The absolute electrofission cross section of ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ was measured in the energy range 40–250 MeV. The data analysis, based on the virtual-photon technique, showed that the excitation mechanism which can cause the fission of ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ is the Levinger’s modified quasi-deuteron, even at energies well above the pion threshold.

• Received 28 January 1985

DOI:https://doi.org/10.1103/PhysRevC.31.2321