Isomeric cross section ratios for reactions Mn⁵⁵(α, n)Co,^58m,g Fe⁵⁶(α, pn)Co^58m,g and Rb⁸⁵(α, 2n)Y^87m,g were measured by the activation method using a stacked-foil technique. The experimental results of the energy dependence of σ_m⁄σ_g for Mn⁵⁵(α, n)Co^58m,g reaction were compared with the calculation using the square-well potential with the interaction radius parameter of r₀=1.7 fermi and the energy level density parameter of a=2 MeV⁻¹ in Fermi gas model.
From the comparison, it seems that as the spin level density parameter either a constant value between σ=3 to σ=4 or the value dependent on nuclear temperature corresponding to 2σ²=14.4T fits comparatively well in experimental results. However, the experimental result on this reaction shows that the σ_m⁄σ_g reaches a maximum value at about 25 MeV and then decrease. This behavior may be interpreted by a mechanism of direct interaction. The energy dependence of σ_m⁄σ_g for Fe⁵⁶(α, pn)Co^59m,g reaction qualitatively indicates that the reaction advances through the compound nucleus formation process, contrary to the results for Co⁵⁹(p, pn)Co^58m,g reaction measured by Meadows et al. in which the same compound nucleus is formed.

View full abstract

The orientations of the water molecules in cobalt dichloride hexahydrate have been established by study of the proton resonance spectrum. The directions of the experimentally determined proton-proton vectors are compared with a hydrogen bonding scheme which is determined from the crystal structure reported by Mizuno. The scheme is then modified to fit the experimental data. The proposed atomic parameters for the hydrogen atoms are x, y, z=(0.097, 0.313, 0.268); (0.427,0.205, 0.205); (0.191, 0.000, 0.549); (0.226, 0.500, 0.162).

View full abstract

The magnetic susceptibility of Ammonium dichromate, Sodium dichromate, Potassium chromate and Potassium Permanganate in state of solution has been determined with the help of a very sensitive and accurate microbalance. The values so obtained have been compared with the calculated ones in accordance the additive law. The deviation between the observed and calculated values has been attributed to the effect of the electric field due to distant atoms on the paramagnetic ion and the change of the ionic radii. The change in the moment values in state of solution indicates that in acqueous solution, hydrogen ion concentration is a highly disturbing source. The higher moment values in state of solution than in crystalline state predict the absence of the long range field and thus a release of a part of quenched magnetic moment is resulted.

View full abstract

Paramagnetic resonance of single crystals of [Cr(NH₃)₆]C1₃ diluted with [Cr(NH₃)₆]Cl₃ has been studied at 9.2 kMc/sec and at room temperature. There are three inequivalent complexes [Cr(NH₃)₆]³⁺ that have their x axis of the crystal field all parallel to the b axis of the crystal (monoclinic) but the y and z axes in different orientations. Parameters D and E in the spin Hamiltonian are also different for the three Cr³⁺ ions. The apparent spin-orbit coupling in the crystal is estimated from the g value and is found to be in between the values for [Cr(H₂O)₆]³⁺ and [Cr(CN)₆]³⁻.
A method is described in the appendix to evaluate E⁄D from the angles for the static magnetic field where the two transitions M=3⁄2↔1⁄2 and −1⁄2↔−3⁄2 coincide, and formulas are derived for the resonance fields for S=3⁄2 which are correct to the sixth order of perturbation.

View full abstract

Electronic states shown in the title are investigated by using molecular orbital technique and an interpretation is made of the observations on EPR, optical absorption etc. in irradiated diamond.
Values of interatomic integrals, which appear in the expression of cohesive energy of a perfect crystal, are firstly modified in such ways that a calculated value of the cohesive energy agrees with the observed one, while values of intra-atomic integrals are set equal to those estimated from the observed values of spectral terms in a free carbon atom. On the basis of these modifications, values of the integrals are then obtained, which are related to electronic states of the vacancies. Energy levels are thus evaluated for V⁰, V⁺, V⁻ etc., which mean each a neutral, a positively ionized and a negatively ionized vacancy etc..
By comparing these energy levels with each other, it may be assumed that after irradiation with particles of high energy, a much greater of V⁻ appear in the natural crystal than any other vacancies, by trapping electrons released within the crystal. Therefrom the following interpretation may be made: (1) Type (a) line in the EPR arises from V⁻ and fades away thermally by recombination of V⁻ with C⁰, a neutral interstitial carbon atom. (2) Type (b) lines arise from V₂⁰, a neutral vacancy pair which has its axis along any one of ⟨110⟩ directions. (3) R 11 line (3.988 ev.) in the optical absorption originates in transitions ⁴A₂→⁴F₁ in V⁻. (4) GR 1 set (1.673∼2.082 ev.) originates in some transition in C⁰. (5) TH 5 lines (2.543∼2.618 ev.) originate in C₂⁰, a neutral interstitial pair. (6) H 3 and 4 sets (2.462∼2.703 ev.) originate in a center, into which C⁰ is anchored at some imperfection inherent in type I crystal.
Finally the method of calculation is discussed critically.

View full abstract

⁺A brief account of the present work is published in the Proceedings of the International Conference on Magnetism and Crystallography in Kyoto, published by the Physical Society of Japan, 1962.
A new approach to the calculation of the temperature dependence of spin wave frequencies in ordered spin state is proposed. The results for ferromagnets agrees with Keffer’s expression. Spin wave frequencies in antiferromagnets in the presence of an anisotropy energy are also calculated. By the present approach it is shown that the antiferromagnetic resonance frequency can be expressed phenomenologically in terms of anisotropy constants and static susceptibilities. The obtained expression of the resonance frequency is valid in any statistical approximation. The observed temperature dependence of the resonance frequency in MnF₂ is discussed by use of this result.

View full abstract

Analyses were made of the published experimental data of the heat capacity and other thermodynamic properties of crystals of simple diatomic molecules to obtain the frequency and the zero-point energy of the molecular libration in the crystalline state. It was found that the crystals of chlorine and heavier halogens have much larger librational force constant and much smaller zero-point energy relative to the static lattice energy than do the crystals of nitrogen, fluorine and carbon monoxide and that the differences in these characteristics are closely related to the differences in the crystal structure and polymorphism.

View full abstract

Theoretical studies on the microscopic origin of the magnetic anisotropy energy of Mn₂Sb and its temperature dependence are reported. As has been observed by Jarrett et al, it is well expressed by E_α=K₁sin²θ. K₁ may be expressed as K₁=K₁^dip+K₁^cry; K₁^dip is the anisotropy constant coming from the magnetic dipolar interaction and its value at absolute zero is calculated by the Ewald-Kornfeld method to be −2.99×10⁶ erg per c.c., or −0.411 cm⁻¹ per atom; K₁^cry comes from the single ion spin energy, which is assumed to be of the form, DS_z². Calculation of the temperature dependence of K₁^dip and K₁^cry based on the molecular field approximation. D-parameters, D_I and D_II, of the two kinds of manganese atoms on magnetically non-equivalent sites are determined to be −6.16 cm⁻¹ per atom and 0.977 cm⁻¹ per atom, respectively, by fitting the calculated K₁ to the experimental one.

View full abstract

If the energy of conduction electrons in a semiconductor is connected with the wave vector by a relation E(k)=(h²⁄2m)(k²−βk⁴), the mobility becomes temperature-dependent through the change of the effective mass with increasing temperature. In the present paper we estimate the mobility change through temperature-dependent mass by using a simple model for semiconductors. According to our result the effect does not seem to be important.

View full abstract

The resistivity and Hall coefficient for current flow along the grain boundary of both tilt and twist Ge bicrystals with various misfit angles and orientations are measured as a function of temperature between 70°K and 250°K. Bulk Ge is doped by Sb and its resistivity is in the range of 3 to 40 Ω cm at 295°K. Twist grain boundary has a p-type property similar to that observed with the tilt one. This possibility is discussed by considering the broken bonds in screw dislocations. For small misfit angle the results show that the energy level of an acceptor type is located at about 0.14 ev above the valence band in both types of boundary. With increasing misfit angle, the energy level tends to approach the valence band and be broadened similarly to the case of impurity band conduction. A model such as two clean surfaces are contacted facing each other is used with the modification of energy level to account for the grain boundary conduction phenomena. By using the low mobility of carrier in an acceptor-like band and in the disturbed region, the temperature dependence of Hall mobility is discussed.

View full abstract

The variations of electron diffraction intensities of thin BiOCl texture films are studied by changing the tilting angle, crystal size of the specimens H and wavelength λ. The results are compared with Blackman’s and Cowley-Moodie’s theories. It is revealed that the experimental results show the same tendency as Blackman’s theory but different in magnitude for large λH values (>4Ų), and agree with Cowley-Moodie’s theory for small λH values (<4Ų).

View full abstract

Image formation of lattice imperfection in an electron microscope is studied theoretically. The treatment is an extension of the dynamical theory of electron diffraction for perfect crystal. The electron after passing through an imperfect crystal diverges due to inhomogeneous lattice distortion around the imperfection. Taking account of this effect the wave function of electron in the crystal is expressed approximately by a superposition of many plane waves. General expressions for the wave function and the intensity distribution of electron on the exit surface of the imperfect crystal are calculated as the functions of lattice displacement.
Examples of numerical calculation are given on the electron-micrographs of dislocation in ordinary bright field images and in moiré fringes.

View full abstract

Loeb’s condition for the onset of a positive burst pulse corona was applied to the case of point-to-point electrodes arrangement and a formula, which gives relations between the field strength to pressure ratio, ratio of ionizing photons to electrons in an avalanche and the effective absorption coefficient for this ionizing radiation, was obtained.
From the measured starting potential versus pressure curve the limitting value of the field strength to pressure ratio for the case of indefinitely high pressure was obtained by extrapolation, and from this value the effective absorption coefficient μ for the burst pulse forming radiation was estimated.
The estimated values for the effective absorption coefficients at 760 Torr are 3700 cm⁻¹ for air, 2375 cm⁻¹ for nitrogen and 2200 cm⁻¹ for oxygen. As these values are of the same order of magnitude as for the radiations in the range of the resonance bands in the ionization continua, the wavelength of the ionizing radiations effective in the positive burst pulse corona formation might be assumed to be in the range of the ionization continua. Moreover the ratios of the numbers of ionizing photons to those of electrons in a burst forming avalanche were deduced. They are approximately 1.6∼1.8 for air, 1.4∼1.5 for nitrogen and 1.8∼1.9 for oxygen.

View full abstract

In order to investigate the processes responsible for a negative resistance of the hollow cathode discharge, several discharge parameters are measured with a Langmuir probe. The vapor density distributions of the sputtered cathode metal are measured by the absorption method of the resonance radiation of the metal atom. Almost all the metal atoms in the central part of the cathode space are found to be ionized or excited.

View full abstract

The mechanisms of negative resistance of hollow cathode discharges are discussed theoretically based on energy balance. Dependence of radiation intensity from the glow determines the behavior of V-i curves of the discharge. In hollow cathode discharges, radiation is mainly due to sputtered metal atoms of the cathode. Conditions for gas and cathode material have been obtained, under which negative resistance appears.

View full abstract

The optical and thermal natures of N (N₁ and N₂) centers in additively colored KCl crystals were investigated. These centers were optically stable, but thermally sensitive. Their thermal stabilities were contrasting, N₁ center being far more stable than N₂ center. They were found to have intimate relations with R center. The investigations of photochemical and thermochemical reactions revealed that N₁ centers were grown as R centers decayed thermally, and conversely the latters were grown by bleaching of the formers with the illumination of N₁ band. Two absorption bands which were intimately connected to N₁ center were observed in R bands region, forming the colloidal bands. Also, one band at the higher energy side of F band was found to be closely related with N₁ center. The natures of N₂ center showed striking resemblances with those of R center. M center, on the other hand, had little relations with N centers, at least directly. Pick’s models of N centers were discussed in the light of the above experimental results.

View full abstract

An experimental study on the thermal glow luminescence in plastically deformed KCl crystals has been carried out. The thermal glow curves of plastically deformed crystals become simple and similar irrespective of the origin of crystals, in contrast with the case of “as-cleaved” crystals. In the case of ultra violet illumination at room temperature, glow curves consist of four peaks at 80°, 160°, 200° and 250°. The intensity of glow peaks increases with deformation. The observed glows are attributed to the interaction of excitons with vacancy clusters. In X-rayed case, three peaks appear at 80°, 140° and 250°C. The peak at 250°C is very outstanding and is considered to be the luminescence due to the recombination of F and V₃ centers. Glows at 80° and 140°C are attributed to the recombination of released electrons from N and M centers with the trapped holes in V₂ centers. The recombination probability of 250°C-glow is enhanced very much by the perturbed field due to the plastic deformation.

View full abstract

Complex color centers of M, R and N in KCl crystal are found to be temporarily bleached under an intense auxiliary F-light illumination. The generations of M′, R′ and N′ centers consisting of complex centers and one more electron are suggested. The thermal stabilities of these F′-type centers are also investigated. In KCl crystals containing only F centers, F′ centers decay thermally by the bimolecular process and the electron trapping cross section of a negative ion vacancy is found to be twice that of F center at near −70°C.

View full abstract

New absorption bands in KCl and KBr crystals are observed in near infra red region. It is considered that they arise from F′ type centers which consist of R₁, R₂ or M center and one more electron. F′ type bands appear during the process of F→F′ conversion in the crystal containing complex centers, and they are located at 1.60 μ, 1.72 μ, 2.15 μ and 1.49μ, 1.60μ, 1.94μ in KBr and KCl crystals, respectively. F′ type centers are thermally unstable than F′ center. These centers are called R₁′, R₂′ and M′.

View full abstract

The inviscid flow of an ionized gas with infinite conductivity in a magnetic shock tube is treated when the driving magnetic field is very strong and varies with time, being induced by the current discharge from capacitors. Two cases are treated; one is the one-dimensional flow with a planar current sheet perpendicular to the flow, and the other is the cylindrically expanding flow with a cylindrical current sheet. The problem is analogous to the hypersonic flow past a slender body, and similarity solutions exist if the driving magnetic field varies proportionally to t^k−1 (t is the time). Numerical results for several values of k are presented. For a general case when the magnetic field varies as an arbitrary function of time, an approximate method of calculation by using the concept of local similarity is also presented.

View full abstract

The steady flow of an incompressible, viscous and electrically conducting fluid due to a rotating disk of infinite radius is investigated in the presence of a transverse magnetic field. This is an extension of the well-known Kármán’s problem to the hydromagnetic case. It is assumed that the magnetic Prandtl number of the fluid is so small that the electric currents flowing in the fluid do not affect the magnetic field.
It is found that the magnitudes of the radial and the axial components of the velocity decrease rapidly as the hydromagnetic interaction parameter N increases, while the velocity gradient of the circumferential component at the disk increases. Therefore, the torque due to viscous friction acting on the disk increases with increasing N. It is also found that both of the displacement-thickness and the angle of yaw at large distances from the disk decrease with increasing N.

View full abstract

Colloidal formation of alkali metals in KCl crystals containing various amount of NaCl was studied by the measurement of optical absorption. The position of the colloidal bands in KCl-NaCl mixed crystals is shorter than that in pure KCl; the position shifts markedly to longer wavelengths with increasing temperature of annealing. At higher temperatures, colloidal bands produced with illumination are not different from those produced in dark, while below 200°C position of the former differs from that of the latter when the time of annealing is short, but approaches to the position of the latter with prolonged treatment.
It is concluded that the colloids in the mixed crystal contain much more sodium proportionately than does the host crystal and the change in the position of the colloidal band is principally due to the change in the ratio of Na to K in K-Na alloy colloids.

View full abstract

The first three lines at the top of the left hand column on page 1049 belong at the top of the right hand column on page 1048.

View full abstract