Title:
|
Spectroscopic studies of isobaric analogue nuclei in the upper f7/2-shell
|
Gamma decays from high-spin states in the A=51 mirror-pair "'Mn and "Fe, and
the A=53 mirror pair 53Fe and 53 Co have been observed up to, and in one nucleus
beyond, the fä band terminating states. For "Fe and 53Co, this represents the first
observation of states of this type. The nuclei were studied in two GAMMASPHERE
experiments with the addition of the FRAGMENT MASS ANALYSER recoil separator
and an ion chamber at Argonne National Laboratory in Chicago, Illinois; and the
MICROBALL light charged particle detector and the NEUTRON SHELL neutron detector
system at Lawrence Berkeley National Laboratory in Berkeley, California.
The observation of these isobaric analogue states allowed a detailed comparison of
the level energies in each mirror pair. The mirror nuclei have the same mass number,
but differing numbers of protons and neutrons. Thus, any difference in excitation
energies can be interpreted as being due mainly to the Coulomb interaction, leading
to a Coulomb Energy Difference (CED) plot as a function of angular momentum. The
changes of the CED with spin have been interpreted in terms of the spatial arrangement
of the valence protons, from rotational alignments and the effects of proton-proton
recoupling.
The observed level energies and the CED have been compared with the results of full
pf shell-model calculations, with the Coulomb interaction included via the Coulomb
Matrix Elements (CME). This comparison has allowed a detailed understanding of the
microscopic mechanisms behind the changes in the CED. The CME were investigated
in a fit to the A=53 CED, which revealed an anomalously high and counter-intuitive
J=2 component. Extensive results from the study of these CME have been presented,
including their role in the evolution of the CED, the physical meaning of the matrix
elements themselves, and in particular the origin of the J=2 anomaly.
|