First direct measurement of the ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ reaction relevant for core-collapse supernovae nucleosynthesis

Understanding the explosion mechanism of a core-collapse supernova (CCSN) is important to accurately model CCSN scenarios for different progenitor stars using model-observation comparisons. The uncertainties of various nuclear reaction rates relevant for CCSN scenarios strongly affect the accuracy of these stellar models. Out of these reactions, the ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ reaction has been found to affect various stages of a CCSN at varying temperatures. This work presents the first direct measurement of the ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ reaction performed using a 34.6 MeV beam of radioactive ${}^{13}\mathrm{N}$ ions and the active-target detector MUSIC (MUlti-Sampling Ionization Chamber) at Argonne National Laboratory. The resulting total ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ reaction cross sections from this measurement in the center-of-mass energy range of 3.26–6.02 MeV are presented and compared with calculations using the Hauser-Feshbach formalism. Uncertainties in the reaction rate have been dramatically reduced at CCSN temperatures.

Figure 1

Plot of the Grid vs Strip0 showing the ${}^{13}\mathrm{N}^{7+}$ beam and contaminants from the primary ${}^{12}\mathrm{C}$ beam.

Figure 2

Energy loss per anode strip of different reaction channels in MUSIC from the present work. Shown are the energy losses for the unreacted ${}^{13}\mathrm{N}$ beam (black), ${}^{13}\mathrm{N}(\alpha ,\alpha ){}^{13}\mathrm{N}$ events occurring in anode strip 4 (blue), and ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ events occurring in anode strip 4 (red).

Figure 3

$\mathrm{\Delta }E\text{−}\mathrm{\Delta }E$ plots for MUSIC anode strip 2 (a), strip 4 (b), and strip 7 (c) showing the separation of the ($\alpha ,p$) events (red points) from ($\alpha ,\alpha$) events (blue points). The range of strips summed for each $\mathrm{\Delta }E$ is shown within parentheses.

Figure 4

Adopted astrophysical $S$ factors (red) as a combination of the present measurement (black circles), direct ${}^{16}\mathrm{O}(p,\alpha ){}^{13}\mathrm{N}$ data (green line) [30], and low energy data from Ref. [23] (black dotted-dashed line). The theoretical cross sections using talys are shown by the dashed blue line.

Figure 5

Theoretical total cross sections populating different excited levels of ${}^{16}\mathrm{O}$ along with the total cross sections from the present work.

Figure 6

The ${}^{13}\mathrm{N}(\alpha ,p){}^{16}\mathrm{O}$ reaction rate based on this work in comparison to the rates using talys, Ref. [23], and REACLIB [19] (upper panel). The same reaction rates as a ratio to the rate from the REACLIB (lower panel).