Iridium metal has been bombarded with protons varying in energy from 8 to 87 Mev. The spallation products were radiochemically separated and decay characteristics and formation cross sections were determined. I t was confirmed that both Pt187 and Pt18%ave half-lives of about 3 hr, and a half-life of 1 3 . 3 3~ 0.2 days was found for IrlS9. An isomeric state of Irla6 with half-life 2.0f 0.5 hr has been found. Fair agreement was obtained between excitation functions for (p,xn) reactions determined experimentally and those predicted by the Jackson model.The (p,pn) yield a t 84 Mev has been compared with that calculated from Monte Carlo cascade data combined with evaporation theory and found to be too high by a factor of 4.
The independent fission yields in thermal neutron induced fission of 235U have been measured to be (9.5 f 1.4) and (1.04 f 0.17). for 1Z4gSb and lZ6gSb, respectively. The total independent yields for all isomers of these nuclides are estimated to be (1.2 f 0.2).for 12"Sb and (3.7 f 0.6) for lZ6Sb using a Huizenga-Vandenbosch approach for estimating population of isomeric states.These data do not seem t o support a 50 proton shell effect on the Zp function, using the "unique" charge distribution curve of Wahl. A revised Wahl plot based on recent information on neutron emission from individual fission fragments is given and discussed in view of shell effects in fission. I t is shown that the effect of the Zp function of the 50 protoil shell is very small.
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