Unique features of structure in an odd-proton $N\approx Z$ nucleus ${}^{69}$As

Abstract

We apply a large-scale shell model to the study of proton-rich odd-mass nuclei with $N\approx Z$. Calculations predict unexpected structure in the ${}^{69}$As nucleus for which a detailed experiment was recently performed. In this odd-proton nucleus, one neutron competes with one proton for occupying the high-$j$ intruder orbit $g_{9/2}$ in the $9/2_1^{+}$ state and almost solely occupies the $g_{9/2}$ orbit in other low-lying positive-parity states. The T=0, J=9 one-proton-one-neutron alignment takes place in the negative-parity states with medium-high spins. A unique coexistence of two lowest bands with positive and negative signs of spectroscopic quadrupole moments is predicted.

7 pages, 5 figures, accepted for publication in Pyhs. Rev. C