Coulomb excitation of the odd-odd isotopes 106, 108In

Abstract

The low-lying states in the odd-odd and unstable isotopes 106,108 In have been Coulomb excited from the ground state and the first excited isomeric state at the REX-ISOLDE facility at CERN. With the additional data provided here the πg −1 9/2 ⊗ νd 5/2 and πg −1 9/2 ⊗ νg 7/2 multiplets have been re-analyzed and are modified compared to previous results. The observed γ-ray de-excitation patterns were interpreted within a shell model calculation based on a realistic effective interaction. The agreement between theory and experiment is satisfactory and the calculations reproduce the observed differences in the excitation pattern of the two isotopes. The calculations exclude a 6 + ground state in 106 In. This is in agreement with the conclusions drawn using other techniques. Furthermore, based on the experimental results, it is also concluded that the ordering of the isomeric and ground state in 108 In is inverted compared to the shell model prediction. Limits on B(E2) values have been extracted where possible. A previously unknown low-lying state at 367 keV in 106 In is also reported.

The Miniball spectrometer

“…An extensive description of this method is given in [64]. In some cases, physics results are obtained for the -in principleunwanted isobaric contaminants [65,66].…”

“…With this Miniball setup a full-energy photopeak efficiency of 5.8% for a multiplicity 1 γ-ray of 1332 keV was reached. This new setup was used to study the β decay of 65,66,67 Fe, revealing the structure of their daughter nuclei 65,66,67 Co. 66,67 Co are interesting nuclei, as they are the one-neutron hole one-proton hole (ν −1 π −1 ) and one-proton hole (π −1 ) partners of 68 Ni (Z = 28, N = 40), respectively [121]. These nuclei provide important information on the strength of the Z = 28 and N = 40 (sub-) shell closures.…”

Nuclear-structure studies of exotic nuclei with MINIBALL

“…For these nuclei it has been realized that the interaction of the last valence protons and neutrons, in particular the monopole component of the residual interaction between those nucleons, can lead to significant shifts in the single-particle energies, leading to the collapse of classic shell closures and the appearance of new shell gaps. The island of inversion around 32 Mg, with neutron-rich nuclei at and close to the magic number N=20 (illustrated in figure 2) shows strongly deformed ground states in Ne, Na, and Mg isotopes. This is related to the reduction of the N=20 shell gap and quadrupole correlations enabling low-lying deformed p h 2 2 intruder states from the higher fp shell to compete with spherical normal neutron p h 0 0 states of the sd-shell.…”

“…This is related to the reduction of the N=20 shell gap and quadrupole correlations enabling low-lying deformed p h 2 2 intruder states from the higher fp shell to compete with spherical normal neutron p h 0 0 states of the sd-shell. The promotion of a neutron pair across the N=20 gap can result in deformed intruder ground states and the two competing configurations can lead to the coexistence of spherical and deformed + 0 states in the neutron rich nuclei 30,32 Mg.…”

“…These findings were exceeding expectations for a semi-magic nucleus. Later on the ( ) B E2 values for the neutron-rich Mg isotopes 30,32,34 Mg were measured by different groups at the intermediate-energy facilities MSU [59,60] and GANIL [61] showing a wide range of results (see figure 3).…”