Observation of new channel in the proton-induced low-energy fission of nuclei from 233Pa to 245Bk

The experimental data on mass and energy distributions (MED) of fragments in the proton-induced fission of target-nuclei from 232Th to 244Cm at proton energy 10.3 MeV have been measured with high relative and statistical accuracy. A new method has been proposed for analysing the MED from low-energy fission of nuclei heavier than Ra, that allows obtaining the information on shapes of mass distributions of independent fission modes. The existence of a fourth fission mode with enhanced kinetic energy conditioned by close-to-sphere shell with neutron number N≈52 formed in light fragments has been revealed for all investigated nuclei.