Microscopic investigation of the alpha +18O system in a three-cluster model.

Abstract

The $^{22}\mathrm{Ne}$ spectrum is investigated with microscopic wave functions defined in the generator-coordinate formalism. This nucleus is described in a three-cluster model, involving an $^{16}\mathrm{O}$ core surrounded by a dineutron and an \ensuremath{\alpha} particle. The $^{18}\mathrm{O}$ cluster is projected out on the ${0}^{+}$ and ${2}^{+}$ states. We propose a band structure of $^{22}\mathrm{Ne}$ with experimental candidates. The model suggests the existence of a ${0}^{+}$ band presenting a marked \ensuremath{\alpha}${+}^{18}$O cluster structure. We present the \ensuremath{\alpha}${+}^{18}$O${(0}^{+}$,${2}^{+}$) collision matrices, and discuss the resonance properties in the $^{18}(\mathit{\ensuremath{\alpha}}$,\ensuremath{\alpha}${)}^{18}$O scattering. Electromagnetic transition probabilities in the $^{22}\mathrm{Ne}$ nucleus are calculated. From the theoretical Coulomb shifts between the mirror $^{22}\mathrm{Ne}$ and $^{22}\mathrm{Mg}$ nuclei, we suggest spin assignments for different $^{22}\mathrm{Mg}$ states. The $^{18}(\mathit{\ensuremath{\alpha}}$,\ensuremath{\gamma}${)}^{22}$Ne capture cross section is calculated, and is used for determining microscopically the nonresonant reaction rate.