424 research outputs found
Calculation of the spectrum of 12Li by using the multistep shell model method in the complex energy plane
The unbound nucleus Li is evaluated by using the multistep shell model
in the complex energy plane assuming that the spectrum is determined by the
motion of three neutrons outside the Li core. It is found that the ground
state of this system consists of an antibound state and that only this
and a and a excited states are physically meaningful
resonances.Comment: 9 pages, 5 tables, 7 figures, printer-friendly versio
Neutron Transfer Studied with a Radioactive beam of 24Ne, using TIARA at SPIRAL
A general experimental technique for high resolution studies of nucleon
transfer reactions using radioactive beams is briefly described, together with
the first new physics results that have been obtained with the new TIARA array.
These first results from TIARA are for the reaction 24Ne(d,p)25Ne, studied in
inverse kinematics with a pure radioactive beam of 100,000 pps from the SPIRAL
facility at GANIL. The reaction probes the energies of neutron orbitals
relevant to very neutron rich nuclei in this mass region and the results
highlight the emergence of the N=16 magic number for neutrons and the
associated disappearance of the N=20 neutron magic number for the very neutron
rich neon isotopes.Comment: Proceedings of the Carpathian Summer School of Physics,
Mamaia-Constanta, Romania, 13-24 June 200
Polarization Effects in Superdeformed Nuclei
A detailed theoretical investigation of polarization effects in superdeformed
nuclei is performed. In the pure harmonic oscillator potential it is shown that
when one particle (or hole) with the mass single-particle quadrupole moment
q_{nu} is added to a superdeformed core, the change of the electric quadrupole
moment can be parameterized as q_{eff}=e(bq_{nu}+a), and analytical expressions
are derived for the two parameters, and . Simple numerical expressions
for q_{eff}(q_\nu}) are obtained in the more realistic modified oscillator
model. It is also shown that quadrupole moments of nuclei with up to 10
particles removed from the superdeformed core of 152Dy can be well described by
simply subtracting effective quadrupole moments of the active single-particle
states from the quadrupole moment of the core. Tools are given for estimating
the quadrupole moment for possible configurations in the superdeformed A
150-region.Comment: 28 pages including 9 figure
Nuclear break-up of 11Be
The break-up of 11Be was studied at 41AMeV using a secondary beam of 11Be
from the GANIL facility on a 48Ti target by measuring correlations between the
10Be core, the emitted neutrons and gamma rays. The nuclear break-up leading to
the emission of a neutron at large angle in the laboratory frame is identified
with the towing mode through its characteristic n-fragment correlation. The
experimental spectra are compared with a model where the time dependent
Schrodinger equation (TDSE) is solved for the neutron initially in the 11 Be. A
good agreement is found between experiment and theory for the shapes of neutron
experimental energies and angular distributions. The spectroscopic factor of
the 2s orbital is tentatively extracted to be 0.46+-0.15. The neutron emission
from the 1p and 1d orbitals is also studied
In-gas-cell laser ionization spectroscopy in the vicinity of 100Sn: Magnetic moments and mean-square charge radii of N=50-54 Ag
In-gas-cell laser ionization spectroscopy studies on the neutron deficient
97-101Ag isotopes have been performed with the LISOL setup. Magnetic dipole
moments and mean-square charge radii have been determined for the first time
with the exception of 101Ag, which was found in good agreement with previous
experimental values. The reported results allow tentatively assigning the spin
of 97,99Ag to 9/2 and confirming the presence of an isomeric state in these two
isotopes, whose collapsed hyperfine structure suggests a spin of 1/2 . The
effect of the N=50 shell closure is not only manifested in the magnetic moments
but also in the evolution of the mean-square charge radii of the isotopes
investigated, in accordance with the spherical droplet model predictions
Structure of superheavy hydrogen 7H
The properties of nuclei with extreme neutronâtoâproton ratios reveal the limitations of state-ofthe-art nuclear models and are key to understand nuclear forces. 7H, with six neutrons and a single proton, is the nuclear system with the most unbalanced neutronâtoâproton ratio ever known, but its sheer existence and properties are still a challenge for experimental efforts and theoretical models. We report here the first measurement of the basic characteristics and structure of the ground state of 7H; they depict a system with a triton core surrounded by an extended four-neutron halo, built by neutron pairing, that decays through a unique fourâneutron emission with a relatively long half-life. These properties are a prime example of new phenomena occurring in almost pure-neutron nuclear matter, beyond the binding limits of the nuclear landscape, that are yet to be described within our current models
Approximate particle number projection with density dependent forces: Superdeformed bands in the A=150 and A=190 regions
We derive the equations for approximate particle number projection based on
mean field wave functions with finite range density dependent forces. As an
application ground bands of even-A superdeformed nuclei in the A=150 and A=190
regions are calculated with the Gogny force.
We discuss nuclear properties such as quadrupole moments, moments of inertia
and quasiparticle spectra, among others, as a function of the angular momentum.
We obtain a good overall description.Comment: 31 pages, 10 figures, 3 appendices. In press in Nucl. Phy
Tracking algorithms for the active target MAYA
The MAYA detector is a Time-Charge Projection Chamber based on the concept of
active target. These type of devices use a part of the detection system, the
filling gas in this case, in the role of reaction target. The MAYA detector
performs three-dimensional tracking, in order to determine physical observables
of the reactions occurring inside the detector. The reconstruction algorithms
of the tracking use the information from a two-dimensional projection on the
segmented cathode, and, in general, they need to be adapted for the different
experimental settings of the detector. This work presents some of the most
relevant solutions developed for the MAYA detector
Lifetime of 19Ne*(4.03 MeV)
The Doppler-shift attenuation method was applied to measure the lifetime of
the 4.03 MeV state in 19Ne. Utilizing a 3He-implanted Au foil as a target, the
state was populated using the 20Ne(3He,alpha)19Ne reaction in inverse
kinematics at a 20Ne beam energy of 34 MeV. De-excitation gamma rays were
detected in coincidence with alpha particles. At the 1 sigma level, the
lifetime was determined to be 11 +4, -3 fs and at the 95.45% confidence level
the lifetime is 11 +8, -7 fs.Comment: 6 pages, submitted to Phys. Rev.
- âŠ