Investigation of low energy pion-nucleus interaction using electrofission data for heavy nuclei at the pion threshold

A theoretical approach to describe electro- and photofission processes at intermediate energies was worked out. Photopion reabsorption mechanisms by two and three nucleons (2NA and 3NA) were incorporated in the calculations. The comparison with electrofission data for preactinides showed that a substantial 3NA component should be added in the pion absorption to fit the data near photopion threshold, in accordance with a recent theoretical estimate. It was also shown that the shape of the fission response curve is sensitive to detailed aspects of the pion mean free path. Received: 10 March 1998 / Revised version: 12 March 1999