Measurement of the ${}^{58}\mathrm{Ni(}\alpha$,$\gamma$)${}^{62}\mathrm{Zn}$ reaction and its astrophysical impact

Cross section measurements of the ${}^{58}\mathrm{Ni(}\alpha$,$\gamma$)${}^{62}\mathrm{Zn}$ reaction were performed in the energy range $E_{\alpha }=5.5\text{to}9.5$ MeV at the Nuclear Science Laboratory of the University of Notre Dame, using the NSCL Summing NaI(Tl) detector and the $\gamma$-summing technique. The measurements are compared to predictions in the statistical Hauser-Feshbach model of nuclear reactions using the SMARAGD code. It is found that the energy dependence of the cross section is reproduced well but the absolute value is overestimated by the prediction. This can be remedied by rescaling the $\alpha$ width by a factor of 0.45. Stellar reactivities were calculated with the rescaled $\alpha$ width and their impact on nucleosynthesis in type Ia supernovae has been studied. It is found that the resulting abundances change by up to 5% when using the new reactivities.

Figure 1

Experimental spectra from the SuN detector for measurements at $E_{\alpha }=7.7$ MeV. The spectra correspond to the ${}^{58}$Ni target (solid black), thick tantalum backing (dotted blue), and normalized room background (dotted-dashed red). The inset shows a zoom around the sum-peak region of the ${}^{58}\mathrm{Ni(}\alpha$,$\gamma$)${}^{62}\mathrm{Zn}$ reaction.

Figure 2

Cross section of the ${}^{58}\mathrm{Ni(}\alpha$,$\gamma$)${}^{62}\mathrm{Zn}$ reaction for the present work (black circles), previous data of Ref. [11] (red triangles), and theoretical calculations from the SMARAGD code [19]. A good description was obtained by modifying the $\alpha$ width and the $\gamma$-to-proton width ratio (dashed line).

Figure 3

Absolute values of the sensitivity of the ${}^{58}\mathrm{Ni(}\alpha$,$\gamma$)${}^{62}\mathrm{Zn}$ cross section as function of energy, when separately varying $\gamma$, neutron, proton, and $\alpha$ widths.