Intermediate Structure in the Photofission Cross Section ofTh232

Abstract
Intermediate structure has been observed in the photofission cross section of Th232 measured with a photon energy resolution <500 eV. The gamma rays, variable in energy, were obtained from the (p, γ) reaction on several nuclei. The average spacing of the observed photofission resonances at an excitation energy of 6.16 MeV is 1.6±0.4 keV. The average areas of the resonances are compared with theoretical expectations for a double-humped and a triple-humped barrier.