134 research outputs found
Role of cross-shell excitations in the reaction 54Fe(d_pol,p)55Fe
The reaction 54Fe(d_pol,p)55Fe was studied at the Munich Q3D spectrograph
with a 14 MeV polarized deuteron beam. Excitation energies, angular
distributions and analyzing powers were measured for 39 states up to 4.5 MeV
excitation energy. Spin and parity assignments were made and spectroscopic
factors deduced by comparison to DWBA calculations. The results were compared
to predictions by large scale shell model calculations in the full pf-shell and
it was found that reasonable agreement for energies and spectroscopic factors
below 2.5 MeV could only be obtained if up to 6 particles were allowed to be
excited from the f_7/2 orbital into p_3/2, f_5/2, and p_1/2 orbitals across the
N=28 gap. For levels above 2.5 MeV the experimental strength distribution was
found to be significantly more fragmented than predicted by the shell model
calculations.Comment: 9 pages, 12 figures, 3 tables, submitted to European Physical Journal
Uncertainty Quantification of Mass Models using Ensemble Bayesian Model Averaging
Developments in the description of the masses of atomic nuclei have led to
various nuclear mass models that provide predictions for masses across the
whole chart of nuclides. These mass models play an important role in
understanding the synthesis of heavy elements in the rapid neutron capture
(-) process. However, it is still a challenging task to estimate the size of
uncertainty associated with the predictions of each mass model. In this work, a
method to quantify the mass uncertainty using \textit{ensemble Bayesian model
averaging} (EBMA) is introduced. This Bayesian method provides a natural way to
perform model averaging, selection, calibration, and uncertainty
quantification, by combining the mass models as a mixture of normal
distributions, whose parameters are optimized against the experimental data,
employing the Markov chain Monte Carlo (MCMC) method using the No-U-Turn
sampler (NUTS). The average size of our best uncertainty estimates of neutron
separation energies based on the AME2003 data is 0.48 MeV and covers 95% of new
data in the AME2020. The uncertainty estimates can also be used to detect
outliers with respect to the trend of experimental data and theoretical
predictions.Comment: 12 pages, 6 figure
Identification of the slow E3 transition 136mCs -> 136Cs with conversion electrons
We performed at ISOLDE the spectroscopy of the decay of the 8- isomer in
136Cs by and conversion-electron detection. For the first time the excitation
energy of the isomer and the multipolarity of its decay have been measured. The
half-life of the isomeric state was remeasured to T1/2 = 17.5(2) s. This isomer
decays via a very slow 518 keV E3 transition to the ground state. In addition
to this, a much weaker decay branch via a 413 keV M4 and a subsequent 105 keV
E2 transition has been found. Thus we have found a new level at 105 keV with
spin 4+ between the isomeric and the ground state. The results are discussed in
comparison to shell model calculations.Comment: Phys. Rev. C accepted for publicatio
First Results on In-Beam gamma Spectroscopy of Neutron-Rich Na and Mg Isotopes at REX-ISOLDE
After the successful commissioning of the radioactive beam experiment at
ISOLDE (REX-ISOLDE) - an accelerator for exotic nuclei produced by ISOLDE -
first physics experiments using these beams were performed. Initial experiments
focused on the region of deformation in the vicinity of the neutron-rich Na and
Mg isotopes. Preliminary results show the high potential and physics
opportunities offered by the exotic isotope accelerator REX in conjunction with
the modern Germanium gamma spectrometer MINIBALL.Comment: 7 pages, RNB6 conference contributio
Molecular and cluster structures in <sup>18</sup>O
We have studied the multi-nucleon transfer reaction 12C ( 7Li ,p) at E
lab = 44 MeV, populating states in the oxygen isotope 18O . The experiments were performed at the Tandem accelerator of the Maier-Leibniz Laboratory in Munich using the high-resolution Q3D magnetic spectrograph. States were populated up to an excitation energy of 21.2MeV with an overall energy resolution of 45keV, and 30 new states of 18O have been identified. The structure of the rotational bands observed is discussed in terms of cluster bands with the underlying cluster structures:
14C\displaystyle \otimes\displaystyle \alphaand
12C ⊗ 2n ⊗ . Because of the broken intrinsic reflection symmetry in these structures the corresponding rotational bands appear as parity doublets
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