707 



TABLE 787.— ESTIMATED VALUES OF THE NEUTRON BINDING ENERGY 

 OF THE DIVIDING NUCLEUS* 



For reference, see footnote 226, p. 667. 



TABLE 788.— THE CRITICAL ENERGY FOR FISSION* 



The experimental values of the critical energy for fission of a number of isotopes have 

 been determined by Koch, McElhinney, and Gasteiger 241 who give the following photo- 

 'fission threshold energies. (The work of Shoupp and Hill 242 on the fast neutron fission 

 energies for Th 232 and U 238 was used for the values given for Th 233 and U 239 .) 



Compound 

 nucleus 



w Th 232 . 

 eoTh 233 . 

 92U 233 .. 



5.40±.22 Mev 



6.3 



S.18±.27 



Compound 

 nucleus 



92U 235 



92U 238 



5.31: 

 5.08: 



.25 Mev 

 .15 



Compound 

 nucleus 



92U 289 

 94PU 238 



6.1 



5.31 = 



.27 



Mev 



* Prepared by J. L. Rhodes, University of Pennsylvania. 

 "iPhys. Rev., vol. 77, p. 329, 1950. 

 242 Phys. Rev., vol. 75, p. 785, 1949. 



TABLE 789.— HALF-LIVES FOR SPONTANEOUS FISSION 243 



These half-lives are calculated on the basis of a half-life of 10 15 years for U 2 



Element 



Z A Half-life 



92U 235 10 15 years 



92U 233 1.4X10 14 



93 Np 237 7.6X1 13 



M Pu 244 6.8X10 16 



94PU 242 7.7X 10 14 



243 Turner, Rev. Mod. Phys., vol. 17, p. 292, 1945. 



TABLE 790.— THE ENERGY RELEASED BY FISSION ON DIVISION OF SOME 

 ATOMS INTO EQUAL PARTS* 



Original 



2 sNi 01 



ooSn 117 

 „ s Er ,a7 

 8 2Pb 20a 

 92U 230 



For reference, see footnote 226, p. 667. 



SMITHSONIAN PHYSICAL TABLES 



