic behavior of Fe/Dy ASF’s.
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Kazuo Itoh, Tsuyoshi Okagaki, Kazuo Kanematsu
1989 Volume 58 Issue 5 Pages
1787-1792
Published: May 15, 1989
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Crystal structure of Y
1−xZr
xFe
2.9 system were ascertained by X-ray diffraction to be classified in four types, PuNi
3 type in
x<0.3, orthorhombic type in 0.3<
x<0.7, C14 like hexagonal type in 0.7<
x<0.85 and C15 type in 0.85<
x<0.95. The Mössbauer spectra of the compounds were explained to be two superimposed hyperfine patterns. It is concluded that a direction of hyperfine field lies in the
c plane for the compounds in 0<
x<0.3 and lies along the
c axis for the compounds in 0.4<
x<0.95.
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Sadamu Takeda, Takahiro Fujiwara, Hideaki Chihara
1989 Volume 58 Issue 5 Pages
1793-1800
Published: May 15, 1989
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The spin-lattice relaxation rate and the line shape of proton NMR of 1,3,5-trichloro-2,4,6-trimethylbenzene were measured between 1.8 and 430 K. Two maxima of the spin-lattice relaxation rate were clearly distinguished at 36.4 and 19.0 K. The maxima are ascribed to fluctuation of intramethyl and intermethyl dipole interactions due to methyl rotation. The activation energy of the rotation of the methyl group over the potential barrier is 2.4 kJ mol
−1 and the tunneling frequency of the methyl group was estimated to be 830 MHz at 36 K. In comparison with the methyl rotation in hexamethylbenzene, the alternate substitution of three chlorine atoms for the three methyl groups substantially reduces the potential barrier hindering the rotation of the methyl groups.
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Tetsuhiko Tomiki, Fujito Fukudome, Minoru Kaminao, Masami Fujisawa, Yo ...
1989 Volume 58 Issue 5 Pages
1801-1810
Published: May 15, 1989
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Optical absorptions in the tail region and the reflectivity at room temperature in the VUV region up to ∼40 eV are measured for YAG single crystals. Various optical constants are derived therefrom as functions of photon energy by means of the Kramers-Kronig relation. The Urbach rule parameters are determined experimentally for the tails intrinsic to YAG single crystals. The exciton peak is inferred to lie near the photon energy of the convergence point (7.012 eV) of the Urbach tails, taking into account the peak position (∼7.0 eV) of the excitation spectrum of Ce
3+-emission from YAG:Ce
3+ phosphors. A tentative interpretation of the spectral features found in the spectra of optical constants in terms of the energy levels of the constituent free ions is given.
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Yoshinori Katayama, Makoto Yao, Yoshitami Ajiro, Masanori Inui, Hirohi ...
1989 Volume 58 Issue 5 Pages
1811-1822
Published: May 15, 1989
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Photoacoustic spectroscopy, ESR and EXAFS measurements have been carried out on the Se chains isolated in the channels of mordenite crystal with 6.7 A diameter. The optical gap is estimated to be 2.3 eV at room temperature, which is much larger than that of trigonal Se. At low temperatures, illumination with the light having energy near or above the optical gap induces new absorption bands at 1.85 and 2.25 eV, which are associated with paramagnetic defects. Higher energy light (>2.9 eV) shifts the absorption edge to lower energy. The fluctuations in the covalent bond length increase with illumination, though the helical chain structure is preserved. These changes vanish by annealing at room temperature. The phenomena are reversible in the illumination and annealing cycle. The photo-induced absorption and the edge shift are reduced when the induced bands are excited optically.
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Masaaki Kobayashi, Kiyoshi Kanisawa, Akira Misu, Yasushi Nagamune, Sho ...
1989 Volume 58 Issue 5 Pages
1823-1830
Published: May 15, 1989
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Experimental results are reported on the yellow series excitons of Cu
2O in magnetic fields up to about 150 T. A diamagnetic shift of the
n=2 exciton, and a Landau level type shift of the
n=3 exciton are observed for the first time. The magnetic field dependence of the exciton spectra is found quantitatively consistent with previous data of the high
n excitons obtained in low magnetic fields. These results are ac-counted for by a theory of a hydrogen atom in magnetic fields. It is concluded that in the yellow series excitons, only one mass-parameter governs both diamagnetic and Landau level type shifts.
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Yasuo Nozue, Takenari Goto
1989 Volume 58 Issue 5 Pages
1831-1837
Published: May 15, 1989
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The time dependence of an excitonic luminescence is measured in anthracene crystals in the picosecond regime at room temperature. The luminescence rise time is within the detection limit at any observation energy. The luminescence decays non-exponentially. The fast decay component, whose decay time is about 0.8 ns, is observed for the luminescence in the strong absorption region. In the weak absorption region, the decay time is larger than 10 ns. Such a remarkable energy-dependence of the decay time is interpreted by taking account of the luminescence reabsorption and the regeneration of excitons. The true radiative decay-time of exeitons is determined to be 0.8±0.1 ns which is about one tenth of that determined in the nanosecond regime.
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Takuya Mukai, Ken-ichi Kan’no, Yoshio Nakai
1989 Volume 58 Issue 5 Pages
1838-1849
Published: May 15, 1989
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Temperature dependence of lifetimes τ
f (fast component) and τ
s (slow component) of the π emission in KI and KBr has been measured precisely to investigate the decay kinetics of zero-field-split triplet sub-levels A
u and B
u of the self-trapped excitons. Spin-lattice relaxation rates
Wab and
Wba between the A
u and the B
u levels are determined directly from the observed values of τ
s and τ
f at various temperatures. In KI, the upward transition rate
Wab was found to decrease while the downward one
Wba approaches to a constant value in lowering temperature. On the other hand, both the upward and the downward ones in KBr decreases in lowering temperature. It is concluded that the one-phonon direct process is effective in KI, whereas a multi-phonon process is effective in KBr.
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Yoshitaka Tanimura, Tetsuhiro Suzuki, Ryogo Kubo
1989 Volume 58 Issue 5 Pages
1850-1859
Published: May 15, 1989
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A general formulation is given for the second order optical process of a three-level system in contact with a heat bath consisting of harmonic oscillators with a proper frequency spectrum producing a Markoffian random perturbation. Elimination of the bath using the influence functional method of Feynman and Vernon yields a continuous fraction expression and the result affords a basis to clarify the relation between the stochastic and dynamical approaches to treat the partial destruction of the quantum coherence of the optical process. As an example, a three-level system with intermediate-state interaction is treated in some detail.
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