Sec. 3.13) BETA PARTICLES 69 



Observation of K capture is possible only through the detection of the K 

 x-radiation following absorption of a K electron. However, identification 

 of K capture is sometimes hampered by a competing positron emission when 

 this is followed by gamma radiation. If internal conversion of the gamma 

 radiation is pronounced, the K x-radiation is then masked by similar radiation 

 produced by the conversion of K electrons. When positron emission is 

 absent or when present but not accompanied by gamma radiation, K capture 

 can be detected unequivocally. In some radioisotopes the gamma radiation 

 exhibits a much greater intensity than is expected from the observed positron 

 activity. This, together with K x-radiation, readily establishes the existence 

 of K capture. 



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