Properties of 187Ta revealed through isomeric decay

Mass-separated Ta-187 114 in a high-spin isomeric state has been produced for the first time by multinucleon transfer reactions, employing an argon gas-stopping cell and laser ionization. Internal gamma rays revealed a T-1/2 = 7.3 +/- 0.9 s isomer at 1778 +/- 1 keV, which decays through a rotational band with perturbations associated with the approach to a prolate-oblate shape transition. Model calculations show less influence from triaxiality compared to heavier elements in the same mass region. The isomer-decay reduced E2 hindrance factor f(nu) = 27 +/- 1 supports the interpretation that axial symmetry is approximately conserved.