The 235U(n. f) reaction cross section was measured relative to neutron-proton elastic scattering for the first time in the energy region from 10 MeV to 440 MeV at the CERN n_TOF facility. extending the upper limit of the only previous measurement in the literature by more than 200 MeV. For neutron energies below 200 MeV. https://www.nacrack.com/