Purity determination of super-enriched¹⁷⁶Yb by neutron activation and thermal neutron capture cross section measurement of the high-spin (16⁺) isomer^178m2Hf

Abstract

Neutron activation analysis has been applied to determine the purity of super-enriched¹⁷⁶Yb as well as a diagnostic to optimize yields from the P.A.R.I.S. mass separator at Orsay. In 25 mass separations carried out during 3 months, 910 mg of super-enriched¹⁷⁶Yb₂O₃ were recovered from the original 7 g of¹⁷⁶Yb₂O₃ (97.5% enrichment). Neutron activation analysis has shown that only two per thousand of the initially present¹⁷⁴Yb remained in the super-enriched product. Using this¹⁷⁶Yb super-enriched (99.998%) target, micro-quantities of the high spin (16⁺) isomer^178m2Hf were produced by the (α,2n) reaction at the U-200 cyclotron in Dubna. Quantities of about 2·10¹² atoms of this isomer have been irradiated by thermal neutron at the ORPHEE Reactor, Saclay. Only the neutron capture giving rise to the isomeric state 25/2⁻ of¹⁷⁹Hf has been measured, by detection γ-rays of this 25.1 days isomer. A cross section of 45±5 barns was obtained for^178m2Hf(n,γ)^179m2Hf.