Photofission of209Bi,232Th and238U in the quasi-deuteron energy region
Photofission cross sections of209Bi,238U and232Th are very different, both in magnitude and in their dependence on the incident photon energy. In fact, in the quasi-deuteron energy region,σf (Bi)<10−2σf(U), withσf(Th) having intermediate values. Alsoσf(Bi) increases monotonically vs.Eγ whileσf(U) andσf(Th) (above 75 MeV) are approximatively constant. We propose here a parametrization of photofission in the quasi-deuteron region, which fits, up toEγ ⋃mπ, the photofission cross sections of these three nuclei.