We report on the observation of a new isomeric state in ${}^{68}$Ni. We suggest that the newly observed state at 168(1) keV above the first 2${}^{+}$ state is a $\mathrm{<ruby><rb>\pi </rb><rt>ぱい</rt></ruby>}(2\mathrm{p}-2\mathrm{h})$ 0${}^{+}$ state across the major $Z=28$ shell gap. Comparison with theoretical calculations indicates a pure proton intruder configuration and the deduced low-lying structure of this key nucleus suggests a possible shape coexistence scenario involving a highly deformed state.

• Received 5 December 2011

DOI:https://doi.org/10.1103/PhysRevC.85.031301