Speaker
D. T. Yordanov
(Instituut voor Kern- en Stralingsfysica)
Description
Since introduced in nuclear physics, the concept of shell structure and magic numbers
has governed our understanding of nuclear matter in atomic nuclei close to stability.
Experimental research in 30Ne, 31Na and 32Mg, systems with a closed neutron sd shell
(N=20), provided evidence for a ground state deformation in these nuclei. The
observed phenomenon is understood as an inversion of the normal spherical ground
state configuration, expected according to the traditional shell model, with deformed
states governed by particle-hole excitations over the N=20 shell gap. The properties
of nuclei in the “Island of inversion” are of particular importance for the
theoretical modelling of the region. The research taking place at the collinear laser
spectroscopy setup COLLAPS at ISOLDE - CERN makes an intriguing contribution in this
aspect. For the first time an unambiguous determination of the nuclear ground state
spin and parity of 33Mg will be reported. A measurement of the hyperfine structure
and the nuclear g-factor will be presented, illustrating the importance of the
technique of nuclear magnetic resonance in combination with laser spectroscopy. The
results will be discussed in the frame of the spherical shell model, showing the
intruder nature of the ground state, associating it with negative parity.
Inconsistencies in the interpretation of former experimental studies will be
discussed and based on the firm ground state spin-parity assignment a new set of
spins and parities for the lowest excited states will be proposed. The coexistence of
different particle-hole excitations in the low lying energy spectrum of 33Mg will be
demonstrated. A parallel interpretation will be given within the deformed shell
model. A review of recent results, obtained at COLLAPS, in the vicinity of the island
of inversion will be given and future prospects will be discussed.
Supported by the German Federal Ministry for Education and Research (BMBF) and the
Belgian Fund for Scientific Research (FWO - Vlaanderen).
Authors
D. T. Yordanov
(Instituut voor Kern- en Stralingsfysica)
G. Neyens
(Instituut voor Kern- en Stralingsfysica)
M. Kowalska
(CERN, Physics Department)
Co-authors
K. Blaum
(Institut für Physik, Universität Mainz)
K. Flanagan
(Instituut voor Kern- en Stralingsfysica)
M. De Rydt
(Instituut voor Kern- en Stralingsfysica)
P. Lievens
(Laboratorium voor Vaste-Stoffysica en Magnetisme, Katholieke Universiteit Leuven)
R. Neugart
(Institut für Physik, Universität Mainz)
W. Nörtershäuser
(Institut für Physik, Universität Mainz)
