Study of the odd-mass nuclei at the beginning of the 2s-1d shell. Theoretical and experimental aspects

Two methods of calculation are investigated in the Bohr-Motelsson-Nilsson model framework, for the properties of the excited states of odd-A nuclei at the beginning of the s-d shell. In the first method, a single nucleon is coupled to the even-even deformed core: it is well adapted to the particle states with positive parity, of the nuclei with /N-Z/=1. In the second calculation, all odd valence nucleons outside an 16O core are considered exactly: this method gives better results than the first one in the case of hole-states with positive parity, of the nuclei with (N-Z)=3. The theoretical results are discussed and the conclusions suggest a choice of experiments. In this context, the 21Ne(t,p) reaction has been performed and yield a set of Jsup(π) and Esub(x) values for neon 23