THE FISSION OF ANTIMONY BY FAST PROTONS

A sample of metallic Sb, which had been purified a number of times by zone melting and had been shown to contain not more than 10/sup -//sup 4/ to 10/ sup -//sup 7/% of Mn, Cu, Zn, As, P, Cr and Ga impurities by neutron activation analysis, was irradiated with 660 mev protons. The spallation products were identified by radiochemical methods, and the yields of each were calculated. There is a great increase in the relative yield of neutron-deficient nuclei formed in fission of Sb as compared to the fission of heavier elements such as U, Th and Bi. Since most of the fission products of Sb were shielded isobars, it was possible to establish the type of distribution of the nuclear charge in the fission of Sb. The half-width for the yield distribution curve for various isobars represents 3 to 4 units of charge as compared to a smaller halfwidth of 2 to 3 units of charge for the fission of U, Th and Bi. If the energy of the incident protons is lowered to 220 Mev, the yield of asymmetrical fission products such as Cl/sup 3//sup 8/, Cl/sup 3//sup 9/, Mn/sup 5//sup 6/ and Co/sup 6//sup 1/ ismore » decreased by a fact or of 10, while the yield of V/sup 4//sup 8/, which is a product of symmetrical fission, remains constant. Calculations show that the fission of Sb is accompanied by the emission of seven protons. The total fission cross-section of Sb for 660 mev protons is 0.25 mbarns. (TTT)« less