Low-, medium-, and high-spin states in the N=Z+1 nucleus Ga63

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.