اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدDetermination of the structure of $^{31}$Ne by full-microscopic framework
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We perform the first quantitative analysis of the reaction cross sections of $^{28-32}$Ne by $^{12}$C at 240 MeV/nucleon, using the double-folding model (DFM) with the Melbourne $g$-matrix and the deformed projectile density calculated by the antisymmetrized molecular dynamics (AMD). To describe the tail of the last neutron of $^{31}$Ne, we adopt the resonating group method (RGM) combined with AMD. The theoretical prediction excellently reproduce the measured cross sections of $^{28-32}$Ne with no adjustable parameters. The ground state properties of $^{31}$Ne, i.e., strong deformation and a halo structure with spin-parity $3/2_{}^-$, are clarified.
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We apply a fully quantum mechanical Coulomb breakup theory under the aegis of post form finite-range distorted wave Born approximation to analyze the elastic Coulomb breakup of $^{29}$Ne on $^{208}$Pb at $244$,MeV/u. We calculate several reaction obs
ervables to quantify its structural parameters. One-neutron removal cross-section is calculated to check the consistency of the ground state configuration of $^{29}$Ne with the available experimental data. A scrutiny of the parallel momentum distribution of the charged fragment reveals a full width at half maximum of $82$,MeV/c, which is in good agreement with the experimental value and indicates a moderate halo for a nearly spherical $^{29}$Ne in the $^{28}$Ne$(0^+) otimes 2p_{3/2} u$ ground state. The energy-angular distributions and average momentum of the charged fragment point to the absence of post-acceleration effects in the breakup process, a desirable result for the elastic breakup.
Halo is one of the most interesting phenomena in exotic nuclei especially for $^{31}$Ne, which is deemed to be a halo nucleus formed by a $p-$wave resonance. However, the theoretical calculations dont suggest a $p-$wave resonance using the scattering
phase shift approach or complex scaling method. Here, we apply the complex momentum representation method to explore resonances in $^{31}$Ne. We have calculated the single-particle energies for bound and resonant states together with their evolutions with deformation. The results show that the $p-$wave resonances appear clearly in the complex momentum plane accompanied with the $p-f$ inversion in the single-particle levels. As it happens the $p-f$ inversion, the calculated energy, width, and occupation probabilities of major components in the level occupied by valance neutron support a $p-$wave halo for $^{31}$Ne.
We apply the Gamow shell model to study $^{25-31}$F isotopes. As both inter-nucleon correlations and continuum coupling are properly treated therein, the structure shape of $^{31}$F at large distance can be analyzed precisely. For this, one-nucleon d
ensities, root-mean square radii and correlation densities are calculated in neutron-rich fluorine isotopes. It is then suggested that $^{31}$F exhibits a two-neutron halo structure, built from both continuum coupling and nucleon-nucleon correlations.
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Marcello Baldo
, Fiorella Burgio (Istituto Nazionale di Fisican Nucleare
, Sezione di Catania
2000
The Bethe-Brueckner-Goldstone many-body theory of the Nuclear Equation of State is reviewed in some details. In the theory, one performs an expansion in terms of the Brueckner two-body scattering matrix and an ordering of the corresponding many-body
diagrams according to the number of their hole-lines. Recent results are reported, both for symmetric and for pure neutron matter, based on realistic two-nucleon interactions. It is shown that there is strong evidence of convergence in the expansion. Once three-body forces are introduced, the phenomenological saturation point is reproduced and the theory is applied to the study of neutron star properties. One finds that in the interior of neutron stars the onset of hyperons strongly softens the Nuclear Equation of State. As a consequence, the maximum mass of neutron stars turns out to be at the lower limit of the present phenomenological observation.
Background: The breakout from the hot Carbon-Nitrogen-Oxigen (CNO) cycles can trigger the rp-process in type I x-ray bursts. In this environment, a competition between $^{15}text{O}(alpha,gamma){^{19}text{Ne}}$ and the two-proton capture reaction $^{
15}text{O}(2p,gamma){^{17}text{Ne}}$ is expected. Purpose: Determine the three-body radiative capture reaction rate for ${^{17}text{Ne}}$ formation including sequential and direct, resonant and non-resonant contributions on an equal footing. Method: Two different discretization methods have been applied to generate $^{17}$Ne states in a full three-body model: the analytical transformed harmonic oscillator method and the hyperspherical adiabatic expansion method. The binary $p$--$^{15}$O interaction has been adjusted to reproduce the known spectrum of the unbound $^{16}$F nucleus. The dominant $E1$ contributions to the $^{15}text{O}(2p,gamma){^{17}text{Ne}}$ reaction rate have been calculated from the inverse photodissociation process. Results: Three-body calculations provide a reliable description of $^{17}$Ne states. The agreement with the available experimental data on $^{17}$Ne is discussed. It is shown that the $^{15}text{O}(2p,gamma){^{17}text{Ne}}$ reaction rates computed within the two methods agree in a broad range of temperatures. The present calculations are compared with a previous theoretical estimation of the reaction rate. Conclusions: It is found that the full three-body model provides a reaction rate several orders of magnitude larger than the only previous estimation. The implications for the rp-process in type I x-ray bursts should be investigated.
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