Excitation energy dependence of fragment mass and total kinetic energy distributions in proton-induced fission of light actinides

Fragment mass and total kinetic energy distributions in the proton-induced fission of 232Th, 233U and 238U at beam energies of 10.0, 11.5 and 13.0 MeV have been measured by a double time-of-flight method. The yields at the fragment mass number A N 132 with the spherical shells of N = 82 and 2 = 50 in the asymmetric fission mode increase with excitation energy of the compound nucleus compared with those at A N 143 with the deformed shell of N = 86 88 in p + 232Th. In contrast, such excitation energy dependence of the yields is not observed in p + 233,238U. The excitation energy dependence of