Speaker
Heather Crawford
(Lawrence Berkeley National Laboratory)
Description
The dominance of intruder configurations in the well-known “island of inversion” surrounding 32Mg has been attributed to a reduced N=20 sd-fp shell gap arising from the tensor monopole component of the effective nucleon-nucleon interaction. At higher masses, a similar mechanism results in a narrowing of the N=40 harmonic oscillator shell closure below Z=28. First evidence for a weakening of the N=40 shell gap, and onset of quadrupole collectivity has been observed in the Cr and Fe isotopes as a steady decrease of the first 2+ energies through N=40. Excited-state lifetime measurements have confirmed collectivity in the Fe isotopes up to N=40, and added to mounting evidence for a new “island of inversion” centered on 64Cr.
The collectivity of 66,68Fe isotopes and 64Cr has been recently studied via intermediate-energy Coulomb excitation at NSCL. Secondary beams of 66Fe, 68Fe and 64Cr were excited on a Bi foil at the target position of the S800 spectrograph, in which recoils were identified. De-excitation gamma rays were detected using the scintillator array CAESAR. Preliminary results for the B(E2) of 66, 68Fe and 64Cr will be presented, and discussed in terms of the evolution of collectivity near Z=24 and N=40.
Primary author
Heather Crawford
(Lawrence Berkeley National Laboratory)
Co-authors
Alexandra Gade
(NSCL/MSU)
Andrew Ratkiewicz
(NSCL/MSU)
Augusto Macchiavelli
(Lawrence Berkeley National Laboratory)
Christopher Campbell
(Lawrence Berkeley National Laboratory)
Cornelius Beausang
(University of Richmond)
Daniel Bazin
(NSCL)
Darren Bleuel
(Lawrence Livermore National Laboratory)
Dirk Weisshaar
(NSCL)
Eda Sahin
(LNL-INFN)
Giacomo de Angelis
(LNL-INFN)
I-Yang Lee
(Lawrence Berkeley National Laboratory)
Jill Berryman
(NSCL)
Kathrin Wimmer
(NSCL)
Marina Petri
(Lawrence Berkeley National Laboratory)
Mario Cromaz
(Lawrence Berkeley National Laboratory)
Paul Fallon
(Lawrence Berkeley National Laboratory)
Richard Hughes
(University of Richmond)
Roderick Clark
(Lawrence Berkeley National Laboratory)
Ryan Winkler
(NSCL)
Stefanos Paschalis
(Lawrence Berkeley National Laboratory)
Timothy Ross
(University of Richmond)
Travis Baugher
(NSCL/MSU)
