152 BELL SYSTEM TECHNICAL JOURNAL 



Such are the cases where there is the strongest proof for the twin 

 doctrines that disintegration is by capture, and that a definite amount 

 of energy is transformed between rest-mass and vis viva. The reader 

 will have noticed in the latter case, that {Ti — To) appeared to be the 

 same for a group which exhibits resonance and for another group which 

 does not. This if certain may be taken to mean, that a particular 

 group of protons — one may speak more graphically, and say: a par- 

 ticular proton in a particular level of the nitrogen nucleus — can be ex- 

 tracted by alpha-particles of a narrowly-limited range of energies be- 

 tween critical energy-values Ka and Kb, and can also be extracted by 

 alpha-particles of any energy superior to a third critical value Kc which 

 is greater than Ka and Kb. There is a good interpretation of this 

 notion in the contemporary theory, which I reserve for the next article. 

 It will also have been noticed that two different values of (Ti — To) 

 were given for a single case, that of aluminium (there are also two for 

 fluorine). This is to be taken as meaning that the residual nucleus 

 may be left in either of two conditions, one of which may be the normal 

 state, while the other must be an excited state (page 138). One then 

 infers that the nucleus when left in the excited state will presently go 

 over to the normal state, emitting a photon having an amount of energy 

 equal to the difference between the two values of {Ti — To). It is 

 very tempting to suppose that the gamma-rays known to be emitted 

 from some elements during alpha-particle bombardments have this 

 origin, but the measurements are not yet precise enough to prove this.*^ 



In a case of disintegration-by-capture, the residual nucleus denoted 

 by z+iM^"*"* in equation (9) might or might not be exactly the same as 

 the nucleus of the known chemical atom (if such there be) of atomic 

 number (Z + 1) and mass-number (A +3). Can this be tested by 

 comparing the rest-mass of the former with the mass of the latter as 

 measured by Aston or Bainbridge? Unfortunately nothing of value 

 can be concluded unless the atoms z+iM"^"^^ and ^M^ have both had 

 their masses determined with an accuracy permitting them to appear in 

 the Table on page 109 ; and on inspecting this table one finds (with some 

 surprise) that this is true for only one of the known processes, viz. the 

 transmutation of fluorine. Assuming disintegration to be with cap- 

 ture, the process would be the following: 



9F» + 2He^ = loNe^^ + ^h^ -f- {T, - To) (11) 



Putting for {Ti— To) the value -M.67 MEV given by Chadwick and 

 Constable, and for the rest-masses of the nuclei the values given in the 



''^ Heidenreich has analyzed the data for boron, and concludes that they permit 

 of this interpretation. {ZS.f. Phys. 87, 675-693; 1933.) 



