Microscopic description of the α+16O system in a multicluster model

The multicluster generator coordinate method is applied to a microscopic study of the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ spectroscopy and of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(α,γ${)}^{20}$Ne capture cross section. The ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ nucleus is described by four α clusters located on the apexes of a tetrahedron. The good quantum numbers of the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and α${+}^{16}$O wave functions are restored by a multiple angular-momentum projection. With respect to the usual two-center approach, where ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ is described by a closed p shell, the five-α model improves different ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ spectroscopic properties. The ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(α,γ${)}^{20}$Ne S factor is reduced by about 30% at astrophysical energies.