CARACTERISATION D'UN LASER Nd : YAG CONTINU A MODES COUPLES

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Deformation of the N=Z nucleus 76Sr using beta-decay studies

A novel method of deducing the deformation of the N=Z nucleus 76Sr is presented. It is based on the comparison of the experimental Gamow-Teller strength distribution B(GT) from its beta decay with the results of QRPA calculations. This method confirms previous indications of the strong prolate deformation of this nucleus in a totally independent way. The measurement has been carried out with a large Total Absorption gamma Spectrometer, "Lucrecia", newly installed at CERN-ISOLDE.Comment: Accepted in Phys. Rev. Letter

Spectroscopy of 34,35Si^{34,35}Si by β\beta decay: sd-fp shell gap and single-particle states

The $^{34,35}Al\beta$ decays were studied at the CERN on-line mass separator ISOLDE by $\beta-\gamma, \beta-\gamma-\gamma$ and $\beta-n-\gamma$ measurements, in order to corroborate thelow-level description of $^{34}Si$ and to obtain the first information on the level structure of the N=21 isotope $^{35}Si$. Earlier observed $\gamma$ lines in $^{34} Al$ decay were confirmed and new gamma transitions following both beta decay and $\beta$-delayed neutron emission were established. The first level scheme in $^{35}Si$, including three excited states at 910, 974 and 2168 keV, is consistent with $J^{\pi} =3/2^{-}$ and $3/2^{+}$ for the first two states respectively. Beta-decay half-life of $T_{1/2} = 38.6 (4)$ ms and beta-delayed neutron branching $P_{n}$ value $(P_{n} =41(13)$ were measured unambiguously. The significance of the single-particle energy determination at N=21, Z=14, for assessing the effective interaction in sd-fp shell-model calculations, is discussed and illustrated by predictions for different n-rich isotopes

Beta-decay in odd-A and even-even proton-rich Kr isotopes

Beta-decay properties of proton-rich odd-A and even-even Krypton isotopes are studied in the framework of a deformed selfconsistent Hartree-Fock calculation with density-dependent Skyrme forces, including pairing correlations between like nucleons in BCS approximation. Residual spin-isospin interactions are consistently included in the particle-hole and particle-particle channels and treated in Quasiparticle Random Phase Approximation. The similarities and differences in the treatment of even-even and odd-A nuclei are stressed. Comparison to available experimental information is done for Gamow-Teller strength distributions, summed strengths, and half-lives. The dependence of these observables on deformation is particularly emphasized in a search for signatures of the shape of the parent nucleus.Comment: 29 pages, 16 figure

The delayed proton emission in the A≃65-77 mass region, statistical aspects and structure effects

In the decay of the series of T sub Z =1/2 nuclei, sup 6 sup 5 Ge, sup 6 sup 9 Se, sup 7 sup 3 Kr and sup 7 sup 7 Sr, a statistical analysis was applied to the beta delayed proton emission to obtain nuclear structure information. New results emerge from this study, in the light of improvements in the experimental techniques and developments of the analysis method. Experimental results are analysed by comparison with a statistical model, in order to extract information on level densities and partial transition widths of the proton emitting nuclei. Limitations of the existing descriptions of processes for nuclei far from stability are pointed out

Structural Study of Interlayer Zr Particles in Exchanged and Pillared Beidellite

Zirconia pillared clays (with synthetic beidellite as host material) were prepared by replacing the sodium interlayer cations by zirconium hydroxy polycations, and then heating to stabilize the structure. The pillaring solution was an aqueous solution of zirconyl chloride, but the structure of the polycation which is intercalated remains unknown. From the XRD data. the interlayer spacing was found to be 9 Å in Zr exchanged beidellite and slightly lower (7Å) after calcination. The local environment of zirconium in solid zirconyl chloride and in the pillaring solution was first examined and then in the ion-exchanged and calcined beidellite. The EXAFS results for zirconyl chloride in the solid state and in aqueous solution, showed that the nearest neighbours and the next-nearest-neighbours environments of Zr are identical in solid and in solution. In the Zr-exchanged beidellite, the Zr cations have the same environment as in the pillaring solution. On the opposite. the mean Zr-O and Zr-Zr distances in the calcined sample are shortened with respect to Zr-exchanged beidellite