High-Energy Electron Scattering and the Charge Distribution of Carbon-12 and Oxygen-16

The scattering of high-energy electrons from ${\mathrm{C}}^{12}$, reported previously, has been extended to 420 Mev. The elastic and inelastic scattering from the first excited level at 4.43 Mev has been studied between 33° and 70°. The new data are in good agreement with what one would expect from the earlier measurements on ${\mathrm{C}}^{12}$ performed at 187 Mev. Additional measurements of the elastic ${\mathrm{O}}^{16}$-scattering cross sections of 240-, 360-, and 420-Mev electrons as functions of the scattering angle furnish information on the size and shape of the ${\mathrm{O}}^{16}$ nucleus. Pronounced diffraction minima in the angular distributions were observed for ${\mathrm{C}}^{12}$ and ${\mathrm{O}}^{16}$. The experimental results are compared with the predictions of a theoretical phase-shift analysis derived for the harmonic-well independent-particle model of the nucleus. Preliminary best fits confirm the shell-model predictions for the charge density distribution of these $p$-shell nuclei. The preliminary analysis of the data shows that the length parameter of the well is 1.66×${10}^{-13\mathrm{}}$ cm for ${\mathrm{C}}^{12}$, and 1.76×${10}^{-13\mathrm{}}$ cm for ${\mathrm{O}}^{16}$, thus indicating a slight variation of the curvature of the harmonic well as the $p$ shell is filled in.