Sec. 6.6] 



FISSION 



157 



Table 23. Ranges of Fission Fragments [36] 

 Extrapolated and mean ranges of plutonium fission fragments in normal air, and the 

 straggling as indicated by the widths at half-height of the differential range curves. 



end activities of the observed chains correspond to earlier known activities 

 produced by other processes. 



The total decay energy associated with the chain activities of the two 

 fragments has been measured by several investigators but with conflicting 

 results because of the difficulties encountered in evaluating with accuracy 

 the energy associated with the very short half-lives and penetrating gamma 

 rays. The average total decay energy is probably between 20 and 30 mev 

 per fission. The fraction of the total energy contributed separately to beta 

 particles and gamma rays is not certain, but Way and Wigner [16] have given 

 an empirical formula for the rate of energy loss by gamma rays in the interval 

 10 < / < 10 7 sec as 



E r = 1.26r K2 mev (fiss)/sec 

 and for the average total energy 



E t = 2.66/ -1 - 2 mev (fissVsec 



Experiments by Bernstein et al. [17] on the yield of gamma rays with 



