We report the electron-induced fission of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ into two ground-state ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ nuclei following monopole excitation at energies between 20 and 22 MeV. The observed cross section exhausts at least (8±2)% of the linear energy-weighted monopole sum rule $S\left(E0\mathrm{}\right)\mathrm{}$ and may form a part of the giant monopole resonance. In addition, we have observed a peak in the ${\theta }_{{}_{}{}^{12}{}_{}{}^{}\mathrm{C}}=45\mathrm{}°$ excitation function between 22.0 and 23.5 MeV with a width (full width at half-maximum) < 1 MeV and a ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ angular distribution, ${sin}^2\left(2\mathrm{}{\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\right)$, indicating $J^{\pi }=2^{+}$.

• Received 22 February 1978

DOI:https://doi.org/10.1103/PhysRevLett.40.1248