Excitation of a 19-MeV Level inC12by Inelastic Electron Scattering

Measurements of inelastic-electron-scattering cross sections for ${\mathrm{C}}^{12}$ have been made for transitions to a level at approximately 19.5 MeV. The cross-section peak corresponding to excitation of this level is clearly visible above the inelastic continuum over the range of momentum transfers from 267 to $643 \frac{\mathrm{MeV}}{c}$ at electron-scattering angles between 40° and 48°. Form factors derived from the experimental data are compared with theoretical form factors calculated by assuming the excitation involves a single-particle-dipole transition to a $T=1\mathrm{}$, $J=1^{-}$ state. A search for levels with higher excitation energies was also undertaken, special attention being focused on the region 30 to 45 MeV. This failed to uncover, within the experimental sensitivity, any levels with excitation energy greater than 20 MeV.