Full Text
Extension of the Ultraviolet Spectrum Toward Short Waves.
K. A. Millican. The extension of the ultraviolet spectrum. Astrophys. Journ. 52, p. 47 (1920).
Lyman, who extended the spectrum to 500 Å, used a vacuum spectrograph with a diffraction grating. In this way he could get rid of all absorbing solid bodies between the light source and the photographic plate. Absorption of the radiation of the spark, which served as the light source and was located in the space of the spectrograph, could be effected by the rarefied gas filling the spectrograph.
I shall mention here only that Richardson and Bazzoni, by a somewhat different method, succeeded in detecting waves of length 420 Å1. Millican, in general using Lyman’s method, strengthened his means. In fact, he used a vacuum of \(10^{-4}\) mm of mercury; a mercury diffusion pump served for the evacuation; the source of light was sparks between electrodes set at a distance of 0.1 to 2 mm, with a large capacitance and a very high voltage (several hundred kilovolts). The duration of exposure did not exceed 30 minutes; the accuracy of the measurements was up to 0.2 Å. The electrodes were of zinc, iron, silver, nickel, and carbon. The shortest wavelength first observed by him was 202 Å with nickel electrodes.
It should be noted that he succeeded in establishing a series of entirely new lines in the far ultraviolet part of the spectrum. Moreover, the lines in the interval from 1200 to 600 Å he ascribes to carbon, and not to helium, as Lyman does, for when electrodes of pure silver are used, these lines are not observed. He explains the appearance of these lines in Lyman’s work in an atmosphere of He by contamination of the He with carbon vapors (evaporation of carbon electrodes during an instantaneous discharge).
T. Molodyi.
New Data on the Artificial Transmutation of Elements.
E. Rutherford and J. Chadwick. The desintegration of Elements by α-Particles. Nature 107, p. 41 (1921).
The improved optics of the apparatus allowed Rutherford to make a series of new observations on the artificial decomposition of elements. It turned out that \(\alpha\)-particles with a range of 7 cm2 produce in hydrogen \(H\)-particles with a range of 29 cm, but the \(H\)-particles arising from nitrogen exhibit a range of 40 cm. Particles with a greater range could also be observed in other substances besides nitrogen. Thus particles with a range greater than 40 cm were observed in boron, fluorine, sodium, aluminum, and phosphorus. It is especially interesting that from aluminum there arise particles with a range of approximately 80 cm. The number of particles in boron and sodium is significantly smaller than in the other elements.
In \(Li, Be, C, O, Mg, Si, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Sn, Ag\), if the action of \(\alpha\)-particles was observed at all, it was very weak. Definitely