New ${\hat{I}}^3$-ray Transitions Observed in ${}^{19}$Ne with Implications for the ${}^{15}$O($\hat{I}\pm$,${\hat{I}}^3$)${}^{19}$Ne Reaction Rate

Abstract

The ${}^{15}$O($\hat{I}\pm$,${\hat{I}}^3$)${}^{19}$Ne reaction is responsible for breakout from the hot CNO cycle in Type I x-ray bursts. Understanding the properties of resonances between $E_x=4$ and 5 MeV in ${}^{19}$Ne is crucial in the calculation of this reaction rate. The spins and parities of these states are well known, with the exception of the 4.14- and 4.20-MeV states, which have adopted spin-parities of 9/2${}^{-}$ and 7/2${}^{-}$, respectively. Gamma-ray transitions from these states were studied using triton-${\hat{I}}^3$-${\hat{I}}^3$ coincidences from the ${}^{19}$F(${}^3$He,$t{\hat{I}}^3$)${}^{19}$Ne reaction measured with GODDESS (Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies) at Argonne National Laboratory. The observed transitions from the 4.14- and 4.20-MeV states provide strong evidence that the $J^{\ddot{I}}€$ values are actually 7/2${}^{-}$ and 9/2${}^{-}$, respectively. These assignments are consistent with the values in the ${}^{19}$F mirror nucleus and in contrast to previously accepted assignments.