106 research outputs found
Ground-state configuration of neutron-rich ³⁵Al via Coulomb breakup
The ground-state configuration of ³⁵Al has been studied via Coulomb dissociation (CD) using the LAND-FRS setup (GSI, Darmstadt) at a relativistic energy of ~ 403 MeV/nucleon. The measured inclusive differential CD cross section for ³⁵Al, integrated up to 5.0 MeV relative energy between the ³³Al core and the neutron using a Pb target, is 78(13) mb. The exclusive measured CD cross section that populates various excited states of ³³Al is 29(7) mb. The differential CD cross section of ³⁵Al -> ³⁴Al + n has been interpreted in the light of a direct breakup model, and it suggests that the possible ground-state spin and parity of ³⁵Al could be, tentatively, 1/2⁺ or 3/2⁺ or 5/2⁺. The valence neutrons, in the ground state of ³⁵Al, may occupy a combination of either l = 3,0 or l = 1,2 orbitals coupled with the ³⁴Al core in the ground and isomeric state(s), respectively. This hints of a particle-hole configuration of the neutron across the magic shell gaps at N = 20,28 which suggests narrowing the magic shell gap. If the 5/2⁺ is the ground-state spin-parity of ³⁵Al as suggested in the literature, then the major ground-state configuration of ³⁵Al is a combination of ³⁴Al (g. s.; 4⁻) circle times ν_(p_(3/2)) and ³⁴Al (isomer; 1⁺) circle times ν _(d_(3/2)) states. The result from this experiment has been compared with that from a previous knockout measurement and a calculation using the SDPF-M interaction
Coulomb dissociation of P 27 at 500 MeV/u
The proton-capture reaction Si26(p,γ)P27 was studied via Coulomb dissociation (CD) of P27 at an incident energy of about 500 MeV/u. The three lowest-lying resonances in P27 have been populated and their resonance strengths have been measured. In addition, a nonresonant direct-capture component was clearly identified and its astrophysical S factor measured. The experimental results are compared to Monte Carlo simulations of the CD process using a semiclassical model. Our thermonuclear reaction rates show good agreement with the rates from a recent compilation. With respect to the nuclear structure of P27 we have found evidence for a negative-parity intruder state at 2.88-MeV excitation energy. © 2016 American Physical Society
Cluster structure of neutron-rich 10Be and 14C via resonant alpha scattering
Neutron-rich10Be and 14C nuclei were studied via resonant α scattering of radioactive 6He and 10Be beams, respectively, produced by the TwinSol facility at the University of Notre Dame. The Prototype Active-Target Time-Projection Chamber (pAT-TPC) was used as a thick gaseous α target to induce resonant scattering and as a device to track reacted particles inside the target, providing continuous excitation functions and angular distributions over a wide range of energies and angles. The experimental results indicate a melting phenomenon of α clusters in the 4+ rotational member of the 10Be ground state and a linear chain alignment of three α clusters in 14C excited states, as recently predicted by an anti-symmetrized molecular dynamics calculation
Knockout and fragmentation reactions using a broad range of tin isotopes
Published VersionProduction cross sections of residual nuclei obtained by knockout and fragmentation reactions of different tin isotopes accelerated at 1A GeV have been measured with the fragment separator (FRS) at GSI, Darmstadt. The new measurements are used to investigate the neutron-excess dependence of the neutron- and proton-knockout cross sections. These cross sections are compared to Glauber model calculations coupled to a nuclear de-excitation code in order to investigate the role of the remnant excitations. This bench marking shows an overestimation of the cross sections for the removal of deeply bound nucleons. A phenomenological increase in the excitation energy induced in the remnants produced in these cases allows us to reproduce the measured cross sections
Coulomb breakup of neutron-rich Na isotopes near the island of inversion
First results are reported on the ground state configurations of the
neutron-rich Na isotopes, obtained via Coulomb dissociation (CD)
measurements as a method of the direct probe. The invariant mass spectra of
those nuclei have been obtained through measurement of the four-momentum of all
decay products after Coulomb excitation on a target at energies of
400-430 MeV/nucleon using FRS-ALADIN-LAND setup at GSI, Darmstadt. Integrated
Coulomb-dissociation cross-sections (CD) of 89 mb and 167 mb up to
excitation energy of 10 MeV for one neutron removal from Na and
Na respectively, have been extracted. The major part of one neutron
removal, CD cross-sections of those nuclei populate core, in its' ground state.
A comparison with the direct breakup model, suggests the predominant occupation
of the valence neutron in the ground state of Na and
Na is the orbital with small contribution in the
-orbital which are coupled with ground state of the core. The ground state
configurations of these nuclei are as Na_{gs (1^+)\otimes\nu_{s,d} and
Na, respectively. The ground state spin
and parity of these nuclei, obtained from this experiment are in agreement with
earlier reported values. The spectroscopic factors for the valence neutron
occupying the and orbitals for these nuclei in the ground state have
been extracted and reported for the first time. A comparison of the
experimental findings with the shell model calculation using MCSM suggests a
lower limit of around 4.3 MeV of the sd-pf shell gap in Na.Comment: Modified version of the manuscript is accepted for publication in
Journal of Physics G, Jan., 201
First direct measurement of Mg(,p)Al and implications for X-ray burst model-observation comparisons
Type-I X-ray burst (XRB) light curves are sensitive to the model's nuclear
input and consequently affects the model-observation comparisons.
Mg(,p)Al is among the most important reactions which
directly impact the XRB light curve. We report the first direct measurement of
Mg(,p)Al using the Active Target Time Projection Chamber.
XRB light curve model-observation comparison for the source
using new reaction rate implies a less-compact neutron star than previously
inferred. Additionally, our result removes an important uncertainty in XRB
model calculations that previously hindered extraction of the neutron star
compactness
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