Open AccessA comparison of the spectra of fluorescent Röntgen radiations
Author(s) -
Joseph C. Chapman
Publication year - 1913
Publication title -
proceedings of the royal society of london. series a, containing papers of a mathematical and physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9150
pISSN - 0950-1207
DOI - 10.1098/rspa.1913.0003
Subject(s) - radiation , homogeneity (statistics) , excited state , homogeneous , thorium , atomic physics , attenuation coefficient , uranium , chemistry , optics , physics , nuclear physics , mathematics , statistics , thermodynamics
In a previous paper published in the 'Proceedings of the Royal Society,' it has been shown that there is a second group of elements consisting of tungsten, gold platinum, bismuth, and the radioactive elements uranium and thorium, which emit secondary fluorescent X-radiation when excited by a suitable primary beam of Röntgen rays. The properties which the radiations of this group (Group L) have been shown to possess in common with the radiations of Group K (elements Cr-I), investigated some year ago by Prof. Barkla, are as follows:—(1) The radiations emitted by any particular element when excited consist of two distinct types: (a ) the scattered radiation, having the same penetrating power as the primary beam and indistinguishable from it; (b ) the homogeneous X-radiation characteristic of the particular element in question. (2) Each element exerts a selective absorption for radiations which are of such a degree of hardness that they lie in the neighbourhood of an "absorption band." In the case of the elements of Group L, to demonstrate the homogeneity of the radiations, allowance had to be made for the scattered radiation which always accompanies the homogeneous constituent, but which in the case of the heavier elements is present in such magnitude as to mask, if no correction is applied, the true homogeneity. In the experiment described in the paper referred to, the absorption in aluminium of the various radiations has been measured. In Tables I and II the absorption coefficient (λ /ρ ) is defined by the equation I = I0 e -λx , whereρ is the density of aluminium.