Nuclear structure investigation of the near-spherical nucleus ⁹³Zr

The excited states of ⁹³Zr have been investigated using the heavy-ion fusion-evaporation reaction ⁸²Se(¹⁸O, α3n) ⁹³Zr at the beam energies of 82 and 88 MeV. Particle-γ -γ and γ -γ coincidence measurements using CsI and HPGe arrays are employed to gain selectivity to Zr isotopic products. The level scheme of ⁹³Zr was extended up to E ≈ 12.5 Mev and I_π = (47/2−) with twenty-six new γ -ray transitions. The observation of γ rays with ≈2 Mev and the associated fragmentation of the γ -ray flux into many competing pathways provide a clear experimental signature for the breaking core. Level structures in ⁹³Zr were interpreted in the framework of the spherical shell model in a model space including the proton orbitals (1 f_5/2, 2p_3/2, 2p_1/2, 1g_9/2) and neutron orbits (1g_9/2, 1g_7/2, 2d_5/2, 1h_11/2). A possible reduction of the Z = 38 subshell spacing gap in ⁹³Zr is discussed.