pp-sdsd shell gap reduction in neutron-rich systems and cross-shell excitations in 20^{20}O

Excited states in $^{20}$O were populated in the reaction $^{10}$Be($^{14}$C,$\alpha$) at Florida State University. Charged particles were detected with a particle telescope consisting of 4 annularly segmented Si surface barrier detectors and $\gamma$ radiation was detected with the FSU $\gamma$ detector array. Five new states were observed below 6 MeV from the $\alpha$-$\gamma$ and $\alpha$-$\gamma$-$\gamma$ coincidence data. Shell model calculations suggest that most of the newly observed states are core-excited 1p-1h excitations across the $N = Z = 8$ shell gap. Comparisons between experimental data and calculations for the neutron-rich O and F isotopes imply a steady reduction of the $p$-$sd$ shell gap as neutrons are added

Changes in νg9/2 shape polarisation across the odd neutron-rich Cr isotopes

Excited states in Cr-57 have been populated to high spin in the C-14(Ca-48, alpha n) reaction at a beam energy of 130 MeV. A regular sequence of stretched quadrupole transitions has been established above the yrast 9/2(+) level. This sequence is interpreted as a rotational band associated with prolate deformation induced by the excitation of the odd neutron into the 1/2(+)[440] orbital. Total Routhian surface calculations, which follow this configuration to high spin, reproduce the observed features of the band. They are also able to account for a similar, but less well developed structure in Cr-55. In contrast, the isomeric yrast 9/2(+) state in Cr-59 appears to be a band-head state dominated by the 9/2(+) [404] configuration, which is favoured at oblate deformations. Such a marked difference presents a significant challenge for theoretical descriptions, but is consistent with features exhibited by the low-lying negative-parity states in C-59. (c) 2005 Elsevier B.V. All rights reserved.Physics, MultidisciplinarySCI(E)37ARTICLE1-2151-15862

Erratum: Changes in νg9/2 shape polarisation across the odd neutron-rich Cr isotopes (Physics Letters, Section B: Nuclear, Elementary Particle and High Energy Physics (2005) 622 (151) DOI: 10.1016/j.physletb.2005. 07.005)

Physics, MultidisciplinarySCI(E)2CORRECTION3-4375-37562

Structure of the neutron-rich Cr isotopes

The low-lying levels in Cr-51,Cr-60 have been populated with C-13,C-14(Ca-48, 2p) reactions using a beam energy of 130 MeV. Prompt electromagnetic radiation was detected using the Gammasphere array, in coincidence with recoiling ions measured with the Fragment Mass Analyzer. The residues were selected and identified on the basis of charge-to-mass ratio, energy-loss and time-of-flight measurements. Preliminary results for Cr-60, when compared to lighter even-even isotopes, indicate a softness in shape which increases with neutron number. The low-lying structure of Cr-59 is clearly inconsistent with the results of a spherical shell-model calculation and requires the inclusion of the nu g(9/2) orbital. The sequence of states can be understood within the Nilsson model assuming a moderate oblate ground-state deformation. This is in contrast to lighter odd-Cr nuclei where there is evidence for prolate deformation after excitation Of g(9/2) neutrons.Physics, NuclearPhysics, Particles & FieldsSCI(E)CPCI-S(ISTP)

Level structure of the neutron-rich Cr56,58,60 isotopes: Single-particle and collective aspects

The structure of the Cr-56,Cr-58,Cr-60 nuclei was investigated at Gammasphere using both deep inelastic and fusion-evaporation reactions. As a result of this work, expanded level schemes are now available for these three neutron-rich, even-even isotopes. Experimental signatures were found for both single-particle and collective excitations whose relative importance varies with neutron number. Together with recent structural information on the odd-A Cr-55,Cr-57,Cr-59 neighbors, the present data highlight the changing role of the g(9/2) orbital with neutron number. Comparisons with shell-model calculations using the recently developed GXPF1A interaction and with total Routhian surface calculations are presented.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000243168500028&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Physics, NuclearSCI(E)58ARTICLE6null7