Investigation of an 8p-4h state at Ex = 12.44 MeV in 20Ne

Abstract

Angular distributions and excitation functions for the 16O(α, α') 16O(6.05 MeV, 0 +) reaction have been measured for incident α-particle energies between 9.52 and 9.80 MeV. covering the region in which a probable 0 + resonance has been reported previously. A pronounced resonance was observed, but the angular distributions were found to be anisotropic, and the excitation functions did not exhibit the lorentzian shape expected from an isolated resonance. These observations are interpreted in terms of a 0 + resonance interfering coherently with a non-resonant background containing partial waves from l = 0 to l = 3. From the analysis the following properties of the 0 + state in 20Ne have been derived: E x = 12.436 ± 0.004 MeV Γ c.m. = 24.4 ± 0.5 keV and ωγ c.m. = 2.82 ± 0.29 keV. A limit on the fraction of the total α-decay strength proceeding to the 6.05 MeV level, Γ α 1 Γ , was obtained from a separate measurement employing the 12 C( 12 C, α) 20 Ne reaction. Taken together with the inelastic scattering results, this required Γ α 1 = 20.8 ± 0.4 keV and Γ α 0 = 3.2 ± 0.4 keV, which correspond to α-particle spectroscopic factors of approximately unity and 1 × 10 −3 for the α-decays from the 12.44 MeV(0 +) state in 20Ne to the 6.05 MeV and ground states of 16O. The large spectroscopic factor to the 6.05 MeV 4p-4h state in 16O indicates that the wave function of the 12.44 MeV state in 20Ne contains a large amount of 8p-4h configurations. Information on a 3 − state at E x = 12.394 ± 0.004 MeV in 20Ne was also obtained: Γ c.m. = 37.3 ± 0.9 keV and ωγ c.m. = 3.3 ± 0.3 keV.