Characterization of the proposed 4-α cluster state candidate in 16O

Abstract

The ${}^{16}\mathrm{O}(\hat{I}\pm ,\hat{I}{\pm }^{\prime })$ reaction was studied at $\hat{I}{¸}_{lab}=0^{\circ }$ at an incident energy of ${\text{E}}_{lab}$ = 200 MeV using the K600 magnetic spectrometer at iThemba LABS. Proton and $\hat{I}\pm$-decay from the natural parity states were observed in a large-acceptance silicon-strip detector array at backward angles. The coincident charged particle measurements were used to characterize the decay channels of the $0_6^{+}$ state in ${}^{16}\mathrm{O}$ located at $E_x=15.097(5)$ MeV. This state is identified by several theoretical cluster calculations to be a good candidate for the 4-$\hat{I}\pm$ cluster state. The results of this work suggest the presence of a previously unidentified resonance at $E_x\approx 15$ MeV that does not exhibit a $0^{+}$ character. This unresolved resonance may have contaminated previous observations of the $0_6^{+}$ state.