Additional $\alpha$-particle optical potential tests below the Coulomb barrier

New results of $(\alpha ,\gamma )$ and $(\alpha ,n)$ reaction cross section measurements close to the reaction thresholds support the setting up of recent parameters of the $\alpha$-particle optical model potential (OMP) below the Coulomb barrier. Particular features of the $\alpha$-particle optical potential at energies below the Coulomb barrier explain the failure of using the OMP parameters obtained by analysis of only $\alpha$-particle elastic scattering at higher energies.

Figure 1

Panels (a) and (c): Comparison of calculated total $\alpha$-reaction cross sections using a former OMP [3] (dash-dotted curve), parameters in Ref. [5] obtained above the Coulomb barrier height $B$, in MeV ($E>B$), by elastic scattering analysis alone (dashed curve), and the OMP parameters of Ref. [5] (dotted curve), as well as comparison of the measured [2] and calculated cross sections of $(\alpha ,\gamma )$ and $(\alpha ,n)$ reactions on ${}^{113,115}\mathrm{In}$ nuclei, respectively, as described in the text. Panels (b) and (d): The latter comparison for the ${}^{113,115}\mathrm{In}$$(\alpha ,n)$ reactions, respectively, that produce ground ${}^{116,118}\mathrm{Sb}$${}^g$ and isomeric ${}^{116,118}\mathrm{Sb}$${}^m$ states. The experimental data for ${}^{113,115}\mathrm{In}$ are taken from Refs. [2] and [9, 10, 11], respectively.