Observations of a High-Spin Yrast Cascade inCr50

Abstract

A ground-state band with spin up to $J^{\pi }={12}^{+}$ was observed in ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$ from the reactions ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, 2p\alpha ){}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}({}_{}{}^{32}{}_{}{}^{}\mathrm{S}, 2p\alpha ){}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}({}_{}{}^{14}{}_{}{}^{}\mathrm{N}, 3pn){}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}({}_{}{}^{12}{}_{}{}^{}\mathrm{C}, 2p){}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$. Spin and parity assignments were made from $\gamma -\gamma$ coincidences, angular distributions, and linear-polarization measurements. The higher-spin states are reasonably well reproduced in the ${\left(1\mathrm{}{f}_{\frac{7}{2}}\right)}^n$ shell-model frame while discrepancies exist for the lower ones. These levels have collective features at lower excitation but very pure shell-model characteristics towards the maximum spin expected in the ${\left(1\mathrm{}{f}_{\frac{7}{2}}\right)}^n$ space.