Table of contents

An examination is made of the effect of a magnetic field on the surface impedance of a metal in which there are two overlapping bands of normal form. In general it is not possible to express the surface resistance, as a function of frequency and field strength, in convenient analytical form, but the results are depicted graphically for a number of special cases.

At low frequencies the relative change in the surface resistance due to the field is independent of frequency and its variation with field strength is very similar to that obtained in d.c. experiments. At high frequencies it is shown that in all cases the magneto-resistance effect ultimately drops to zero. The frequency region in which this phenomenon occurs is determined by the relaxation time and lies in the far infra-red for normal metals. From a comparison with the available experimental results for bismuth it is inferred that the relaxation time in bismuth is abnormally large.

Experiments are described which show that there is an exact similarity between optical diffraction from a plane grating containing only a few lines and x-ray diffraction from a built-up multilayer, of barium stearate for instance, when the multilayer consists of a few monolayers. The diffraction maxima given by Bragg's law are accompanied by subsidiary maxima equal in number to N-2 where N is the number of `unit cells' (i.e. the number of repeat distances in the direction perpendicular to the plane of the monolayers). The formulae for the x-ray case are given and several experimental examples are cited.

The method of Morpurgo is extended to deal with both central and tensor forces, each having Yukawa-type radial dependence. The method is applied to calculate the binding energy of ⁴He for one set of Pease-Feshbach force parameters. It is shown that the inclusion of a second D state in the trial wave function leads to a large increase in binding energy.

The specific ionization in oxygen near atmospheric pressure has been measured over the momentum range 3 × 10⁸ eV/c<p<3 × 10¹⁰ eV/c, excluding collisions involving energy transfers greater than 1 keV. The measurement was based upon drop counts in the positive ion column of tracks in a cloud chamber independent of the system used to measure momentum. Modification of ionization due to polarization phenomena is shown to become important at momenta greater than about 6 × 10⁹ eV/c.

The variational method is used to obtain approximate wave functions for the 1sσ_g and 2pσ_g states of H₂⁺. Their accuracy is assessed by comparing various quantities computed using the approximate wave functions with the exact values of these quantities. The dependence of the total kinetic and potential energies on the nuclear separation is briefly discussed.

The mathematical theory of the asymmetrical top and of triatomic molecules has been considerably simplified by removing two of the Eulerian angles from the wave equation by a special artifice. Asymptotic expressions for the eigenvalues of the former and the centrifugal and Coriolis corrections to be applied to the energy levels of the latter have been obtained in closed forms for values of J exceeding 9 without solving any secular equation.

Rotational analyses of the 1,0,0,0 and 0,1 bands of the β system of NS have been carried out. It is found that the transition is ²Δ-²Π and not ²Π-²Π as has hitherto been supposed. The rotational constants of the state A²Δ are: B_ν = 0.6960₄ - 0.0069₅ (ν + ½); r_e = 1.576₈Å. In the same spectral region there occur the c²Σ-X²Π system (γ-bands) and other weaker bands which may belong to a system B(²Π)-X²Π.

Corrections to 1954 Proc. Phys. Soc. A 67 265