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Abstract.Coulomb breakup of unstable neutron rich nuclei 29,30 Na around the 'island of inversion' has been studied at energy around 434 MeV/nucleon and 409 MeV/nucleon respectively. Four momentum vectors of fragments, decay neutron from excited projectile and γ-rays emitted from excited fragments after Coulomb breakup are measured in coincidence. For these nuclei, the low-lying dipole strength above one neutron threshold can be explained by direct breakup model. The analysis for Coulomb breakup of 29,30 Na shows that large amount of the cross section yields the 28 Na, 29 Na core in ground state. The predominant ground-state configuration of 29,30 Na is found to be 28 Na(g.s) ⊗ ν s 1/2 and 29 Na(g.s) ⊗ ν s 1/2 , respectively.

Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Seidlitz, M., Muecher, D., Reiter, P., Bildstein, V., Blazhev, A., Bree, N., ... Wiens, A. (2011). Coulomb excitation of , 181-186. https://doi.org/10.1016/j.physletb.2011.05.009 Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date: 11-04-2019Physics Letters B 700 (2011) © 2011 Elsevier B.V. All rights reserved. MotivationShell structure is one of the most important frameworks for understanding nuclear structure and the properties of atomic nuclei. Recent experimental and theoretical findings indicate that magic numbers are subject to the proton-to-neutron ratio and new magic numbers are revealed when going to more exotic nuclei. Such a new magic number was proposed at N = 16 for some nuclei be- ground state for these nuclei [6]. Later shell model calculations by Warburton et al. [7] showed that the 1 f 7/2 orbital becomes lower in energy, reducing the sd shell gap and an anomalous inverted level structure was proposed, which is based on 2-particle 2-hole (2p2h) neutron cross shell configurations in the ground state. ExperimentThe Coulomb excitation experiment was performed at the REX-ISOLDE facility at CERN [37,38] The scattered beam and recoiling target nuclei were detected by a CD-shaped 500 μm thick double sided silicon strip detector (DSSSD), consisting of four identical quadrants [40]. Each quadrant comprised 16 annular strips at the front side and 24 radial strips at the back side for identification and reconstruction of the trajectories of the scattered nuclei. The detector covered forward angles between 16.4 • and 53.3 • in the laboratory system. De-excitation γ -rays following Coulomb excitation of projectile and target nuclei were detected by the MINIBALL γ -spectrometer, consisting of eight triple cluster detectors in close geometry, each containing three 6-fold segmented HPGe crystals [41]. The photopeak efficiency of the array at 1.3 MeV was 8% after cluster addback. The high segmentation of the setup ensured a proper Doppler correction for in-flight γ -ray emission at v/c ∼ 8% by combining the angular information of the γ -ray with the direction and velocity of the scattered beam particle that was detected in coincidence.Two additional particle detectors were used downstream after the scattering chamber to monitor the position of the beam and M. Seidlitz et al. / Physics Letters B ...

Excited states in 96 Ag were populated in fragmentation of an 850-MeV/u 124 Xe beam on a 4-g/cm 2 Be target. Three new high-spin isomers were identified and the structure of the populated states was investigated. The level scheme of 96 Ag was established, and a spin parity of (13 − ), (15 + ), and (19 + ) was assigned to the new isomeric states. Shell-model calculations were performed in various model spaces, including πν(p 1/2 , g 9/2 , f 5/2 , p 3/2 ) and the large-scale shell-model space πν(gds), to account for the observed parity changing M2 and E3 transitions from the (13 − ) isomer and the E2 and E4 transitions from the (19 + ) core-excited isomer, respectively. The calculated level schemes and reduced transition strengths are found to be in very good agreement with the experiment.

Discrete g rays directly connecting states of a superdeformed (SD) band in 194 Hg to the yrast states have been discovered. Thus, the excitation energies and spins of all members of the lowest SD band are established for the first time, together with their likely parity. The SD band decays from its 10 1 and 12 1 states, which lie 4204.8 and 4407.4 keV above the normal-deformed yrast states of the same spins.Superdeformation has been a central focus in the study of nuclear structure. Long cascades of rotational transitions between superdeformed (SD) states have been observed in nuclei with mass ϳ130, 150, 190 [1,2], and 80 [3]. While the rotational transitions have been easy to detect with modern Ge arrays, it has been much harder to localize the SD bands (in excitation energy and spin) and to link them to the normal-deformed (ND) yrast states. For example, in the mass 150 and 190 regions, the intraband transitions of more than 100 SD bands have been found; yet, despite many attempts, there is no band for which the exact excitation energies, spins, and parity have been conclusively determined. The location of a SD band in 143 Eu was proposed [4], based on a twophoton sum-peak technique. However, the low statistics of the peaks suggest that confirmation is needed, and their placements in the level scheme require substantiation by coincidence relationships. In contrast, in the mass 130 region, some strongly deformed bands lie only ϳ0.8 MeV above the ND yrast states and it has then been possible to identify many of the decay pathways between the SD and less deformed ND states [5]. Therefore, one of the most pressing challenges in the study of superdeformation in the A 150 and 190 regions is the accurate determination of the excitation energies, spins, and parities of the parent levels of the known SD band transitions.The SD bands in these regions are especially interesting because they lie at high energy, yet they are isolated in a well-defined minimum (false vacuum) at the point where they decay out to the ND states in the true vacuum. The decay is believed to occur when a SD level, embedded in a sea of hot ND states, acquires a small component of a hot compound state, and decays through this component [6]. This description is supported by the measured g decay spectrum, which has a statistical quasicontinuous character [7], and by its agreement with a calculation of the statistical spectrum [8]. From the measured decay spectrum, Henry et al. [7] deduced that the SD state of 192 Hg lies 4.3 6 0.9 MeV above the ND yrast line at the point of decay. A similar value is expected in 194 Hg since its quasicontinuous spectrum [9] is almost identical to that in 192 Hg.Decay from SD bands and from resonant thermalneutron capture both represent statistical deexcitation of narrow highly excited states. The g decay spectra contain sharp high-energy primary g rays (from decays to low-lying states) and low-energy secondary g rays (from subsequent transitions between the low-lying states), in addition to the quasicontinuous componen...