Low-spin particle-core and hole-core excitations in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ca</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>41</mml:mn><mml:mo>,</mml:mo><mml:mn>47</mml:mn><mml:mo>,</mml:mo><mml:mn>49</mml:mn></mml:mrow></mml:mmultiscripts></mml:math> isotopes studied by cold-neutron-capture reactions
Аннотация
We present recent results on the structure of the one-valence-particle $^{41}\mathrm{Ca}$ and $^{49}\mathrm{Ca}$ nuclei and the one-valence-hole $^{47}\mathrm{Ca}$ nucleus. The isotopes of interest were populated via the cold-neutron-capture reactions $^{40}\mathrm{Ca}(n,\ensuremath{\gamma}), ^{48}\mathrm{Ca}(n,\ensuremath{\gamma})$, and $^{46}\mathrm{Ca}(n,\ensuremath{\gamma})$, respectively. The experiments were performed at the Institut Laue-Langevin, within the EXILL campaign, which employed a large array of high-purity germanium (HPGe) detectors. The $\ensuremath{\gamma}$ decay and level schemes of these nuclei were investigated by $\ensuremath{\gamma}$-ray coincidence relationships, leading to the identification of 41, 10, and 6 new transitions in $^{41}\mathrm{Ca}, ^{47}\mathrm{Ca}$, and $^{49}\mathrm{Ca}$, respectively. Branching ratios and intensities were extracted for the $\ensuremath{\gamma}$ decay from each state, and $\ensuremath{\gamma}$-ray angular correlations were performed to establish a number of transition multipolarities and mixing ratios, thus helping in the spin assignment of the states. The experimental findings are discussed along with microscopic, self-consistent beyond-mean-field calculations performed with the hybrid configuration mixing model, based on a Skyrme SkX Hamiltonian. The latter suggests that a fraction of the low-spin states of the $^{41}\mathrm{Ca}, ^{49}\mathrm{Ca}$, and $^{47}\mathrm{Ca}$ nuclei is characterized by the coexistence of either 2p-1h (two-particle--one-hole) and 1p-2h excitations, or couplings between single-particle or single-hole degrees of freedom and collective vibrations (phonons) of the doubly-magic ``core.''