Proton spin-flip probabilities in the scattering of ¹²C(p, p′)¹²C(4.44 MeV) were measured in the energy range between 12 to 14 MeV. The differential cross sections in the elastic and inelastic scattering were also measured. The measurement were done in detail around the resonance in the elastic scattering cross section at 13.1 MeV. In this energy region, the spin-flip probability shows a remarkable energy dependence in contrast with a rather monotonous one of inelastic scattering cross section. The measurements were done by the (p, p′ γ) coincidence technique due to Schmidt.

View full abstract

A new transition of 49.630±0.010 keV decaying with a half-life of 24.4±1.0 hr was found in ¹⁵⁶Tb. The isotope assignment was made by the energies of L- and M-subshell internal conversions and the mass assignment by yield ratios of various Tb isotopes at different bombarding energies. The multipolarity of the transition is determined to be E1 from the L-subshell ratios. The decay scheme concerning this new transition is unknown yet.

View full abstract

The production asymmetry in the reaction γ+n→π⁻+p is measured at 90° in the center-of-mass system and at five photon energies from 357 to 555 MeV. Linearly polarized photons are obtained by means of the coherent breamsstrahlung process from a silicon single crystal. Negative pions and recoiling protons from a liquid-deuterium target are detected simultaneously so that events originated from neutrons almost at rest in the deuterons are selected. The asymmetry data are compared with the dispersion-relation calculation of Berends, Donnachie, and Weaver, and with that of Schmidt et al. It is shown that the contribution from the Roper P₁₁ (1470) resonance is small in the pion photoproduction process.

View full abstract

The differential cross sections, asymmetry ratios and recoil-nucleon polarizations of pion photoproduction on protons and neutrons below 500 MeV have been studied. It is shown that the dispersion theory of Berends, Donnachie and Weaver is unfavorable because of their inadequate treatments of the P₁₁ (1470) and D₁₃ (1518) resonances. The phenomenological analysis shows that the effect of the Roper P₁₁ (1470) resonance is negligible and the isovector amplitude is dominant in the multipole amplitudes leading to the final D₁₃ state. The experimental data are also favorably explained by the crude dispersion-theoretical model of Schmidt et al.

View full abstract

Decay of ⁴²K was investigated by a Ge(Li) detector and a 5″φ×4″ NaI scintillation counter. Two gamma-ray peaks were newly observed at 0.692 and 1.228 MeV in the gamma-gamma coincidence spectrum. The 0.587 MeV gamma-ray, previously reported by McCullen et al., could not be seen and the upper limit of the intensity of this gamma-ray relative to the 0.900 MeV gamma was 0.7%.

View full abstract

The lattice dynamics of yttrium and titanium have been studied using authors’ new electron-force model described in an earlier paper. Dispersion relations along [0001] and [01\bar10] directions have been drawn for both the metals. The present θ-T curves show good agreement with the experimental values.

View full abstract

The boson creation and annihilation operators of excitons are introduced and the fermion Hamiltonian of high density electrons and holes is expanded in terms of these boson operators. Then a nonlinear integral equation for the high density excitons is derived and it is solved in two ways: 1) by the perturbational method and 2) exactly for a simple model of the Coulomb interaction in the random phase approximation and the effective mass approximation for the two band model of a conduction band and a valence band. As a result, the cutting down effects of both the band edges due to formation of high density excitons are shown to overcome the exchange self-energy of the electrons and the holes composing the high density excitons.

View full abstract

In terms of a two-particle Green function, we formulated the three-phonon process. The spectral function of the Green function is the dynamical structure factor of liquid and there are two exact sum rules for it. Using Puff’s expression for the dynamical structure factor, it is shown that one can reproduce results obtained by Pethick and ter Haar who formulated the three-phonon process in terms of a single-particle function. In the framework of this theory we can put problems in connection with the fluctuation-dissipation theorem. A sum rule for the width Γ(k, ω), which is expressed as the time Fourier transform of the time correlation function of the random force acting upon the density fluctuation, is obtained. As long as k²Γ<<k_BT, the liquid structure factor S(k) is given by
(Remark: Graphics omitted.).
The connection between the width Γ(k, ω) and the lifetime of phonons is discussed. Properties of the random force are also discussed.

View full abstract

The lattice dynamics of zirconium and hafnium have been studied using authors’ electron force model. Dispersion relations along [0001] and [01\bar10] directions are being drawn. The present θ-T curves show good agreement with the experimental values.

View full abstract

A one-dimensional lattice gas with repulsive potential u₁>0 between nearest neighbors and attractive potential u₂<0 between second neighbors is discussed. In the limit of u₁, |u₂|→∞ while keeping u₁+u₂=finite<0, a phase transition is expected. However, in the case when both u₁ and |u₂| are finite but large, a diffuse phase transition is obtained. This model is regarded as a lattice gas version of the helix-coil transition in polypeptides. The distribution of the zeroes of the grand partition function is also discussed through computer calculation.

View full abstract

In an interacting spin system, spin resonance and relaxation are studied. From the von Neumann equation, a generalized Bloch equation is derived directly by making use of the method of orthogonal operators expansion, which has been developed in a previous paper. The linearization conditions, i. e., (spin energy) <<kT and the spin I=1⁄2, which were required in earlier theories, are eliminated. The theory is valid at all temperatures and for arbitrary spin. At high temperatures, the result coincides with Argyres and Kelley’s one for a system of independent spins except for the definition of relaxation times. The theory is also applicable to the rigid lattice. The steady-state magnetization is studied.

View full abstract

It is shown that the “tetradic” interpretation of Kubo’s H^× operator is convenient in writing the equation of motion for two-time Green’s function. In the formulation, the tetradics are used to express an anti-commutator of an operator as well as the commutator. For the Green’s function defined in terms of a commutator, the resulting equation of motion is equivalent to the one recently derived by Shimizu. A new approximation scheme is proposed on the basis of the obtained expression. Its lowest approximation is applied to the Heisenberg ferromagnet. It is shown how the results of the decouplings due to Tyablikov and others are derived as special cases in the present approximation scheme.

View full abstract

The degree of dynamic nuclear polarisation in a multi-level electron-nuclear coupled spin system is computed in the high temperature limit when the first order forbidden transitions are saturated by an appropriate microwave field. Both the cases of either the hyperfine or the nuclear Zeeman interaction dominating over the other are discussed. In the latter case the enhancement of nuclear magnetic resonance is also calculated and compared with the available experimental data.

View full abstract

The Néel temperature, T_N, where the energy gap, g, tends to zero is calculated. A flow of electrons between the octahedral Fermi surfaces of the electron and hole bands and the other free Fermi surfaces (called the reservoir) is taken into account. It is shown that the Fermi energy depends appreciably on temperature due to the flow of electrons, so that the calculated T_N is different from that given in a previous paper where the temperature-dependence of the Fermi energy neglected. However, the overall agreement with experimental results is found still satisfactory. The order of the phase transition is studied by calculating dg²⁄dT at T_N. It is found that although dg²⁄dT changes considerably with the density of states of the reservoir, this change is not large enough to bring out first-order transition. Finally, a comment is made on a related theory proposed by Mitsudo et al.

View full abstract

A theory of translational and orientational melting with application to liquid crystals is presented in a manner analogous to that of Kirkwood and Monroe by introducing both translational and orientational order parameters.

View full abstract

The ESR of Vo²⁺ ions in single crystals of ammonium magnesium sulphate and potassium magnesium sulphate is observed. The V–O axis is found to have four possible orientations giving rise to four magnetic complexes in each crystal. In both the crystals the V–O axis of two magnetic complexes lies in the (\bar110) plane while the axis of the other two complexes lies in the plane perpendicular to (\bar110). In (NH₄)₂Mg₂(SO₄)₃ the populations in the four possible orientations of V–O axis are in the ratio of 2:1:2:1 while the populations are in the ratio of 2:3:2:3 in K₂Mg₂(SO₄)₃. The complexes with identical populations are equivalent but for the change in the relative directions of their axes. The vanadyl hyperfine lines in (NH₄)₂Mg₂(SO₄)₃ show an additional anisotropic hyperfine structure of five lines which is apparently due to superhyperfine interaction of the unpaired spins of the transition metal ion, with some of the protons of the surrounding (NH₄)⁺ molecules. All the spectra in both the crystals have been analysed using the spin-Hamiltonian corresponding to rhombic symmetry and the spin Hamiltonian parameters are presented.

View full abstract

Mössbauer and magnetic studies characterize that iron is in spin free, ⁶S 3d⁵ state in sp³d² bonding in iron (III) acetate and its chloro-derivatives. The inductive effect does not influence the s-electron density at the Fe atom. It is concluded that for trinuclear basic iron acetate, all the iron atoms are in equivalent positions and the linear chain structure proposed by Starke is untenable.

View full abstract

Pure samples of three hexavalent iron compounds, K₂FeO₄, SrFeO₄ and BaFeO₄, were prepared and measurements of magnetic susceptibility and Fe⁵⁷ Mössbauer effect were carried out down to 2°K. Those were antiferromagnetic at low temperature and the Néel temperatures of K₂FeO₄ and BaFeO₄ were about 5°K and 10°K respectively. The internal magnetic field extrapolated to 0°K was 140 kOe for K₂FeO₄ and 130 kOe for BaFeO₄. Because the Néel temperature of SrFeO₄ was below 2°K, the internal field was estimated from the spectrum in the presence of an external field (50 kOe). The obtained value was also about 140 kOe and the sign was found to be negative.

View full abstract

A theory of light scattering in a magnetic metal using the spin-dependent electric polarizability is developed and is applied to Raman scattering by magnons in heavy rare earth metals. An important mechanism for one- and two-magnon scatterings arises from the coupling of radiation field with the 4f localized moments via spin-orbit interaction. There are also indirect mechanisms in which electric polarizability of the conduction electrons are modulated by the s–f exchange interaction. Contributions of these mechanisms to the spin-dependent polarizability are estimated. We present calculations of the scattering symmetries and intensities for one- and two-magnon processes in systems with ferro-magnetic, spiral and conical spin structures, with application to Tb and Dy, assuming the first mechanism is predominant. In the cases of spiral and conical structures the magnons with wave vectors ±k₀ and ±2k₀ are excited, where k₀ is the wave vector describing the periodicity of the static spin arrangement.

View full abstract

Multiplication processes of dislocations in thick foils are continuously observed by high-voltage electron microscopy. When an applied stress reaches a certain value, which is lower than the apparent yield stress, some segments of grown-in dislocations existing on a single slip plane become active in proportion to their length. Each of them emits 10∼20 dislocations through the Frank-Read mechanism. Pole-dislocations of them, however, are also moved out with increase of the stress. These processes are closely related to cross-slip. With increase of the stress, main process of multiplication is switched to that of double cross-slip type, whose source number increases exponentially with increasing the stress. This stage is responsible to the apparent yield phenomenon. Besides these, generation of dislocations at stress-concentrated parts, such as voids, crack tips so on, are also continuously observed.

View full abstract

Nisida and Horii have made detailed measurements of the concentration dependence of the far infrared absorption by Sb donors in Ge. A qualitative explanation of these observations is proposed, in which the strain produced by the donors themselves is able to account for the linewidths and asymmetry of the absorption lines in the low concentration range.

View full abstract

Linear thermal expansions along crystallographic axes for NaH₃(SeO₃)₂ and NaD₃(SeO₃)₂, and those along the b axis for the Na(H_1−xD_x)₃(SeO₃)₂ system in the entire range of x were measured in their transition temperature regions.
It is found that the replacement of hydrogen by deuterium shows a large isotope effect in saturated spontaneous strains in the [010] plane, but no isotope effect along the [010] direction. Linear thermal expansions for the crystals of the Na(H_1−xD_x)₃(SeO₃)₂ system in the range 0<x<0.4 show rather complicated behavior due to the existence of three phase transitions. The phase diagram of this system shows unusual isotope effect in the transition temperatures. Present results suggest that there are strong couplings between protons (or deuteron) and lattices of Na⁺ and SeO₃⁻⁻ ions in NaH₃(SeO₃)₂ (or NaD₃(SeO₃)₂).

View full abstract

Some optical properties of GaTe single crystals, such as absorption coefficient, photoconductivity and reflectivity, have been measured. The crystal is usually p-type with carrier density 10¹⁶ cm⁻³, mobility 15 cm²/volt·sec and resistivity 20Ω·cm at room temperature. In the measurement of the photoconductivity, a minimum of the photoresponse corresponding to the strong line structure of absorption is observed and therefore the line structure is interpreted to be due to the formation of excitons. The energy gap and exciton binding energy are deduced from the shape of the absorption curve near the edge. The energy gap is 1.797 eV at 77°K and 1.700 eV at 300°K and the temperature coefficient ∂E_g⁄∂T is found to be −4.35×10⁻⁴eV/°K. The exciton binding energy and the reduced effective mass associated with conduction and valence band are 0.025 eV and 0.089 m₀, respectively. The reflectivity is found to change rapidly at the photon energy corresponding to the exciton absorption.

View full abstract

Formation of interstitial centers in pure and Na⁺- and Li⁺- doped KBr by X-irradiation at LHeT and at LNT is studied. The results are discussed in terms of the dynamic and static interaction of the interstitial centers with monovalent impurities. It is shown that the interstitial centers are stabilized by the association with the monovalent impurities and that the stability of the complex is higher for Li⁺ than for Na⁺. The optical transitions of interstitial centers are discussed.

View full abstract

Reflectivity spectra of NaH₃(SeO₃)₂ crystals were measured form 16 to 400 cm⁻¹ at 300°K and 202°K, and complex dielectric constants were derived using the K. K. dispersion relation. The results suggest that the dielectric dispersions occur around a few tens of cm⁻¹ with a wide distribution of dispersion frequency.

View full abstract

Total ionization cross section of Mg by electron impact has been measured absolutely by the crossed beam technique. Intensity of neutral Mg beam is determined by the deposition method. Mg atoms deposited onto a beam collector are quantitatively analyzed by atomic absorption spectrophotometry. The absolute cross sections at 22.4 eV, 106 eV, 492 eV and 1000 eV are determined to be 9.1, 3.9, 1.7 and 1.0×10⁻¹⁶ cm², respectively. Systematic errors are estimated to be within −15% and +8%. Relative cross section is obtained as a function of electron energy from the threshold to 1130 eV. The results are compared with some experimental results and theoretical calculations by other workers.

View full abstract

Rotational excitation cross sections of H₂⁺ by electron impact are evaluated in the adiabatic approximation from phase-shifts of previous papers based on the method of single center polarized orbitals. In consonance with classically averaged fixed-nuclei cross sections of the previous papers, we find here that the quantitative changes due to polarization and permanent distortion on rotational excitation are also small. However the relative sizes of these two effects are interchanged with permanent distortion here being more important; the reasons for this are easily seen. In the first part of the paper, generalizations of the formulae of the adiabatic theory for a charged molecular target (molecular ion) are given. It is concluded in that case that the adiabatic theory can be made to be accurate down to an energy k²>>(m⁄M)ΔE (rotational). In the case of neutral target molecules it is argued that the lower limit is given by k²≥1.65ΔE (rotational), and that the theory of Gerjuoy and Stein can be used at lower impacting energies.

View full abstract

The floating potential of a probe in a high density seeded plasma is described with the classical electrostatic probe theory extended to include emission. In general, this emission consists of ions, atoms, and electrons. The rate at which these particles are emitted depends on the probe temperature and on its surface coverage by the seed. Since the ion arrival is governed by how the surface floats electrically with respect to the plasma, a coupled situation can exist. The problem in formulated in terms of two-temperature description where plasma electrons retain their temperature as they approach the surface. The theory is developed in general for probes biased to a surface where emission conditions can be known, and then it is specialized to catalytic and noncatalytic surfaces. The noncatalytic situation is correlated with some data for an atmospheric argon plasma seeded with potassium. A computational scheme is used to calculate the equilibrium fluxes from a surface which is absorbing seed.

View full abstract

Ion extraction model for plasma-sheath system from an RF plasma and its equivalent circuit are presented. A qualitative explanation of the energy anomalies is discussed. The energy dispersion of ions under the assumption that the ion velocity is modulated by a time variation of plasma potential, is calculated; that is in good agreement with experiments.

View full abstract

In a very short discharge tube, the oscillation with a frequency of a few kHz appears in the afterglow with a relatively weak magnetic field. The frequency of the observed oscillation is much lower than the ion cyclotron frequency. The critical magnetic field B_c, when the instability sets up, is proportional to the pressure P and B_c⁄P becomes smaller in the shorter tube. The diffusion deviates from the classical value, when the magnetic field exceeds B_c.
The oscillation is theoretically analysed to be due to an instability enhanced by the large axial density gradient. The theory is based on the two fluid model which takes the axial density gradient into account, neglecting the ion and electron inertia terms. The observed frequency, the relation between B_c and P or the tube length, and the relation between P and the oscillation amplitude can be explained by the present theory.

View full abstract

The electron plasma frequency of a plasma depends on the number density, while the Larmor frequency is proportional to the magnetic field. The applied magnetic field is supposed to be so strong that the Larmor frequency is sufficiently larger than the collision frequency. When the considered plasma is very dilute, the plasma frequency is small compared with the Larmor frequency. In such situations, starting from the Vlasov equation, and using a similar expansion procedure to the method due to Chew, Goldberger and Low, the macroscopic equations governing the plasma in the fluid dynamic stage are obtained in the form of two fluid model. Using these equations, the propagation of plane waves is studied and the dispersion relation for a wave propagating in an arbitrary direction is obtained. It is shown that there exist six wave modes.

View full abstract

Magnetohydrodynamic (hereafter called MHD) non-steady Beltrami flow between two infinite parallel walls is discussed with an impressed magnetic field transverse to the walls. Exact solutions of modified Navier-Stokes equations are obtained using both Laplace transform and normal mode methods. Expressions for the induced magnetic field and the skin-friction are also obtained. Numerical values of velocity, skin friction and induced magnetic field are calculated for different values of Hartmann number at different times and the results are tabulated and several conclusions are drawn.

View full abstract

A perturbation method to deal with non-linear waves propagating in a slightly inhomogeneous medium is applied to the physical problems: (1) the sound wave propagating in a duct whose cross-sectional area changes slowly along its length; as special cases, the spherical and the cylindrical waves at large distances from the origin are included. (2) the sound wave propagating through a stratified layer. (3) the hydromagnetic wave across a non-uniform magnetic field; in this case the inhomogeneity is caused by the equilibrium state where the mechanical pressure is in balance with the magnetic one. All these examples are concerned with the case in which a simple wave solution is realized if the medium is homogeneous and characteristics are obtained from those in the homogeneous medium by a local transformation of the coordinate. This transformation shows explicitly that under certain conditions the waves grow due to the inhomogeneities and promote shock formation.

View full abstract

A theoretical analysis is made of the flow of an incompressible non-Newtonian viscous liquid through a straight pipe of circular cross section flowing under a constant pressure gradient. The pipe is rotated about an axis perpendicular to it. Secondary motion is set up due to the interaction between the Coriolis forces and the pressure gradient. Assuming that the angular velocity about the axis of rotation is small, a solution is developed by successive approximation, the first approximation corresponding to the Newtonian flow discussed by Barua. The stream lines in the central plane and the projection of the stream lines on the cross section of the pipe are compared with those of a Newtonian liquid. An expression for the rate of outflow has been obtained.

View full abstract

Perturbation method developed by Asano and Taniuti is extended with respect to (1) the expansion about the steady state, (2) the order of the stretching and (3) additional source terms. The method is applied, as an example, to the propagation of acoustic waves of small but finite amplitude in the steady one-dimensional flow through a duct of varying cross section. The presence of a small external force and an energy supply is also taken into account.

View full abstract

The flow of an electrically conducting gas past a slender body of an arbitrary cross section, in the presence of a crossed magnetic field, is dealt with by the magnetohydrodynamic Stokes approximation. Using a concept of the slender body theory, the perturbation velocity and the induced electric fields are shown to be quasi-two-dimensional. The fields are developed into the power-series of a parameter, Q, defined by the product of the magnetohydrodynamic Reynolds number and the pressure number. It is found that the induced electric field without any space charge remains finite even if the parameter, Q, tends to zero, and that in the case of finite value of Q some space charges appear and the flow becomes rotational.

View full abstract