Nuclear charge distribution in proton fission of [thorium]

The independent formation cross-sections of 30 min Cs^130, 6.5d Cs^132, 2.9 hr Cs^134m, 2.1 yr Cs^134g, 13 d Cs^136, 32 min Cs^138, 18 d Rb^86, and cumulative formation cross-sections of 30 yr Cs^137 and 17 min Xe^138 produced in the fission of Th^232 by 20 by 85 Mev. protons have been measured radiochemically. Charge distribution curves were constructed at 20, 30, 39, 50, 51, 65, 15 and 85 Mev. With increasing proton energy these curves broaden and the most probable charge shifts towards the line of beta stability. These effects are interpreted in terms of fission-spallation competition. Detailed calculations on the basis of two empirical postulates on charge distribution have been attempted. Previously published experimental results on proton induced fission of uranium have also been incorporated in these calculatlons to make a comparative study. It was also possible to determine the isomerratio Cs^134m/Cs^134g in these experiments and to compare the results with theoretical calculations at the lowest energies studied. Some qualitative conclusions could be drawn about the angular momentum distribution during the fission process