118 



ADVEXTUKES IX RADIOISOTOPE KESEAKC'H 



Table 1. — SELF-DirrrsioN in Lead Single Crystals Diffusion 



CONSTANT (D) OF TllB IN LeAD (SELF-DirFL'SION CONSTANT OF LeAD) 



1 In all cases where there is no remark single crystals grown by the K^-l■opoulos 

 method were used ; in items 6, 8 and 13 these consisted of Kahlbaum lead and 

 in all other items of lead from the Akkumulatorfabrik, Hagen, ^^'estphalia. 



Table 2. — Diffl'sion Constant of ThB in Cold-Worked Lead 



The results discussed above relate to a temperature range which 

 extends from the melting point of lead (327°) to 182°. Below the latter 

 temperature the self-diffusion can be followed by making use of the 

 recoil effect. As has already been mentioned, this method does not 

 make use of the decrease in ionization after diffusion but the recoil 

 yield is determined. While the range of this a-radiation in lead is 3 X 10-^ 

 cm the range of the recoil particles extends only to a thickness of about 

 one hundred atom layers (4.7 x 10-® cm). In corresponding degree to 



