Shell model calculations in the full pf -shell are carried out for the A=50, 51 and 52 isobars. The most frequently used effective interactions for the pf -shell, KB3 and FPD6 are revisited and their behaviour at the N=28 and Z=28 closures examined. Cures to their -relatively minor-defaults are proposed, and a new mass dependent version called KB3G is released. Energy spectra, electromagnetic transitions and moments as well as beta decay properties are computed and compared with the experiment and with the results of the earlier interactions. A high quality description is achieved. Other miscellaneous topics are addressed; the Coulomb energy differences of the yrast states of the mirror pair 51 Mn-51 Fe and the systematics of the magnetic moments of the N=28 isotones.

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Gamma rays from the N = Z-2 nucleus (50)Fe have been observed, establishing the rotational ground state band up to the state J(pi) = 11+ at 6.994 MeV excitation energy. The experimental Coulomb energy differences, obtained by comparison with the isobaric analog states in its mirror (50)Cr, confirm the qualitative interpretation of the backbending patterns in terms of successive alignments of proton and neutron pairs. A quantitative agreement with experiment has been achieved by exact shell model calculations, incorporating the differences in radii along the yrast bands, and properly renormalizing the Coulomb matrix elements in the pf model space.

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