Table of contents

The total intensity of light scattered at 90° by specimens of natural and synthetic NaCl single crystals has been investigated as a function of wavelength from 6600Å to 2500 Å. The scattered intensity is found to be of an order 40 times greater than that expected from thermal theory, and the wavelength function is not inverse fourth power throughout the spectral region studied.

Therefore only a small part of the scattering can be attributed to thermal fluctuations and the bulk is attributed to a submicroscopic block structure of the crystals. From the wavelength function an estimate has been made of the linear dimension of the blocks, and this is found to differ little from specimen to specimen and from place to place in one specimen; it is of the order 1500 Å. Thus the above-mentioned structure seems to be an intrinsic feature of the real structure of single crystals.

Results are given of experiments to measure the drift velocities of electrons diffusing in hydrogen under the influence of both electric and magnetic fields. Two cases are considered (a) the magnetic field B in the same direction as the electric field Z, (b) B perpendicular to Z. The experimental results are interpreted in terms of a convenient microscopic model.

Measurements have been made to demonstrate the effect of temperature on irreversible magnetic viscosity in different types of precipitation alloys: Pt-Co, Ni₃Au and Alnico in an undeveloped state. In this type of alloy, the intensity of magnetization varies as a function of time according to the law I = S₀ ln t + const. On the activation energy model of irreversible magnetic viscosity if ΔE is the change in activation energy produced by a small change in applied field ΔH, ΔE = qΔH. For the Alnico and Ni₃Au specimens the two magnetic viscosity parameters S₀ and kT/q are approximately linearly related to temperature. For Pt-Co the viscosity parameters and the coercivity decrease rapidly with increasing temperature. The results are interpreted in terms of Néel's disperse field theory of magnetization with the additional assumption that strains set up between coherent precipitate and matrix are responsible for the production of the disperse fields. It is predicted from the observations of magnetic viscosity that in Pt-Co the disregistry between precipitate and matrix decreases on increasing the temperature. This has been verified by measurements of the differential thermal expansion between the material of precipitate and the matrix by x-ray methods.

Strong electric fields have been applied in a direction normal to the surfaces of germanium single crystals; such fields have been shown to have a large effect on the surface recombination velocity of injected minority carriers. The variation is in the same sense for n-type and p-type samples. A possible theoretical model for this asymmetry is discussed.

The variation with concentration of the dielectric constant of aqueous ionic solutions at low frequencies is explained in terms of the radial ordering of solvent molecules about the ions, and by the effects of temporarily linked ion pairs.

It is shown that, if the mobility and diffusion coefficient of the current carriers are subjected to a much smaller fractional change as a function of position in the barrier layer than is the electric field, then many results of the general theory of barrier layer rectifiers remain essentially unchanged.

In this paper calculations are given showing how the ionization coefficient α, and the total multiplication in the avalanche, vary with the distance travelled when the positive ions formed have an appreciable effect. The time taken for an avalanche to develop is also worked out. Plane parallel geometry is considered, and two important cases are treated, namely constant field at the electrodes, or constant potential across them. A simple and exact solution is obtained for constant field, and an approximate solution for constant potential. The latter shows that α may decrease or increase depending on the initial conditions, and that it tends finally to a constant value. The equations are general and thought to be of wide application.