Abstract
IN the light of the standard measurements of the -ray spectra of radium-B and -C by Ellis and Skinner (Roy. Soc. Proc., A, vol. 105, p. 60, 1924) it was thought advisable to remeasure the spectra of thorium-B, -C, and -D. This has been done, using the now well-known focussing method, and the results will be published in due course. The purpose of this letter is to direct attention to two lines of high energy, namely, 2.55 and 2.62 million volts, with a possible third of slightly greater energy. The detection of these lines has been made possible by the preparation of thorium-B sources of greater strength than usual. There is no doubt of their existence, as they appear very clearly and sharply on the photographic plate. What is most remarkable is the fact that these lines correspond to the conversion of a -ray of energy 2.64 million volts in the K and L levels of an atom of atomic number 82 or 83, despite the fact that their energy is some twenty-eight times as great as that of the K level of an atom of that atomic number. This shows that the quantum relations hold for these high energy values in exactly the same way as they have been shown to do for the lower ones. From an examination of the plates, it is seen that these lines lie beyond the region of the continuous background, and this fact may be of importance in atomic theories. Another point of interest is that there appear to be no lines between these and those of an energy of about 0.8 million volts.
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BLACK, D. High Energy -Ray from Thorium Disintegration Products. Nature 115, 226 (1925). https://doi.org/10.1038/115226b0
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DOI: https://doi.org/10.1038/115226b0
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