Evidence for $\alpha$-cluster structure in ${}^{21}\mathrm{Ne}$ in the first measurement of resonant ${}^{17}\mathrm{O}+\alpha$ elastic scattering

The first study of resonances in ${}^{17}\mathrm{O}+\alpha$ elastic scattering was carried out using the thick target inverse kinematics method. The data were analyzed in the framework of an R-matrix approach. Many $\alpha$-cluster states were found in the ${}^{21}\mathrm{Ne}$ excitation region of the 9–13 MeV excitation energy including the first observation of a broad $l=0$ state in an odd-even nucleus, which is likely the analog of the broad $0^{+}$ at 8 MeV in ${}^{20}\mathrm{Ne}$. The observed structure in ${}^{21}\mathrm{Ne}$ appeared to be strikingly similar to that populated in the resonant ${}^{16}\mathrm{O}+\alpha$ scattering in ${}^{20}\mathrm{Ne}$. The results are also useful for refinement of data on an ${}^{17}\mathrm{O}(\alpha ,n)$ reaction important for astrophysics.

Figure 1

Excitation function for ${}^{17}\mathrm{O}(\alpha ,\alpha ){}^{17}\mathrm{O}$ elastic scattering. The bold (red) line is the R-matrix fit. The inset is a zoomed-in region of the excitation function to demonstrate the influence of the $l=0$, 3.70 MeV resonance.

Figure 2

R-matrix fit (bold red curve) of the excitation functions for the elastic scattering of $\alpha$ particles from ${}^{17}\mathrm{O}$.

Figure 3

Comparison of $\alpha$-cluster resonances in ${}^{21}\mathrm{Ne}$ and ${}^{20}\mathrm{Ne}$. The $l=1$ levels at 1.315 and 1.55 MeV are from Ref. [7].