ARTIFICIAL RADIOACTIVITY 



93 



Voorhis [1936]). It ejects a high-speed (1.4-Mev) beta particle from 

 its nucleus. This ejection is followed by the emission of a very hard 

 gamma ray, and the end product is a stable magnesium nucleus. The 



,H 2 +„Na 23 - 



»uNa +,H + Energy 



High-speed deuteron 



Heavy hydrogen 

 nucleus 



Stable 

 nucleus 



Proton 



{ Na 24 } 



Unstable isotope 

 radiosodium 



.24 



Beta particle 

 ,0 1.4 million electron-volts 



3 Mev 



u 



Na' 



> 12 Mg"+? 



7-ray emission 



24 i -x 



Fig. 11-16. Radiosodium produced by deuteron bombardment. A possible sub- 

 stitute for radium. Its gamma ray is more energetic than any emitted by radium. 



beta particle and gamma radiation possess energy of 1.4 and 3 million 



electron volts respectively. The latter artificially induced radioactive 



emission is more penetrating than any of the natural radium radiations. 



Radiophosphorus preparations may be obtained by bombarding red 



,H 2 + 15 P 31 - 



-> 15 P 32 +,H , + Energy 



High-speed deuteron 

 (0 



2 Mev 



Red phosphorus N 

 stable nucleus v . 



Beta particle 

 1.69 Mev 



( p 32 ; 



Unstable isotope 

 radiophosphorus 



Stable sulphur 



unexcited 

 No 7 observed 



^32 



^, fi S 32 +T 



Fig. 11-17. Radiophosphorus produced by bombarding red phosphorus with 

 high-speed deuterium ions, from a cyclotron. 



phosphorus with high-speed deuterium ions, obtained by means of the 

 cyclotron. The reaction is shown in Fig. 11-17. This reaction involves 

 a beta decay emission without the accompanying gamma radiation. 

 The resulting radiophosphorus (i 5 P 32 ) has a half -life of 14.30 days 

 (Cacciapuoti [1938]). 



