Isospin symmetry and proton decay: Identification of the 10+ isomer in Ni54

Abstract

The γ decays from an isomeric 10+ state at 6457 keV in the nucleus 2854Ni26 have been identified using the GSI fragment separator in conjunction with the RISING Ge-detector array. The state is interpreted as the isobaric analog of the 6527-keV 10+ isomer in 2654Fe28. The results are discussed in terms of isospin-dependent shell-model calculations. Clear evidence is presented for a discrete ℓ=5 proton decay branch into the first excited 9/2- state of the daughter Co53. This decay is the first of its kind observed following projectile fragmentation reactions. © 2008 The American Physical Society.