400 BELL SYSTEM TECHNICAL JOURNAL 



reaction from energy-of-rest-mass to kinetic energy, equal to about 

 17 MEV in the first case and to about 23 MEV in the second. The 

 continuous distribution of alpha-particles up to range 7.8 cm (Fig. 9 

 in the Second Part) is due to impacts of deutons against Li'^, and thus 

 may still be attributed to a transmutation in which three nuclei, — a 

 neutron and two alpha-particles — spring from the merger of a deuton 

 with a Li^ nucleus. Of the other attributions I shall presently speak. 



The transmutations arising from the impact of deutons on deuterium 

 are in some ways unique. They are the first to be known in which 

 the two colliding particles are identical, both being H^ nuclei; one of 

 them appears to be much the most abundant yet observed, in the 

 sense that a given number of bombarding particles produces an 

 unprecedentedly great number of detectable fragments; each of them 

 results in the formation of a nucleus long sought but never certainly 

 detected till 1934. 



The better-known of these reactions is described by the equation, 



,H2 + ,W = iH" + iRi + {Tr - To). (1) 



It is both somewhat amusing and somewhat annoying to realize that 

 this is not a transmutation at all in the formerly-proper sense of the 

 word, since there is no change of one element into another! the hydro- 

 gen isotope of mass-number 2 is changed into hydrogen isotopes of 

 mass-numbers 1 and 3 respectively; it will be desirable to enlarge the 

 scope of the term "transmutation" to cover cases like this one. 

 The H^ nuclei resulting from this reaction were vividly demonstrated 

 by Tuve and Hafstad when they projected deutons into divers gases 

 in an ionization-chamber — air, carbon dioxide, ordinary hydrogen, 

 and deuterium successively; there were no emerging protons (of range 

 superior to 3.5 cm, the minimum observable) from any of the three 

 first named, but from the last there was the "very large yield" of 

 one proton per several thousand impinging deutons. Another estimate 

 of yield has been supplied from the Cavendish school, by Oliphant 

 Harteck and Rutherford; theirs refers to impacts by deutons of 

 energy 0.1 MEV, a value considerably smaller than those of Tuve's 

 research; they find that the number of protons coming forth from a 

 thick layer of deuterium is of the order of a millionth of the number 

 of such deutons entering the layer. The estimates do not seem 

 incompatible, especially as the Cambridge people find the number of 

 fragments to be mounting very rapidly as the deuton-energy To 

 increases;*^ and they show that any possibility of a slight admixture 



* The "thick layers" are fihns of certain compounds of hydrogen in which a 

 large proportion of the usual H' atoms have been replaced by H- atoms. The curve 



