Elastic Scattering of Alpha Particles by Carbon

By using a propane gas target and 4.0- to 7.6-Mev alpha particles from an electrostatic generator the elastic scattering differential, cross section of carbon has been measured with high resolution at five angles. A phase-shift analysis of the data indicates levels in ${\mathrm{O}}^{16}$ with the following energies, angular momenta, and parities: 10.36 Mev, $J=4, +$; 11.25 Mev, $J=0, +$; 11.51 Mev, J=2, +; 11.62 Mev, J=3, -; and 12.43 Mev, $J=1, -$. Reduced widths of the 10.36, 11.25, and 11.62 Mev levels approach the Wigner limit for single-particle excitation. Comparison is made with levels predicted by the alpha-particle nuclear model.