Elastic Scattering of Alpha Particles byO18

Abstract

The differential elastic scattering cross section of alpha particles by ${\mathrm{O}}^{18}$ has been measured for alphaparticle energies between 2.4 and 3.5 MeV and for ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=90.0\mathrm{}°, 125.3°, 140.7°, 152.3°, \mathrm{and} 164.4°$ in order to determine the level parameters of excited states in ${\mathrm{Ne}}^{22}$. The resonances were analyzed using the single-level and two-level approximation to determine reduced widths and resonance energies of the levels. Scattering anomalies were observed at bombarding alpha-particle energies of 2.48, 2.56, 2.72, 2.90, 3.17, and 3.33 MeV which correspond to excited states of ${\mathrm{Ne}}^{22}$ with the following energies, angular momenta, and parities: 11.70 MeV, $J^{\pi }=2^{+}$; 11.76 MeV, $J^{\pi }=1^{-}$; 11.89 MeV, $J^{\pi }=1^{-}$; 12.04 MeV, $J^{\pi }=0^{+}$; 12.26 MeV, $J^{\pi }=0^{+}$; 12.39 MeV, $J^{\pi }=2^{+}$. For bombarding alpha-particle energies in the vicinity of 3.5 MeV, it was found necessary to include the effects of two levels above 3.5 MeV to fit the scattering data: 12.57 MeV, $J^{\pi }=1^{-}$ and 12.61 MeV, $J^{\pi }=1^{-}$. None of the levels observed have reduced widths greater than 9% of the Wigner limit.