The structure of neutron-rich isotopes ${}^{60}\mathrm{Cr}$ and ${}^{62}\mathrm{Cr}$ was studied via proton inelastic scattering in inverse kinematics. The deformation lengths ($\delta$) for ${}^{60}\mathrm{Cr}$ and ${}^{62}\mathrm{Cr}$ were extracted as 1.12(16) and 1.36(14) fm, respectively, providing evidence for enhanced collectivity in these nuclei. An excited state at 1180(10) keV in ${}^{62}\mathrm{Cr}$ was identified for the first time. We adopted $4^{+}$ as its spin and parity, leading to the rapid increase of the $E_x(4^{+})/E_x(2^{+})$ ratio, which indicates the development of large deformation in ${}^{62}\mathrm{Cr}$ near $N=40$. Importance of the admixture of the $gd$-shell component above $N=40$ is also discussed by comparing with a modern shell model calculation.

• Received 3 July 2008

DOI:https://doi.org/10.1103/PhysRevLett.102.012502