AUGER DISRUPTIONS 109 



atom and is subsequently communicated to the neighborhood of the 

 atom. 



The connotation for interpretations in radiation chemistry and biology 

 is obvious. Many effects are known which have yields, per "total" 

 number of ionization acts, of magnitude 10"" or less. The possible role 

 of "Auger disruptions" should merit earnest consideration in some of 

 these cases. Effective dosages, in any instance where this mechanism is 

 operative — if any such be found — would be illusory if computed on the 

 basis of total ionization. There the number of K ionizations of C, N, 

 or would be the relevant measure. 



It is possible to calculate this number purely from theory. Figure 3 

 presents the results of calculations, for protons penetrating water, which, 

 it is hoped, may be useful for comparison with practical cases for which 

 this mechanism may be considered. 



For non-aqueous media studied in radiation chemistry more elaborate 

 calculations would have to be made, account being taken in the case of 

 atoms of intermediate or high atomic number of electron ejection and 

 subsequent Auger effects in other inner shells as well. With increasing 

 atomic number the yield of ejections from any given inner shell decreases, 

 the fraction of ejections which lead to Auger transitions also decreases, 

 but the energy transfer per ejection increases; indeed, a cascade of suc- 

 cessive Auger effects should occur, leading in some instances to an atom 

 or molecule with many electrons missing. Because of the importance, 

 for very swift charged particles penetrating atoms of intermediate or 

 high atomic number, of energy transfer to electronic shells other than 

 the valence shell. Auger processes might well have conspicuous effects 

 in media in which such atoms preponderate. 



For biological media the yield of Auger disruptions is greater than is 

 suggested by the values given for water, for two reasons. First, the 

 effect increases, other factors being the same, with the ratio of the total 

 number of K electrons in C, N, and to the total number of electrons 

 other than K electrons in atoms of the medium. This ratio is greater 

 for biological media than for water: for water it is 1 : 4; for carbohydrates 

 and for glycine it is 1:3; for dry virus it is about 1:2.9. Second, and 

 more important, the probability for ejection of a K electron from an 

 atom of atomic number Z by a charged particle increases rapidly as Z 

 decreases: for high particle energies this increase is as Z~^; for very low 

 (heavy) particle energies it is as Z"^^. The total number of Auger dis- 

 ruptions for any medium can be computed approximately from theory 

 if the atomic composition of the medium is known. It is notable, and 

 merits emphasis, that the effect for the K shell is relatively great (the 

 ratio of number of Auger disruptions to total number of ionization acts 



