Search for particle–hole excitations across the N=28 shell gap in 45,46Ar nuclei Original Research Article

The structure of the N≃28 45,4618Ar27,28 nuclei has been investigated through in-beam γ-ray spectroscopy using the fragmentation reaction of a 60 A MeV 48Ca beam on a thin Be target. γ-ray energies, intensities, γγ coincidences and γ-ray angular anisotropies have been measured. The level scheme of 45Ar is proposed for the first time, while that of 46Ar has been extended to states above the previously known 2+ first excited state. An isomeric state at 537 keV of 0.34+0.32−0.15 ns lifetime has been found in 45Ar from the line-shape analysis of the γ ray connecting the first excited state to the ground state. The experimental results are interpreted using shell-model calculations.