Search for particle-hole excitations across the N = 28 shell gap in 45,46 Ar nuclei

Abstract The structure of the N ≃28 45,46 18 Ar 27,28 nuclei has been investigated through in-beam γ -ray spectroscopy using the fragmentation reaction of a 60  A  MeV 48 Ca beam on a thin Be target. γ -ray energies, intensities, γγ coincidences and γ -ray angular anisotropies have been measured. The level scheme of 45 Ar is proposed for the first time, while that of 46 Ar 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 45 Ar 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.