Photon scattering off 52Cr: Two-phonon E1 strength at the N = 28 shell closure?

Results of a natCr(γ,γ') experiment at the S-DALINAC are reported for energies up to 7 MeV utilizing a Euroball Cluster detector. The excitation of a J=1 state at 5544 keV is observed which is believed to belong to 52Cr because of the strength of the signal and the large natural abundance. By a variety of empirical arguments a quadrupole-octupole-coupled two-phonon 1- character is suggested for this transition. Quasiparticle random-phase-approximation (QRPA) calculations are able to reproduce the energy and B(E1) transition strength remarkably well. The underlying microscopic structure is suggested to be more complex than a pure two-phonon picture. Furthermore, the calculations indicate a pure neutron (2p3/2-1 2p1/2) magnetic dipole structure for an excitation experimentally seen at 5098 keV which would provide a direct measure of ground-state correlations in 52Cr. (orig.)