  Study of the ground-state properties of Kr, Sr and Zr isotopes has been
performed in the framework of the relativistic mean field (RMF) theory using
the recently proposed relativistic parameter set NL-SH. It is shown that the
RMF theory provides an unified and excellent description of the binding
energies, isotope shifts and deformation properties of nuclei over a large
range of isospin in the Z=40 region. It is observed that the RMF theory with
the force NL-SH is able to describe the anomalous kinks in isotope shifts in Kr
and Sr nuclei, the problem which has hitherto remained unresolved. This is in
contrast with the density-dependent Skyrme Hartree-Fock approach which does not
reproduce the behaviour of the isotope shifts about shell closure. On the Zr
chain we predict that the isotope shifts exhibit a trend similar to that of the
Kr and Sr nuclei. The RMF theory also predicts shape coexistence in heavy Sr
isotopes. Several dramatic shape transitions in the isotopic chains are shown
to be a general feature of nuclei in this region. A comparison of the
properties with the available mass models shows that the results of the RMF
theory are generally in accord with the predictions of the finite-range droplet
model.
