Abstract
The neutron-rich nuclei Nb and Mo have been investigated by means of β-γ and isomer spectroscopy following in-flight fission of a U beam at 345 MeV/nucleon at the RIBF facility. A T1/2 = 150(30) ns isomer at 313 keV has been identified in Nb. The lowlying levels in Nb have been also populated following the β-decay of Zr. The observed hindrances of the electromagnetic transitions deexciting the isomeric state are discussed in terms of possible shape coexistence. For Mo, spectroscopic information on the low-lying levels of the quasi-γ band built on the 2+2 state at 494 keV has been obtained for the first time. The experimental finding of the 2+2 state being lower than the 4 + 1 level suggests that axiallyasymmetric γ softness is substantially enhanced in this nucleus. The experimental results are compared with model calculations based on the general Bohr Hamiltonian method.
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