The $\gamma$ decay from Coulomb excitation of ${}^{68}\mathrm{Ni}$ at $600\mathrm{MeV}/\mathrm{\text{nucleon}}$ on a Au target was measured using the RISING setup at the fragment separator of GSI. The ${}^{68}\mathrm{Ni}$ beam was produced by a fragmentation reaction of ${}^{86}\mathrm{Kr}$ at $900\mathrm{MeV}/\mathrm{\text{nucleon}}$ on a ${}^9\mathrm{Be}$ target and selected by the fragment separator. The $\gamma$ rays produced at the Au target were measured with HPGe detectors at forward angles and with ${\mathrm{BaF}}_2$ scintillators at backward angles. The measured spectra show a peak centered at approximately 11 MeV, whose intensity can be explained in terms of an enhanced strength of the dipole response function (pygmy resonance). Such pygmy structure has been predicted in this unstable neutron-rich nucleus by theory.

• Received 19 September 2008

DOI:https://doi.org/10.1103/PhysRevLett.102.092502