The Emission and Transmission of Roentgen Rays

Abstract

OF recent years much interesting work has been done to connect the atomic weight of an element with its power of emitting and transmitting various kinds of radiation. One may mention McOlelland's 2 work on the secondary radiation given out by a substance exposed to the j3 and y rays of radium, and Professor J. J. Thomson's 3 results, which brought out the relation existing between atomic weight and the intensity of the emitted secondary Eoentgen radiation. In each case an increase in atomic weight was accompanied by an increase in the amount of secondary radiation. Kleeman 4 has obtained a similar result in the case of the secondary radiation produced by the y rays from radium. Benoist 6 in 1901, working with the absorption by various elements of a definite beam of Eoentgen rays, obtained a smooth curve approximating to a rectangular hyperbola by plotting atomic weight against a factor related to kjp (i.e., the absorption of unit mass per unit area), where p is the density of the screen, and A is the co-efficient of absorption. A is defined by the exponential relation for a homogeneous beam I = I 0 e — i n which I 0 is the intensity of the incident beam, and I that of the emergent beam from a layer of thickness d. It follows from Benoist's curve that kjp increases with the atomic weight, and more rapidly in the region of low atomic weights. Crowther 6 measured the absorption by different elements of the /8 rays from uranium, and obtained a periodic relation between atomic weight and kjp. It was thought that a careful study of the Eoentgen radiation emitted by various elements, when used as anticathodes in a discharge tube, might be repaid by the discovery of some sort of relation between their atomic weights and the quantity and quality of the Eoentgen rays given out and transmitted under various conditions.