Crystal blocking measurements of the induced fission time in the 232Th+p and 232Th+3He reactions

The crystal blocking technique has been used to measure the induced fission lifetimes for the 232,233Pa and 232U nuclei produced in the 232Th+p and 232Th+3He reactions at bombarding energies of protons and 3He included in the 6.8-7.8 MeV and 20.8-23.4 MeV ranges, respectively. The experimental fission lifetimes observed in these reactions vary from 10-16 to 10-14 s, depending on the projectile energy. Experimental data have been compared with the statistical model calculations that take into account the existence of both classes of excited states of fissioning nucleus, realized in the first and second potential wells of the double-humped fission barrier. By the analysis of the measured decay times it is possible to determine the absolute values of the level density in the second well, type of shape symmetry in the second well, and also the unknown early values of the shell correction for the investigated fissioning nuclei at the deformation corresponding to the second potential well