The scattering of 187-Mev electrons from ${\mathrm{C}}^{12}$, reported previously, has been extended to 138°. It has been possible to separate the elastic scattering from the inelastic scattering and to resolve the inelastic groups from the 4.43-, 7.65-, and 9.61-Mev nuclear levels. "Absolute" values were obtained by comparing the scattering from carbon with the scattering from hydrogen and computing the proton cross section. The angular distribution of the elastically-scattered electrons falls off more steeply than the angular distribution of the inelastically-scattered electrons. Analysis of the data, using the Born approximation, shows that the root-mean-square radius of ${\mathrm{C}}^{12}$ (corrected for breakdown of the Born approximation) is (2.37±0.05)×${10}^{-13\mathrm{}}$ cm with a surface thickness of (2.0±0.4)×${10}^{-13\mathrm{}}$ cm. The corresponding value of $r_0$, the "classical" radius parameter, is (1.33±0.02)×${10}^{-13\mathrm{}}$ cm which is larger than that found from electron-scattering measurements for the heavy nuclei and is in agreement with the trend for light nuclei. The scattering from the 4.43-Mev and 7.65-Mev levels is larger than that predicted by some shell-model calculations. The transition from the ground state to the 9.61-Mev level appears to be either quadrupole or electric monopole, which gives a spin and parity assignment of either $2^{+}$ or $0^{+}$.

• Received 19 June 1956

DOI:https://doi.org/10.1103/PhysRev.104.225