Spin and parities of 19Ne states of astrophysical interest*

Observations of classical nova ejecta show discrepancies with theoretical predictions, particularly for the quantity of material ejected by the explosion. This discrepancy could be resolved with the detection of $\gamma$ rays originating from $^{18}$F. However, theoretical predictions of the flux of these $\gamma$ rays are limited by large uncertainties in the $^{18}$F destruction rates. These uncertainties are caused mainly by the incomplete knowledge of the influence of low energy resonances on the cross section for the main $^{18}$F destruction reaction $^{18}$F(p,$\alpha$)$^{15}$O. In this work we searched for states in the compound nucleus ($^{19}$Ne) relevant at nova temperatures and determined their spin and parities (J$^{\pi}$) when possible. In particular, we found that the state at 6.130 MeV (a proton sub-threshold resonance at E$_{CM}$=-280 keV) has a J$^{\pi}$=3/2$^+$, which opens the possibility for interference in the cross section with the well known broad resonances at E$_{CM}$ = 332 keV and 665 keV. We will present our experimental results and will highlight their effect on the $^{18}$F(p,$\alpha$)$^{15}$O reaction rate.