169 research outputs found
94 β -Decay Half-Lives of Neutron-Rich 55 Cs to 67 Ho : Experimental Feedback and Evaluation of the r -Process Rare-Earth Peak Formation
Spectroscopy of F
The structure of the weakly-bound F odd-odd nucleus,
produced from Na nuclei, has been investigated at GANIL by means of
the in-beam -ray spectroscopy technique. A single -line is
observed at 657(7) keV in F which has been ascribed to the decay of
the excited J= state to the J=1 ground state. The possible presence of
intruder negative parity states in F is also discussed.Comment: 3 pages, 1 figure, accepted for publication in Physical Review
Nuclear structure study of 19,20,21N nuclei by gamma spectroscopy
The structure of neutron rich nitrogen nuclei has been studied by use of
neutron removal reaction and inelastic scattering. Mass and charge deformations
have been deduced for the first excited state of 21N, which indicates the
partial persitence of the N=14 subshell closure in nitrogen isotopes. The
spectroscopic information obtained on the structure of 19,20,21N confirms the
results from a previous experiment
Collapse of the N=28 shell closure in Si
The energies of the excited states in very neutron-rich Si and
P have been measured using in-beam -ray spectroscopy from the
fragmentation of secondary beams of S at 39 A.MeV. The low 2
energy of Si, 770(19) keV, together with the level schemes of
P provide evidence for the disappearance of the Z=14 and N=28
spherical shell closures, which is ascribed mainly to the action of
proton-neutron tensor forces. New shell model calculations indicate that
Si is best described as a well deformed oblate rotor.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev. let
Intruder configurations in 29Ne at the transition into the island of inversion: Detailed structure study of 28Ne
Detailed γ -ray spectroscopy of the exotic neon isotope 28Ne has been performed for the first time using
the one-neutron removal reaction from 29Ne on a liquid hydrogen target at 240 MeV/nucleon. Based on
an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been
constructed for 28Ne and the negative-parity states are identified for the first time. The measured partial
cross sections and momentum distributions reveal a significant intruder p-wave strength providing
evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f -wave
strength was observed to bound final states. Large-scale shell-model calculations with different effective
interactions do not reproduce the large p-wave and small f -wave strength observed experimentally,
indicating an ongoing challenge for a complete theoretical description of the transition into the island
of inversion along the Ne isotopic chain
Structure of 136Sn and the Z = 50 magicity
The first 2+ excited state in the neutron-rich tin isotope 136Sn has been identified at 682(13) keV by measuring γ -rays in coincidence with the one proton removal channel from 137Sb. This value is higher than those known for heavier even-even N = 86 isotones, indicating the Z = 50 shell closure. It compares well to the first 2+ excited state of the lighter tin isotope 134Sn, which may suggest that the seniority scheme also holds for 136Sn. Our result confirms the trend of lower 2+ excitation energies of even-even tin isotopes beyond N = 82 compared to the known values in between the two doubly magic nuclei 100Sn and 132Sn. © The Author(s) 2014.published_or_final_versio
Theoretical description of deformed proton emitters: nonadiabatic coupled-channel method
The newly developed nonadiabatic method based on the coupled-channel
Schroedinger equation with Gamow states is used to study the phenomenon of
proton radioactivity. The new method, adopting the weak coupling regime of the
particle-plus-rotor model, allows for the inclusion of excitations in the
daughter nucleus. This can lead to rather different predictions for lifetimes
and branching ratios as compared to the standard adiabatic approximation
corresponding to the strong coupling scheme. Calculations are performed for
several experimentally seen, non-spherical nuclei beyond the proton dripline.
By comparing theory and experiment, we are able to characterize the angular
momentum content of the observed narrow resonance.Comment: 12 pages including 10 figure
- …