157 research outputs found
Single-Proton Removal Reaction Study of 16B
The low-lying level structure of the unbound system B has been
investigated via single-proton removal from a 35 MeV/nucleon C beam. The
coincident detection of the beam velocity B fragment and neutron allowed
the relative energy of the in-flight decay of B to be reconstructed. The
resulting spectrum exhibited a narrow peak some 85 keV above threshold. It is
argued that this feature corresponds to a very narrow (100 keV)
resonance, or an unresolved multiplet, with a dominant + configuration which decays by d-wave neutron
emission.Comment: 16 pages, 5 figures, 1 table, submitted to Phys. Lett.
Search for Superscreening effect in Superconductor
4 pages, 3 figures, Expérience au GANIL avec SPIRAL/EXOGAMThe decay of O() and Ne() implanted in niobium in its superconducting and metallic phase was measured using purified radioactive beams produced by the SPIRAL/GANIL facility. Half-lives and branching ratios measured in the two phases are consistent within one-sigma error bar. This measurement casts strong doubts on the predicted strong electron screening in superconductor, the so-called superscreening. The measured difference in screening potential energy is 110(90) eV for Ne and 400(320) eV for O. Precise determinations of the half-lives were obtained for O: 26.476(9)~s and Ne: 17.254(5)~s
Structure around the island of inversion with single-neutron knockout reactions at GANIL
CERN-Proceedings-2010-001 available at http://www.fluka.org/Varenna2009/procmat.htmInternational audienceThe nuclear structure of the 31Mg nucleus has been studied with the singleneutron knockout reaction. We report on the preliminary results of an experiment performed with the EXOGAM array coupled, for the first time, to the SPEG spectrometer at GANIL.We present a provisional result for the inclusive single-neutron knockout cross section of σinc= 90(5) mb. Preliminary exclusive cross sections for the measured bound states, including the ground state, are also presented. Finally, preliminary longitudinal momentum distributions for the ground state and first excited state are also shown. These results are compared to Monte Carlo Shell-Model calculations in the sd-pf region
Spectroscopy of the unbound nucleus 18Na
Expérience GANIL, SPIRALInternational audienceThe unbound nucleus 18Na, the intermediate nucleus in the two-proton radioactivity of 19Mg, is studied through the resonant elastic scattering 17Ne(p,17Ne)p. The spectroscopic information obtained in this experiment is discussed and put in perspective with previous measurements and the structure of the mirror nucleus 18N
Study of Na at SPIRAL
NESTERInternational audienceThe excitation function for the elastic-scattering reaction p18Ne, p18Ne was measured with the first radioactive beam from the SPIRAL facility at the GANIL laboratory and with a solid cryogenic hydrogen target. Several broad resonances have been observed, corresponding to new excited states in the unbound nucleus 19Na. In addition, two-proton emission events have been identified and are discussed
Re-examining the transition into the N=20 island of inversion: structure of 30Mg
Intermediate energy single-neutron removal from Mg has been employed
to investigate the transition into the N=20 island of inversion. Levels up to
5~MeV excitation energy in Mg were populated and spin-parity assignments
were inferred from the corresponding longitudinal momentum distributions and
-ray decay scheme. Comparison with eikonal-model calculations also
permitted spectroscopic factors to be deduced. Surprisingly, the 0
level in Mg was found to have a strength much weaker than expected in
the conventional picture of a predominantly intruder configuration
having a large overlap with the deformed Mg ground state. In addition,
negative parity levels were identified for the first time in Mg, one of
which is located at low excitation energy. The results are discussed in the
light of shell-model calculations employing two newly developed approaches with
markedly different descriptions of the structure of Mg. It is concluded
that the cross-shell effects in the region of the island of inversion at Z=12
are considerably more complex than previously thought and that
configurations play a major role in the structure of Mg.Comment: Physics Letters B, Volume 779, 10 April 2018, Pages 124-12
Shell evolution approaching the N=20 island of inversion : Structure of 26Na
The levels in 26Na with single particle character have been observed for the first time using the d(25Na, pγ) reaction at 5 MeV/nucleon. The measured excitation energies and the deduced spectroscopic factors are in good overall agreement with (0+1)hω shell model calculations performed in a complete spsdfp basis and incorporating a reduction in the N=20 gap. Notably, the 1p3/2 neutron configuration was found to play an enhanced role in the structure of the low-lying negative parity states in 26Na, compared to the isotone 28Al. Thus, the lowering of the 1p3/2 orbital relative to the 0f7/2 occurring in the neighbouring Z=10 and 12 nuclei - 25,27Ne and 27,29Mg - is seen also to occur at Z=11 and further strengthens the constraints on the modelling of the transition into the island of inversion
New approach to the nuclear in beam spectroscopy of neutron rich nuclei at N=20 using projectile fragmentation
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Low-lying single-particle structure of 17C and the N = 14 sub-shell closure
The first investigation of the single-particle structure of the bound states of 17C, via the C transfer reaction, has been undertaken. The measured angular distributions confirm the spin-parity assignments of and for the excited states located at 217 and 335 keV, respectively. The spectroscopic factors deduced for these states exhibit a marked single-particle character, in agreement with shell model and particle-core model calculations, and combined with their near degeneracy in energy provide clear evidence for the absence of the sub-shell closure. The very small spectroscopic factor found for the ground state is consistent with theoretical predictions and indicates that the strength is carried by unbound states. With a dominant valence neutron configuration and a very low separation energy, the excited state is a one-neutron halo candidate
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