High-Spin Neutron Particle-Hole States in EvenN=28Isotones

In addition to the known ${\left(f_{\frac{7}{2}}\right)}^n$ multiplets, states with spins ranging up to ${10}^{+}$ (${11}^{+}$) have been identified in ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$, and ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ via ($\alpha , 2n\gamma$) reactions. Shell-model calculations including excitations of one particle from the $N=28\mathrm{}$ core successfully account for the newly observed states and indicate their $2p_{\frac{3}{2}}$ neutron character in ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$ and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$. The experimental results also require configuration mixing of about 20% for the lowlying $f_{\frac{7}{2}}$ states.