The relative intensities of the groups in the magnetic β-ray spectra of radium B and radium C

Source abstract

Abstract It is well known that the study of the energy of the groups of homogeneous β-particles emitted by radio-active bodies has led to many important results, of these the chief is that these groups are due to the conversion of the characteristic γ-rays emitted by the body during the disintegration. From the measurement of the energy of these groups, it has been possible to deduce the energy or frequency of the γ-rays, and there appears to be evidence indicating that the γ-rays are associated with a nuclear level system in the manner familiar from X-ray and optical spectra. This opens up a promising field of work, since a knowledge of these level systems, and the way they varied from body to body would be an important addition to our all too scanty knowledge of the nucleus. Unfortunately, it must be admitted that the existing measurements of the β-ray groups are not of sufficient accuracy to provide a unique determination of the level system, they indicate strongly that the level systems exist, but it is difficult to deduce the actual arrangement with any certainty. An increase in the accuracy of the β-ray measurement would undoubtedly lead to interesting conclusions, but no simple way has as yet been proposed by which this can be achieved. Instead of attempting this method we have attacked the β- and γ-ray problem from another side. Previous investigations have been concerned chiefly with the energy of the individual electrons comprising the β-ray groups and of the γ-rays which can be deduced from them, but it is clear that any theory of their role in the disintegration must also take into consideration their intensities. This seems to be a more promising method of advance than that of trying to increase the accuracy of measurements already carried to a fraction of a per cent., since even approximate values of the intensities would be valuable. There are three main lines along which intensity measurements can usefully be made, one of which is the subject of the present paper. Considered by itself, each is interesting, but since it appears likely that the most valuable results will be obtained by comparing all three, it is permissible to refer briefly to them here.