N=40Neutron Subshell Closure in theNi68Nucleus

Abstract

The ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ni}$ nucleus has been identified among the products of deep-inelastic reactions of ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$ projectiles bombarding ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ targets. Three new states, including the high-lying $2^{+}$ (2033 keV) and the 0.86 ms $5^{-}$ isomer, indicate a substantial subshell closure at neutron number $N=40\mathrm{}$. The level structure and the observed very slow $E3\mathrm{}$ transition speed are discussed within the shell model.