The differential cross sections for elastic scattering of alpha-particles by ${\mathrm{O}}^{16}$ were measured in a gas-scattering chamber using alpha-particles accelerated in an electrostatic generator over the energy region from 0.94 to 4.0 Mev. Cross sections were measured at $\theta \left(\mathrm{cm}\right)=168.0\mathrm{}°; 140.1°; 124.6°; \mathrm{and} 90.0°$. Because both particles have zero spin the partial wave analysis is exceptionally simple and fixes unambiguously the angular momentum and parity of each level. The resonances were analyzed using the Wigner-Eisenbud one-level approximation to determine the width and resonant energy of each resonance. Five scattering anomalies were observed which correspond to excited states of ${\mathrm{Ne}}^{20}$ with the following energies, angular momenta, and parities: 6.738 Mev, $J=0^{+}$; 7.182 Mev, $J=3^{-}$; 7.218 Mev, $J=0^{+}$; 7.450 Mev, $J=2^{+}$; and 7.854 Mev, $J=2^{+}$. The uncertainty in these energies is about 10 kev, most of which is due to the uncertainty of the energy loss in the gas. None of the levels have reduced widths greater than two percent of the single particle width.

• Received 9 January 1953

DOI:https://doi.org/10.1103/PhysRev.90.839