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

The scattering of high-energy electrons from C¹², 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 C¹² performed at 187 Mev. Additional measurements of the elastic O¹⁶-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 O¹⁶ nucleus. Pronounced diffraction minima in the angular distributions were observed for C¹² and O¹⁶. 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 cm for C¹², and 1.76×{}10^-13 cm for O¹⁶, thus indicating a slight variation of the curvature of the harmonic well as the p shell is filled in.