157 research outputs found
Study of internal structures of 9,10Be and 10B in scattering of 4He from 9Be
A study of inelastic scattering and single-particle transfer reactions was
performed by an alpha beam at 63 MeV on a 9$Be target. Angular distributions of
the differential cross sections for the 9Be(4He,4He')9Be*, 9Be(4He,3He)10Be and
9Be(4He,t)10B reactions were measured. Experimental angular distributions of
the differential cross sections for the ground state and a few low-lying states
were analyzed in the framework of the optical model, coupled channels and
distorted-wave Born approximation. An analysis of the obtained spectroscopic
factors was performed.Comment: 16 pages, 7 figures, 3 tables, regular paper, mispritns are corrected
in new versio
Unveiling the intruder deformed 0 state in Si
The 0 state in Si has been populated at the {\sc Ganil/Lise3}
facility through the -decay of a newly discovered 1 isomer in
Al of 26(1) ms half-life. The simultaneous detection of pairs
allowed the determination of the excitation energy E(0)=2719(3) keV and
the half-life T=19.4(7) ns, from which an electric monopole strength of
(E0)=13.0(0.9) was deduced. The 2 state is
observed to decay both to the 0 ground state and to the newly observed
0 state (via a 607(2) keV transition) with a ratio
R(2)=1380(717). Gathering all
information, a weak mixing with the 0 and a large deformation parameter
of =0.29(4) are found for the 0 state, in good agreement with
shell model calculations using a new {\sc sdpf-u-mix} interaction allowing
\textit{np-nh} excitations across the N=20 shell gap.Comment: 5 pages, 3 figures, accepted for publication in Physical Review
Letter
Prolate-Spherical Shape Coexistence at N=28 in S
The structure of S has been studied using delayed and
electron spectroscopy at \textsc{ganil}. The decay rates of the 0
isomeric state to the 2 and 0 states have been measured for the
first time, leading to a reduced transition probability
B(E2~:~20= 8.4(26)~efm and a monopole
strength (E0~:~00
=~8.7(7)10. Comparisons to shell model calculations point
towards prolate-spherical shape coexistence and a phenomenological two level
mixing model is used to extract a weak mixing between the two configurations.Comment: 5 pages, 3 figures, accepted for publication in Physical Review
Letter
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
Properties of odd nuclei and the impact of time-odd mean fields: A systematic Skyrme-Hartree-Fock analysis
We present a systematic analysis of the description of odd nuclei by the
Skyrme-Hartree-Fock approach augmented with pairing in BCS approximation and
blocking of the odd nucleon. Current and spin densities in the Skyrme
functional produce time-odd mean fields (TOMF) for odd nuclei. Their effect on
basic properties (binding energies, odd-even staggering, separation energies
and spectra) is investigated for the three Skyrme parameterizations SkI3, SLy6,
and SV-bas. About 1300 spherical and axially-deformed odd nuclei with 16 < Z <
92 are considered. The calculations demonstrate that the TOMF effect is
generally small, although not fully negligible. The influence of the Skyrme
parameterization and the consistency of the calculations are much more
important. With a proper choice of the parameterization, a good description of
binding energies and their differences is obtained, comparable to that for even
nuclei. The description of low-energy excitation spectra of odd nuclei is of
varying quality depending on the nucleus
Structure of the N=27 isotones derived from the Ar(d,p)Ar
Expérience GANIL/SPIRAL, détecteur CATS, détecteur MUST, 7 figures,International audienceThe Ar(d,p)Ar neutron transfer reaction was performed at 10~A.MeV. Measured excitation energies, deduced angular momenta and spectroscopic factors of the states populated in Ar are reported. A satisfactory description of these properties is achieved in the shell model framework using a new interaction. The model analysis is extended to more exotic even-Z nuclei down to Si to study how collectivity impacts the low lying structure of N~=~27 neutron-rich nuclei
In-beam spectroscopic studies of S nucleus
The structure of the S nucleus has been studied at GANIL through the
one proton knock-out reaction from a Cl secondary beam at 42
AMeV. The rays following the de-excitation of S were
detected in flight using the 70 BaF detectors of the Ch\^{a}teau de
Cristal array. An exhaustive -coincidence analysis allowed an
unambiguous construction of the level scheme up to an excitation energy of 3301
keV. The existence of the spherical 2 state is confirmed and three new
-ray transitions connecting the prolate deformed 2 level were
observed. Comparison of the experimental results to shell model calculations
further supports a prolate and spherical shape coexistence with a large mixing
of states built on the ground state band in S.Comment: 6 pages, 5 figures, accepted for publication in Physical Review
Neutron-rich nuclei produced at zero degrees in damped collisions induced by a beam of 18O on a 238U target
Cross sections and corresponding momentum distributions have been measured for the first time at zero degrees for the exotic nuclei obtained from a beam of 18O at 8.5 MeV/A impinging on a 1 mg/cm2 238U target. Sizable cross sections were found for the production of exotic species arising from the neutron transfer and proton removal from the projectile. Comparisons of experimental results with calculations based on deep-inelastic reaction models, taking into account the particle evaporation process, indicate that zero degree is a scattering angle at which the differential reaction cross section for production of exotic nuclei is at its maximum. This result is important in view of the new generation of zero degrees spectrometers under construction, such as the S3 separator at GANIL, for example
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