The absolute intensities and internal conversion coefficients of the y-rays of radium B and radium C

Abstract

It is well known that with many radioactive bodies the departure of the disintegration particle is followed by the emission of γ-rays. In addition to γ-rays of frequencies v 1 , v 2 , ..., it is observed that there is an electronic emission consisting of several homogeneous groups whose energies can be written The energies of these groups are identical with those that would be produced by photoelectric absorption in the parent atom of the γ-rays emitted from the nucleus, and this phenomenon is frequently described as the internal conversion of γ-rays. By this is meant that in every case when the nucleus emits energy E this occurs in the form of radiation of frequency E/ h , but that this does not always escape as such from the atom. In a fraction a of the cases the radiation is absorbed in the electronic structure and gives rise to a photoelectron, in the remaining fraction (1 — α) the γ-ray is emitted clear of the atom. The quantity a is termed the coefficient of internal conversion. Smekal* and others have pointed out that there is no need and even no justification to consider the γ-ray ever to be emitted in the case of those atoms which give photoelectrons. All that can be truly inferred from the experimental facts is that the atom as a whole is capable of emitting energy E, and this it may do either in the form of a quantum of radiation hv = E, or in the form of an electron of energy E — K, or E — L, etc., followed by the appropriate excited K-, L-, X-radiations. The greater portion of this energy E is certainly resident in the nucleus, so that this second standpoint implies some type of what may be termed collision interaction between the nucleus and the electronic structure of the atom.