180 ISOTOPIC TRACERS AND NUCLEAR RADIATIONS [Chap. 7 



Table 27. The Natural Radioactive Series and Alpha Particles 



Isotope 



Symbol 



Half-life 



Range, 



cm in 



air 



Energy, 

 mev 



Velocity 

 3 X 10'° 



cm/sec 



Disinte- 

 gration 

 energy, 

 mev 



Relative 



intensity 



Uranium-radium Series 



Actinium-uranium Series 



Actinium-uranium 

 Uranium Y 



AcU 

 UY 



235 

 231 



7.07 X 10 s y 

 24 . 64 h 



4.52 

 0- 



