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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Kouassi, J. Dalmasso, M. Hussonnois, V. Barci, and G. Ardisson

Abstract  

The -decay of225Ac to221Fr excited states has been reinvestigated using high-resolution -spectroscopy for single and - coincidence measurements. Twenty nine221Fr nuclear excited states were proposed; ten of which are newly observed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Kouassi, J. Dalmasso, H. Maria, G. Ardisson, and M. Hussonnois

Abstract  

The decay of a225Ac source in equilibrium mixture with its decay products was investigated using high-resolution HP/Ge/ detectors. Energies and intensities of more than 78 -photons were measured with an improved accuracy; 44 of them are reported for the first time. A tentative221Fr level scheme was built on the basis of good energy sum relationships; seven new221Fr excited levels are proposed at 496.9, 570.9, 603.5, 630.7, 637.7, 649.0 and 758.9 keV.

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Abstract  

The168mLu (T 1/2=6.7 min) (EC + β+) decay was reinvestigated by direct γ and γ-γ coincidence measurements using a continuous radiochemical separation from its168Hf parent produced by156Gd(16O,4n) reaction. Energies and intensities of 171 γ-transitions assigned to168Lu decay were accurately measured, among the 97 were found for the first time.

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Abstract  

233U -decay was reinvestigated using a radiochemically purified source and high efficiency HPGe coaxial detectors; the lowenergy -spectrum was also measured using a LEPS detector. The energy and intensity values of one hundred sixty three -lines were determined, from which forty eight are newly reported with respect to the last study of Canty et al. A revised229Th level scheme was built, using the Ritz combination principle, in which nine levels are newly observed, at 371.3, 381.8, 465.5, 569.2, 584.9, 605.1, 620.8, 656.9 and 749.9 keV.

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Abstract  

Zinc and nickel hexacyanoferrates (II) present a high affinity for223Fr and no retention for223Ra in hydrochloric acid solutions with concentrations greater than 0.5N. Hydrated antimony pentoxide is the best sorbent for223Ra. Incorporated in a composite exchanger, it could be used for decontamination purposes.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: F. Monroy-Guzman, D. Trubert, L. Brillard, J. Kim, M. Hussonnois, and O. Constantinescu

Abstract  

The behaviour of the elements Zr, Hf, Nb, Ta and Pa has been investigated on macroporous anion exchange resin BIORAD AGMP 1 in HF medium (from 0.02 to 2M). All the studied elements show strong adsorption properties at low HF concentration. The adsorption was found to be highly dependent on H+ and F concentrations. The distribution of possible adsorbable complexes is discussed.

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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+) isomer178m2Hf were produced by the (,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 -rays of this 25.1 days isomer. A cross section of 45±5 barns was obtained for178m2Hf(n,)179m2Hf.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: D. Trubert, M. Hussonnois, L. Brillard, J. Kim, V. Barci, G. Ardisson, Z. Szeglowski, and O. Constantinescu

Abstract  

The (EC, +) decay of168Hf, produced by the156Gd (16O,4n) reaction, has been studied, with high efficiency HPGe coaxial detectors, using on-line measurements with the RACHEL setup. Off-line measurements were also carried out using catcher collection technique. Energies and intensities of 119 -lines are reported among these only two were known in the earlier study ofChu andReednick. The168Lu level scheme built on the basis of single - and X-spectra and - coincidence measurements, allows the interpretation of 79 -transitions, between 38 excited states reported for the first time.

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Abstract  

A method for deep decontamination of high spin178m2Hf isomer from microquantities of Sc, Fe, Co, Ni, Sb and Ag was elaborated using ion exchange separation on Dowex-1 in Hf and CH3COOH–HCl media.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: J. Kim, J. Morel, M. Etcheverry, N. Coursol, D. Trubert, O. Constantinescu, S. Karamian, Yu. Oganessian, Ch. Briancon, and M. Hussonnois

Abstract  

Nowadays large interest is attached to the production of exotic beams and targets for nuclear structure and reaction studies. The nucleus178Hf, with is long-lived (T 1/2=31 years) high-spin isomeric statel =16+ at a relatively low-excitation energy (2.446 MeV), is indeed a unique probe for studying phenomena in a new way. A wide research program has been underway in the framework of the Hafnium Collaboration which now concems around 80 scientists. Various targets have been prepared and adapted to different types of experiments. Irradiation processes with high-intensity beams, high-purity chemistry methods and isotopic separations have been developed. The obtaining of appreciable amounts of very high purity178m2Hf by isotopic separation, has made it possible for us to carry out -ray measurements with good statistics and high energy resolution with a -spectrometer, in order to use this isomer as a calibration standard in the 200 to 600 ke V energy range. For example, relative to the main -rays, energies have been determined with an absolute uncertainty of about 2 e V and photon emission probabilities with a relative uncertainty better than 1%.

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