Formation of Radium E and Polonium by Deuteron Bombardment of Bismuth

The direct production of RaE and Po by deuteron bombardment of bismuth has been reinvestigated. Present results indicate that as the deuteron energy is lowered from 8.8 to 7.3 Mev, the production ratio of RaE/Po increases 25 percent but as the deuteron energy is dropped from 7.3 Mev to 5.5 Mev, the ratio more than doubles. The trend is in agreement with the Oppen-heimer-Phillips reaction in which RaE is produced by a d, p reaction and Po is produced by a d, n reaction. Assuming these reaction cross sections to be respectively proportional to Bethe's OP penetration factor and to the Gamow-Condon-Guerney penetration factor, best agreement of the variation with energy of the ratios of these cross sections is obtained with a nuclear radius of 2.0A1/2×10^-13 cm for bismuth.