Nuclear charge dispersion in the fission of 233U by protons of medium energy

Abstract

Independent yields and excitation functions have been determined for the formation of cesium isotopes with masses 129 ≤ A ≤ 138 in the fission of 233U with protons of energies between 20 and 80 MeV. The energies at which the various excitation functions reach their maxima have been compared with those obtained for the same isotopes from fissioning systems with targets of different neutron-to-proton (N/Z) ratios. The neutron-deficient species have a higher probability of being produced at lower energies from targets with lower N/Z ratios. Charge dispersion curves have been obtained and these show the familiar broadening and displacement of Zp, the most probable charge, towards stability with increase in bombardment energy. Values of ZA – Zp have been compared with those obtained from other fissioning systems, and predictions made for values of Zp in the fission of systems yet unstudied, e.g. 235U and 239Pu. In addition Zp values were calculated for 233U fission, assuming compound nucleus formation up to a proton energy of 50 MeV, assuming pre- and post-fission neutron evaporation on the equal charge displacement and unchanged charge division postulates. Experimental values were found to lie between the two predictions.