Measurement of photofission excitation of 237NP

The angular distribution of 237Np fission fragments was measured over the energy range 7.4 MeV–9.2 MeV in steps of 0.4 MeV of bremsstrahlung radiation. Lexan polycarbonate films (SSNTD) were used to detect the fission fragments. The photon intensity from the Microtron accelerator at a distance of 15 cm from the bremsstrahlung converter (tantalum target) facility was estimated to be 1010 photons s−1 using the code EGS-4. The photofission cross-section was calculated using the angular distribution of fission fragments and the results were compared with those obtained using the code EMPIRE-II and various barrier parameters of the RIPL-1, RIPL-2 libraries and with the new analytical fission barrier formula based on the Hugenholtz–Van Hove theorem. The results are in good agreement with the prediction of the RIPL-1 barrier parameter and analytical fission barrier formula.

► Fission with photons is a powerful tool for investigating the complex dynamics of the excitation of heavy nuclei.
► The nuclear fission mechanism at low excitations is closely connected with the concepts of fission channel proposed by Age Bohr.
► The measurements of angular distribution of fission fragments are an important source which provides information on the nuclear states at the saddle configuration and these states are characterized by J, K and M.