Using a stilbene scintillation detector, the angular distributions of fast photoneutrons of energies greater than two bias values of 7.4 MeV and 8.7 MeV were measured for Pb, Bi and Ta at 25.5 MeV end point energy of the bremsstrahlung. For Pb and Bi, the angular distributions were found to be asymmetric about 90 degrees with respect to the gamma-ray beam axis and were strongly peaked in a forward direction, but in the case of Ta not so obviously.
The angular distributions were fitted to W(θ)=A+Bsin²θ+Ccosθ, using a least squares analysis. The present experiment indicates that, in the high energy region of the (γ, n) spectrum, C/A increases with the detecting threshold energy for neutrons and on the otherwise B/A decreases with the energy.

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One of the major causes for the breakdown of the effective mass theory of shallow impurity states in semiconductors is the rapid variation of the potential in the impurity core region. A formalism is developed for treating this breakdown and then applied to the ground state of donor impurities in silicon in the following cases: 1) a simple coulomb potential; 2) potentials that account both for the spatial dependence of the dielectric constant and for the difference between the charge distributions of the core of the impurity atom and the silicon atom it replaces for P, As, and Sb impurities. It is shown that the breakdown is negligible for a coulomb potential and for P impurities, but significant for As and Sb impurities.

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NMR signals of the potassium in KH₂PO₄ were detected by means of the double resonance technique in the rotating reference frame, and the electric quadrupole coupling constants and associated parameters were determined in the paraelectric (290°K) and ferroelectric (77°K) phases. At 290°K, the electric field gradient at the site of the potassium is axially symmetric (η=0) and |eQq⁄h|=1.68 MHz for K³⁹. At 77°K, |eQq⁄h|=1.479 MHz for K³⁹ and 1.796 MHz for K⁴¹ with the asymmetry parameter η=0.696. The major principal axis of the electric field gradient tensor coincided with the Z(c)-axis in both phases. The values of the electric field gradient were calculated by using point charge model in both paraelectric and ferroelectric phases and compared with the experimental ones.

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The temperature dependences of electrical resistivity and thermal expansion were measured for face-centered cubic Fe₆₅(Ni_1−xMn_x)₃₅ ternary alloys. The electrical resistivity of ferromagnetic alloys (x<0.3) decreases with increasing magnetic ordering. In contrast to this, the resistivity of antiferromagnetic alloys (x>0.3) increases below the Néel temperature and shows a resistance minimum. These behaviors are explained in terms of the magnetic scattering by induced moments below the magnetic ordering temperature. The expansion of volume due to the magnetic ordering was observed in both ferro- and antiferromagnetic alloys. To explain the volume expansion by the magnetic ordering, a new mechanism of magnetovolume effect based on the change of cohesive energy due to the spin polarization in 3d band is proposed.

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The energies of the localized magnons around an impurity spin in a linear chain of ferromagnet in the case of S=S′=1⁄2 were calculated, where S and S′ are the magnitude of the host and impurity spin, respectively. Two types of the localized magnons were obtained; one is the s type which is the energy of the ground state when the impurity spin couples antiferromagnetically with its nearest neighboring host spins, and it is already obtained by Wang and Callen, and the other is the p type. An approximate method to get the ground state for S′≥1 is proposed. The energies of the two localized magnons were calculated by solving approximately the Dyson equation for Green functions. The spin wave method by Ishii, Kanamori and Nakamura is discussed.

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Paramagnetic resonance of Cr³⁺ spins in TiO₂ single crystals were investigated in detail and two sets of weak absorption signals were observed in addition to usual Cr³⁺ resonance lines. By analysing both the directions of the local symmetry axes and the magnitude of spin Hamiltonian parameters D and E of these two groups I and II, it is concluded that these resonances come from substitutional Cr³⁺ spins coupled with the second and the third neighbor oxygen vacancies respectively. Spin Hamiltonian parameters determined for each group are given by
Group I, g=1.98±0.005, D=5.10±0.10 GHz, E=−1.41±0.05 GHz
Group II, g=1.98±0.005, D=−16.5±1.0 GHz, E=−3.9±0.5 GHz.

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Electron spin resonance study has been carried out on dilute copper manganese alloys over a temperature range from 1.8°K to 300°K. The relaxation rate is found to increase linearly with temperature over the temperature range where the susceptibility obeys Curie-Weiss’ law. The temperature gradient of the relaxation rate has a concentration independent value of 0.96×10⁸ (sec.⁻¹, deg.⁻¹) for samples with manganese concentration between 0.03 and 0.3 atomic percent in the temperature range below 20°K. Above 0.3 atomic percent, it decreases to a value of 0.34×10⁸ (sec.⁻¹, deg.⁻¹) for the sample with 5.2 atomic percent manganese. The g-value of the localized spin is 2.010±0.005. It is shown that the experimental results for low concentration samples are well understood in terms of s–d interaction model. According to this model, observed relaxation rate should depend sensitively on the relaxation rate of conduction electron spins as observed, and this relaxation rate was determined as 4.6×10¹³ c (sec.⁻¹) where c is the manganese concentration.

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Calculations of the band structure of Bi₂Te₃ are carried out by means of a pseudopotential approach. The pseudopotential used in the calculation is the model potential of Abarenkov, Animalu and Heine. The spin-orbit term is included from the start. The inclusion of the spin-orbit term serves to avoid band overlap throughout the Brillouin zone. The secular equations derived from the matrices of the pseudopotential Hamiltonian are solved at 7 symmetry points and along lines between the symmetry points and also at points on the reflection plane near the extrema of the conduction and the valence bands. The resulting band structure is consistent with galvanomagnetic experiments, and band parameters agree with one of the two sets presented by Efimova et al. on the basis of an analysis of their galvanomagnetic experiment.

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Temperature dependences of the electrical resistivities due to the s–f exchange interaction and the quadrupole scattering are calculated for Pr and Nd of the hcp, fcc and the La-type crystal structures. The magnetic states of 4f electrons are determined from other experimental results. In general we get reasonable agreement between the calculation and the experiment both in the absolute values and in the temperature dependences. The sharp discrepancy on the temperature dependences of the resistivities for the two different samples of Pr is attributed on the basis of the present calculation to the possibility that the old sample is of hcp rich and the new sample fcc rich.

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An investigation of photo and thermochemical reactions in additively colored and subsequently annealed (at 550°C) single crystals of ‘Pure’ Optovac NaCl crystals has been made and utilising the colloid evolution as a criterion our crystals could be classified as: (1) Those which revealed the colloids and those which did not; (2) Those which revealed the colloids and also exhibited the coexistence of F centers and colloids above about 250°C.
Prolonged annealing revealed that the colloids are stable up to about 250°C and that they became unstable above this temperature. Our results in this regard are compared with the results of Doyle on KCl.
It is proposed that the diffusion of neutral F centers via the vacancy mechanism results in their clustering and when the cluster attains a critical size the F center electrons enter the valence levels of the alkali ions to form metal atoms of the colloids. Our results, as well as the results in the literature, are discussed in the light of our tentative mechanism.

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Deformation potential constants of wurtzite type CdS are calculated by the OPW method. The results are as follows:
D₁¹−D₁⁶=−6.2 eV and D₂¹−D₂⁶=−5.2 eV.
The experimental values to be compared with these are respectively
C₁+C₃⁄2=−3.05±0.5 eV and C₂+C₄⁄2=−2.95±0.5 eV.

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The electron spin resonance absorption of Cu²⁺ ion doped in KDP single crystals were studied both in paraelectric and ferroelectric phases. There are two kinds of Cu²⁺ sites in the crystals. It is inferred from the angular dependence of the ESR spectrum that one site is the potassium lattice site for which one of the eight nearest protons is missing, and the other is the potassium lattice site with which a potassium vacancy is associated at one of the nearest sites. The intensity of the ESR absorption abruptly changed when passing through the Curie temperature. This is accounted for as being caused by the abrupt change of the dielectric constant for microwave frequency. The effect of the application of electric field on the ESR spectrum was studied in the ferroelectric phase. The direct evidence for domain switching is obtained by the reversal of the polarity of the field.

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ESR measurements of Fe³⁺ in ZnO were used to determine the g shift and to compare the data with a theory proposed by Watanabe. The results agree very well with the assumed molecular cluster model.

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Dynamical behaviors of the soft mode in displacive-type ferroelectrics such as SrTiO₃ and BaTiO₃ are studied theoretically. (1) It is pointed out from the irreversible thermodynamical view point that the critical slowing-down appears directly through frequency, and not directly through damping as in order-disorder phenomena and in magnetic systems. (2) The well-known Lyddane-Sachs-Teller and Cochran-Kurosawa relations for the uniform mode are generalized on the quantum-statistical basis to Ω_k=\sqrte²⁄Mχ_k, where Ω_k is the frequency of the soft mode with wave vector k, e the effective charge on an ion, M the reduced mass of positive and negative ions, χ_k the wave length dependent electric susceptibility. (3) The damping constant Γ_k is calculated explicitly, whereby the neutron experiments in SrTiO₃, KTaO₃ and BaTiO₃ due to Cowley, and Shirane et al. are explained. (4) An anomalous increase in Γ_k near the paraelectric Curie point is predicted together with a characteristic behavior of SrTiO₃ from others.

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The low frequency dielectric constant of thiourea was measured along the b-direction in the temperature region from 25°C to −120°C at various hydrostatic pressure up to 7 kbar. The pressure-temperature phase diagram was obtained. The initial pressure coefficients for the V-IV transition temperature (−72.0°C), the IV-III transition temperature (−94.0°C), the III-II transition temperature (−96.8°C) and for the II-I transition temperature (−103.0°C) are −19±2°C kbar⁻¹, −34±1°C kbar⁻¹, −31±1°C kbar⁻¹ and −26±1°C kbar, respectively. the V-VI transition pressure, which is 3.3 kbar at room temperature, decreases with lowering temperature. The phase VI is not identical with any of low temperature ferroelectric phases.

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The dynamical behavior of the acoustic mode in displacive-type ferroelectrics such as BaTiO₃ and SrTiO₃ is studied theoretically. The phenomenological theory of sound attenuation near the phase transition point due to Landau and Khalatnikov is extended to the system in which kinetic energy plays an essential role, so as to be applicable to displacive-type ferroelectrics. The nature implied in the phenomenological theory is examined. The dependence of the attenuation constant and the velocity change of sound upon temperature and wave number is explicitly calculated on the quantum-statistical basis by employing the Silverman Hamiltonian. Thereby the occurrence of anomalies in both the attenuation constant and sound velocity near the Curie points is predicted.

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Quenching experiments are performed with pure impure crystals of Cu₂O, the latter of which contained small quantities of Zn, Ni and Ag. As regards the impure crystal quenched from 950°C to room temperature, all absorption lines appearing in the yellow and the green region of its spectrum taken at 77°K shift to red. The Ag-mingled crystal shows that it is much larger in line-shift than the others, whereas it reveals very small line-shifts when slowly cooled within the above limits of temperature. The large shift is inferred to be due to numerous “complexes” which consist of Ag⁺-ions and Cu⁺-ion vacancies. As to the pure crystal rapidly cooled, its absorption spectra display slight line-shifts, sharp lines about the yellow region when observed at 4.2°K and disturbed lines of absorption in the green series, while normal lines in the yellow, their interpretations being examined.

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In the luminescence spectra of the ⁵D₀→⁷F₁ transition of Y₂O₂S:Eu³⁺, satellite lines separated from the main lines by several cm⁻¹ were observed. Under the excitation by 365 mμ radiation, the intensity of the main line increases linearly with the concentration of Eu³⁺, whereas that of the satellite lines increases as the 1.36 th power of the concentration. When Gd³⁺ is codoped in Y₂O₂S:Eu³⁺ keeping the concentration of Eu³⁺ constant, the intensity of the satellite lines relative to the main line increases with the concentration of Gd³⁺. It is concluded that the satellite lines originate from the splitting and shift of the crystalline-field components resulting from a slight lattice distortion around a pair of Eu³⁺ ions or that of an Eu³⁺ ion and a Gd³⁺ ion which occupy two nearest cation sites.

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Several states of dislocations in nominally pure NaF single crystals are identified by means of two different techniques. The electrolytic coloration is caused by formation of metal Na colloidal particles, which decorate dislocations in the NaF. The chemical etchings, with two different etchants, reveal the dislocations of different characteristics. The two techniques are proposed as the methods for definite observation of the dislocations. The phenomena related to slip, climb and precipitation in the early stage are discussed in connection with the observed dislocations.

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It is observed that the tuning curves of some pulsed laser oscillations with D₂O molecules are subject to a remarkable periodic modulation in the presence of interaction with other simultaneous laser oscillations. Cascade or competitive correlations are found in the following pairs of laser lines: 33.90 and 74.49 μm, 35.07 and 73.31 μm, 36.31 and 71.95 μm, 61.20 and 71.95 μm, 61.20 and 56.82 μm, 72.20 and 218.5 μm and 73.31 and 84.27 μm. Some characteristics relating to a coupled laser transition are discussed.

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Singlet exciton band structures in single stranded homogeneous polynucleotides have been determined within the framework of Frenkel exciton model without or with interband configuration mixing. Intermonomer interactions are taken into account to a distance of the order of 20Å using the best available π-electron molecular orbitals obtained by us in the previous study. Configuration mixing between lowest nine exciton bands is taken into account explicitly. Mixing process seems to be very important to determine reliable band widths, especially in poly A. Obtained band widths are 0.64 eV in poly A, 0.34 eV in poly U, 0.55 eV in poly G and 0.26 eV in poly C respectively without configuration mixing and 0.25 eV in poly A, 0.34 eV in poly U, 0.49 eV in poly G and 0.23 eV in poly C respectively with configuration mixing. In poly A and poly U the absorption maximum corresponding to the lowest excitation slightly shifts to the short wave length side from that of monomer. On the contrary, appreciable red shifts can be found in poly G and poly C.

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Deviations from pairwise additivity of dispersion energies between two parallel linear chains and between two parallel square lattices (for the latter, an asymptotic form at large separation) are calculated with a Drude (harmonic oscillator) model. In the case of normal paraffin crystal the deviation is practically negligible in the neighborhood of the equilibrium separation on the contrary to a conclusion by Zwanzig. The fact may be a reason why the assumption of pairwise additivity has been successfully applied to paraffin crystal and graphite lattice.

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Simultaneous integro-differential equations which are derived by the coupled Hartree-Fock approximation are solved self-consistently. By use of the solutions, the dipole polarizabilities and the shielding factors of Ne, Mg and Ar atoms are calculated. The obtained values of the polarizability of these atoms are 0.3494 ų, 12.04 ų and 1.570 ų respectively (experimental values are 0.395 ų, 7.0±1.8∼7.4±1.8 ų and 1.642 ų respectively). The dipole shielding factors of these atoms are 0.9994, 1.002 and 1.014 respectively, and agree with the exact theoretical value 1.0 within 1%.

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Time rates of growing and damping of resistive instability in gaseous plasma in the crossed electric and magnetic fields are obtained experimentally. The discharge tube used has a coaxial cylindrical configuration with a grid, and works in the state of “anode glow mode”. The gas used is Ne, Ar and Hg. The damping rate is measured by means of an external excitation of damping waves by supplying a rectangular pulse to the grid. The growth rate is obtained by an observation of the transient of self-excitation of waves by abrupt change of the magnetic field strength beyond the critical field. Those experimental results are compared with those obtained theoretically using equations of three component fluid model.

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PIG discharges with uniform magnetic field configuration and Divertor type field configuration are studied. Low frequency fluctuations in the plasma column are observed by a Langmuir probe and two photo-transisters. In the case of uniform field configuration, the frequencies of fluctuation agree well with the theory by Hoh and Simon. In the case of Divertor type field configuration, the amplitude of fluctuation is small compared with that for uniform field configuration.
Plasma parameters (space potential, particle density and electron temperature) are measured for both magnetic field configurations. The most remarkable difference between two types of field configurations exists in radial electric field intensity. In a uniform configuration, the radial electric field E_r is about 3–4 V/cm. Whereas in a Divertor type field configuration, E_r is only 0.2 V/cm or less. This small E_r results in a rather quiescent PIG discharge in a Divertor type field configuration.

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In a linear z-pinch discharge of helium, the continuum emission at the maximum contraction of the plasma and some forbidden lines during the succeeding period of a few μsec were observed at the initial gas pressure of 6.0 Torr. At the maximum contraction the plasma was found to be a black body in the direction through the axis of the discharge tube and a gray body in the direction perpendicular to the axis. From the intensity of continuum and optical thickness the temperature and the electron density have been determined to be (1.5±0.2)×10⁴°K and 5∼7×10¹⁸ cm⁻³, respectively. The intensity ratios of the forbidden lines to the allowed ones as well as their shifts were measured in n ³L–2³P series. From these results it has been proved that the electron density of the plasma changes from 1 to 0.1×10¹⁸ cm⁻³ in a few μsec after the maximum contraction.

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The motion of the air bubble, produced during Taylor instability of superposed fluids in a cylindrical tube is studied. The effects of surface tension and curvature of the interface are taken into account in the analysis which includes the non-linear terms also in an approximate manner. Both the unsteady and the steady state of the motion are considered. Variation of the height of the vertex of the bubble with time is given for various values of the parameter which is the ratio of the surface tension force to the gravitational force. The steady state velocity of the bubble given by the theory agrees closely with the experiment of Davies and Taylor.

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