Nuclear structure of iridium-190,192,194

Abstract

<p>The nuclear structures of ¹⁹⁰,¹⁰²,¹⁹⁴Ir were investigated with single-nucleon transfer reactions. The (d,t) reactions into ¹⁹⁰,¹⁰²,¹⁹⁴Ir used 18 MeV deuterons beams, and the (d,p) reactions into ¹⁹²,¹⁹⁴Ir utilized beams of 16 MeV deuterons. Single-proton transfer experiments were also performed on targets of ¹⁸⁹Os. The (α,t) reaction employed beams of 30 MeV α-particles, and the (³He,d) reactions used a 28 MeV ³He beam. The reaction products were analyzed with a magnetic spectrograph, and detected with photographic plates. The energy resolutions (FWHM) of the detected particles were typically ≃5.7 keV for (d,t), ≃8.9 keV for (d,p), ≃10 keV for (α,t), and ≃15 keV for (³He,d) reactions. For the single-neutron transfer reactions, spectra were recorded at a large number of angles (≥15). The angular distributions of cross sections were fitted with theoretical distributions from DWBA calculations, and the spectroscopic factors were obtained. For the (d,t) reactions, the fits to the angular distributions were performed in many cases with 2 l-values. By comparing the ratios of (α,t) and (³He,d) cross sections, the dominant transferred l-value was determined. Level energies, parities, spectroscopic strengths, and possible spin values were determined up to approximately 1 MeV excitation energy in ¹⁹⁰,¹⁹²Ir and 700 keV in ¹⁹⁴Ir. In order to obtain more information regarding the spins of levels in ¹⁹²Ir, multi-dimensional scaling programs were applied to known γ-ray intensities. The method appeared to be successful, and spins were suggested for many low-lying levels. The experimental results were compared with the IBFFM for ¹⁹²,¹⁹⁴Ir, ESUSY for ¹⁹²Ir, and the Nilsson model for ¹⁹⁰,¹⁹²Ir. The formalism for dealing with mixed configurations in the target ground state was developed, and significant effects were found for the single-proton transfer cross sections since the ¹⁸⁹Os target had significant admixed amplitudes. It was found that the models can only approximate the structure of odd-odd Ir nuclei.</p>