Low-spin particle-core and hole-core excitations in Ca41,47,49 isotopes studied by cold-neutron-capture reactions

We present recent results on the structure of the one-valence-particle41Ca and49Ca nuclei and the one-valence-hole47Ca nucleus. The isotopes of interest were populated via the cold-neutron-capture reactions40Ca(n,γ),48Ca(n,γ), and46Ca(n,γ), respectively. The experiments were performed at the Institut Laue-Langevin, withinthe EXILL campaign, which employed a large array of high-purity germanium (HPGe) detectors. Theγdecay and level schemes of these nuclei were investigated byγ-ray coincidence relationships, leading to theidentification of 41, 10, and 6 new transitions in41Ca,47Ca, and49Ca, respectively. Branching ratios andintensities were extracted for theγdecay from each state, andγ-ray angular correlations were performedto establish a number of transition multipolarities and mixing ratios, thus helping in the spin assignment ofthe states. The experimental findings are discussed along with microscopic, self-consistent beyond-mean-fieldcalculations performed with the hybrid configuration mixing model, based on a Skyrme SkX Hamiltonian. Thelatter suggests that a fraction of the low-spin states of the41Ca,49Ca, and47Ca nuclei is characterized by thecoexistence of either 2p-1h (two-particle–one-hole) and 1p-2h excitations, or couplings between single-particleor single-hole degrees of freedom and collective vibrations (phonons) of the doubly-magic “core.”