HYPERFINE-STRUCTURE MEASUREMENTS IN THE GROUND-STATE OF RADIOACTIVE EU-150(+) IONS

The hyperfine constants A and B for magnetic dipole and electric quadr upole interaction in the S-9(4) ground state of unstable Eu-150(+) ion s have been determined with high precision in an optical microwave dou ble-resonance experiment. The ions were produced by nuclear reactions at the ISOLDE facility at CERN, collected on a foil, reevaporated, and stored in a Paul ion trap. Three of eight possible hyperfine transiti ons between different F sublevels have been observed with well resolve d Zeeman substructure in a residual magnetic field. Analysis of the tr ansition frequencies and extensive second-order hyperfine correction y ield values of A = 559 010 325(40) Hz, B = -926.2(3.0) kHz. A prelimin ary value for the nuclear quadrupole moment Q (Eu-150(+)) = 1.264(23) b has also been obtained.