The longitudinal and transverse form-factor spectra for electroexcitation of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ giant resonance were determined separately. Results are presented for an excitation energy range of from 15 to 30 MeV and for a momentum-transfer range of 0.84-1.56 ${\mathrm{F}}^{-1\mathrm{}}$. We have found levels with the following excitation energies (MeV), spins, and parities: 18.6 ($3^{-}$), 19.6 ($4^{-}$), 20.0 ($2^{+}$), 20.6 ($3^{+}$), 21.6 ($3^{-}$), 22.0 ($1^{-}$), 22.7 ($1^{-}$), and 23.8 ($1^{-}$). We have also found new evidence of the spin-isospin mode for the 22.7-MeV ($1^{-}$) excitation.

• Received 20 July 1970

DOI:https://doi.org/10.1103/PhysRevLett.25.874