Measurement of ${}^{23}\mathrm{Na}(\alpha ,p){}^{26}\mathrm{Mg}$ at Energies Relevant to ${}^{26}\mathrm{Al}$ Production in Massive Stars

${}^{26}\mathrm{Al}$ is an important radioisotope in astrophysics that provides evidence of ongoing nucleosynthesis in the Galaxy. The ${}^{23}\mathrm{Na}(\alpha ,p){}^{26}\mathrm{Mg}$ reaction has been identified by a sensitivity study as being one of the most important reactions for the production of ${}^{26}\mathrm{Al}$ in the convective C/Ne burning shell of massive stars. Owing to large uncertainties in previous experimental data, model calculations are used for the reaction rate of ${}^{23}\mathrm{Na}(\alpha ,p){}^{26}\mathrm{Mg}$ in this sensitivity study. Current experimental data suggest a reaction rate a factor of $\sim 40$ higher than model calculations. However, a new measurement of this reaction cross section has been made in inverse kinematics in the energy range $E_{\mathrm{c}.\mathrm{m}.}=1.28–3.15\mathrm{MeV}$ at TRIUMF, and found to be in reasonable agreement with the model calculation. A new reaction rate is calculated and tight constraints on the uncertainty in the production of ${}^{26}\mathrm{Al}$, due to this reaction, are determined.

Figure 1

Schematic of experimental setup inside the TUDA scattering chamber. The copper cone is not shown.

Figure 2

Background subtracted spectra are shown at three energies (blue) with the Monte Carlo simulation overlapped (red). An example of the gas out data overlapped with the gas in data is shown in the inset in (b).

Figure 3

Experimental cross sections from the present work and Almaraz-Calderon et al. [13] are plotted with theoretical cross section calculations using the codes Non-Smoker [12] and smaragd [18].

Figure 4

Reaction rates calculated using this work compared to the Non-Smoker rate adopted in the JINA REACLIB compilation [12] and the rate calculated by Almaraz-Calderon et al. in Ref. [13]. Also shown in the inset is the ratio of the rate calculated in this work to the Non-Smoker rate. Highlighted in gray is the range of temperatures used for the sensitivity study of nucleosynthesis in the $\mathrm{C}/\mathrm{Ne}$ convective burning shell by Illiadis et al. [9]