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The transition rates for the 2(1)+ states in (62,64,66)Fe were studied using the recoil distance Doppler-shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N = 40. The results are interpreted using the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N = 40 as governed by the number of valence protons with respect to Z ≈ 30. The trend of collectivity suggested by the experimental data is described by state-of-the-art shell-model calculations with a new effective interaction developed for the fpgd valence space.

Rare isotope beams of neutron-deficient 106,108,110Sn from the fragmentation of 124Xe were employed in an intermediate-energy Coulomb excitation experiment. The measured B(E2,0(1)(+)-->2(1)(+)) values for 108Sn and 110Sn and the results obtained for the 106Sn show that the transition strengths for these nuclei are larger than predicted by current state-of-the-art shell-model calculations. This discrepancy might be explained by contributions of the protons from within the Z = 50 shell to the structure of low-energy excited states in this region.

In-beam γ -ray spectroscopy of 66,68 Fe following intermediate-energy one-and two-proton knockout from cobalt and nickel secondary beams has been performed at the National Superconducting Cyclotron Laboratory. New transitions have been observed in 66 Fe and 68 Fe. This is the first observation of γ -ray transitions in 68 Fe. In addition, 64 Cr was produced using the 9 Be( 66 Fe, 64 Cr)X two-proton knockout reaction. An unexpectedly low inclusive cross section is observed for this reaction, an order of magnitude smaller than for the 9 Be( 68 Ni, 66 Fe)X reaction. This observation is discussed in terms of a significant structural difference between 66 Fe and 64 Cr and considerable admixtures of ν(pf ) n−2 (g 9/2 ) +2 configurations in the ground and excited states of 64 Cr at N = 40.

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