Reevaluation of the ${}^{22}\mathrm{N}\mathrm{a}(p,\gamma )$ Reaction Rate: Implications for the Detection of ${}^{22}\mathrm{N}\mathrm{a}$ Gamma Rays from Novae

Understanding the processes which create and destroy ${}^{22}\mathrm{N}\mathrm{a}$ is important for diagnosing classical nova outbursts. Conventional ${}^{22}\mathrm{N}\mathrm{a}(p,\gamma )$ studies are complicated by the need to employ radioactive targets. In contrast, we have formed the particle-unbound states of interest through the heavy-ion fusion reaction, ${}^{12}\mathrm{C}({}^{12}\mathrm{C},n){}^{23}\mathrm{M}\mathrm{g}$ and used the Gammasphere array to investigate their radiative decay branches. Detailed spectroscopy was possible and the ${}^{22}\mathrm{N}\mathrm{a}(p,\gamma )$ reaction rate has been reevaluated. New hydrodynamical calculations incorporating the upper and lower limits on the new rate suggest a reduction in the yield of ${}^{22}\mathrm{N}\mathrm{a}$ with respect to previous estimates, implying a reduction in the maximum detectability distance for ${}^{22}\mathrm{N}\mathrm{a}$ $\gamma$ rays from novae.

Figure 1

(top panel) Contribution of individual resonances to the total reaction rate for the ${}^{22}\mathrm{N}\mathrm{a}(p,\gamma )$ reaction. The contributions are labeled with $E_p$ (lab) in keV. (inset, top left) Spectrum from $\gamma \mathrm{\text{−}}\gamma \mathrm{\text{−}}\gamma$ cube gated on 2739 and 1600 keV transitions. (Inset, bottom right) Spectrum from $\gamma \mathrm{\text{−}}\gamma \mathrm{\text{−}}\gamma$ cube gated on 450 and 1600 keV transitions. (bottom panel) Comparison of the total reaction rates normalized to the analytical rate presented by Angulo et al. [19]. The shaded region is the uncertainty in the rates given in the Angulo compilation [19]. The solid lines bound the uncertainties in the present work.