Low energy and momentum transfer fission of 227Np and 238U by intermediate energy photons

Low-energy and momentum transfer photonuclear processes leading to nuclear fission of 238U and 237Np were studied using the tagged photon beam at the storage ring VEPP-3 INP (Novosibirsk) in the energy range Eγ=60-240 MeV (ΔEγ=30 MeV). The probability of (γ,xf) reaction, where f denotes fission fragments, x is a particle lighter than nucleon emitted in forward direction in a small solid angle (∼ 10-4 sr), was measured to be 5-10% as compared with the total fission cross section. In the framework of the Bethe-Heitler theory, the inelastic pair production cross section (γA → e+e-f) as an example of the low-energy transfer processes was evaluated. For such process theoretical values are less than experimental ones by 2-3 orders of magnitude