Abstract
The fusion-evaporation reaction $^{28}\mathrm{Si}+^{40}\mathrm{Ca}$ at 122 MeV beam energy was used to populate excited states in the $N=Z+1$ nucleus $^{63}\mathrm{Ga}$. With the combination of the Gammasphere spectrometer and the Microball CsI(Tl) charged-particle detector array, the level scheme of $^{63}\mathrm{Ga}$ was extended by more than a factor of two in terms of number of $\ensuremath{\gamma}$-ray transitions and excited states, excitation energy $({E}_{x}>30\phantom{\rule{0.16em}{0ex}}\mathrm{MeV})$, and angular momentum $(I>30\phantom{\rule{0.16em}{0ex}}\ensuremath{\hbar})$. Nine regular sequences of states were newly established in the high-spin part of the level scheme. The majority of these rotational band structures could be connected to the previously known part of the level scheme by high-energy $\ensuremath{\gamma}$-ray transitions in the energy range ${E}_{\ensuremath{\gamma}}=4--6\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$. Low-spin states were assessed by shell-model calculations. The high-spin rotational bands were interpreted and classified by means of cranked Nilsson-Strutinsky calculations.
Highlights
The structure of nuclei located in the vicinity of the doubly magic nucleus 56Ni can be expected to be described by the spherical shell model within the full N = 3 f p model space, which comprises the f7/2 orbital below, and the p3/2, f5/2, and p1/2 orbitals above the N = Z = 28 shell gap
While this was found to be the case for low-spin states in mass A ≈ 50–60 nuclei [1,2,3,4,5], the situation quickly becomes more complex for slightly heavier N ≈ Z nuclei and likewise as a function of excitation energy and angular momentum
Quadrupole deformation was found to increase with the number of particle-hole excitations across the shell gap and the number of particles placed in the g9/2 intruder orbitals
Summary
The structure of nuclei located in the vicinity of the doubly magic nucleus 56Ni can be expected to be described by the spherical shell model within the full N = 3 f p model space, which comprises the f7/2 orbital below, and the p3/2, f5/2, and p1/2 orbitals above the N = Z = 28 shell gap While this was found to be the case for low-spin states in mass A ≈ 50–60 nuclei [1,2,3,4,5], the situation quickly becomes more complex for slightly heavier N ≈ Z nuclei and likewise as a function of excitation energy and angular momentum. The feature of increasing deformation with an increasing number of particles placed in the g9/2 intruder orbitals could be delineated
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