The low-lying states in Zr106 and Zr108 have been investigated by means of β-γ and isomer spectroscopy at the radioactive isotope beam factory (RIBF), respectively. A new isomer with a half-life of 620±150ns has been identified in Zr108. For the sequence of even-even Zr isotopes, the excitation energies of the first 2+ states reach a minimum at N=64 and gradually increase as the neutron number increases up to N=68, suggesting a deformed subshell closure at N=64. The deformed ground state of Zr108 indicates that a spherical subshell gap predicted at N=70 is not large enough to change the ground state of Zr108 to the spherical shape. The possibility of a tetrahedral shape isomer in Zr108 is also discussed.
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