Alpha-cluster states in 18O

Abstract

The excitation function of elastic α -particle scattering on 14 C has been measured in the laboratory energy range 16.3–19.2 MeV using a backscattering technique with a thick target. These data were analyzed together with the old low-energy data of G.L. Morgan et al. in the framework of the R -matrix formalism. Spin-parity assignments were made for 32 states in 18 O in the excitation range 9–20 MeV. The estimates of the widths of the states are also presented. The 0 + and 0 − α -cluster bands appeared to be well separated by 5.6 MeV (as in 16 O and 20 Ne). We have not found a confirmation of existence of the negative-parity molecular states proposed by M. Gai et al. We observed an effect of a doubling of α -cluster levels in 18 O similar to that found in 22 Ne.