Speaker
Dr
B.P. Crider
(NSCL / MSU)
Description
The N = 40 subshell closure, which arises from the energy separation of the νpf shell and the νg9/2 single-particle state, has long been investigated for its impact on nearby neutron-rich nuclei. The fragility of this N = 40 subshell closure is highlighted by the sudden onset of collectivity as protons are removed from the νf7/2 single-particle state. Cross-shell excitations have been used to describe the observation of shape coexistence between spherical and prolate-deformed configurations. Within the neutron-rich odd-A Co isotopes, shape coexistence is supported through the identification of a (1/2⁻) shape isomer found at low energies alongside higher-spin states associated with the normal-order configurations. For ⁶⁸Co, a recent paper on a β-decay study at the National Superconducting Cyclotron Laboratory (NSCL) [1] concluded that the lowest-energy state can be attributed to a deformed configuration, further extending the presence of shape coexistence to this nucleus. This work reports on ⁶⁸Co as determined from the analysis of new data from NSCL utilizing the selectivity of low-spin β decay from ⁶⁸Fe to populate ⁶⁸Co. An expanded description of the low-lying structure of ⁶⁸Co will be presented.
This work was supported in part by the National Science Foundation (NSF) under Contract No. PHY-1102511 (NSCL) and Grant No. PHY-1350234 (CAREER), by the Department of Energy National Nuclear Security Administration (NNSA) under Grant No. DE-NA0002132 and Award No. DE-NA0003221 and through the Nuclear Science and Security Consortium under Award No’s DE-NA0000979 and DE-NA0003180, by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract No. DE-AC-06CH11357 (ANL) and Grant No’s. DE-FG02-94ER40834 (UM) and DE-FG02-96ER40983 (UT), and by the U.S. Army Research Laboratory under Cooperative Agreement W911NF-12-2-0019.
References:
[1] S.N. Liddick et al., Phys. Rev. C 85, 014328 (2012).
Primary author
Dr
B.P. Crider
(NSCL / MSU)
Co-authors
A. Spyrou
(NSCL / MSU)
Mr
A.C. Dombos
(NSCL / MSU)
Dr
A.D. Ayangeakaa
(ANL)
Dr
C.J. Chiara
(U.S. Army Research Laboratory / Oak Ridge Associated Universities Fellowship Program)
Dr
C.J. Prokop
(LANL)
Dr
D. Seweryniak
(ANL)
Dr
F. Recchia
(Università degli Studi di Padova)
Dr
H.M. David
(ANL)
Dr
J. Chen
(NSCL / MSU)
Ms
J. Harker
(University of Maryland / ANL)
Dr
J.J. Carroll
(U.S. Army Research Laboratory)
Dr
M. Al-Shudifat
(Al al-Bayt University)
Dr
M.P. Carpenter
(ANL)
Dr
N.R. Larson
(NSCL / MSU)
Prof.
R. Grzywacz
(University of Tennessee)
R. Lewis
(NSCL / MSU)
Dr
R.V.F. Janssens
(ANL)
Dr
S. Go
(University of Tennessee)
Dr
S. Suchyta
(NSCL / MSU)
Dr
S. Zhu
(ANL)
Dr
S.J. Quinn
(NSCL / MSU)
Prof.
S.N. Liddick
(NSCL / MSU)
Dr
T. Lauritsen
(ANL)
Prof.
W.B. Walters
(University of Maryland)