306 SECTIONAL TRANSACTIONS.— A. 



Monday, September 5. 



Discussion on The conservatio7i of energy and nuclear phenomena (Dr. 

 C. D. Ellis ; Prof. C. G. Darwin, F.R.S. ; Prof. O. W. Richardson, 

 F.R.S. ; Dr. Mott) :— 



Dr. C. D. Ellis. 



The majority of nuclear phenomena appear to be controlled by the same 

 general laws that apply to the outside electronic structure. In particular, it 

 is possible to explain what is actually observed as the aggregate of a number 

 of similar processes, involving, for example, a nucleus and a-particle or 

 nucleus and quantum, in each of which energy is conserved. In one case, 

 however, that of the (3-ray type of radioactive disintegration, this method 

 of description meets with difficulties. This problem has often been dis- 

 cussed, and it is generally recognised that of the possible explanations 

 there are two which deserve special consideration. The first is that energy 

 is not conserved exactly in each elementary process, the second is that in 

 contradistinction to the non-radioactive elements, the different nuclei of a 

 radioactive element are not identically the same. A considerable amount 

 of new experimental material has been published in the last year which 

 bears on these problems, and which justifies reopening the discussion. 

 On the one hand, our knowledge of the nuclei of the lighter elements has 

 been extended both from spectroscopic evidence and from the study of 

 artificial disintegration, and on the other hand, new experimental methods 

 have added greatly to our information about the emission of a-particles 

 from the radioactive elements. There appears to be a close connection 

 between the energies of the a-particles in the nucleus and the frequencies 

 of the y-rays, which is entirely in accord with the validity of the energy 

 principle and the principles of quantum mechanics. A detailed considera- 

 tion of these points tends only to strengthen the view that the nucleus is 

 governed by the same laws as the electronic structure and to render more 

 acute the contrast with the P-ray type of disintegration. Important new 

 information about the P-ray disintegration has been obtained by different 

 workers, and a review of the present position shows it to be now more 

 definite and more susceptible to attack. 



Prof. O. W. Richardson, F.R.S. 



We have listened to a most lucid account by Dr. Ellis of a very puzzling 

 group of phenomena associated with the emission of electrons, or P-rays, 

 by radioactive bodies. I believe this to be one of the most important 

 unsolved problems outstanding in present-day physics, and that its ultimate 

 solution will be found to be intimately bound up with the structure of the 

 nucleus. As we have seen, it leads, on the face of it, to a contradiction of 

 the principle of the conservation of energy. 



This is not the first time that this principle has found itself in difficulties. 

 On previous occasions it has evaded the difficulty by calling into existence 

 a new kind of potential energy and thus balancing the account. This 

 method of escape is not possible in the present case, because it would be 

 necessary to invoke a special potential energy for each atom concerned in 

 P-ray nuclear disruption, or, at any rate, for each of a considerable 

 number of groups of such atoms emitting (3-rays within a certain range 

 of velocities. 



I believe that this difficulty is essentially connected with the smallness 



