24 SECONDARY ELECTRONS 



atomic number, since the electronic stopping power does not vary rapidly with 

 Z. For example, in an atom of zinc there are 30 electrons; if all these electrons 

 are regarded as free, the Zn atom would have about 30 times higher chance of 

 becoming ionized than a hydrogen atom. On the other hand, one should also 

 remember that some of the essential trace elements are located in very important 

 spots in the cells: zinc, for example, is an essential component of some enzjones. 

 The question I want to ask is : Are reliable estimates available for the chance 

 of an atom becoming doubly ionized when a charged particle flies by, particularly 

 if the latter has a high rate of energy loss (for example, a low-energy alpha 

 particle) ? 



Morrison : 



Under these circumstances, internal conversion may be appreciable. 



Fang: 



If one considers the situation electron by electron, all take the same amount of 

 energy, but strongly tied electrons take more energy and are less likely to be 

 ionized. That is to say, zinc, with atomic number 31, does not have 30 times 

 the probability of ionization as compared with the hydrogen atom. 



