The experimental studies of ²⁷Al (γ, p) reaction are described. Firstly, this reaction was studied at maximum bremsstrahlung energies E_γ(max)=22, 20 and 15 MeV. The energy spectrum of the product protons showed existence of many groups which were supposed to arise from 26 states of ²⁷Al of energies 9.99≤E_x≤20.4 MeV. Secondly, the existence of these states was examined in the ²⁶Mg(p, p′), (p, p′ γ), (p, n), (p, γ), ²⁵Mg(d, p) and ²⁷Al(p, p′) reactions. The results are consistent with that of the initial photonuclear reactions. Differences of features were found below and in the giant resonance region of ²⁷Al. The integrated cross sections and the γ-ray widths for the ground state transitions in this reaction were estimated numerically.

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Targets of separated isotopes ¹⁸²W and ¹⁸³W were bombarded with a 15 MeV deuteron beam, and outgoing protons were analyzed with a broad range magnetic spectrograph and nuclear emulsion plates. Empirical single-particle cross sections were determined from the observed cross sections and angular distributions of the reactions leading to low-lying levels of ¹⁸³W. Observed cross sections and angular distributions for the levels of ¹⁸⁴W were compared with the cross sections which were obtained by using the above empirical single-particle cross sections and the spectroscopic factors calculated from the pairing theory. For the members of the ground state rotational band and the γ-vibrational band in ¹⁸⁴W excellent agreements were obtained. Reasonably good agreements were found for six higher levels below 1800 keV, if they were interpreted as the rotational members of possible two-quasiparticle states. For the first two levels of the lowest excited K=0⁺ band cross sections were determined.

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Characters of the noise associated with relative scattering measurement in nuclear emulsions are studied as functions of cell size and of track separation in depth of emulsion for three stacks having independent histories. It is found that the noise is divided into two characteristic types according to cell size. For short cell size, the noise is random Gaussian type and for long cell size more than about 3 mm, essentially, ordinary C or S shape. Although the track to track separation in depth is in usual limited severely in the relative scattering, it is shown that this limitation can be removed by cancelling the noise, in such a way that for short cell size is applied the subtraction method between the second and third order differences and for long cell size ordinary higher order difference method. This increases greatly the applicability of the relative scattering method.

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Theories of Mayer and Lebowitz-Percus are examined which treat the N⁻¹ dependence of the distribution functions in the canonical ensemble consisting of the systems with the particle number N. It is found that the expressions obtained by Lebowitz and Percus are more accurate than Mayer’s ones. The same long-range correlations of the distribution functions are given by both the theories.

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Temperature dependence of magnon sideband with respect to the intensity, shift and broadening is studied theoretically in the entire temperature range by using the moment expansion method. The assumption of the Néel state for the ground state of the antiferromagnets is reasonable for intensity and shift but is incapable of explaining the magnitude of the width.
Numerical calculations are carried out for ⁶A_1g→⁴A_1g, ⁴E_g transition of RbMnF₃ by means of the random phase decoupling approximation for spin correlation functions and the results are presented. The results agree with those of the spin wave theory at low temperatures. At the high temperature limit, both the intensity and shift also agree with those given by the pair spectra theory. The effect of exciton transfer is also considered. The numerical result of the shift is compared with experiments.

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The temperature-dependent magnon energies and magnon sidebands in MnS have been studied theoretically by the spin wave approximation including magnon-magnon interaction and neglecting exciton-magnon interaction. Results found are: (1) the temperature renormalization factor for magnon energies depends strongly on magnon wavevector and is different from that for the sublattice magnetization; (2) the line shape is insensitive to temperature, and the peak position, which corresponds to the magnon energy at k=1.2π[1,1,0]⁄a, shifts slowly with temperature; (3) the integrated intensity of the cold band is almost constant at low temperatures but decreases slightly with increasing temperature in contrast to a rapid increase predicted from the free spin wave theory. For the hot band, the intensity increases more slowly than predicted from the free spin wave theory. The total intensity increases gradually with temperature. The sublattice magnetization, the peak position, and the integrated intensity as functions of temperature are compared with observed results.

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In order to investigate the cause of anomalous properties of the γ-phase iron-nickel alloys with Invar compositions, the Mössbauer effect spectra of these alloys were measured as a function of temperature. Especially, the influences of phase mixture (α+γ), cold-work and external magnetic field were examined. From these measurements, it was concluded that there exist transition states between the α and γ phases, and they cause a diversity of hyperfine fields in the Invar-type alloy. Many hyperfine fields thus produced make the Invar alloy an assembly of various magnetic transition points, which, as a result, gives rise to the anomalies of physical properties.

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It is shown that the flow stress and the stress relaxation of Ni and Ni–Co alloy single crystals in a plastic region are affected significantly by applying an alternating magnetic field. This “magneto-plastic effect” can be interpreted in terms of a concept that oscillating magnetic domain walls give a force on the dislocation. The magnitude of the shear stress drop caused by this effect depends upon the plastic strain, total strain rate, magnetostriction constants, total volume swept out by the oscillating domain walls and frequency of the alternating magnetic field. The activation volume of the glide dislocation in thermally activated process is reduced to about one half of its original value by this effect. Further, on the basis of the experimental results obtained through this effect, a role of the short range stress to the flow stress is discussed in some detail.

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Cr₂As is known as an antiferromagnet with the Néel temperature T_N of 393 K. Its magnetic structure is determined by neutron diffraction by using single crystals as well as powdered samples. The magnetic structure obtained has such a symmetry that any isotropic exchange interaction vanishes between Cr(I) and Cr(II) sublattices, while dipole-dipole like interactions remain finite between them. Values of 0.40±0.08 μ_B and 1.34±0.06 μ_B are obtained for the magnetic moments of Cr(I) and Cr(II) respectively. Contrary to a previous study, it is observed that the magnetizations of Cr(I) and Cr(II) sublattices vanish at the same temperature, T_N. This inconsistency is considered to come from the mis-indexing of lines which are actually due to Cr₂O₃ contamination in the previous work.

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Defect clusters are observed to form in aluminum during examination at about 20°C in a high voltage electron microscope operating at 1000 kV with a beam current of 0.1 μA in a 5 μm diameter spot. As the electron dose increased, the clusters grow into resolvable dislocation loops. The defect clusters are identified as vacancy loops of Frank type. When the temperature is raised gradually to 70°C during electron irradiation, defect clusters grow into larger loops and eventually disappear with 70°C irradiation. Furthermore, no electron damage is observed in the specimen irradiated at 70°C without previous 20°C irradiation. In a quenched specimen, production rate of the defect clusters is larger compared with an annealed specimen and large quenched-in loops are found to shrink during 20°C irradiation. The damage rate is discussed in relation to nucleation and growth of the loops under vacancy supersaturated environment.

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Ordered phases in the Co–Pd alloy system are studied by electron diffraction, using evaporated single crystal films of the alloys with Pd content extending from 20 to 100 at.%.
Two types of the ordered states are found in this system; one is the Ll₂ type (Cu₃Au type) and exists over the range of composition of Pd between 60 and 90 at.%. The temperature of order-disorder transition is 830°C for the 80 at.% Pd alloy. The other has the structure of Ll₀ type (CuAuI type) and exists within a narrow region of composition around CoPd. This phase is accompanied by two-phase regions over fairly wide ranges at both sides of it. The transition temperature is estimated to be higher than 850°C.

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The moving domain caused by double injection was detected in n-type Ge at high electric field. This phenomenon is closely related to the current instability observed. It was found that the period of oscillation is determined by the transit time of the density perturbation through a sample. The dependence of the oscillation frequency on current density is explained by the variation of the ambipolar drift velocity. The transit time observed is in qualitative agreement with the theoretical results calculated from the ambipolar drift velocity.

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Effect of intense far-infrared radiation on magneto-absorption, photoconduction and photo-Hall effect on n-InSb containing 2.5×10¹³ cm⁻³ electrons were investigated at liquid helium temperatures by using an HCN laser. Saturation of impurity cyclotron resonance (ICR) and enhancement of conduction-electron cyclotron resonance (CCR) with the radiation intensity were found. This can be explained by the effect of relaxation processes where the electrons excited to impurity state (010) drop to Landau state N=0 and accumulate there. The relaxation time for the ICR saturation was obtained as 7×10⁻⁹ sec at 1.7 K.
The photoconductivity and the photo-Hall effect were analysed on the basis of the two-band conduction model. The result demonstrates that with an increase of the radiation intensity the number of conduction electrons increases consistently with the proposed relaxation processes, and in addition the impurity-band mobility also increases.

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An experimental arrangement for determining nonlinear indices of dielectric constant by means of second harmonic detection which was favorable to avoid the influence of space charge was devised. The temperature dependence of the nonlinearity of the dielectric constant in the vicinity of the Curie point was measured for ferroelectric triglycine sulfate. The result shows that (∂²P⁄∂E²)₀=const×(ΔT)^γ₁₄ with γ₁₄=−(2.4±0.2) below the Curie temperature, which is in good agreement with the prediction in the mean field theory.

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The optical spectra of tetragonal HgI₂ single crystals were investigated at 4.2 K and 79 K in 2∼6 eV region of photon energy. The main part of the dichroic optical spectra is well described by the optical transition from three p-like valence bands, which are split due to spin orbit interaction and crystal field perturbation, to an s-like conduction band. The optical structures, which seem to be due to exciton series, were observed in the fundamental absorption edge for an ordinary light. The tail part of the absorption edge was well expressed by Urbach Rule.

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The velocity-field characteristic in vapour-grown n-GaAs has been measured between 300 K and 4.2 K by using a microwave heating technique. The threshold field decreases with decreasing temperature on the contrary to the results by Ruch and Kino; this behaviour is in good agreement with the theory by Ruch and Fawcett. The negative differential mobility behaves in a similar way to the low field mobility between 300 K and 4.2 K. At temperatures below about 60 K, the electron mobility at fields up to 1 kV/cm becomes larger in magnitude than the low-field value because of decrease in ionized impurity scattering in hot electron region. The velocity-field relation up to 1 kV/cm is well explained in terms of polar optical phonon and ionized impurity scattering.

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Detailed structural studies of HCl single crystal were performed by X-ray and neutron diffraction experiments. A face-centered cubic lattice with a twelve-fold disordered orientation of HCl molecules was found only above 120 K. Below 120 K, the molecules form hydrogen bonded zigzag chains and a synthetic twin structure of an orthorhombic lattice with the (101) twin boundary is realized. No appreciable change of the crystal structure was seen in the diffraction experiments at the transition point 98 K. The mechanism of the phase transition can be explained by considering a fluctuation of chains and molecular flippings.

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Photoconductivity in n-InSb irradiated with an intense light beam from a Q-switched CO₂ laser was measured in transverse magnetic fields at temperatures from 175 K to 17 K. In zero or low magnetic fields normal photoconductivity was always observed. As the magnetic field was increased, however, the photoconductivity decreased in magnitude and finally changed the sign from positive to negative, for example, in a magnetic field exceeding several hundreds gauss at 90 K. This anomalous phenomenon was not observed in longitudinal magnetic fields. It was confirmed from the measurement of photo-Hall effect that the negative photoconductivity is not due to a decrease in electron concentration. A qualitative speculation in terms of the two-carrier transverse magnetoresistance is presented.

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The paraelectric-to-ferroelectric phase transformation of (NH₄)₂Cd₂(SO₄)₃ is conjectured to be caused by an instability of three degenerate pairs of conjugate lattice vibration modes with a wave length such that the condensation of each pair of conjugate waves should triple the primitive unit cell. This was explained in a previous paper with a model in which the spontaneous polarization vector arises parallel to the wave normal of the condensed soft waves. Reality of this model, however, seems difficult because of a certain severe requirement for its ferroelectricity. The present paper proposes a model in which P_s arises perpendicular to the wave normal. This model implies no such severe requirement.

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Luminescence due to Br⁻-ions in NaCl has been investigated at liquid nitrogen temperature by varying the amount of Br⁻-ions from 1×10⁻³ to 1.4×10⁻² mole fraction. Two emission bands, having their maxima at about 4.0 eV and 5.15 eV, were observed with UV-light excitation. The 4.0 eV luminescence is known to enhance linearly with increasing Br⁻-ion concentration. Ratio of the intensity of the 5.15 ev luminescence to that of the 4.0 eV luminescence was found to vary in proportion to the Br⁻-ion concentration, suggesting that the intensity of the 5.15 eV luminescence varies with square of Br⁻-ions concentration. This means that the 5.15 eV luminescence is caused by (Br⁻)₂-center. Presence of the absorption band of (Br⁻)₂-center was also confirmed in the low energy side of the absorption band due to Br⁻-ion monomer.

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The electromotive force and its temperature-dependence of fused salts of the ThCl₄–NaCl system were measured with a Th(s)/ThCl₄–NaCl(l)/Cl₂(g) cell using highly purified ThCl₄(ThCl₄ 0.22–0.70 mole fraction, 600°–750°C). To discuss the formation and existence of complex ion in the melts, the equation of excess stability d\barF₁^E⁄d(1−N₁)², where N₁ is the mole fraction of ThCl₄ and \barF₁^E the excess partial molar free energy of ThCl₄, derived by Darken was adopted. Curves of the excess stability plotted against N₁ show a maximum at around N₁=0.35 corresponding to the congruently melting compound Na₂ThCl₆.
Meanwhile, plots of the equivalent conductivity and the isotherms, calculated from the previously reported values against N₁ revealed a large negative deviation from the additivity at N₁=0.33(550°C–750°C). From these both results the existence of the anionic complex ion [ThCl₆]²⁻ in the fused state was inferred.

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The X-ray critical scattering in NiCr₂O₄ in the vicinity of its Jahn-Teller phase transition has been investigated in order to clarify the nature of the interaction between local distortions. The results are summarized as follows:
(i) The critical scattering due to correlation of local distortions has been observed up to 100 K above the transition temperature.
(ii) Relative intensities of the critical scattering around various reciprocal lattice points confirm that the correlation of local distortions propagates through acoustic type displacement field, showing that the indirect pair interaction via strain field is dominant to cause Jahn-Teller phase transition in NiCr₂O₄.
(iii) The characteristics of the anisotropy of the critical scattering show a singularity at k=0, indicating that the interaction is of long range.
The above results are in very good agreement with the theory recently developed by Kataoka and Kanamori.

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Host lattice dependences of luminescence spectra and relaxation properties of Tb³⁺ are described. Reduced matrix elements relevant to the transitions are calculated and compared with observations. The spectra and the decay times of the ⁵D₄→⁷F_J transitions are in qualitative agreement with the calculations. The electric-dipole transition of ⁵D₄→⁷F₅ has the largest probability in the ⁵D₄→⁷F_J emission transitions within the framework of the Judd-Ofelt approximation. When the crystal field acting on Tb³⁺ is very strong, the intensity of ⁵D₄→⁷F₃ can become comparable to that of ⁵D₄→⁷F₅. Magnetic-dipole transitions always have the largest probability for ⁵D₄→⁷F₅. Spontaneous multiphonon relaxation of ⁵D₃→⁵D₄ is sometimes a dominant decay mechanism of the ⁵D₃ state. The observed multiphonon relaxation rates are ∼2×10² in YPO₄-, ∼8×10³ in YBO₃- and ∼2×10⁴ in ScBO₃-groups in units of sec⁻¹.

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Behavior of the optically pumped atoms in the oscillating rf field is analized classically in terms of the macroscopic magnetization, in the case that the static magnetic field has components both parallel and perpendicular to the rf field. The theory predicts that the g-factor is modified by the rf field when the Hanle effect and the parametric resonance take place, and that the effect makes its appearance in the variation of width and maxima of lines of the Hanle effect and the parametric resonance. The modification of the g-factor is also derived by the quantum mechanical treatment.
The theoretical predictions are quantitatively verified by the experiments with cesium vapor.

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A new method is proposed for determining the magnitude of the coupling constant, the asymmetry parameter and the orientation of the principal axes of the electric field gradient tensor at the site of a quadrupole nucleus with half integral spin. A function is constructed from the first order splitting of the nuclear quadrupole resonance absorption line produced by a small magnetic field. The parameters of the EFGT are determined from the behaviour of this function for rotation of the crystal around certain axes. A goniometer has been constructed for effecting these rotations and measurement have been made on a single crystal of Ba(ClO₃)₂, H₂O at the site of chlorine nuclei. It has been found that the chlorines in the unit lattice can be grouped in two sets with two different EFGT having the same value of eqQ=58.6873±.0001 MHz and η=0.027±.007 but different orientations of the principal axes.

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It is theoretically shown that the rate constant for reaction of electron transfer from highly excited atoms A^** to polyatomic molecules B,
A^**+B→A⁺+B⁻, (1)
at thermal velocities is equal to that of non-dissociative thermal electron capture by the molecules B,
e+B→B⁻, (2)
based on the assumption that the negative ion formed in reaction (1) is the same species as that formed in reaction (2). The result obtained is in reasonable agreement with experimental data for reaction (1) between Ar and SF₆. From both the present study of reaction (1) and the previous work on the ionization of the highly excited atoms by collision with polar molecules (M. Matsuzawa; J. chem. Phys. 55 (1971) 2685), it can be concluded that knowledge of inelastic scattering of a slow electron by molecules is very useful for the understanding of some kind of reactions of the highly excited atoms with these molecules.

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The ion density of a hydrogen plasma is determined from attenuation of the hydrogen atom beam mainly due to the resonant charge-exchange reaction between protons and hydrogen atoms. Then the measurable density is from 10¹³ to 10¹⁵ cm⁻³. It is extended from 10⁹ to 10¹⁵ cm⁻³ by using a potassium atom beam. The electron temperature from 20 to 150 eV is measured with an argon atom beam. Some results by these methods are compared with those by other diagnostics.

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Parametric excitations of ion plasma oscillations are investigated by using a simple model based on the modulation of ion density in the uniform electron background. This model is useful to calculate the higher order nonlinear terms, and gives a good interpretation to the new nonlinear phenomena observed in a mercury vapour plasma without magnetic field. The nonlinear effects observed are; (1) the frequency shift and the amplitude increase of the resonant oscillations with increasing of pumping power, (2) the existence of the resonance frequency region, and (3) the asymmetrical parametric excitation with hysteresis.

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The electrical conductivity of xenon plasma produced by shock waves was measured by means of a conductivity probe, similar to that described by Lin, Resler and Kantrowitz. Measurements were made for initial xenon pressures P₁ of 1–10 Torr. The shock Mach numbers M_s ranged from 8.4 to 24.5. The maximum electrical conductivity agreed with theoretical values within a factor of two. For low shock Mach numbers, the decrease in electrical conductivity and the decrease in continuum emission intensity were much faster than the theoretical decreases based on continuum radiation loss. These results indicate that line radiation losses cannot be disregarded for low shock Mach numbers. With increasing the shock Mach numbers, it was shown that e. g. at P₁=2 Torr and M_s\gtrsim20, two observed decreases could be almost explained by continuum radiation loss alone.

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Cyclotron instabilities in a finite plasma pressure is investigated without use of the electrostatic approximation. A “ring” distribution is taken for the ion velocity distribution function and electron is assumed cold. It is shown that the coupling between a quasi-electrostatic wave and an extraordinary ion cyclotron wave causes an instability with small growth rate. Finite plasma pressure has a stabilizing effect on the quasi-electrostatic instability and reduces the growth rate.

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Numerical studies of steady, one-dimensional, quasi-shock waves in a collisionless plasma are made for the case where the shock waves are propagating along a uniform magnetic field. It is supposed that the flows of ions and electrons ahead of the shock wave consist of two cold streams respectively, which have different velocities from each other. Numerical computations are carried out using fluid equations for the streams and Maxwell’s equations for the electromagnetic field. Behind the wave front the plasma and magnetic field oscillate rather irregularly about mean values, which are different from the values ahead of the wave front.

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Experimental studies were made on the motion of vortex rings ejected from a circular or a lenticular orifice into water. The vortex rings were made visible by fine grains of tin made by electrolysis, and photographs were taken. The diameters and the traveling velocities of the vortex rings were determined from these photographs. There is a favorable range of impulse to produce the stable vortex ring. The traveling velocity of the vortex ring is composed of the velocity of the jet flow and the self-induced velocity of the vortex; the former decays rather rapidly and the latter decreases slowly in time as \sqrtνt, where t is the time and ν is the kinematic viscosity of water. The vortex ring ejected from a lenticular orifice changes its shape intermittently, and the period of deformation is prolonged continually, while the traveling distance during one period is nearly constant.

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A stability conditions is obtained for a general configuration of a high intensity neutralized electron beam and is applied to cylindrical beam systems. Neutralized cylindrical beam systems are stable if the total beam current sufficiently exceeds 10⁴ ampere.

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Nuclear Magnetic Resonance (NMR) of Co⁵⁹ has been investigated in the three metamagnetic phases of CoCl₂·2H₂O at liquid helium temperatures. The hyperfine field in zero external field at 0 K was found to be +421.1±0.4 kOe, which agrees well with the calculated value where the orbital contribution is dominant. When the external field H₀ was applied parallel to b-axis, the interaction of the nucleus with the electronic moment induced by H₀ was observed to be about 0.29 times the direct coupling with the external field. The jumps of the hyperfine field were also observed as the manifestation of the changes of the exchange interactions of Co²⁺ spin with adjacent linear chains. The most striking feature of the data is the effects of the spin reduction of 0.1∼1% depending on H₀ caused by the magnon bound states in an approximate Ising system to CoCl₂·2H₂O.

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