Production, chemical and isotopic separations of the long-lived isomer¹⁷⁸Hf^m2(T_1/2=31 years)

Abstract

The nucleus 178Hf, with its long-lived (T1/2=31 y) high-spin isomeric state Ipi =16+, is a challenge for new and exotic nuclear physics studies. The authors describe the first experiments they 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 176Yb (4He, 2n) using an enriched target has been studied by measuring the excitation functions and the isomeric to ground-state ratio. About 3*1014 isomeric atoms have been produced up to now in irradiations with high-intensity beams ( approximately=100 mu A) at the U-200 cyclotron in Dubna. Chemical separation methods could be checked using about 1013 atoms of the isomer. Isotopic separation experiments have been performed in Orsay and preliminary results are given for the separation efficiency.