Abstract
LONDON. Royal Society, May 15.—M. L. E. Oliphant and P. B. Moon: The liberation of electrons from metal surfaces by positive ions. When helium ions strike a metal surface they liberate electrons, the number depending upon the metal and the condition of its surface. Velocity distribution of electrons, liberated from a clean surface of molybdenum by positive ions of helium, shows a sharp cut-off at a lower limit of 2-3 volts, and a sharply defined upper limit at 20-2 volts. Maxima were observed in experimental qurves at 2, 5, 6-8, 17-0, and 20 0 volts. The results can be explained quantitatively on the basis of modern theories of the metallic state.—O. W. Richardson and U. Andrewes: A comparative study of the excitation of soft X-rays from single crystal surfaces and from poly crystalline surfaces of graphite and aluminium. The curves obtained by plotting the photoelectric yield of the soft X-rays per unit thermionic current against the exciting primary voltage show discontinuous rates of increase at certain voltages which coincide with those which give similar discontinuities with the polycrystalline specimens. They are, however, fewer in number and tend to run in groups. The voltages at which the discontinuities occur appear to have a numerical structure resembling that which connects the null frequencies of band systems. The crystal curves are steeper at moderate voltages and flatter at high voltages than the polycrystalline curves.—O. W. Richardson and S. Ramachandra Rao: (1) The excitation of soft X-rays from some polycrystalline metal surfaces. Measurements have been made of large numbers of soft X-ray critical potentials for cobalt, nickel, tungsten and pure and also impure copper. Variation of photoelectric yield with magnitude of thermionic current and with inclination of anticathode is examined. Many of the inflections only appear after the targets have been heated to a high temperature.(2) The excitation of soft X-rays from a single crystal face of nickel. The soft X-ray critical potentials for the 100 face are less numerous than for polycrystalline nickel. The total yield is also lower at high and higher at low voltages with the crystal specimen. S. Ramachandra Rao: (1) Total secondary electron emission from polycrystalline nickel. Applied potentials from 1 to 550 volts were used. Several peaks are obtained below 30 volts and a large number of inflections above 30 volts. The effect of bombarding in hydrogen is also studied.(2) Total secondary electron emission from a single crystal face of nickel. The potentials at which inflections appeared agree very well with the soft X-ray discontinuities from the same crystal face obtained by Richardson and Rao. The bearing on soft X-ray discontinuities is discussed. O. W. Richardson: The emission of secondary electrons and the excitation of soft X-rays. The first act seems to be the excitation of a structure electron by the primary which is returned as part of the high energy group of secondaries. The low energy group and the X-rays result from the return of the excited structure electrons to the ground state. The agreement of the soft X-ray with the secondary electron breaks is accounted for, since both are excitation potentials of the structure electrons. The hypothesis gives a natural explanation of the band-like structure of the discontinuities already found empirically for C and Al and here extended to Ni.W. A. Bone, L. Horton, and S. H. Ward: Researches on the chemistry of coal (6). The main coal-substance can be readily oxidised by means of alkaline permanganate to carbonic anhydride, acetic, oxalic, and benzene carboxylic acids; about one-third of the carbon of the coal substance appeared in C-rings of benzenoid acids. Under ‘optimum conditions’ the character and proportions of the various oxidation products do not vary much with the maturity and geological age of the coal, and colloidal ‘humic acids’ are formed as intermediate oxidation products. The constituents of bituminous coals mainly responsible for their ‘coking propensities’ are benzenoid in character, and in all probability during the ‘maturing process’ they developed from phenols and phenolic esters, found in immature brown coals. On carbonising coals at various temperatures up to 1000° C. their proportionate ‘benzenoid’ structure first increases, attaining a maximum at about 500° - 600° C., but afterwards diminishes, although a completely ‘carbonised’ coke still retains some of it.—L. Rosenhead: The spread of vorticity in the wake behind a cylinder. The trail of vortices in the wake behind a cylinder is taken to be a symmetrical double row of rectilinear vortices of circular section. The stability of such a system to three-dimensional disturbances is investigated. There is also a discussion of the stability of an isolated rectilinear vortex of circular section to three-dimensional disturbances.—L. J. Freeman: The spectra of trebly-ionised oxygen (O IV) and trebly-ionised nitrogen (N IV). About 50 lines in the spectrum of trebly-ionised oxygen (O IV) have been newly classified. All the doublet and quartet terms of principal quantum number 3 have been identified. In the spectrum of trebly-ionised nitrogen (N IV), combinations of the 3p term with 3s 2S and 3d 2D have been observed. Provisional classifications have been given for four other lines.—G. Temple: (1) The group properties of Dirac's matrices. An account of the group properties of a set of operators (Ax, A2, A3, A4), with operand, particularly with reference to a generalised form of Dirac's wave equation 4 2pnAn + (2vtmc/n)l/=0, n in which the A's are not restricted to be matrices. (2) The operational wave equation and the energy levels of the hydrogen atom. Dirac's methods can be modified and generalised to suit an extension of his linear wave equation based on the preceding paper, which is applied to the problem of the undisturbed hydrogen atom. It proves possible to obtain the energy levels, quantum numbers, and wave functions.:—J. Hargreaves: The effect of nuclear spin on the optical spectra. (3) The interaction energy of the nuclear and electron magnets is calculated for the cases of nuclear spins of J, 1, 1J, and 4J quanta. A description is also given of the hyperfine structure of the Zeeman effect, and it is found that the ‘cosine’ law holds. The results agree very well with observations for bismuth.
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Societies and Academies. Nature 125, 801–803 (1930). https://doi.org/10.1038/125801a0
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DOI: https://doi.org/10.1038/125801a0