Abstract
LONDON. Royal Society, Feb. 6.—A. H. Davis and E. J. Evans: Measurement of absorbing power of materials by the stationary wave method. The paper describes an apparatus set up for determining the acoustical absorption coefficient of small samples of material for sound, incident perpendicularly, and discusses the theory of the method and of its corrections. Stationary wave coefficients for certain practical materials are compared with coefficients obtained by a ‘reverberation’ method, in which random incidence of sound is employed.—J. W. Fisher and H. T. Flint: The equations of the quantum theory. These equations are obtained by analogy with Maxwell's equations applied to empty space. They are expressed by means of a five-dimensional system of co-ordinates with the adoption of a metric after the manner of Weyl and Eddington in four-dimensions. The quantum problem is shown to be a radiation problem in five-dimensions, and the equations proposed are invariant.—J. Hargreaves: The effect of nuclear spin on the optical spectra (2). The paper contains a general method for dealing with the effect of a nuclear spin of possibly more than half a quantum, by the use of multiple wave functions, and is applied in detail to the cases of a nuclear spin of 1, 1, and 4 quanta respectively. The interaction energy of the nucleus and electron spins is neglected, without effect on the kinematical problem of determining the multiplet intensities.—E. Rudberg: Characteristic energy losses of electrons scattered from incandescent solids: The velocity distribution of an initially homogeneous beam of electrons, after scattering from a solid target kept at incandescence, has been studied by means of a magnetic deflection apparatus. The curves show a sharp peak due to reflected electrons and several small maxima for slightly lower values of the energy. These maxima are characteristic of the substance forming the target, their positions with respect to the reflected peak remain constant for a wide range of bombarding voltages, and when target and electron gun are rotated, are also independent of angle of scattering. These maxima are associated with inelastic collisions with the target atoms, involving definite energy changes, such as excitation and ionisation.—J. A. Gaunt: Continuous absorption: This paper investigates afresh the problem of the rate of absorption of light by electrons which are initially bound to a nucleus, or free and ‘colliding’ with a nucleus, and after absorption are free in either case. Such a process gives rise to a continuous absorption spectrum and is the main source of the general opacity in stellar atmospheres and interiors. The interest and difficulty of the problem lie in the effective evaluation of the formal quantum theoretical expression for the absorption coefficient. Kramers' classical formula is asymptotically correct in the region in which one would expect it to be so by the correspondence principle. The deviations of astrophysical significance are found. The discrepancy between the requirements of Eddington's stellar theory and Kramers' formula is probably retained by the quantum theory of continuous absorption.
Article PDF
Rights and permissions
About this article
Cite this article
Societies and Academies. Nature 125, 256–259 (1930). https://doi.org/10.1038/125256b0
Issue Date:
DOI: https://doi.org/10.1038/125256b0