PRODUCTION, CHEMICAL AND ISOTOPIC SEPARATIONS OF THE LONG-LIVED ISOMER HF-178(M2) (T1/2 = 31 YEARS)

The nucleus Hf-178, with its long-lived (T1/2 = 31 y) high-spin isomeric state I(pi) = 16+, is a challenge for new and exotic nuclear physics studies. We describe the first experiments we have performed in order to produce a reasonable microweight quantity of this hafnium isomer with an isomeric to ground-state ratio as high as possible (here 5%). The reaction Yb-176 (He-4, 2n) using an enriched target has been studied by measuring the excitation functions and the isomeric to ground-state ratio. About 3 x 10(14) isomeric atoms have been produced up to now in irradiations with high-intensity beams (congruent-to 100-mu-A) at the U-200 cyclotron in Dubna. Chemical separation methods could be checked using about 10(13) atoms of the isomer. Isotopic separation experiments have been performed in Orsay and preliminary results are given for the separation efficiency.