NUCLEAR FISSION 277 



ization-density and the range and the energy all taken together, it 

 may be inferred that in both charge and mass these particles much 

 exceed the a-particles ; but here, better data and fuller theory are 

 urgently required.^ 



Now we will consider the energies of the particles according to the 

 data of Kanner and Barschall of Princeton. 



If the immediate products of the fission are really just a pair of 

 fragments nearly but not quite identical, we may expect a distribution- 



Fig. 2 — Distribution-in-energy of fission-fragments of uranium. 

 (Kanner and Barschall ; Physical Review) 



in-energy curve with two sharp peaks. If different fissions result in 

 different fragment-pairs, the peaks must be broadened. If three or 

 more particles are formed at a fission, there should be a broad con- 

 tinuous distribution of energies. This third of the possibilities is well 

 excluded by the curve of Fig. 2; it remains to be seen whether the 

 breadths of the humps speak for the second over the first. 



* The inferring of charge and mass from energy, range and ionization-density is 

 much practiced in the field of cosmic-ray research, in which, however, the particles 

 usually have charge e and masses between the proton-mass and the electron-mass. 



