“Complete” high-spin structure of57Co

Abstract

A comprehensive high-spin decay scheme has been deduced for ${}^{57}\mathrm{Co}$ using the Gammasphere Germanium detector array coupled to the $4\ensuremath{\pi}$ charged-particle detector system Microball. Following the fusion-evaporation reaction of ${}^{28}\mathrm{Si}{(}^{36}\mathrm{Ar},1\ensuremath{\alpha}{3p)}^{57}\mathrm{Co}$ at 136 MeV beam energy about 90 excited states have been observed in ${}^{57}\mathrm{Co},$ which are connected by some 230 $\ensuremath{\gamma}\ensuremath{-}\mathrm{r}\mathrm{a}\mathrm{y}$ transitions. The proposed level scheme reaches 16 MeV excitation energy at a spin of $17\ensuremath{\Elzxh}--18\ensuremath{\Elzxh}.$ With its complexity the level scheme of ${}^{57}\mathrm{Co}$ appears to be ``complete'' up to 1 or 2 MeV above the yrast line. This aspect is further investigated through a comparison of the data with spherical shell-model calculations.