Based on available experimental data, a new set of Nilsson parameters is proposed for proton-rich nuclei with proton or neutron numbers $28<~N<~40.$ The resulting single-particle spectra are compared with those from relativistic and nonrelativistic mean field theories. Collective excitations in some even-even proton-rich nuclei in the upper $\mathrm{pf}$ shell are investigated using the projected shell model with the new Nilsson basis. It is found that the regular bands are sharply disturbed by band crossings involving ${1g}_{9/2}$ neutrons and protons. Physical quantities for exploring the nature of the band disturbance and the role of the ${1g}_{9/2}$ single-particle are predicted, which may be tested by new experiments with radioactive beams.

• Received 28 February 2000

DOI:https://doi.org/10.1103/PhysRevC.62.021601