[en] The improved facilities of the ISOLDE isotopic separator on-line with the 600 MeV synchrocyclotron at CERN opened the possibility to reach nuclei very far from stability (as far as 22 neutrons deficient in the Cs region and 27 neutrons deficient in the Hg region). Simultaneously the development of on-line spectrometry allowed the study of nuclei with very short half-lives and low counting rates. Results recently obtained in the odd-A iridium region are presented after a short summary of recent on-line devices developments and results. (Auth.)

[en] Resonance ionization spectroscopy was performed on neutron deficient iridium isotopes ^182-189Ir, ¹⁸⁶Ir^m and stable isotopes ^191,193Ir. Hyperfine spectra were recorded from the optical transition at 351,7 nm between the 5d⁷6s²⁴F_9/2 ground state and the 5d⁷6s6p ⁶F_11/2 excited state. Radioactive iridium isotopes were obtained from β⁺/EC decay of radioactive mercury nuclei deposited on a graphite substrate. The radioactive mercury nuclei were produced at the ISOLDE facility at CERN through spallation reactions, by bombarding a molten lead target with the 1 GeV proton beam delivered by the PS-Booster. Magnetic dipole moments and spectroscopic quadrupole moments were extracted from the hyperfine spectra. The mean square charge radius variations, as deduced from the measured isotopic shift, show a sharp change between ¹⁸⁷Ir and ¹⁸⁶Ir^g, accompanied by a sudden increase in deformation: from β2 ∼ 0,16 to β2 > 0, 2. These results were analysed in the framework of an axial rotor plus one or two quasiparticles. The wave functions of the osmium and platinum cores which are used in order to describe the iridium nuclei were calculated from the HF+BCS method with the Skyrme SIII effective interaction. The cores were constrained to take the deformation parameters extracted from the isotopic shift measurements. One shows then that this sudden deformation change corresponds also to a change in the proton state that describes the odd nuclei ground state or that participates in the coupling with the neutron in odd-odd nuclei. This state is identified with the π3/2⁺[402] orbital for the smaller deformations nuclei and with the π1/2^-[541] orbital stemming from the h_9/2 subshell for bigger deformations nuclei. (author)

[en] Laser spectroscopy measurements have been performed on neutron-deficient and stable Ir isotopes using the COMPLIS experimental setup installed at ISOLDE-CERN. The radioactive Ir atoms were obtained from successive decays of a mass-separated Hg beam deposited onto a carbon substrate after deceleration to 1kV and subsequently laser desorbed. A three-color, two-step resonant scheme was used to selectively ionize the desorbed Ir atoms. The hyperfine structure (HFS) and isotope shift (IS) of the first transition of the ionization path 5d⁷6s²⁴F_9/2→5d⁷6s6p⁶F_11/2 at 351.5nm were measured for ^182-189Ir, ¹⁸⁶Ir^m and the stable ^191,193Ir. The nuclear magnetic moments μ_I and the spectroscopic quadrupole moments Q_s were obtained from the HFS spectra and the change of the mean square charge radii from the IS measurements. The sign of μ_I was experimentally determined for the first time for the masses 182≤A≤189 and the isomeric state ¹⁸⁶Ir^m. The spectroscopic quadrupole moments of ¹⁸²Ir and ¹⁸³Ir were measured also for the first time. A large mean square charge radius change between ¹⁸⁷Ir and ¹⁸⁶Ir^g and between ¹⁸⁶Ir^m and ¹⁸⁶Ir^g was observed corresponding to a sudden increase in deformation: from β₂≅+0.16 for the heavier group A = 193, 191, 189, 187 and 186m to β₂≥+0.2 for the lighter group A=186g, 185, 184, 183 and 182. These results were analyzed in the framework of a microscopic treatment of an axial rotor plus one or two quasiparticle(s). This sudden deformation change is associated with a change in the proton state that describes the odd-nuclei ground state or that participates in the coupling with the neutron in the odd-odd nuclei. This state is identified with the π3/2 ⁺[402 ] orbital for the heavier group and with the π1/2^-[541 ] orbital stemming from the 1h_9/2 spherical subshell for the lighter group. That last state seems to affect strongly the observed values of the nuclear moments. (orig.)

[en] The method of inversion of the eigenvalue problem previously developped for nuclei with axial symmetry is extended to asymmetric equilibrium shapes. This new approach to the asymmetric rotator model is applied to the odd-mass Iridium isotopes. A satisfactory and coherent description of the observed energy spectra is obtained, especially for the lighter isotopes. (orig.)

[en] The method of inversion of the eigenvalue problem previously developed for nuclei with axial symmetry is extended to asymmetric equilibrium shapes. This new approach of the asymmetric rotator model is applied to the odd-mass iridium isotopes. A satisfactory and coherent description of the observed energy spectra is obtained, especially for the lighter isotopes

[en] Laser spectroscopy measurements have been performed on neutron deficient iridium isotopes. The hyperfine structure and isotope shift of the optical Ir I transition 5d⁷6s²⁴F_9/2^→ 5d⁷6s6p ⁶F_11/2 at 351.5 nm have been studied for the ^182-189Ir, ¹⁸⁶Ir¹m and ^191,193Ir isotopes. The nuclear magnetic and quadrupole moments were obtained from the HFS measurements and the changes of the mean square charge radii from the IS measurements. A large mean square charge radius change between ¹⁸⁷Ir and ¹⁸⁶Ir and between ¹⁸⁶Ir¹m and ¹⁸⁶Ir¹g has been observed

No abstract available

[en] Excitation functions of the reactions natIr(p,xn)188,189,191Pt and natIr(p,x)186,187,188,189,190,192Ir were measured up to 70 MeV for practical applications. The measured experimental data were compared with the earlier results and analyzed using theoretical calculations based on the model code Alice-IPPE, The new experimental data show significant deviations from the earlier experimental results. Good agreement was found on average with the model calculation. Applications are also discussed

[en] Cross sections of proton-induced nuclear reactions on highly enriched ¹⁹²Os were measured up to 66 MeV by using the stacked-foil irradiation technique. Excitation functions are presented for the reactions ¹⁹²Os(p,n)¹⁹²Ir, ¹⁹²Os(p,3n)¹⁹⁰Ir, ¹⁹²Os(p,4n)¹⁸⁹Ir, ¹⁹²Os(p,5n)¹⁸⁸Ir, ¹⁹²Os(p,6n)¹⁸⁷Ir and ¹⁹²Os(p,7n)¹⁸⁶Ir. No earlier experimental cross-section data could be found in the literature except for the ¹⁹²Os(p,n)¹⁹²Ir process. Our new experimental results are compared with theoretical predictions by means of the theoretical model code ALICE/ASH. Integral thick-target yield calculations were also performed for the ¹⁹²Os(p,n)¹⁹²Ir and ¹⁹²Os(p,3n)¹⁹⁰Ir reactions to evaluate the ¹⁹⁰Ir contamination level, as a function of energy, in the case of ¹⁹²Ir productions.

No abstract available