685 research outputs found
Rotational properties of nuclei around No investigated using a spectroscopic-quality Skyrme energy density functional
Nuclei in the mass region represent the heaviest systems where
detailed spectroscopic information is experimentally available. Although
microscopic-macroscopic and self-consistent models have achieved great success
in describing the data in this mass region, a fully satisfying precise
theoretical description is still missing.
By using fine-tuned parametrizations of the energy density functionals, the
present work aims at an improved description of the single-particle properties
and rotational bands in the nobelium region. Such locally optimized
parameterizations may have better properties when extrapolating towards the
superheavy region.
Skyrme-Hartree-Fock-Bogolyubov and Lipkin-Nogami methods were used to
calculate the quasiparticle energies and rotational bands of nuclei in the
nobelium region. Starting from the most recent Skyrme parametrization, UNEDF1,
the spin-orbit coupling constants and pairing strengths have been tuned, so as
to achieve a better agreement with the excitation spectra and odd-even mass
differences in Cf and Bk.
The quasiparticle properties of Cf and Bk were very well
reproduced. At the same time, crucial deformed neutron and proton shell gaps
open up at and , respectively. Rotational bands in Fm, No, and
Rf isotopes, where experimental data are available, were also fairly well
described. To help future improvements towards a more precise description,
small deficiencies of the approach were carefully identified.
In the mass region, larger spin-orbit strengths than those from
global adjustments lead to improved agreement with data. Puzzling effects of
particle-number restoration on the calculated moment of inertia, at odds with
the experimental behaviour, require further scrutiny.Comment: 9 pages, 10 figures; to be published in Physical Review
Deformations and quasiparticle spectra of nuclei in the nobelium region
We have performed self-consistent Skyrme Hartree-Fock-Bogolyubov calculations
for nuclei close to No. Self-consistent deformations, including
as functions of the rotational frequency, were determined for
even-even nuclei Fm, No, and Rf. The
quasiparticle spectra for N=151 isotones and Z=99 isotopes were calculated and
compared with experimental data and the results of Woods-Saxon calculations. We
found that our calculations give high-order deformations similar to those
obtained for the Woods-Saxon potential, and that the experimental quasiparticle
energies are reasonably well reproduced.Comment: 6 pages, 2 figures; ICFN5 conference proceeding
Detailed spectroscopy of doubly magic Sn-132
The structure of the doubly magic Sn-132(50)82 has been investigated at the ISOLDE facility at CERN, populated both by the beta(-) decay of In-132 and beta(-)-delayed neutron emission of In-133. The level scheme of Sn-13(2) is greatly expanded with the addition of 68 gamma transitions and 17 levels observed for the first time in the beta decay. The information on the excited structure is completed by new gamma transitions and states populated in the beta-n decay of In-133. Improved delayed neutron emission probabilities are obtained both for In-132 and In-133. Level lifetimes are measured via the advanced time-delayed beta gamma gamma(t) fast-timing method. An interpretation of the level structure is given based on the experimental findings and the particle-hole configurations arising from core excitations both from the N = 82 and Z = 50 shells, leading to positive- and negative-parity particle-hole multiplets. The experimental information provides new data to challenge the theoretical description of Sn-132.Peer reviewe
Homotopy Theory of Strong and Weak Topological Insulators
We use homotopy theory to extend the notion of strong and weak topological
insulators to the non-stable regime (low numbers of occupied/empty energy
bands). We show that for strong topological insulators in d spatial dimensions
to be "truly d-dimensional", i.e. not realizable by stacking lower-dimensional
insulators, a more restrictive definition of "strong" is required. However,
this does not exclude weak topological insulators from being "truly
d-dimensional", which we demonstrate by an example. Additionally, we prove some
useful technical results, including the homotopy theoretic derivation of the
factorization of invariants over the torus into invariants over spheres in the
stable regime, as well as the rigorous justification of replacing by
and by as is common in the current
literature.Comment: 11 pages, 3 figure
Commissioning of the spede spectrometer with stable beams
The SPectrometer for Electron DEtection (SPEDE) has been constructed for in-beam nuclear structure studies using radioactive ion beams. SPEDE employs a silicon detector for detecting conversion electrons. It is designed to be used in conjunction with the MINIBALL spectrometer at HIE-ISOLDE, CERN.Peer reviewe
Shape coexistence at the proton drip-line: First identification of excited states in 180Pb
Excited states in the extremely neutron-deficient nucleus, 180Pb, have been
identified for the first time using the JUROGAM II array in conjunction with
the RITU recoil separator at the Accelerator Laboratory of the University of
Jyvaskyla. This study lies at the limit of what is presently achievable with
in-beam spectroscopy, with an estimated cross-section of only 10 nb for the
92Mo(90Zr,2n)180Pb reaction. A continuation of the trend observed in 182Pb and
184Pb is seen, where the prolate minimum continues to rise beyond the N=104
mid-shell with respect to the spherical ground state. Beyond mean-field
calculations are in reasonable correspondence with the trends deduced from
experiment.Comment: 5 pages, 4 figures, submitted to Phys.Rev.
First observation of excited states in 173Hg
The neutron-deficient nucleus 173Hg has been studied following
fusion-evaporation reactions. The observation of gamma rays decaying from
excited states are reported for the first time and a tentative level scheme is
proposed. The proposed level scheme is discussed within the context of the
systematics of neighbouring neutron-deficient Hg nuclei. In addition to the
gamma-ray spectroscopy, the alpha decay of this nucleus has been measured
yielding superior precision to earlier measurements.Comment: 5 pages, 4 figure
Search for Fingerprints of Tetrahedral Symmetry in
Theoretical predictions suggest the presence of tetrahedral symmetry as an
explanation for the vanishing intra-band E2-transitions at the bottom of the
odd-spin negative parity band in . The present study reports on
experiment performed to address this phenomenon. It allowed to determine the
intra-band E2 transitions and branching ratios B(E2)/B(E1) of two of the
negative-parity bands in .Comment: presented by Q.T. Doan at XLII Zakopane School of Physics: Breaking
Frontiers: Submicron Structures in Physics and Biology, May 2008. 5 pages,
minor corrections. To be published in the proceeding
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